Multimodal Concepts for Integration of Cytotoxic Drugs

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Contents

I

MEDICAL RADIOLOGY

Radiation Oncology Editors: L. W. Brady, Philadelphia H.-P. Heilmann, Hamburg M. Molls, Munich

Contents

III

J. M. Brown · M. P. Mehta · C. Nieder (Eds.)

Multimodal Concepts for Integration of Cytotoxic Drugs With Contributions by G-One Ahn · K. K. Ang · N. H. Andratschke · M. Bastasch · C. Belka · J. Bourhis · J. M. Brown B. L. D. M. Brücher · T. A. Buchholz · S. Choi · H. Choy · C. H. Crane · W. Dörr · J. Dunst D. B. Evans · J. Fleckenstein · A. Fyles · H. Geinitz · M. R. Gilbert · D. E. Hallahan · Z. Han P. M. Harari · H. Harada · G. Hariri · M. Hiraoka · D. Khuntia · G. Lammering · Z. Liao F. Lordick · K. A. Mason · L. Milas · M. Milosevic · M. P. Mehta · M. Molls · C. Nieder A. Oza · P. W. T. Pisters · D. Riesenbeck · C. Rödel · C. Rübe · J. N. Sarkaria · R. Sauer K. Shibuya · H. D. Thames · A. M. Traynor · G. Varadhachary · R. A. Wolff · A. Zietman F. Zimmermann

Series Editor’s Foreword by

L. W. Brady · H.-P. Heilmann · M. Molls With 73 Figures in 83 Separate Illustrations, 12 in Color and 73 Tables

123

IV

Contents

J. Martin Brown, PhD Division of Radiation and Cancer Biology Department of Radiation Oncology Stanford School of Medicine 269 Campus Drive Center for Clinical Science and Research, Rm 1255 Stanford, CA 94305-5152 USA Minesh P. Mehta, MD Department of Human Oncology University of Wisconsin Hospital Medical School 600 Highland Ave., K4 312-3684 Madison, WI 53792 USA

Carsten Nieder, MD Department of Radiation Oncology Klinikum rechts der Isar der Technischen Universität München Ismaninger Strasse 22 81675 München Germany

Medical Radiology · Diagnostic Imaging and Radiation Oncology Series Editors: A. L. Baert · L. W. Brady · H.-P. Heilmann · M. Molls · K. Sartor Continuation of Handbuch der medizinischen Radiologie Encyclopedia of Medical Radiology Library of Congress Control Number: 2005939063

ISBN-10 3-540-25655-5 Springer Berlin Heidelberg New York ISBN-13 978-3-540-25655-7 Springer Berlin Heidelberg New York This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, speciﬁcally the rights of translation, reprinting, reuse of illustrations, recitations, broadcasting, reproduction on microﬁlm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer-Verlag. Violations are liable for prosecution under the German Copyright Law. Springer is part of Springer Science+Business Media http//www.springer.com ¤ Springer-Verlag Berlin Heidelberg 2006 Printed in Germany The use of general descriptive names, trademarks, etc. in this publication does not imply, even in the absence of a speciﬁc statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Product liability: The publishers cannot guarantee the accuracy of any information about dosage and application contained in this book. In every case the user must check such information by consulting the relevant literature. Medical Editor: Dr. Ute Heilmann, Heidelberg Desk Editor: Ursula N. Davis, Heidelberg Production Editor: Kurt Teichmann, Mauer Cover-Design and Typesetting: Verlagsservice Teichmann, Mauer Printed on acid-free paper – 21/3151xq – 5 4 3 2 1 0

Contents

V

Foreword

For decades the combination of radiation therapy and chemotherapy have played an increasingly important role in cancer treatment. Progress has been made, but a variety of concepts have failed to achieve the success sought. Basic to the use of combined integrated multimodality treatment is an understanding of the theoretical background of radiation, drugs and, most importantly, the interaction between the two regimens. Even though there are numerous publications on the topic, this volume – Multimodal Concepts for Integration of Cytotoxic Drugs and Radiation Therapy – makes an important niche for itself in clinical management. In the preclinical part of the volume, the necessary background of radiation biology as the basis for combined treatment is given with special reference to specific drugs and delivery techniques. The clinical part summarizes the knowledge to date of successful combined modality treatment for primary brain tumors, brain metastases, head and neck cancers, gastric cancers, lung cancers, breast cancers, anal and rectal tumors, bladder cancers as well as gynecologic malignancies. Acute and late toxicity is discussed as are special problems related to treating the elderly and patients with co-morbidity. Every oncologist doing combined modality treatment will find this a valuable source of information. Philadelphia Hamburg Munich

Luther W. Brady Hans-Peter Heilmann Michael Molls

Contents

VII

Preface

Over the last century, the curative potential of radiation therapy for solid tumors has increased. Despite these advances there are major challenges to further improvements that result from the complexities of human tumors that are often not simulated in preclinical models. In clinical practice normal tissue tolerance remains the most important limitation to adequate tumor dose delivery. Doses resulting in high tumor control probability will often cause unacceptable toxicity, a problem related to the width of the therapeutic window. Major avenues of progress in overcoming this limitation in the last decades have included the introduction of altered fractionation regimens, and technical advances resulting in better target visualization and more conformal dose distribution with steeper dose gradients. Illustrative examples of such technologies include stereotactic radiotherapy (and radiosurgery), intensity-modulated treatment, helical tomotherapy, and image-guided radiotherapy. In addition, there is a major new interest in the refinement and evaluation of particle beam therapy. Another way of achieving better tumor control rates, both within the target volume and potentially also at microscopic distant sites, is by combining ionizing radiation with cytotoxic chemotherapy. Besides simple additive cell kill without added local toxicity and spatial cooperation, several other mechanisms can lead to increased efficacy. These mechanisms depend on drug type and concentration, drug target, metabolism, timing of administration, microenvironmental and genetic factors, etc. The principles of such combined modality approaches have been defined in appropriate models and successfully transferred through translational research into clinical practice. In several common solid tumor types, landmark clinical studies have clearly demonstrated the benefit of combined modality treatment. The number of patients undergoing such treatment has been increasing steadily for the last two decades. Clinical optimization of combination regimens is ongoing but with tremendous challenges, related to the development and incorporation of new compounds, especially the so-called “molecularly targeted” agents that interfere with important signal transduction pathways, angiogenesis, tumor microenvironment, etc. The challenge can be illustrated very well by modeling glioblastoma multiforme as an example; three common pathways are believed to confer a proliferative advantage and resistance to apoptotic death in this disease, including dramatic oversecretion of VEGF which drives angiogenesis, EGFR overexpression/activation which drives proliferation, and PTEN deletions, which drive antiapoptotic properties. Over 40 targeted drugs now exist to block these pathways at one or more points, and if selected for combination with radiotherapy in various permutations and combinations, over 4000 possible therapeutic regimens could be developed for testing purposes. This clearly poses an enormous challenge in terms of understanding the biology, and conducting well thought out research.

VIII

Contents

Every clinician and researcher involved in development and optimization of innovative combined modality approaches, or in treating patients will find valuable information about the principles of such treatment and the effects of the various compounds in this volume. The comprehensive clinical chapters focus on results of recent studies and provide data pertinent to everyday practice with regard to dosing, toxicities and supportive care. Special emphasis is also placed on treatment of elderly patients, given the demographics in most developed countries. In the future, combined modality treatment will undergo further substantial refinement, and will continue to play an important role in the treatment of solid tumors. Such refinement includes better response evaluation and prediction and better tailoring of regimens to an individual patient. Stanford Madison Munich

J. Martin Brown Minesh P. Mehta Carsten Nieder

Contents

IX

Contents

Preclinical Part. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1

1 Biological Basis of Combined Radio- and Chemotherapy Claus Belka, Carsten Nieder and Michael Molls . . . . . . . . . . . . . . . . . . . . . . . .

3

2 Combinations of Antimetabolites and Ionizing Radiation Hiroshi Harada, Keiko Shibuya, and Masahiro Hiraoka. . . . . . . . . . . . . . . . . .

19

3 Combinations of Taxanes and Ionizing Radiation Luka Milas, Kathryn A. Mason, Zhongxing Liao and Kian K. Ang . . . . . . . . .

35

4 Combinations of Topoisomerase Inhibitors and Ionizing Radiation . . . . . . . . . . . . . Michael Bastasch and Hak Choy

53

5 Combinations of Hypoxia-Targeting Compounds and Radiation-Activated Prodrugs with Ionizing Radiation G-One Ahn and J. Martin Brown . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

67

6 Combinations of Platinum Compounds and Ionizing Radiation Carsten Nieder and Florian Lordick . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

93

7 Combinations of Cytotoxic Drugs, Ionizing Radiation and Angiogenesis Inhibitors Carsten Nieder and Nicolaus H. Andratschke . . . . . . . . . . . . . . . . . . . . . . . . . . . 103 8 Combinations of Cytotoxic Drugs, Ionizing Radiation and EGFR Inhibitors Guido Lammering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115 9 Combinations of Cytotoxic Drugs, Ionizing Radiation and Mammalian Target of Rapamycin (mTOR) Inhibitors Jann N. Sarkaria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127 10 Combinations of Ionizing Radiation and Other Sensitizing Agents Minesh P. Mehta . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139 11 Radiotherapy and Tumor-Targeted Drug Delivery Zhaozhong Han, Ghazal Hariri and Dennis E. Hallahan. . . . . . . . . . . . . . . . . 151

X

Contents

Clinical Part . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

163

12 Applications in Malignant Brain Tumors Carsten Nieder and Mark R. Gilbert . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

165

13 Applications in Head and Neck Cancer Deepak Khuntia, Anne M. Traynor, Paul M. Harari and Jean Bourhis . . .

187

14 Applications in Esophageal and Gastric Cancer Frank Zimmermann and Björn L. D. M. Brücher . . . . . . . . . . . . . . . . . . . . . . . . .

197

15 Novel Chemoradiation in Localized Pancreatic Cancer: Clinical Studies Christopher H. Crane, Gauri Varadhachary, Peter W. T. Pisters, Douglas B. Evans, and Robert A. Wolff . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

215

16 Applications in Lung Cancer Jochen Fleckenstein and Christian Rübe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

231

17 Integration of Radiation Therapy and Systemic Therapy for Breast Cancer Seungtaek Choi, Howard D. Thames, and Thomas A. Buchholz. . . . . . . . . . .

251

18 Applications in Rectal and Anal Cancer Claus Rödel and Rolf Sauer. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

267

19 Concomitant Radiation and Chemotherapy in Muscle-Invasive Bladder Cancer Jürgen Dunst, Claus Rödel, and Anthony Zietman. . . . . . . . . . . . . . . . . . . . . .

285

20 Applications to Gynecological Cancers Anthony W. Fyles, Michael Milosevic and Amit Oza. . . . . . . . . . . . . . . . . . . .

303

21 Early and Late Treatment-Induced Toxicity Wolfgang Dörr, Dorothea Riesenbeck, and Carsten Nieder . . . . . . . . . . . .

317

22 Feasibility of Combined Chemo- and Radiation Treatment in Elderly/Comorbid Patients Hans Geinitz . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

333

Subject Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

341

List of Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

345

Biological Basis of Combined Radio- and Chemotherapy

1

I. Preclinical Part

Biological Basis of Combined Radio- and Chemotherapy

1

3

Biological Basis of Combined Radio- and Chemotherapy Claus Belka, Carsten Nieder and Michael Molls

CONTENTS 1.1 1.1.1 1.2 1.2.1 1.2.2 1.2.2.1 1.2.2.2 1.2.2.3 1.3 1.3.1 1.3.2 1.3.3 1.4 1.4.1 1.4.2 1.5 1.6 1.7 1.8 1.9

Introduction 3 Clinical Relevance of Combined Modality Approaches 3 Basic Considerations 5 Therapeutic Gain 5 Additivity, Synergism, and Sub-Additivity 6 Synergism (Supraadditivity) 6 Additivity 7 Infra (Sub)-Additivity (Protection) 7 Interaction of Radiation and Chemotherapy 8 Spatial Interaction 8 Role of Repopulation 8 Role of Hypoxia 9 Molecular Interactions 10 DNA Damage 10 Radiation Sensitization Via Cell Cycle Synchronization 11 Potential Influences on Programmed Cell Death Pathways 12 Effects of Protracted Drug Exposure 13 Combination of Radiation with Hormonal Ablation 14 Radiation-Induced Chemotherapy Resistance 14 Conclusion 14

1.1 Introduction 1.1.1 Clinical Relevance of Combined Modality Approaches The introduction of combined modality approaches was a highly significant step in the evolution of curative radiation treatment. Parallel to analy-

C. Belka, MD Department of Radiation Oncology, University Hospital, Eberhard-Karls Universität Tübingen, Hoppe-Seyler-Strasse 3, 72076 Tübingen, Germany C. Nieder, MD; M. Molls, MD Department of Radiation Oncology, Klinikum rechts der Isar der Technischen Universität München, Ismaninger Strasse 22, 81675 Munich, Germany

sis of altered fractionation schedules, combined treatment has actively been investigated in recent decades in both preclinical and clinical studies around the world. When judged at this time, the most pronounced increase in therapeutic gain was probably seen by combining radiation with chemotherapy. Unfortunately, most of the recent gains in local control and also survival achieved with now accepted, more conventional combined approaches are somewhat covered by the enthusiasm created by various new and so-called targeted drugs (Nieder et al. 2003), most of which are still to demonstrate their full therapeutic potential. Meanwhile a huge body of evidence supports the use of combined modality approaches based on the combination of ionizing radiation with cytostatic drugs. In this regard, several randomized phase-III trials for many relevant cancer sites provide a sound basis for level one evidence-based decisions. This holds true especially for glioblastoma multiforme (Stupp et al. 2005), head and neck cancers including nasopharyngeal cancer and laryngeal cancer (Brizel et al. 1998; Forasteriere et al. 2003; Budach et al. 2005), esophageal cancer (Minsky et al. 2002), colorectal- and anal cancer (Sauer et al. 2004; Bartelink et al. 1997), cervical cancer (Green et al. 2001), as well as lung cancer (SchaakeKoning et al. 1992). The most important aim of curative cancer treatment is to eradicate all tumor cells. With regard to the amount of quantitative cell kill, it has to be emphasized that important differences exist between ionizing radiation and chemotherapy (Fig. 1.1). In principle, radiation treatment can be designed to cover the whole tumor with a homogeneously distributed full radiation dose, capable of inactivation of all tumor cells. In contrast, pharmacotherapy is limited by the fact that the dose of the active, cell killing form of the compound is variable within the tumor and its cells (Fig. 1.2). This results from problems in the delivery of drugs (perfusion, interstitial fluid pressure, tissue pH, etc.), cellular uptake, efflux, inactivation, and resistance. In many instances, the agent

C. Belka et al.

4

Tumor cells

1010 108 106 104

y

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Ionizing Radiation Fig. 1.2. Comparison between tumor dose distribution in radiation treatment and pharmaceutical treatment. Illustrative tumor sections from a squamous cell carcinoma demonstrate biological heterogeneity, reﬂected by the differently colored areas, within the tumor. Homogenous radiation dose distribution within the tumor irrespective of differences in biology, physiology, functional factors, structure, and morphology. Heterogeneous dose distribution for drug treatment, related, for example, to regional differences in perfusion, pH, metabolism, etc. Drug molecules are shown as red circles. (Courtesy W. Müller-Klieser, Johannes Gutenberg University, Mainz, Germany)

Homogeneous dose distribution. Tumor cell kill depends on intrinsic radiosensitivity, local physiology and biochemical status of the tumor subvolumes. In principle, the whole tumor can be covered by the radiation dose required to kill all tumor cells.

does not reach the relevant therapeutic targets in the required concentration and for a sufficient time period. These issues, which are addressed in the drug-specific chapters, gain complexity with simultaneous administration of two or more drugs. Such multi-agent regimens with different modes of action might be valuable when each agent kills different tumor cells, which would not become inactivated by the other agents; however, sometimes all agents might act on the same cell, causing much more damage than necessary for cell death. As illustrated in Fig. 1.1, the quantitative cell kill of ionizing radiation is significantly larger than that of chemotherapy

othe rapy

rap

Resection

102 0

Chem

the dio Ra

Fig 1.1. Differences in quantitative cell kill and time course. Inﬂuence of different therapeutic modalities on number of tumor cells during a course of treatment, based on the models by Tannock (1989, 1992). The dashed line represents the border between microscopic and macroscopic tumors, deﬁned as a size of approximately 5 mm. Compared with surgical resection and fractionated radiotherapy, multiple courses of chemotherapy (in this case six, indicated by arrows) are less efﬁcient in cell kill. While microscopic disease might be eradicated (lower chemotherapy curve), clinical evidence suggests that most macroscopic solid tumors (exception: more sensitive testicular cancers) will shrink temporarily but eventually regrow from surviving residues (upper chemotherapy curve). As shown in the inset, the strength of chemotherapy in combination with radiation treatment (besides of spatial cooperation) is the modiﬁcation of the slope of the curve

4

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Pharmaceuticals Inhomogeneous dose distribution. Tumor cell kill depends on delivery of the drug, uptake in tumor tissue and cells, local physiology, biochemical status, multidrug resistance etc. Often, subvolumes and relevant therapeutic targets are not covered by the full drug dose.

(Tannock 1992, 1998). The magnitude of this effect might vary with cell type, culture conditions, drug, exposure time, etc. Experimental evidence suggests, however, that single radiation doses result in 1% or less cell survival compared with 1050% with cytotoxic drugs (Epstein 1990; Kim et al. 1992; Simoens et al. 2003; Eliaz et al. 2004). Although clinically impressive remissions of solid tumors might occur after chemotherapy, the underlying cell kill is often not larger than 12 log and pathological examination of tissue specimens reveals residual viable tumor cells. Even with modern drug combinations, pathological complete remission (pCR) after neo-

Biological Basis of Combined Radio- and Chemotherapy

5

adjuvant chemotherapy is seen in only 1036% of breast cancer cases (Evans et al. 2005; Reitsamer et al. 2005; Von Minckwitz et al. 2005) and 920% of cervical cancer cases (Buda et al. 2005; Modarress et al. 2005). In a randomized setting, the pCR rate in cervical cancer was much lower after neoadjuvant chemotherapy alone than after radiochemotherapy (10 vs 43%; p<0.05; Modarress et al. 2005). The definitive cure rates without local treatment would certainly be lower than the pCR rates, because some surviving clonogen tumor cells, which are not readily detectable, might still be present. As mentioned above, the curves shown in Figure 1.1 depend on several variables related to patient selection, tumor microenvironment and sensitivity, agent and dose, etc. They are meant to illustrate the principle; however, the results of some neoadjuvant chemotherapy trials demonstrate a certain variability in the steepness of these curves. In most clinical situations, chemotherapy augments the radiation-induced cell kill within the irradiated volume and may improve distant control. To maximize augmentation of cell kill, optimization of parameters of drug exposure is necessary. It has been shown, for example, that continuous infusion is better than bolus administration of 5-fluorouracil (5-FU). The following example illustrates the efficacy of chemotherapy as a radiation enhancer. In the large randomized FFCD 9203 trial in rectal cancer preoperative radiotherapy (45 Gy in 25 fractions) resulted in a pCR in 4%, whereas the addition of 5-FU and folinic acid improved this figure to 12% (Gerard et al. 2005). While radiation alone can be considered as a curative treatment in a variety of early-stage solid tumors (especially T1-2 N0 M0, e.g., skin, anal, cervix, larynx, lung, and prostate cancers), long-term control with chemotherapy alone is rarely observed. Even in the adjuvant situation, chemotherapy often fails to control micrometastatic Ideal

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1.2.1 Therapeutic Gain Therapeutic gain is defined by an increase of tumor control and finally survival without a parallel increase in the severity of specific side effects (Fig. 1.3). Only few reports are available, proving

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disease. Current concepts of cancer biology suggest that most traditional chemotherapy approaches fail to eradicate cancer stem cells, which are slow-cycling cells that often express multidrug resistance (MDR) proteins (Miller et al. 2005). Previous strategies of chemotherapy intensification, either by local delivery, systemic high-dose treatment, or simultaneous administration of several non-cross-resistant drugs, e.g., 8-drugs-in-1-day, were mostly disappointing (Farquhar et al. 2005). Among newer concepts is the so-called metronomic chemotherapy, which refers to prolonged administration of comparatively low doses of cytotoxic drugs with minimal or no drug-free breaks. This strategy is thought to have an antiangiogenic basis and shows encouraging results in preclinical models (Shaked et al. 2005). It is now also combined with maximum-tolerated dose chemotherapy and targeted agents in vivo (Pietras and Hanahan 2005). Although the well-accepted combination of hormonal ablation with radiotherapy, especially in the primary curative setting of locally advanced prostate cancer (Bolla et al. 2002), is not a combination of chemotherapy with radiation per se, there are many similarities so that the combination of androgen deprivation and radiation are also covered herein.

0 40 60 Dose (Gy)

40 60 Dose (Gy)

Tumor control Normal tissue damage probability Therapeutic gain

Fig. 1.3. Therapeutic gain. Therapeutic gain is deﬁned as the resulting beneﬁt when tumor control is weighted against the normal tissue damage. In an ideal setting (left panel) the probability of normal tissue damage is minimal at a dose level with a maximal probability of tumor control. More realistically (middle panel), doses required to achieve local control are associated with a certain, but low, probability of normal tissue damage. In situations where the doses required to control the tumor are continuously higher than the doses being toxic, treatment will be palliative in most cases

C. Belka et al.

6

that the combination of radiation and chemotherapy actually results in an increased therapeutic gain. A very nice preclinical example is the comprehensive studies with cisplatin and 5-FU in different tumors transplanted into mice, which were reported by Kallman et al. 1992. In our opinion, this group has demonstrated in an excellent fashion how clinically relevant experiments of radiochemotherapy can be designed. Also worth mentioning is a clinical example, i.e., a randomized German phase-III trial (Budach et al. 2005), where a total of 384 stage-III and stage-IV head and neck cancer patients were randomly assigned to receive either 30 Gy (2 Gy/day) followed by 1.4 Gy b.i.d. to a total dose of 70.6 Gy concurrently with 5-FU and mitomycin-C (C-HART) or 14 Gy (2 Gy/day) followed by 1.4 Gy b.i.d. to a total dose of 77.6 Gy (HART). The overall treatment time was equal in both groups. At 5 years, the locoregional control and overall survival rates were significantly better in the radiochemotherapy arm compared with the radiation-only arm. Interestingly, the maximum acute reactions of mucositis, moist desquamation, and erythema were significantly lower in the chemoradiotherapy arm compared with radiotherapy alone. No differences in late reactions and overall rates of secondary neoplasms were observed; thus, this trial impressively documents that the combination of radiotherapy with chemotherapy agents may effectively widen the therapeutic window; however, it is clear that although the specific toxicities may not be increased, new toxicities in terms of hematoxicity will be added; thus, the net effect of radiochemotherapy results from a cooperation regarding tumor control and, in parallel, a diversification of toxicities. Independently of the term “therapeutic gain,” the interaction of radiation with chemotherapy follows a precise nomenclature based on some groundbreaking theoretical considerations published in the late 1970s (Steel 1979; Steel and Peckham 1979). In every case of a scientific description and quantification of the effects of combined modality therapy in appropriate models, it is highly recommended to adhere to the proposed nomenclature. The complexity of effects increases with each step of investigation, i.e., from cell culture to tumor bearing animal to cancer patient (Wurschmidt et al. 2000). A thorough examination of all possible treatment combinations and administration schedules for a given drug plus radiation is very challenging, as can be seen in the publication by Kallman et al. (1992), who studied in depth the radiosensitizing effects of cisplatin. Although extensive discussion

of radiobiological principles is beyond the scope of this chapter, a few definitions shall be mentioned. Since the introduction of mammalian cell survival curves, the parameters D0 and N have been used as quantitative measures of inherent radiation sensitivity, as was the shoulder width Dq (Thames and Suit 1986). The ratio alpha/beta is a measure of fractionation sensitivity.

1.2.2 Additivity, Synergism, and Sub-Additivity When combining two treatment modalities the resulting net effect on cell killing is mainly described by the terms “additivity, synergism, and sub-additivity,” which are derived from experimental work. They are not applicable to the clinical situation and do not reflect the results of clinical trials, where changes from radiation as a monotherapy to multimodal treatment usually do not result in extraordinarily favorable cure rates (or supraadditivity), although they have led to important gradual improvement. It appears prudent to refer to the term “enhancement of radiation effect” within a clinical context. 1.2.2.1 Synergism (Supraadditivity)

The term “synergism” describes a situation where the combination of both drugs induces more cell kill than the addition of either treatment alone. The term radiosensitization is also used in this regard; however, it should only be employed when the drug used is devoid of any intrinsic potential (Figs. 1.4, 1.5). Regardless of nomenclature, the resulting effect is a shift of the tumor control curve to the left. The biomathematical relationship of a given interaction is tested mainly using the so-called isobologram analysis (Fig. 1.5), which is applicable to experimental conditions only. The dose-response relationship of either trigger is used to generate a mathematical description of the resulting curve. Both equations are then used to plot the so-called envelope of additivity. In the next step, observed effects of a given combination are plotted into the isobologram. In case of any dose-response relationship below the envelope of additivity, the dose response relationship for this individual interplay is synergistic. In other words, less radiation and drug dose were needed to achieve a certain effect than

Biological Basis of Combined Radio- and Chemotherapy

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Fig. 1.4. Impact of a combined modality approach on theoretical radiation survival curves. Generally, the impact of radiation on cell survival with or without any additional treatments is determined using a clonogenic assay. Three major patterns of behavior might be distinguished when a radiation response is modiﬁed by the addition of a drug. It has to be taken into account that in reality these patterns are frequently not as pure as shown here. Pattern 1 (left): the addition of a drug (no intrinsic cell kill by the given drug) increases the radiation sensitivity (gray line); thus, the resulting curve is bended to the right. Pattern 2 (middle): the addition of a drug (signiﬁcant intrinsic cell kill by the given drug) does not inﬂuence the radiation sensitivity at all (gray curve); however, the intrinsic cell killing via the drug alone leads to a parallel shift of the dose response curve downwards. Pattern 3 (right): the addition of a certain drug (gray curve) protects against radiation-mediated cell kill and the resulting curve bends to the left.

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Dose of agent A Fig. 1.5. Isobologram analysis. The mathematic degree of a given interaction of two treatment modalities is generally described using isobolograms. As an example, three characteristic patterns are displayed for the interaction of the death ligand tumor necrosis factor-related apoptosis-inducing ligand (TRAIL, agent A) with radiation (agent B) for the end-point apoptosis induction. The left isobologram is an example for pure additivity. The observed dose response relationship (dot) falls into the calculated envelope of additivity for the given level of cell kill. In the case of the isobologram displayed in the middle, the observed dose response (dot) for the given level of apoptosis induction is above the calculated envelope of additivity indicating an interaction less than additive. The right isobologram shows a case of clear synergism with the required dose for the given level of cell kill (dot) being below the calculated envelope of additivity for the given level of cell kill

that calculated from the dose-response equation for both triggers. It is important in this regard to notice that synergistic effects for a given combination can occur only on certain dose levels, whereas other dose combinations act only additively or even less than additively (Wurschmidt et al. 2000).

expected from the calculated additive combinatory effect. The observed dose-response relationship for a given dose-effect combination will fall into the envelope of additivity. If one uses colony formation assays as end points, a simple parallel shift of the radiation response curves merely excludes synergism and strongly suggests additivity (Fig. 1.4).

1.2.2.2 Additivity

1.2.2.3 Infra (Sub)-Additivity (Protection)

The term additivity is used to describe situations where both triggers act completely independent of each other resulting in a net kill not larger than

This term describes situations where the drug interferes negatively with the efficacy of ionizing radiation, or vice versa.

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1.3 Interaction of Radiation and Chemotherapy 1.3.1 Spatial Interaction On a large scale, chemotherapy and radiation may be effective on several levels. The concept of spatial interaction was devised to mean that chemotherapy and radiation act on spatially distinct compartments of the body, resulting in a net gain in tumor control. The concept of spatial interaction does not take into account any drug-radiation interaction on the level of the tumor itself, but rather assumes that radiation or chemotherapy would be active in different compartments, respectively. In a narrow sense, this concept describes the fact that chemotherapy would be employed for the sterilization of distant microscopic tumor seeding, whereas radiation would achieve local control (Fig. 1.6). Obviously, this is a theoretical consideration only, since chemotherapy also increases local control and radiotherapy reduces distant metastasis via increased local control rates; thus, when integrating the concept of spatial interaction into a more complete view on combined modality, spatial cooperation is still of major importance

Spatial interaction (classical)

(Fig. 1.6). In a more narrow sense, the aspect of spatial interaction is of major importance when one attempts to adequately cover sanctuary sites during multi-modality approaches for certain types of leukemia and lymphomas. Next to spatial effects, several other important mechanisms may increase the efficacy of a combined treatment approach. In this regard, inhibition of repopulation and effective killing of hypoxic radio-resistant cells may contribute to the efficacy of a combined treatment.

1.3.2 Role of Repopulation The fractionated treatment of tumors with ionizing radiation is associated with the phenomenon of repopulation (Kim and Tannock 2005). Speaking simply, a certain amount of tumors cells repair the induced damage in between two fractions and proliferate. Repopulation may neutralize around 0.5 Gy/day; however, the range of repopulation is considerably large and may reach levels exceeding 4 Gy (Trott 1990; Baumann et al. 1994; Budach et al. 1997). Based on these findings, radiation biologists advocated the use of accelerated radia-

Spatial interaction (complex)

XRT

XRT

CHX CHX

CHX CHX CHX

CHX affects local control Æ Improved local control & less secondary seeding

CHX

CHX CHX

XRT mediated local control Æ Less secondary seeding

CHX

Fig. 1.6. Spatial interaction. In a classical interpretation (left panel) the term spatial interaction refers to the fact that chemotherapy is effective on tumor compartments where radiation has no efﬁcacy, and vice versa, resulting in a generally increased control rate. In a more complex view, spatial interaction is relevant on multiple interacting levels: increased local control by radiation reduces the risk of a secondary seeding. Furthermore, the interaction of radiation with chemotherapy increases local control; thus, in addition to the classical spatial interaction, several levels of interacting feedback loops exist, which increase efﬁcacy of spatial interactions

Biological Basis of Combined Radio- and Chemotherapy

tion schedules; however, the acute and late effects of such approaches turned out to be more intense so that the final value of those approaches in terms of a real therapeutic gain remains unclear (Horiot et al. 1997; Dische et al. 1997; Beck-Bornholdt et al. 1997). The phenomenon of repopulation must also be taken into account when trying to design combined modality regimens. In theoretical models, cell loss from neoadjuvant chemotherapy preceding fractionated radiation treatment might trigger accelerated repopulation (Fig. 1.7). Then, a certain percentage of the daily radiation dose is wasted to counteract increased tumor cell proliferation. Under such conditions, despite of a response to chemotherapy, cell survival after radiotherapy is not better than after the same course of radiotherapy alone (yet toxicity results from both modalities). Whether such effects are more important than reduced interstitial fluid pressure (IFP) and improved oxygenation might depend on tumor type. The clinical observation that the combination of 5-FU, mitomycin C, or cisplatin with radiation is of value in rapidly proliferating squamous cell cancers has led to the suspicion that the addition of drugs may influence the potential of cancer cells to 1010

1010 Rapid repopulation

Number of viable tumor cells

109 108

108

107

107

106

Slow repopulation

No prior chemotherapy

109

106

After response to chemotherapy

105

105 a

b Treatments with radiation

Fig. 1.7a,b. Inﬂuence of tumor cell repopulation on outcome. a Cell survival during a fractionated course of radiotherapy depends not only on the proportion of cells killed with each dose (which is equal for the two examples shown), but also on the rate of proliferation of surviving cells between the fractions, which differs from the two curves. b Hypothetical diagram to illustrate the number of surviving cells in a tumor during treatment with radiation alone, or during radiation treatment in a tumor that has responded to neoadjuvant chemotherapy (i.e., cell number reduced to 1% at start of radiotherapy) but where proliferation has been stimulated. Despite neoadjuvant chemotherapy, ultimate cell survival is similar. (From Tannock 1989)

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repopulate. At least for mitomycin C this effect was documented precisely using an xenograft model (Budach et al. 2002). In this model, transplanted tumors were treated with 11 u 4.5 Gy fractionated radiation under ambient conditions with or without mitomycin C followed by a graded top-up dose on days 16, 23, 30, or 37 given under hypoxic conditions. Repopulation in the interval between the fractionated treatment and the top-up dose accounted for 1.33 Gy top-up dose per day in animals not receiving mitomycin C, but only 0.68 Gy in animals receiving the drug; thus, at least mitomycin C may increase the efficacy of radiation by the inhibition of repopulation.

1.3.3 Role of Hypoxia As known for years, radiation-induced cell kill is strongly dependent on the presence of adequate oxygen tensions. In most larger tumors, e.g., head and neck cancers, areas of hypoxia and even anoxia are present leading to an increased radiation resistance of clonogenic tumor cell within such areas (Molls and Vaupel 1998; Stadler et al. 1999; Nordsmark et al. 2005). It has been speculated that chemotherapeutic agents especially those which kill even hypoxic cells (mitomycin C) may overcome global radiation resistance simply by killing radioresistant hypoxic cells, thereby being of special value in highly hypoxic tumors (Teicher et al. 1981; Rockwell 1982). Comparing the effects of several cytostatic drugs in combination with radiation on the growth of a C3H mammary carcinoma, it turned out that cyclophosphamide, adriamycin, and mitomycin C had the most significant effect on the proportional cell kill of hypoxic cells. In contrast, bleomycin and cisplatin did not exert strong effects on hypoxic cells (Grau and Overgaard 1988). In addition, it has clearly been shown that tumor blood flow in xenografts is increased after mitomycin-C treatment (Durand and Le Pard 1994). Using two different squamous cell carcinomas, the latter authors tested the drug’s influence on outcome of radiation treatment with or without hypoxia (Durand and LePard 2000). The authors did not report an increased killing of hypoxic cell by mitomycin C, nor a consistent increase in tumor blood flow rates; however, mitomycin C in combination with radiation was associated with a slight increase in cell killing of hypoxic subpopulations of the xenograft system. Based on

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ation of hypoxic tumors; however, it still remains speculative whether or to what amount the efficacy of a combined treatment is strictly related to specific influences on the hypoxic cell compartment (Fig. 1.8).

this observation it was concluded that the efficacy of a combined treatment with mitomycin C and radiation cannot be rationalized on either a complementary cytotoxicity or on drug-induced improvement in tumor oxygenation secondary to an increased blood flow. In the case of paclitaxel it has been tested whether the enhanced killing by the combination of paclitaxel and radiation is connected to the presence of oxygen. Using a MCA-4 xenograft system, the authors could show that in the absence of oxygen the paclitaxelmediated change of the TCD50 value is strikingly less prominent (Milas et al. 1994, 1995); thus, it can be concluded that at least in part the influence of paclitaxel on the radiation response is mediated via an optimized oxygenation. In a clinical trial of neoadjuvant chemotherapy in breast cancer, paclitaxel significantly decreased the mean interstitial fluid pressure and improved oxygenation, effects which were not observed in a randomized control group receiving doxorubicin (Taghian et al. 2005). In conclusion, several sets of data indicate that the efficacy of chemotherapy in combination with radiation may be related to an increased oxygen-

1.4 Molecular Interactions 1.4.1 DNA Damage One of the underlying molecular aspects of the efficacy of the combination of radiation and chemotherapy, which has been understood in some more detail, is influence on DNA repair. The induction of DNA damage is probably one of the most crucial events after irradiation of cells. In this regard, ionizing radiation triggers a wide array of lesions including base damage, single-strand breaks, and notably, double-strand breaks (DSB). After irradiation, different molecular systems are involved in recogni-

• Less repopulation XRT

CHX XRT XRT

CHX

• Independent killing of clonogenic tumor cells

CHX

CHX XRT

o2 o2 o2

• Improved blood flow • Improved oxygenation • Enhanced killing of hypoxic cells

• Accumulation in vulnerable phases of the cell cycle

Fig. 1.8. Mechanisms of chemoradiation on a cellular level. At least four major mechanisms contribute to the efﬁcacy of the combination of radiation with chemotherapy. In general, the addition of chemotherapy adds to the combined effect simply by an independent killing of clonogenic tumor cells. This mechanism is backed up by several more interactive pathways: Chemotherapy may induce a certain re-assortment of tumor cells in more vulnerable phases of the cell cycle, chemotherapy may reduce the level of re-population during a course of fractionated radiotherapy, and, ﬁnally, chemotherapy may partially overcome hypoxia-mediated radiation resistance

Biological Basis of Combined Radio- and Chemotherapy

tion and repair of the damage. Whereas most of the induced damage is quickly repaired, DSB repair is slow and unrepaired DSBs are considerably important for the final induction of cell death. Many chemotherapeutic agents, especially those known to be of value in combination with radiation, also induce considerable DNA damage or interfere with effective DNA repair; therefore, two general patterns of interactions may be separated: (a) the combination of the drug with radiation directly leads to more damage; (b) the drug may interact with DNA repair pathway thus increasing the level of DNA damage more indirectly; however, none of the potential mechanisms acts without the other in real settings. Cisplatin, for example, acts by complex formation with guanosine residues and subsequent adduct formation ultimately resulting in intra- and interstrand crosslinks. This type of damage is mostly removed by base excision repair and mismatch repair. Several sets of data suggest that single-strand damage induced by radiation in close vicinity to DNA damage triggered by cisplatin results in a mutual inhibition of the damage-specific repair system; thus, the amount of resulting damage leads to an increased net cell kill (Begg 1990; Yang et al. 1995). Similarly, etoposide, which is a strong topoisomerase-IIa-directed toxin, exerts DSB mostly during the S-phase of the cell cycle (Berrios et al. 1985; Earnshaw and Heck 1985). Again, several lines of evidence show that the combination of both agents results in a strongly increased level of damage (Giocanti et al. 1993; Yu et al. 2000). The biochemical pathways implicated in DNA repair and DNA synthesis overlap in several regards; thus, drugs acting on the synthesis of DNA putatively also interfere with the repair of DNA damage induced by ionizing radiation. Several prototypical radiation sensitizers, including 5-FU, fludarabine, and gemcitabine, may act via these mechanisms. Besides cisplatin, 5-FU is probably the most commonly employed drug in clinical combined modality settings. Basically, 5-FU inhibits thymidilate synthase thereby reducing the intracellular pool of nucleoside triphosphates (Pinedo and Peters 1988; Miller and Kinsella 1992). In addition, the drug is integrated into DNA via fluoro-deoxyuridine, also contributing to its anti-neoplastic effects. Several lines of evidence suggest that the amount of 5FU integrated into DNA directly correlates with the radiosensitizing effect. In addition, the complementation of the cell culture medium with higher levels of thymidine reverses the effects of 5-FU on the radi-

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ation sensitivity (McGinn et al. 1996; Lawrence et al. 1994). Gemcitabine, which is another radiation sensitizer, was also shown to deplete the pool of deoxynucleosides and is integrated into DNA. The drug is known to exert a pronounced radiosensitizing effect in squamous cancer cells, as well as adenocarcinoma cells from pancreatic cancer. In vitro this effect was especially pronounced during the Sphase passage (Robertson et al. 1996; Lawrence et al. 1997; Rosier et al. 1999). Although few data regarding the mechanistic basis of the interaction between radiation and gemcitabine are available, the exact mechanism remains elusive. The radiation sensitizing effect was seen over a prolonged time period (~48 h) after incubation of HT29 cells with low doses of gemcitabine (100 nm). During the first 48 h the level of S-phase cells increased, whereas the amount of deoxynucleotides remained low even up to 72 h (Shewach et al. 1994; Lawrence et al. 1997); thus, it seems likely that, similar to the observations made with 5-FU, the depletion of the deoxynucleotide pools in combination with an increased killing of cells in S-phase is a mechanism responsible for an enhanced radiation susceptibility mediated by gemicitabine; however, in terms of an increased therapeutic gain, clinical trials indicated that gemcitabine is a problematic drug due to a parallel increase in the radiation sensitivity of normal tissues.

1.4.2 Radiation Sensitization Via Cell Cycle Synchronization The fact that striking differences in the radiation sensitivity occur as cells move through the different phases of the cell cycle has stimulated the speculation that the efficacy of a combined treatment may also be related to possible effects on the reassortment of cells in more vulnerable cell cycle phases. Several experimental settings provide evidence that cell cycle effects are involved in the modulation of the efficacy of combined modality approaches. In this regard the use of a temperature-sensitive p53 mutant allows the analysis of cell cycle effects very nicely. The underlying hypothesis was that fluoropyrimidine-mediated radiosensitization occurs only in tumor cells that inappropriately enter S-phase in the presence of drug resulting in a subsequent repair defect of the radiation-induced

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damage. The use of the mutated p53 allowed p21mediated arrest prior to S-phase entry when cells are grown under 32qC, in contrast to no arrest in cells grown at the nonpermissive temperatures of 38qC. The radiation-sensitizing effect of fluoropyrimidine was directly connected to the lacking G1 arrest when cell were grown under nonpermissive temperatures; thus, the fluoropyrimidine-mediated radiosensitization clearly requires progression into S-phase (Naida et al. 1998). In an extension of these findings, Naida et al. (1998) analyzed the effects of fluorodeoxyuridine on the radiation sensitivity in HT29 and SW620 human colon cancer cells under nearly complete inhibition of thymidylate synthase (both cell lines harbor a similar p53 mutation). Interestingly, only the HT29 cells were sensitized. As an underlying feature, the authors found that only the HT29 cells progressed into S-phase and demonstrated increased cyclin E-dependent kinase activity. In contrast, SW620 cells were found to be arrested just past the G1-S boundary and an increase in kinase activity was not detectable; thus, the findings underline the requirement of an S-phase transition for the efficacy of halogenated fluoropyrimidines in combination with radiation. These findings also highlight the role of molecules involved in cell cycle regulation as key players for the modulation of a combined modality approach (McGinn et al. 1994; Lawrence et al. 1996a–c). In addition to the fact that the S-phase transition is required for the radiosensitization effect, it has also been shown that fluoropyrimidines under defined dosage conditions facilitate the accumulation of cells in Sphase (Miller and Kinsella 1992). In addition to the findings on halogenated fluoropyrimidines, several other sets of data obtained with paclitaxel (reviewed in Chap. 3) suggest that an increased radiation sensitivity occurred at the time of a taxane-induced G2-M block; however, the situation for taxane combinations is highly complex in so far as other data provide evidence that the mitotic arrest is not sufficient for the effects of paclitaxel (Geard and Jones 1994; Hennequin et al. 1996). The picture becomes even more complicated when taking into account that radiation was shown to decrease the net killing of taxanes (Sui et al. 2004). In this regard, it has been shown that the combination of paclitaxel and gamma radiation did not produce a synergistic or additive effect in a breast cancer and epidermoid cancer cell model. Instead, the overall cytotoxicity of the combination was lower than that of the drug treatment alone. Especially apoptosis induction was

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found to be strikingly reduced. A detailed analysis revealed that radiation resulted in cell cycle arrest at G2 phase preventing the G1-M transition-dependent cytotoxic effects of paclitaxel. Furthermore, radiation inhibited paclitaxel-induced INBD degradation and bcl-2 phosphorylation and increased the protein levels of cyclin B1 and inhibitory phosphorylation of p34(cdc2). Taken together, the impact of chemotherapyinduced cell cycle alterations as major mechanism for the efficacy of the combined action is still questionable. In clinical settings, the importance of an adequate cell cycle progression for the efficacy of radiochemotherapy approaches has been impressively documented. In the case of a neoadjuvant 5-FU based radiochemotherapy for rectal cancer, it has been shown that a decrease of the cell cycle inhibitory protein p21 during neoadjuvant treatment is strongly associated with an improved disease-specific survival. This finding has been corroborated by the observation that a parallel increase of the expression level of the proliferation marker ki-67 is similarly associated with an improved outcome (Rau et al. 2003); thus, preclinical findings on the action of 5-FU in combination with radiation are clearly reflected by clinical observations.

1.5 Potential Influences on Programmed Cell Death Pathways In order to inactivate a tumor cell, several distinct yet overlapping pathways may be activated. Besides the induction of pure apoptosis, other cell inactivation modalities, including programmed necrosis, mitotic catastrophe (which recently turned out to be an abortive form of apoptosis), senescence, or terminal differentiation, may be triggered (Belka 2005). The influence of a combined modality treatment on any of these end points has never been analyzed in greater detail; thus, only very few data are available showing that the combination of paradigmatic radiation sensitizers with radiation quantitatively alters the induction of certain predefined cell death modalities (Fig. 1.9). In case of gemcitabine, the efficacy of a combined treatment in terms of apoptosis induction has been analyzed in more detail using HT29 colon cancer cells, UMSCC-6 head and neck cancer cells, and A549 lung cancer cells. A key feature was that all cell systems differ substantially in the ability to undergo

Biological Basis of Combined Radio- and Chemotherapy

13

XRT

XRT

Bax p53 CER Bad Mito Noxa CHX

CHX

• Increase of DNA damage • Inhibition of DNA damage repair CHX

• Enhanced activation of death pathways • Activation of non-cross active death pathways

• Influences on cell cycle control (p53 & p21)

Fig. 1.9. Mechanisms of chemoradiation on a molecular level. The most prominent points of interaction of radiation with chemotherapy being of importance for the efﬁcacy of a combined modality treatment are found on the level of DNA damage induction and repair, cell death induction, and cell cycle control

radiation-induced apoptosis, with HT29 being the most apoptosis sensitive cell in this experimental setting. It turned out that the radiosensitization of HT29 cells was accompanied by an increase in apoptosis, whereas in UMSCC-6 cells and A549 cells, the radiosensitizing effect was mediated via non-apoptotic mechanisms; thus, this effect is rather a celltype-specific feature than a general property of the drug. In the case of taxanes, it has been speculated that the fact that radiation-induced apoptosis relies on the intactness of the p53 system (Guner et al. 2003), and the p53 independence of taxane-induced apoptosis (Wahl et al. 1996) may be an optimal prerequisite for a combined treatment; however, as stated above, the reality seems to be different (Sui et al. 2004). In the case of definitive treatment approaches in esophageal or rectal cancer, the importance of apoptosis signaling has been documented. Esophageal cancer patients with lack of the pro-apoptotic Bax molecule have significantly reduced outcome rates (Sturm et al. 2001). Similar findings have been observed for neoadjuvant radiation or radiochemotherapy in patients with rectal tumors with a low expression of Bax (Chang et al. 2005; Nehls et al. 2005).

1.6 Effects of Protracted Drug Exposure More than 30 years ago, in vitro studies demonstrated increased efficacy when tumor cells were exposed to mitomycin C or several other drugs for a prolonged time (Shimoyama et al. 1975). This finding was confirmed in clinical trials of continuous infusion vs bolus 5-FU (Seifert et al. 1975). Furthermore, and probably related to avoidance of peak concentrations, reduced normal tissue toxicity was observed. In principle, these divergent effects on tumor and normal tissues improve the therapeutic window. As reviewed more extensively in Chap. 2, longer exposure times of 5-FU result in enhanced cell killing also in the context of simultaneous radiation therapy (Moon et al. 2000). A combined analysis of more than 3100 patients with rectal cancer treated with preoperative radiochemotherapy demonstrated that the pCR rate was significantly higher when continuous infusion 5-FU was used, as compared with other modes of delivery of 5-FU (Hartley et al. 2005). Protracted exposure is currently also tested for other drugs such as temozolomide. Whether such regimens hold promise depends on the mode of action of the drug, cell-cycle specificity, pharmacokinetics, etc.

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1.7 Combination of Radiation with Hormonal Ablation A special situation emerges when the combination of radiation with a hormonal ablative measure is analyzed. As supported by several large randomized trials, the immediate combination of hormonal ablation with radiotherapy is of crucial value for the treatment of locally advanced high-risk prostate cancer (Bolla et al. 2002; Roach et al. 2003). The underlying mechanisms of the interaction remain unclear so far. Initially, it was speculated that apoptosis induction via hormone withdrawal is responsible for the efficacy of the combined treatment; however, a detailed experimental analysis revealed that although a supra-additive induction of apoptosis occurred after treatment of LNCaP cells with radiation and androgen deprivation (AD), this did not translate into an altered radiation sensitivity per se (Pollack et al. 2001). The experimental setting used is this paper, however, does not allow the determination of the proportion of the clonogenic cells killed solely by the growth conditions (AD), since the authors deliberately corrected for the different plating efficacies; thus, the only conclusion which can be reached is the fact that AD does not directly influence the radiation sensitivity on the cellular level. In vivo it thus seems likely that the efficacy of AD is purely related to a depletion of clonogenic tumor cells by the drugs.

1.8 Radiation-Induced Chemotherapy Resistance Most of the available data clearly underline that the combination of radiation with cytotoxic drugs increases the level of cell kill; however, it has to be mentioned that few data are available showing that radiation may also negatively influence the efficacy of chemotherapy. In most cases, radiation was shown to trigger an up-regulation of the two important MDR-associated proteins, p-glycoprotein and multidrug resistance protein 1 (Hill et al. 2000; Nielsen et al. 2001; Henness et al. 2002). It is unclear how relevant this phenomenon is in reality since also the opposite phenomenon, i.e., down-regulation of MDR proteins, has clearly been observed (Ryu et al. 2004); thus, there seems to be a cell-typespecific influence of radiation on the expression and

functional relevance of MDR associated proteins under certain in vitro situations. The relevance for any clinical application is not known yet.

1.9 Conclusion Although the combination of chemotherapeutic agents or hormonal ablative measures is of high relevance in diverse clinical settings, the underlying cellular and molecular mechanisms are only understood to a very limited degree. On a large scale, spatial interaction is clearly relevant for an improved general therapeutic ratio. Going into a smaller scale, it is completely unclear to which quantitative amount influences on the proportion of hypoxic cells or the amount of repopulation are responsible for the efficacy of combined modality treatment. In cases of the observed molecular interaction it is even harder to draw a clear picture as to how far the general action of combined treatment can be attributed to alterations of DNA damage, cell cycle control, or triggering of defined cell death pathways. Compared with the relatively homogenous models used for description of experimental end points, definition of important basic principles and development of sound combination regimens, the clinical situation is complicated by more heterogeneous tumors with changes in physiological and microenvironmental parameters over time, and even differences between the primary tumor itself and regional lymphatic metastases, which receive identical treatment. Under clinical circumstances, clear-cut definitions of additivity, synergism, etc., are of lesser value. A considerable proportion of gradual refinement of commonly administered regimens was achieved in subsequent clinical trials rather than preclinical studies; however, the ultimate goal of cure in all patients requires further substantial advances. There has been a long-lasting interest in prediction of individual response, e.g., by means of pretherapeutic ex vivo chemosensitivity testing in cell culture or determination of molecular marker genes (Shimizu et al. 2004; Staib et al. 2005). More recently, treatment monitoring early during a course of chemotherapy or radiochemotherapy by means of positron emission tomography, diffusion magnetic resonance imaging, and other biological imaging methods has shown promising results (Weber 2005). The same holds true for clinical assessment of breast cancer after two cycles of chemotherapy

Biological Basis of Combined Radio- and Chemotherapy

(von Minckwitz et al. 2005). Nevertheless, treatment individualization, also with regard to normal tissue toxicity and drug metabolism, e.g., based on single nucleotide polymorphisms (Efferth and Volm 2005; Robert et al. 2005), continues to be an area of active investigation.

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Biological Basis of Combined Radio- and Chemotherapy Reitsamer R, Peintinger F, Prokop E, Hitzl W (2005) Pathological complete response rates comparing 3 versus 6 cycles of epidoxorubicin and docetaxel in the neoadjuvant setting of patients with stage II and III breast cancer. Anticancer Drugs 16:867–870 Roach M III, DeSilvio M, Lawton C et al (2003) Phase III trial comparing whole-pelvic versus prostate-only radiotherapy and neoadjuvant versus adjuvant combined androgen suppression: Radiation Therapy Oncology Group 9413. J Clin Oncol 21:1904–1911 Robert J, Morvan VL, Smith D et al (2005) Predicting drug response and toxicity based on gene polymorphisms. Crit Rev Oncol Hematol 54:171–196 Robertson JM, Shewach DS, Lawrence TS (1996) Preclinical studies of chemotherapy and radiation therapy for pancreatic carcinoma. Cancer 78:674–679 Rockwell S (1982) Cytotoxicities of mitomycin C and X rays to aerobic and hypoxic cells in vitro. Int J Radiat Oncol Biol Phys 8:1035–1039 Rosier JF, Beauduin M, Bruniaux M et al (1999) The effect of 2’-2’ difluorodeoxycytidine (dFdC, gemcitabine) on radiation-induced cell lethality in two human head and neck squamous carcinoma cell lines differing in intrinsic radiosensitivity. Int J Radiat Biol 75:245–251 Ryu JS, Um JH, Kang CD et al (2004) Fractionated irradiation leads to restoration of drug sensitivity in MDR cells that correlates with down-regulation of P-gp and DNA-dependent protein kinase activity. Radiat Res 162:527–535 Sauer R, Becker H, Hohenberger W et al (2004) Preoperative versus postoperative chemoradiotherapy for rectal cancer. N Engl J Med 351:1731–1740 Schaake-Koning C, van den Bogaert W, Dalesio O et al (1992) Effects of concomitant cisplatin and radiotherapy on inoperable non-small-cell lung cancer. N Engl J Med 326:524– 530 Seifert P, Baker LH, Reed ML (1975) Comparison of continuously infused 5-FU with bolus injection in treatment of patients with colorectal carcinoma. Cancer 36:123–128 Shaked Y, Emmenegger U, Francia G et al (2005) Low-dose metronomic combined with intermittent bolus-dose cyclophosphamide is an effective long-term chemotherapy treatment strategy. Cancer Res 65:7045–7051 Shewach DS, Hahn TM, Chang E et al (1994) Metabolism of 2’,2’-difluoro-2’-deoxycytidine and radiation sensitization of human colon carcinoma cells. Cancer Res 54:3218–3223 Shimizu D, Ishikawa T, Ichikawa Y et al (2004) Current progress in the prediction of chemosensitivity for breast cancer. Breast Cancer 11:42–48 Shimoyama M (1975) The cytocidal action of alkylating agents and anticancer antibodies against in-vitro cultured yoshida ascitis sarcoma cells. J Jpn Soc Cancer Ther 10:63–72 Simoens C, Korst AE, De Pooter CM et al (2003) In vitro interaction between ecteinascidin 743 (ET-743) and radiation, in relation to its cell cycle effects. Br J Cancer 89:2305–2311 Stadler P, Becker A, Feldmann HJ et al (1999) Influence of the hypoxic subvolume on the survival of patients with head and neck cancer. Int J Radiat Oncol Biol Phys 44:749–754 Staib P, Staltmeier E, Neurohr K (2005) Prediction of indi-

17 vidual response to chemotherapy in patients with acute myeloid leukaemia using the chemosensitivity index Ci. Br J Haematol 128:783–791 Steel GG (1979) Terminology in the description of drug-radiation interactions. Int J Radiat Oncol Biol Phys 5:1145–1150 Steel GG, Peckham MJ (1979) Exploitable mechanisms in combined radiotherapy–chemotherapy: the concept of additivity. Int J Radiat Oncol Biol Phys 5:85–91 Stupp R, Mason WP, van den Bent MJ et al (2005) Radiotherapy plus concomitant and adjuvant temozolomide for glioblastoma. N Engl J Med 352:987–996 Sturm I, Petrowsky H, Volz R et al (2001) Analysis of p53/ BAX/p16(ink4a/CDKN2) in esophageal squamous cell carcinoma: high BAX and p16(ink4a/CDKN2) identifies patients with good prognosis. J Clin Oncol 19:2272–2281 Sui M, Dziadyk JM, Zhu X, Fan W (2004) Cell cycle-dependent antagonistic interactions between paclitaxel and gamma-radiation in combination therapy. Clin Cancer Res 10:4848–4857 Taghian AG, Abi-Raad R, Assaad SI et al (2005) Paclitaxel decreases the interstitial fluid pressure and improves oxygenation in breast cancers in patients treated with neoadjuvant chemotherapy: clinical implications. J Clin Oncol 23:1951–1961 Tannock IF (1989) Combined modality treatment with radiotherapy and chemotherapy. Radiother Oncol 16:83–101 Tannock IF (1992) Potential for therapeutic gain from combined-modality treatment. Front Radiat Ther Oncol 26:1– 15 Tannock IF (1998) Conventional cancer therapy: promise broken or promise delayed? Lancet 351 (Suppl 2):SII9– SII16 Teicher BA, Lazo JS, Sartorelli AC (1981) Classification of antineoplastic agents by their selective toxicities toward oxygenated and hypoxic tumor cells. Cancer Res 41:73–81 Thames HD, Suit HD (1986) Tumor radioresponsiveness versus fractionation sensitivity. Int J Radiat Oncol Biol Phys 12:687–691 Trott KR (1990) Cell repopulation and overall treatment time. Int J Radiat Oncol Biol Phys 19:1071–1075 Wahl AF, Donaldson KL, Fairchild C et al (1996) Loss of normal p53 function confers sensitization to Taxol by increasing G2/M arrest and apoptosis. Nat Med 2:72–79 Weber WA (2005) Use of PET for monitoring cancer therapy and for predicting outcome. J Nucl Med 46:983–995 Wurschmidt F, Bardenheuer MJ, Muller WU, Molls M (2000) Chromosomal aberrations induced in mice bone marrow by treating with cisplatin and irradiation. Strahlenther Onkol 176:319–323 Yang LX, Douple EB, O’Hara JA, Wang HJ (1995) Production of DNA double-strand breaks by interactions between carboplatin and radiation: a potential mechanism for radiopotentiation. Radiat Res 143:309–315 Yu YQ, Giocanti N, Averbeck D et al (2000) Radiation-induced arrest of cells in G2 phase elicits hypersensitivity to DNA double-strand break inducers and an altered pattern of DNA cleavage upon re-irradiation. Int J Radiat Biol 76:901– 912

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2

19

Combinations of Antimetabolites and Ionizing Radiation Hiroshi Harada, Keiko Shibuya, and Masahiro Hiraoka

CONTENTS 2.1 2.1.1 2.1.1.1 2.1.1.2 2.1.2 2.1.2.1 2.1.2.2 2.1.3 2.2 2.2.1 2.2.2 2.2.3 2.2.4 2.3 2.3.1 2.3.1.1 2.3.1.2 2.3.2 2.3.3 2.4

Antimetabolites: Classes, Intracellular Metabolism, and Mechanisms of Action 19 Pyrimidine Analogs 19 5-Fluorouracil 19 Gemcitabine 21 Folic Acid Analogs 22 Methotrexate 22 Pemetrexed 23 6-Mercaptopurine as an Example for Purine Analogs 23 Mechanisms of Radiosensitization with Antimetabolites 24 dNTP Depletion 24 Cell Cycle Distribution 25 Checkpoint and p53 25 Apoptosis 26 Interactions of Antimetabolites with Radiation: Preclinical to Clinical 26 5-Fluorouracil and its Prodrugs: Capecitabine, UFT, and S-1 26 5-Fluorouracil 26 Prodrugs of 5-FU: UFT; S-1; and Capecitabine 28 Gemcitabine 29 Pemetrexed 30 Conclusion 30 References 31

2.1 Antimetabolites: Classes, Intracellular Metabolism, and Mechanisms of Action Antimetabolites have antineoplastic activity, which is attributed to the fact that their structure is very similar to the normal metabolites required for cell function and replication. After intracellular modification, the antimetabolites interact with intracel-

H. Harada, MD K. Shibuya, MD M. Hiraoka, MD PhD Department of Radiation Oncology and Image-Applied Therapy, Graduate School of Medicine, Kyoto University, Sakyo, Kyoto, 606-8507, Japan

lular enzymes and show cytotoxic effects by (a) substituting for a normal metabolite incorporated into key molecules, such as DNA and RNA, and (b) occupying the catalytic site of a key enzyme and competing with a normal metabolite. Consequently, they interfere with DNA synthesis and proliferation of the cancer cell. Until recently, several kinds of antimetabolites have been developed and are categorized into three major groups, pyrimidine analogs (see Fig. 2.1a), folic acid analogs (see Fig. 2.1b) and purine analogs (see Fig. 2.1c). The mechanisms of action of representative agents in each class are briefly described herein.

2.1.1 Pyrimidine Analogs 2.1.1.1 5-Fluorouracil

5-Fluorouracil (5-FU) is a nucleoside analog of uracil in which a fluorine atom is inserted into the C-5 position in place of hydrogen (see Fig. 2.1a; Longley et al. 2003). It has been widely applied for the treatment of various kinds of cancers, particularly for colorectal and breast cancers. 5-FU requires metabolic activation to form its cytotoxic metabolites (see Fig. 2.2; Malet-Martino and Martino 2002; Longley et al. 2003). 5-FU is converted to 5-fluorouridine-5’monophosphate (5-FUMP) directly by orotate phosphoribosyltransferase (OPRT) or indirectly via an intermediate metabolite, 5-fluorouridine (5-FUrd), by uridine phosphorylase and uridine kinase. 5FUMP is subsequently phosphorylated to 5-fluorouridine-5’-diphosphate (5-FUDP) by pyrimidine monophosphate kinase and further to a cytotoxic metabolite, 5-fluorouridine-5’-triphosphate (5FUTP) by pyrimidine diphosphate kinase. The 5FUTP can mimic uridine-5’-triphosphate (UTP), and be recognized by RNA polymerases as the substrate. This leads to the incorporation of 5-FU in all classes of RNA, disrupting normal RNA func-

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b Folic acid analog

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Gemcitabine hydrochloride

Methotrexate H2N

NH2 H N

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OO ONa

6-mercaptopurine

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Fig. 2.1a-c. Structures of antimetabolites. a Pyrimidine analogs, gemcitabine hydrochloride, and 5-ﬂuorouracil. b Folic acid analogs, methotrexate and pemetrexed. c Purine analog, 6-mercaptopurine

Urd OPRT

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RNA function

RNA damage

DNA damage

DNA replication DNA repair

Fig. 2.2. Metabolism and mechanism of action of 5-ﬂuorouracil. 5-ﬂuorouracil (5-FU), 5-ﬂuorouridine-5’-monophosphate (5-FUMP), orotate phosphoribosyltransferase (OPRT), 5-ﬂuorouridine (5-FUrd), uridine phosphorylase (UP), uridine kinase (UK), 5-ﬂuorouridine-5’-diphosphate (5-FUDP), pyrimidine monophosphate kinase (PMK), 5-ﬂuorouridine-5’-triphosphate (5-FUTP), pyrimidine diphosphate kinase (PDK), RNA polymerase (RNAP), uridine (Urd), Uridine-5’-monophosphate (UMP), uridine-5’-diphosphate (UDP), uridine-5’-triphosphate (UTP), 5-ﬂuoro-2’-deoxyuridine (5-FdUrd), thymidine kinase (TK), 5-ﬂuoro-2’-deoxyuridine-5’-monophosphate (5-FdUMP), 5-ﬂuoro-2’-deoxyuridine-5’-diphosphate (5-FdUDP), 5-ﬂuoro-2’deoxyuridine-5’-triphosphate (5-FdUTP), thymidylate synthase (TS), thymidine-5’-monophosphate (dTMP), 2’-deoxyuridine5’-monophosphate (dUMP), thymidine-5’-triphosphate (dTTP), 2’-deoxyuridine-5’-triphosphate (dUTP), DNA polymerase (DNAP)

Combinations of Antimetabolites and Ionizing Radiation

tion. The misincorporation inhibits the processing of pre-ribosomal RNA to mature ribosomal RNA (Kanamaru et al. 1986), the modification of tRNAs (Santi and Hardy 1987) and the splicing of mRNAs (Doong and Dolnick 1988), leading to profound effects on cellular metabolism and viability. After the conversion of 5-FU to 5-fluoro-2’deoxyuridine (5-FdUrd), the 5-FdUrd is sequentially phosphorylated to cytotoxic 5-fluoro-2’-deoxyuridine-5’-monophosphate (5-FdUMP), to 5-fluoro2’-deoxyuridine-5’-diphosphate (5-FdUDP), and finally to cytotoxic 5-fluoro-2’-deoxyuridine-5’triphosphate (5-FdUTP). The 5-FdUMP and the 5-FdUTP exert their antitumor effects through the inhibition of thymidylate synthase (TS) (Santi et al. 1974; Sommer and Santi 1974) and incorporation into DNA, respectively. TS is responsible for the production of thymidine-5’-monophosphate (dTMP) from 2’-deoxyuridine-5’-monophosphate (dUMP) through the transfer of a methyl group from 5,10methylenetetrahydrofolate (CH2THF). This reaction is fully responsible for the production of de novo source of thymidylate, which is necessary for DNA replication and repair. The 5-FdUMP binds to the nucleotide-binding site of TS, forms a stable ternary complex with TS and CH2THF, and interferes with the access of normal substrate dUMP to the nucleotidebinding site, resulting in the inhibition of dTMP synthesis (Santi et al. 1974; Sommer and Santi 1974). Depletion of dTMP directly results in the subsequent depletion of thymidine-5’-triphosphate (dTTP) and induces an imbalance of the deoxynucleotide pool through various feedback mechanisms. As a result of these actions, 5-FU inhibits DNA synthesis and repair, leading to lethal DNA damage (Yoshioka et al. 1987; Houghton et al. 1995). In addition, TS inhibition is accompanied by the accumulation of its substrate, dUMP, which might be subsequently metabolized to 2’-deoxyuridine-5’-triphosphate (dUTP; Mitrovski et al. 1994; Aherne et al. 1996). Both the dUTP and a 5-FU metabolite, 5-FdUTP, can be misincorporated into DNA. UracilDNAglycosylase (UDG) hydrolyzes the (F)uracil-deoxyribose glycosyl bond of the dUTP and the 5-FdUTP residues in DNA, generating a single strand break; however, since the depletion of dTTP, which is caused by the TS inhibition, as mentioned above, reduces the efficacy of the repair of such strand breaks, the misincorporated dUTP and 5-FdUTP are hard to be removed, leading to cell death. The misincorporation of 5-FU-metabolites into DNA and the imbalance of intracellular nucleotides results in various detrimental effects on DNA synthesis.

21

2.1.1.2 Gemcitabine

Gemcitabine (dFdCyd), 2’-deoxy-2’,2’-difluorocytidine, is a nucleoside analog of deoxycytidine in which two fluorine atoms are inserted into the deoxyribofuranosyl ring (see Fig. 2.1a). It shows broad-spectrum activity in the treatment of solid malignancies, particularly for pancreatic (Kaye 1994; Rothenberg et al. 1996) and non-small cell lung cancer (Gatzemeier et al. 1996; Crino et al. 1999). In order for dFdCyd to produce its cytotoxic effects, dFdCyd requires the following intracellular modifications (see Fig. 2.3): The dFdCyd is firstly phosphorylated by deoxycytidine (dCyd) kinase to the 5’-monophosphate of dFdCyd (dFdCMP; Heinemann et al. 1988). Subsequent phosphorylations yield the active metabolites diphosphate (dFdCDP) and triphosphate (dFdCTP) nucleotides (Heinemann et al. 1988). These metabolites have the potential to interfere with multiple steps of DNA synthesis and are directly and indirectly responsible for the cytotoxic properties of dFdCyd. The dFdCTP form competes with dCTP for incorporation into DNA, and the incorporation of dFdCTP into DNA is strongly correlated with the inhibition of further DNA synthesis (Huang et al. 1991). Once the dFdCTP is incorporated into the end of the elongating DNA strand, only one more deoxynucleotide is added, and thereafter the DNA polymerases are unable to proceed, resulting in the termination of the DNA synthesis. Moreover, proof-reading exonucleases, such as DNA polymerase epsilon, are unable to remove the incorporated dFdCTP from the penultimate position and are unable to repair the growing DNA strands. This action is termed “masked chain termination” (Plunkett et al. 1995). The dFdCDP form, on the other hand, can inhibit ribonucleotide reductase, which is responsible for the reactions that synthesize the deoxynucleotides required for DNA synthesis and repair (Baker et al. 1991). The inhibition of this enzyme causes a reduction in the concentrations of the DNA precursor pool (Heinemann et al. 1990). The reduction in the dNTP (particularly dCTP) leads to the following “self-potentiation.” Firstly, the reduction enhances the incorporation of dFdCyd-derived nucleotides into DNA, because dFdCTP competes with dCTP for incorporation into DNA, as mentioned above (Huang et al. 1991). Secondly, the reduction enhances the phosphorylation of the dFdCyd and increases the intracellular dFdCDP and dFdCTP because the dCyd kinase is negatively regulated

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dFdCyd Cyd / dCyd

dCyd

dFdU

deaminase

inhibition

dCyd kinase

dFdCMP

dCMP CDP

dCDP

dCTP

e otid cle onu ctase b i R edu r

depletion of dCTP

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dFdCTP

DNAP

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dCMP deaminase

facilitation

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Masked chain termination

Termination of DNA synthesis

Fig. 2.3. Metabolism and mechanism of action of gemcitabine. Gemcitabine (dFdCyd), gemcitabine-5’-monophosphate (dFdCMP), gemcitabine-5’-diphosphate (dFdCDP), gemcitabine-5’-triphosphate (dFdCTP), 2’deoxycytidine (dCyd), 2’-deoxycytidine-5’-monophosphate (dCMP), 2’-deoxycytidine-5’-diphosphate (dCDP), 2’-deoxycytidine-5’-triphosphate (dCTP), cytidine-5’-diphosphate (CDP), DNA polymerase (DNAP), 2’-deoxy-2’,2’-diﬂuorouridine (dFdU), dFdU-5’-monophosphate (dFdUMP)

by the dCTP (Shewach et al. 1992a). Finally, the reduction suppresses the deamination (inactivation) of dFdCyd and its derivatives because dCTP is essential as a co-factor for the activity of dCMPdeaminase (Hertel et al. 1990). As a result of these mechanisms, dFdCyd exhibits cell phase specificity, primarily killing cells undergoing DNA synthesis (S-phase) and also blocking the progression of cells through the G1/S-phase boundary (Hertel et al. 1990). Yet, additional observations suggest that other effects are implicated in the interaction with ionizing radiation also (Rosier et al. 2004).

2.1.2 Folic Acid Analogs 2.1.2.1 Methotrexate

Methotrexate (MTX), 4-amino 10-methyl folic acid (see Fig. 2.1b), is an analog of folic acid that has been widely used for the treatment of childhood acute lymphoblastic leukemia (ALL) and a number of other malignant diseases, such as lymphoma,

osteosarcoma, breast cancer, and head and neck cancer (Chu et al. 1996). The MTX is taken up by cells via the reduced folate carrier (RFC), such as RFC1, and is then converted within the cells by folylpolyglutamate synthase to methotrexate polyglutamates (MTXPGs; see Fig. 2.4; Chabner et al. 1985). The MTXPGs are retained longer in cells compared with MTX (Jolivet et al. 1983) and compete with some cellular folate cofactors (e.g., 10-formyl-tetrahydrofolate, 5,10-methylene-tetrahydrofolate and 5,10-methenyl-tetrahydrofolate) for the interaction with dihydrofolate reductase (DHFR). This results in the inhibition of the activity of DHFR, thereby decreasing the amount of reduced folate, which is the carbon donor for the purine ring formation in the critical pathways for DNA synthesis, DNA repair and cell replication, such as de novo purine synthesis (DNPS) and thymidine synthesis (Allegra et al. 1985a,b). In addition, MTXPGs directly inhibit phosphoribosyl pyrophosphate amidotransferase (PRPPAT), glycinamide ribonucleotide formyltransferase (GARFT) and 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase (AICARFT), which are also key enzymes in the DNPS pathway (Segal et al. 1990; Kremer 1994). The DNPS inhi-

Combinations of Antimetabolites and Ionizing Radiation

23

MTX Extracellular

facilitation

RFC1

inhibition

Intracellular

MTX Folylpolyglutamate synthase

MTXPGs

DHFR PRPPAT GARFT AICARFT

DNPS TS

DNPS

DNA synthesis DNA repair cell replication

Fig. 2.4. Metabolism and mechanism of action of methotrexate. Methotrexate (MTX), MTX polyglutamates (MTXPGs), dihydrofolate reductase (DHFR), phosphoribosyl pyrophosphate amidotransferase (PRPPAT), glycinamide ribonucleotide formyltransferase (GARFT), 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase (AICARFT), de novo purine synthesis (DNPS), thymidine synthase (TS). Pemetrexed has been reported to show antineoplastic activity through almost the same mechanism as MTX

bition by both MTX and its metabolite results in purine depletion, leading to the inhibition of DNA synthesis, decreased cell proliferation and significant cytotoxicity.

MTX (see Fig. 2.4), leading to a subsequent decline in cell proliferation, which is particularly significant in rapidly proliferating tumor cells.

2.1.2.2 Pemetrexed

2.1.3 6-Mercaptopurine as an Example for Purine Analogs

Pemetrexed, L-glutamic acid, N-[4-[2-(2-amino4,7-dihydro-4-oxo-1H-pyrrolo[2,3-d]pyrimidin5- yl)ethyl]benzoyl]-, disodium salt, heptahydrate (see Fig. 2.1b), is a multi-targeted folate analog that exerts its antineoplastic activity in many kinds of human malignancies, e.g., breast, pancreatic, colorectal, head and neck, gynecological, and nonsmall cell lung cancers (Hanauske et al. 2001), by disrupting folate-dependent metabolic processes. It gains entry to cells via the reduced folate carrier, and once inside a cell, it is intracellularly converted to polyglutamate forms, tri- and pentaglutamate, by folylpolyglutamate synthetase. This modification prolongs its intracellular retention (Mendelsohn et al. 1999). The polyglutamate forms inhibit DHFR, TS, and GARFT, all of which are folate-dependent enzymes responsible for the de novo biosynthesis of thymidine and purine nucleotides (Shih et al. 1997). As a result of these processes, pemetrexed inhibits DNA synthesis by almost the same mechanism as

6-Mercaptopurine (6-MP) is a 6-thiopurine analog of purine bases (see Fig. 2.1c), such as hypoxanthine and guanine, and has been in clinical use for over 30 years as an antileukemic agent. 6-MP is a prodrug that requires activation to exert its cytotoxic effect (see Fig. 2.5). It is first converted by hypoxanthineguanine phosphoribosyl transferase (HGPRT) into 6-thioinosine monophosphate (6-TIMP; Lennard 1992). It is subsequently metabolized by a two-step process involving inosine monophosphate dehydrogenase (IMPDH) into 6-thioxanthine monophosphate (6-TXMP), and by guanosine monophosphate synthetase into 6-thioguanosine 5’-monophosphate (6-TGMP). 6-TGMP is further metabolized by a series of kinases and reductases to deoxy-6-thioguanosine 5’-triphosphate (dGS). The resultant dGS can be incorporated into DNA and trigger cell cycle arrest and apoptosis (Swann et al. 1996). In addition, thiopurine methyltransferase (TPMT) also can

H. Harada et al.

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these activities and have reported significant tumor growth delay with the combination of antimetabolites and ionizing radiation in animal models; however, the mechanism of radiosensitization has yet to be fully understood. Initial studies have focused, as the mechanism, on the modulation of the metabolism of deoxynucleotides, the changes in cell cycle distribution, the role of the tumor suppressor protein p53, and the induction of apoptosis.

2.2.1 dNTP Depletion

Fig. 2.5. Metabolism and mechanism of action of 6-Mercaptopurine. 6-Mercaptopurine (6-MP), hypoxanthine-guanine phosphoribosyl transferase (HGPRT), 6-thioinosine monophosphate (6-TIMP), inosine monophosphate dehydrogenase (IMPDH), 6-thioxanthine monophosphate (6-TXMP), guanosine monophosphate synthetase (GMS), 6-thioguanosine 5’-monophosphate (6-TGMP), deoxy-6-thioguanosine 5’-triphosphate (dGS), DNA polumerase (DNAP), thiopurine methyltransferase (TPMT), S-methyl-thioinosine 5’-monophosphate (MeTIMP), phosphoribosyl pyrophosphate amidotransferase (PRPPAT)

convert the 6-TIMP into S-methyl-thioinosine 5’monophosphate (MeTIMP). The resultant MeTIMP acts as a strong inhibitor of PRPPAT, which is responsible for de novo purine synthesis (Tay et al. 1969; Allan and Bennett 1971); thus, 6-MP treatment results in purine depletion, leading to the inhibition of DNA synthesis and proliferation, and antileukemic effect.

2.2 Mechanisms of Radiosensitization with Antimetabolites In addition to the cytotoxic effect of these antimetabolites themselves, they have been reported to enhance the effect of radiation as potent radiosensitizers in vitro. Recent in vivo studies have confirmed

Antimetabolite-induced perturbation of the intracellular dNTP pool and its radiosensitizing effect are summarized in Table 2.1. In the case of dFdCyd, it increases the radiosensitivity of cells even under conditions in which the drug alone shows no cytotoxicity (Shewach et al. 1994). The dFdCydmediated sensitization has been reported not to be dependent either on the intracellular concentration of dFdCTP or on the dFdCTP/dCTP ratio, but correlates to the dFdCDP-mediated decrease in intracellular dATP pools (Shewach et al. 1994); therefore, it has been hypothesized that the depletion of the dATP pool level by the dFdCyd treatment is a key factor in enhancing radiosensitivity (Shewach et al. 1994; Shewach and Lawrence 1995; Lawrence et al. 1996, 1997). In addition, it has been reported that a 5-FU-derivative, 5FdUrd, which depletes the intracellular TTP level but not dATP pools under the radiosensitizing condition, decreases the efficiency of repair of radiation-induced DNA damage (Bruso et al. 1990; Heimburger et al. 1991). Likewise, a thymidine analog, 5-bromo-2’-deoxyuridine (BrdU), which is known to be incorporated into DNA and decrease the intracellular dCTP and TTP pools (Shewach et al. 1992b), increases the radiation-induced DNA damage, and moreover, decreases damage repair (Iliakis et al. 1989; Ling and Ward 1990). Furthermore, hydroxyurea, whose primary activity is the depletion of intracellular dNTP levels, can enhance the sensitivity of the cell to radiation (Sinclair 1968a). Taken together, perturbation of the balance of intracellular nucleosides seems to play an important role in causing radiosensitization, at least in part. This hypothesis is consistent with the reports showing that imbalances of the intracellular dNTP pool produce errors in DNA replication (Kunz 1982; Bebenek et al. 1992; Martomo and Mathews 2002).

Combinations of Antimetabolites and Ionizing Radiation

25

Table 2.1. Antimetabolite-induced imbalance of intracellular dNTP pool and its radiosensitizing effect Antimetabolite

Imbalance of dNTP

Effect

Reference

dFdCyd (gemcitabine)

dATP depletion

Radiosensitization in vitro and in vivo

Shewach et al. (1994), Shewach and Lawrence (1995), Lawrence et al. (1996), Lawrence et al. (1997)

5-FU (5-FdUrd)

TTP depletion

Decrease in repair of DNA damage induced by radiation

Bruso et al. (1990), Heimberger et al. (1991)

BrdU

dCTP and TTP depletion

Increase in radiation-induced DNA damage and decrease in damage repair

Iliakis et al. (1989), Ling et al. (1990)

Hydroxyurea

dNTPs depletion

Radiosensitization in vitro

Sinclair et al. (1968a,b)

2.2.2 Cell Cycle Distribution

4 3 2 1

M

G1

S

G2

DNA content (per cell)

Relative Radioresistance

The cell cycle for mammalian cells is composed of four sequential phases: mitosis (M-phase); gap 1 (G1); DNA synthetic phase (S-phase); and gap 2 (G2), followed again by M-phase (see Fig. 2.6). It is known that cells are the most radioresistant in the S-phase, while they are radiosensitive in the M- and G2phases (Sinclair 1968b; Pawlik and Keyomarsi 2004). Moreover, cells at the G1/S-boundary and in early S-phase are more radiosensitive than those in late S-phase (Latz et al. 1998); therefore, cell cycle modulation with an antimetabolite also seems to be very important for the radiation-enhancing effect. The cell cycle effect of dFdCyd seems to be concentration dependent (Tolis et al. 1999; Cappella et al. 2001). It was reported that low concentrations (IC50 values) of dFdCyd cause cell cycle arrest in early Sphase (Merlin et al. 1998), and increasing concentrations of the drug results in a shift of this arrest to the early S-phase and moreover to the G1/S-boundary (Pauwels et al. 2003). The radiation-enhancing effect of dFdCyd, therefore, could be explained by the accumulation of dFdCyd-treated cells in these radiosensitive phases. Indeed, the percentage of early S-phase cells was reported to correlate with the radiosensitizing effect (Pauwels et al. 2003); however, it is still unclear both why radiosensitization occurs in cells at early S-phase and whether such a mechanism is responsible for the radiosensitizing property of the other antimetabolites, which exhibit the same kind of cell phase specificity. In addition, it has also been reported that both dFdCyd and 5-FU selectively radiosensitize cells in S-phase, which are relatively radioresistant, whereby the fluctuation of radiosensitivity within the cell cycle is eliminated or at least reduced (Latz et al. 1998). Although the mechanism causing the above

Radioresistance DNA content per cell

M

Cell Cycle

Fig. 2.6. Cell cycle phase-dependent radiosensitivity of cells. The cell cycle for mammalian cells is composed of four sequential phases: mitosis (M-phase); gap 1 (G1), DNA synthetic phase (S-phase) and gap 2 (G2), followed by M-phase again. The DNA content in each cell phase (dashed curve) and the relative radioresistance (solid curve) of the cell are shown

phenomenon still remains unclear, the treatment may reduce the repair of radiation-induced cellular damage and increase the probability of the fixation of damage being lethal in S-phase cells.

2.2.3 Checkpoint and p53 In response to a stress signal, p53 protein is activated by post-translational modifications and leads to the transcription of various genes, which determine whether the cell will continue to progress, arrest in checkpoints and repair the DNA damage, induce cell senescence, or trigger apoptosis (Levine 1997; Jin and Levine 2001). Cells expressing wild-type p53 were reported to accumulate in the G1/S cell-

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cycle checkpoint in response to many DNA-damaging agents including irradiation (Linke et al. 1997; Ostruszka and Shewach 2000). This arrest allows the cells not only to repair the DNA damage, but also to inhibit the replication of the cells with damaged genomic DNA (Sak et al. 2000). On the other hand, cells expressing mutant p53 were reported to continue to progress into S-phase and G2-M after the treatment and irradiation (Ostruszka and Shewach 2000). This may affect the radiosensitivity of cells. Indeed, the p53 status and the inappropriate progression of cells into S-phase in the presence of drugs, such as 5-FU and 5-FdUrd as well as dFdCyd, has been reported to affect radiation sensitivity. This conclusion is firstly derived from the result that 5-FdUrd enhances the radiosensitivity of cells expressing G1/S cyclins in the presence of the drug, but not of cells expressing no activated cyclins (Lawrence et al. 1996). It is further confirmed by the report that 5-FdUrd greatly increases the radiosensitivity of a cell, which can progress into S-phase after irradiation because of the expression of mutant-type p53, but hardly shows a radiosensitizing effect on a cell expressing wild-type p53 (Naida et al. 1998). Likewise, a previous study suggested that a cell line that has no ability to progress through S-phase after dFdCyd and radiation is not radiosensitized because of the expression of wildtype p53 (Ostruszka and Shewach 2000). Yet, other reports have suggested that, regardless of the p53 status, dFdCyd can enhance the radiosensitivity of cells, as shown by Robinson and Shewach (2001), in whose study both wild-type p53-expressing cells and mutant p53-expressing cells displayed high dATP depletion and S-phase accumulation after dFdCyd treatment, both of which we recognize as important factors in radiosensitization. That article suggests that p53 function alone might not determine the radiosensitivity in the presence of antimetabolites.

2.2.4 Apoptosis Although antimetabolites are known to induce the expression of proapoptotic effector proteins, the level is not sufficient to induce cellular apoptosis. In the case that the intracellular checkpoint system is working, the damage of genomic DNA is repaired and the intracellular level of proapoptotic factors decreases during the cell cycle arrest; however, during the above period, if the cells are exposed

to irradiation, the expression of proapoptotic factors is further induced, leading to apoptosis. This mechanism may be a reason why the maximum radiosensitization with dFdCyd and with 5-FU occurs when cells are incubated with the drug before radiation.

2.3 Interactions of Antimetabolites with Radiation: Preclinical to Clinical 2.3.1 5-Fluorouracil and its Prodrugs: Capecitabine, UFT, and S-1 2.3.1.1 5-Fluorouracil

Since 5-FU was first introduced in 1957, it has been playing an essential part in the treatment of a wide range of solid tumors, such as epithelial malignancies in the gastrointestinal tract, pancreatic cancer, breast cancer, or head and neck cancer. Although the single-agent response rates are not so high, 5-FU-containing treatment regimens produced a highly significant survival improvement for several malignancies. Heidelberger et al. (1958) demonstrated very early that doses of radiation, which were inhibitory but not curative for rodent tumors, were made curative by combination with 5-FU. Subsequently, results in experimental animals (Vermund et al. 1961) and quantitative studies showed that 5-FU could enhance cell killing by radiation (Bagshaw 1961; Berry 1966). These early observations led to a series of clinical investigations from the 1960s to 1970s. Firstly, controlled studies in gastric adenocarcinoma (Moertel et al. 1969) and head and neck squamous carcinoma (Gollin et al. 1972) showed improved response and survival rates by combined therapy with radiation and 5-FU; however, other studies could not achieve any remarkable results (Helsper and Sharp 1962; Hall et al. 1967; Stein and Kaufman 1968; Sato et al. 1970). These negative, or less impressive results, were considered to be caused not only by the organ or tumor-specific characteristics, but also by some factors which depend on the administration schedule. During those periods, bolus 5-FU had been usually given with fractionated radiotherapy. In 1982, Byfield et al. (1982) demonstrated that cell killing was maximized if the cells were continu-

Combinations of Antimetabolites and Ionizing Radiation

ously exposed to 5-FU following irradiation. In 1994, a well-controlled study in patients with rectal cancer [Mayo/North Center Cancer Treatment Group (NCCTG) 86-47-51’s protocol], comparing protracted venous infusion (PVI) with bolus injection during radiotherapy, showed that PVI resulted in a significant improvement in both the time to relapse and survival (O’connell et al. 1994). As 5-FU has cell-cycle specificity and a short plasma half-life, the prolonged exposure of cells to the agent would theoretically result in enhanced cell killing. Presently, as a standard method, 5-FU is administered by PVI or by bolus infusion for consecutive days during radiation. Table 2.2 shows the representative studies conducted to test the efficacy of chemoradiotherapy with 5-FU for several cancers. As for the patients with colorectal lesions, we need to be very careful about gastrointestinal toxicities. Miller et al. (2002) analyzed the NCCTG trial and showed that patients who received 5-FU by PVI had a higher risk of severe or life-threatening diarrhea compared with those with bolus infusion during pelvic radiotherapy. Patients with locally advanced (T3 or T4) rectal cancer had been recommended to receive radiotherapy and chemotherapy either preoperatively or postoperatively. Although the results

27

of the clinical trials of the National Surgical Adjuvant Breast and Bowel Project (NSABP) showed that chemoradiation altered neither the incidence of distant metastases nor survival, there was a reduction in the locoregional relapse (see Table 2.2; Wolmark et al. 2000). To reduce the toxicities and to enhance the survival for colorectal cancer, optimizing the regimen of chemoradiation is still under active investigation. For the treatment of esophageal cancer, the randomized study, EST-1282, was undertaken by the Eastern Cooperative Oncology Group (ECOG) to determine whether the combined use of 5-FU, mitomycin C (MMC) and radiation therapy improved the survival of patients compared with radiation therapy alone. In that study, 5-FU was delivered by continuous infusion for 96 h, initiated on day 2 and day 28 during radiation therapy (Smith et al. 1998). The result was that patients treated with chemoradiation had a longer median survival than patients receiving radiation therapy alone. The Radiation Therapy Oncology Group (RTOG) compared radiotherapy of 64 Gy in 32 fractions alone with chemoradiotherapy of 50 Gy in 25 fractions with cisplatin/5-FU, showing that combined therapy significantly increased the overall survival (Cooper et al. 1999).

Table 2.2. Randomized trials of chemoradiation with 5-ﬂuorouracil (5-FU) Study

Treatment

No. of patients

Krook et al. (1991)

S+RT

Mayo/NCCTG79-47-51

Median survival (months)

Survival (%)

Follow-up (years)

100

35

7 (median)

S+RT+5-FU

104

55

7 (median)

O’Connell (1994)

S+RT+bolus 5-FU

332

60

4

Mayo/NCCTG86-47-51

S+RT+infusional 5-FU

328

70

4

Wolmark et al. (2000)

S+5-FU/LV

348

6265

5

NSABP R-02

S+5-FU or MOF/LV+RT

346

6265

5

Rectal cancer

Pancreatic cancer Moertel et al. (1981)

RT 60 Gy

5.2

Gastrointestinal Tumor

RT 40 Gy+5-FU

9.6

Study Group (GISTG)

RT 60 Gy+5-FU

9.2

GISTG (1988)

RT 54 Gy+5-FU

10.5

GISTG (1988)

SMF

8

Esophageal cancer Cooper et al. (1985)

RT64 Gy

62

9.3

0 (5 years)

8

RTOG 85-01

RT50 Gy+CDDP/5-FU

61

14.1

26 (5 years)

8

S surgery, RT radiotherapy, SMF STZ, mitomycin C and 5-FU, MOF 5-FU, semustine, and vincristine, LV leucovorin, CDDP cisplatin.

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2.3.1.2 Prodrugs of 5-FU: UFT; S-1; and Capecitabine

A prodrug is defined as a pharmacologically inactive compound that is converted into an active agent by a metabolic biotransformation. The prodrugs of 5-FU are characterized by a pyrimidine ring with a fluorine atom in position 5. The first generations of prodrugs of 5-FU were represented by 5-fluoro2’-deoxyuridine (5-FdUrd), which was more efficiently metabolized by the liver than 5-FU. As for the second generation, ftorafur (FTO, 1-(2-tetrahydrofuryl)-5-fluorouracil, Tegaful or Futraful) and 5’-deoxy-5-fluorouridine (5’d5-FUrd, doxifluridine or Furtulon) were developed with the intention of possible oral administration. They are designed to be well absorbed from the gastrointestinal tract and enzymatically converted into 5-FU by hepatic microsomal cytochrome P-450. The third-generation compounds include those preferentially activated in the tumor: capecitabine, and the dehydropyrimidine dehydrogenase (DPD) inhibitory compounds; UFT (FTO+uracil); and S-1 [FTO+5-chloro-2, 4-dihydroxypyrimidine (CDHP; gimestat)+potassium oxonate (OXO; otastat)]. 2.3.1.2.1 UFT

Although prolonged continuous exposure has been demonstrated to have advantages over bolus administration in rectal, head and neck, and esophageal cancers, another dimension for the timing of FU in the clinic is illustrated by the animal models, which demonstrate daily cyclic patterns of mitosis and enzyme activity. The activities of DPD, which inactivates FU, have been shown to vary significantly over 24 h. Because the pharmacokinetics and sensitivity of 5-FU are determined by DPD, stabilization of the pharmacokinetics of 5-FU and the enhancement of its efficacy have been attempted by means of DPD inhibition. The UFT is a small molecule, a combination agent utilizing FTO and uracil in molar proportions of 1:4. Uracil is a competitive and irreversible inhibitor of DPD. This combination ratio was chosen based on preclinical models that suggested tumor selectivity, which produces a constant reserve of 5-FU and its active metabolites and minimizes production of inactive and potentially toxic metabolites (Fujii et al. 1979). Later, some other preclinical studies demonstrated that this combination resulted in significant improvements in the tumor to normal tissue and tissue serum ratios of 5-FU (Taguchi

1997). By the stabilization and prolongation of the effective half-life of FU, the opportunity for synergy with radiation had been considered to be greater. To date, there has been a limited number of published studies combining UFT with radiation therapy, but recently a phase-I trial examined the use of the oral delivery of UFT/leucovorin with conventional RT of 45 Gy for pancreatic cancer. Results compared favorably with continuous-infusion regimens showing the potential benefit (Childs et al. 2000). In preoperative and postoperative rectal cancer therapy, several studies are ongoing (Rosenthal et al. 2000). For unresectable non-small cell lung cancer, Ichinose et al. (2005) conducted a multi-institutional phase-II study in which the combination of chemotherapy of UFT plus cisplatin was given with concurrent radiotherapy, showing a satisfactory response (overall response rate 81%) with no severe toxicities. 2.3.1.2.2 S-1

An oral formulation of 5-FU with DPD inhibitors makes oral absorption very reliable and allows protracted exposure without the need for a venous catheter infusion pump; however, the results of several phase-I trials showed that the dose-limiting toxicity (DLT) was gastrointestinal reactions (diarrhea, nausea, vomiting; Gonzalez Baron et al. 1993; Muggia et al. 1996; Pazdur et al. 1998). The pharmacology study showed that the occurrence of these toxic effects correlated significantly with the maximum plasma concentration and area under the concentration-vs-time curve (AUC 0–6 h) of 5-FU (Ho et al. 2000). The next strategy in the 1990s was to develop new kinds of drugs to alleviate the gastrointestinal toxicities, without reduction of the high plasma concentration of 5-FU. S-1 (or TS-1) is a combination of FTO and two compounds, CDHP and OXO, which was developed in 1996 by Japanese groups. The CDHP and OXO were designed to act as modulators of 5-FU. The CDHP is a reversible and strong inhibitor of DPD. In vitro, CDHP is 180 times more potent than uracil (Tatsumi et al. 1987). The OXO accumulates in the gastrointestinal tissues and competitively inhibits the enzyme orotate phosphoribosyl transferase (OPRT), which converts 5-FU to 5-FUMP. The phosphorylation of 5-FU within the digestive tract by OPRT has been considered the cause of gastrointestinal toxicities. In a preclinical study of Yoshida sarcoma-bearing rats, the administration of OXO with UFT mark-

Combinations of Antimetabolites and Ionizing Radiation

edly reduced the injury of gastrointestinal tissues and/or severe diarrhea without influencing the antitumor effect of UFT (Shirasaka et al. 1993). The optimal molar ratio of the three constituents (FTO/CDHP/OXO) in S-1 is 1:0.4:1. Several preclinical studies in experimental models of rodent tumors or human xenografts demonstrated that S1 significantly inhibited tumor growth with lower gastrointestinal toxicities (Takechi et al. 1997; Fukushima et al. 1998; Cao et al. 1999). Clinically, S-1 has been approved for use in Japan for gastric cancer, head and neck cancer, colorectal cancer, and non-small cell lung cancer, and in Korea for advanced or recurrent gastric cancer, head and neck cancer, and unresectable metastatic or recurrent colorectal cancer. Presently, several trials of newly combined chemotherapy of S-1 plus cisplatin or CPT-11 with radiotherapy for head and neck cancer, colorectal cancer, and non-small cell lung cancer are ongoing. 2.3.1.2.3 Capecitabine

Capecitabine (N4-pentyloxycarbonyl-5’-deoxy-5fluorovytidine) is an oral fluoropyrimidine carbonate that is converted to 5-FU through a cascade of three enzymes: carboxylesterase; cytidine (Cyd) deaminase; and thymidine phosphorylase (TP). These enzymes have been known to have unique tissue localization patterns: carboxylesterase is almost exclusively located in high concentrations in the liver and hepatoma, but not other tumors and normal tissues, Cyd deaminase is located in high concentration in the liver and various types of solid tumors, and TP is more concentrated in various types of tumor tissues than in normal tissues (Miwa et al. 1998). Oral capecitabine passes intact through the intestinal tract almost completely to be first converted in the liver; thus, theoretically, gastrointestinal injury should not occur with this compound. Schuller et al. (2000) demonstrated that in the resected samples of patients with colon cancer, the concentration of 5-FU was on average 3.2 times higher than in adjacent healthy tissues. In 1995, TP was reported to be identical with plateletderived endothelial cell growth factor (PD-ECGF; Haraguchi et al. 1994; Moghaddam et al. 1995), which is expressed at higher levels in a wide variety of solid tumors compared with adjacent normal tissues. PD-ECGF/TP was suggested to be able to confer resistance to apoptosis induced by hypoxia, and degradation products of thymidine are involved in this

29

resistance (Kitazono et al. 1998). Takebayashi et al. (1996) reported that higher levels of PD-ECGF/ TP expression in colorectal carcinomas were associated with more aggressive malignant growth and unfavorable clinical outcome; thus, a tumor-specific enzyme is responsible for the local production of the cytotoxic agent, 5-FU, from capecitabine, i.e., capecitabine should increase the concentration of active FU in tumor site and decrease the concentration in healthy normal tissues with a reduction of toxicity. Moreover, in human cancer xenografts, a number of chemotherapeutic agents, such as paclitaxel and docetaxel (Sawada et al. 1998), and cyclophosphamide (Endo et al. 1999), and radiation (Sawada et al. 1999), upregulate TP. Sawada et al. (1999) demonstrated that a single-dose local irradiation of 5 Gy increased the TP levels by up to 13-fold 9 days after irradiation. They also observed that whole-body irradiation upregulated TP in a tumor, but it did not increase the enzyme level in the liver. Capecitabine has been approved in more than 50 countries, e.g., in metastatic breast cancer (Blum 2001). On the basis of two large phase-III studies, capecitabine has been approved as a firstline alternative to IV FU/LV in advanced metastatic colorectal cancer (Hoff et al. 2001; Van Cutsem et al. 2001) and recently, capecitabine has been used in combination therapy with CPT-11 or oxaliplatin with promising results in phase-II studies. PhaseIII studies comparing capecitabine plus oxaliplatin with standard FU/LV/oxaliplatin (FOLFOX) are in progress. The clinical benefits of combined therapy with capecitabine and radiation are under investigation. The efficacy and safety of combined chemotherapy with capecitabine lends support for its use in chemoradiotherapy.

2.3.2 Gemcitabine Gemcitabine exhibits cell phase specificity, primarily killing cells undergoing DNA synthesis (S-phase) and also blocking the progression of cells through the G1/S-phase boundary. Gemcitabine has recently been shown to be a potent radiosensitizer in preclinical studies using human tumor cell lines, caused by perturbation of nucleotide metabolism, cell cycle modulation, or caspase activation and apoptosis (see section 2.1.1.2); however, the mechanisms have not been fully elucidated. Even at very low concentrations, gemcitabine has been shown to be a powerful radiation sensitizer (Mason 1999). Lawrence

H. Harada et al.

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et al. (1996, 1997) showed that 100-nm gemcitabine, which was noncytotoxic, radiosensitized HT29 cells up to 48 h after drug removal. During this period, there was an increase in the S-phase population and dNTP pools remained depleted throughout the 72-h period after drug treatment. Actually, the most common method of clinical administration is by short-term infusion (30–90 min), which is relevant to the minimalization of normal tissue toxicity, while maintaining synergistic effects during radiotherapy. Gemcitabine has shown promising clinical effectiveness against a range of solid tumors, most importantly non-small cell lung cancer, breast cancer, and pancreatic cancer; however, because of the radiosensitization of both tumor and normal tissues, the therapeutic window is extremely narrow (Rube et al. 2004). Some clinical trials of concurrent radiotherapy with gemcitabine for non-small cell lung cancer or head and neck cancer revealed severe pulmonary or esophageal toxicities. Many investigators are now attempting to define the optimal dosing and schedule for concurrent gemcitabine and radiation therapy.

2.3.3 Pemetrexed Pemetrexed is a novel agent that inhibits several enzymes of thymidylate and purine synthesis, disrupting metabolic processes essential for cell replication. A large, randomized phase-III trial was conducted to compare pemetrexed/cisplatin with cisplatin in the treatment of malignant mesothelioma, and the combination of pemetrexed/cisplatin demonstrated superiority in the response rate, survival, and quality of life (Hazarika et al. 2005). Now several clinical trials are ongoing for malignant mesothelioma, non-small cell lung cancer, pancreatic cancer, head and neck cancer, breast cancer, and colorectal cancer. Among new combination therapies, those in progress include pemetrexed with carboplatin, oxaliplatin (Scagliotti et al. 2005), or gemcitabine (Monnerat et al. 2004) for lung cancer, with gemcitabine for pancreatic cancer (Oettle et al. 2005), and with irinotecan for colorectal cancer (Hochster et al. 2005); however, a randomized phase-III study of pemetrexed plus gemcitabine vs gemcitabine in patients with advanced pancreatic cancer showed that pemetrexed plus gemcitabine regimen was not superior in overall survival or toxicities, but other studies demonstrated that the combinations had good tolerance and were at least

as active as previous, more toxic regimens. As for the combination with radiation, there are some preclinical studies to assess the radiosensitizing potential of pemetrexed. Bischof et al. (2002) demonstrated that pemetrexed enhanced the radiation-induced cell inactivation at moderately toxic exposures and over many hours after drug removal by in vitro survival assays. They also demonstrated the high antiendothelial/antitumoral efficacy of the concurrent administration of irradiation, pemetrexed and VEGFR inhibitor (SU5416) in vitro (Bischof et al. 2004). Clinical trials of combinations of pemetrexed and radiation with or without other chemotherapeutic agents for malignant mesothelioma and nonsmall cell lung cancer are now ongoing.

2.4 Conclusion Antimetabolite agents have remarkable antineoplastic activities, and their radiosensitizing effects have been reported for several decades both preclinically and clinically. Although the mechanisms of radiosensitization have not been fully understood, several preclinical studies have focused on the modulation of the metabolism, the changes in cell cycle distribution, the role of p53, and the induction of apoptosis. Chemoradiation with antimetabolites has become the standard therapy for the treatment of a wide range of solid tumors. Especially 5-FU has been one of the most commonly used anticancer drugs in combination with radiotherapy. Recently, oral 5-FU prodrugs are emerging in the clinical area, such as UFT, S-1, and capecitabine. They have new characteristics related to unique metabolic patterns or enzymatic inhibitors of degradation. These pharmacological features and oral formulation allow protracted exposure of FU to the tumor tissues without the need for a central venous catheter or infusion pump. The clinical trials have just started, but the preliminary results of the combination of oral 5-FU prodrugs and radiation are very encouraging. Other newer antimetabolite agents, such as gemcitabine or pemetrexed, have been developed and clinically investigated for several years. As for the combination with radiation, gemcitabine is being established in the key role of systemic therapy in locally advanced pancreatic cancer, and chemoradiation with gemcitabine is becoming one of the standard therapies, as an alternative to 5-FU and radiation.

Combinations of Antimetabolites and Ionizing Radiation

Currently, several combined chemotherapies of these antimetabolites with other active agents, such as cisplatin, CPT-11, or taxanes, are under investigation. We need to determine the efficacy of chemoradiation using these newly combined chemotherapy regimens, as compared with previous standard chemoradiotherapies for each tumor. In the future, the assessment of combinations with novel molecular targeted therapies, such as, for example, those studied in tumor xenografts treated with C225, gemcitabine, and radiation (Buchsbaum et al. 2002), is also warranted.

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Combinations of Taxanes and Ionizing Radiation Luka Milas, Kathryn A. Mason, Zhongxing Liao, and Kian K. Ang

CONTENTS 3.1 3.2 3.2.1 3.2.2 3.3 3.3.1 3.3.2 3.3.3 3.4 3.4.1 3.4.2 3.4.3 3.4.4 3.5 3.5.1 3.6 3.6.1 3.6.2 3.6.3 3.6.4 3.7 3.8 3.9

Introduction 35 Cytotoxic and Antitumor Activities of Taxanes 36 Origin and Chemical Structure 36 Cytotoxic and Antitumor Activities 36 Mechanisms of Cell Cytotoxicity by Taxanes 37 Mitotic Arrest and Apoptosis 37 Other Mechanisms of Cytotoxicity by Taxanes 38 Effect of Taxanes on Molecular Signaling 39 Interaction of Taxanes With Radiation 40 Modification of In Vitro Cellular Radiosensitivity 40 Supra-Additive Interactions 40 Additive Effect 41 Sub-Additive Interaction 41 In Vivo Interaction of Taxanes and Radiation 42 Enhancement of Tumor Radioresponse 42 Mechanisms of Taxane-Induced Enhanced Tumor Radioresponse 43 Cell Cycle Effects 44 Increased Tumor Oxygenation 44 Inhibition of Tumor Angiogenesis 45 Stimulation of Anti-Tumor Immune Responses 46 Anti-Metastatic Effects of Taxanes 46 Normal Tissue Radioresponse and Therapeutic Gain 46 Conclusion 48 References 49

L. Milas, MD, PhD, Professor K. A. Mason, MS Z. Liao, MD, Associate Professor Department of Experimental Radiation Oncology, University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030-4009, USA K. K. Ang, MD, PhD, Professor Departments of Experimental Radiation Oncology and Radiation Oncology, University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030-4009, USA

3.1 Introduction For many decades radiotherapy has been a major treatment modality for locally or regionally confined cancers. Its curative success has commonly been high, yet treatment failures remain frequent particularly in large advanced disease, which adversely impacts overall cure rate and patient survival. Improvements in radiotherapy have continuously been made through a number of strategies including technological innovations that allow delivery of higher radiation doses to the tumor or lower doses to normal tissues, and in the implementation of radiotherapy strategies that modulate biological response of tumors or normal tissues to radiation, or by combining radiotherapy with chemical or biological agents. Among all these improvement strategies, combining chemotherapeutic drugs with radiation has, perhaps, had the strongest impact on current cancer radiotherapy practice. This combination has been in use for several decades, but has recently become a common treatment option in many clinical settings, particularly a combination approach in which chemotherapeutic drugs are administered during the course of radiotherapy (concurrent chemoradiotherapy). Recent clinical trials clearly demonstrated superiority of concurrent chemoradiotherapy to radiotherapy alone in controlling local–regional disease and in improving patient survival (Brizel et al. 1998; Furuse et al. 1999; Herskovic et al. 1992; Milas et al. 2003b; Morris et al. 1999). There is a strong biological rationale for combining chemotherapeutic drugs with radiotherapy. By their independent cytotoxic action chemotherapeutic agents reduce the number of cells in tumors undergoing radiotherapy and in addition these agents may render the remaining tumor cells more sensitive to killing by ionizing radiation. This radiosensitizing property of chemotherapeutic agents constitutes a major rationale for concurrent chemoradiotherapy. Because of their systemic activity,

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chemotherapeutic drugs may also act on metastatic disease, which is an additional benefit of combined chemoradiotherapy. When combined with radiotherapy most chemotherapeutic agents are selected based on their known clinical activity in particular disease sites. Alternatively, agents could be chosen based on their efficacy in overcoming resistance mechanisms associated with radiotherapy. Recent clinical successes of concurrent chemoradiotherapy were made using traditional drugs, such as cisplatin and 5-FU that in addition to being strong cytotoxic agents on their own are also known for their potent radiosensitizing properties (Brizel et al. 1998; Furuse et al. 1999; Herskovic et al. 1992; Milas et al. 2003b; Morris et al. 1999). These clinical therapeutic achievements have led to extensive research on exploring newer chemotherapeutic agents including taxanes, nucleoside analogs, and topoisomerase inhibitors for their interactions with radiation. Some of these newer agents exhibit potent radioenhancing properties, and as such have already entered clinical testing in combination with radiotherapy. Preclinical research plays a critical role in developing effective anticancer agents as well as in obtaining full insight into the radiomodulating potential of such agents and their ability to increase therapeutic ratio when combined with radiotherapy. In this chapter, we review preclinical findings on the interaction of taxanes with ionizing radiation.

3.2 Cytotoxic and Antitumor Activities of Taxanes

European Yew Tree (Taxus baccata; Mangatal et al. 1989). Chemically, both paclitaxel and docetaxel are complex poly-oxygenated diterpine structures (Fig. 3.1). PG-Taxol is paclitaxel conjugated to polyglutamate polymer that allows increased and more selective uptake of paclitaxel by tumors (Li et al. 1999; Singer et al. 2005). ABI-007 is an albuminstabilized, lyophilized, Cremophor-free, nanoparticle formulation of paclitaxel designed to overcome insolubility problems of paclitaxel (Sparreboom et al. 2005).

Fig. 3.1 Chemical structure of paclitaxel and docetaxel

3.2.1 Origin and Chemical Structure

3.2.2 Cytotoxic and Antitumor Activities

Compared with most common chemotherapeutic agents, taxanes chronologically belong to a newer class of anticancer agents. Paclitaxel and doxetaxel, as prototypes of taxanes, are the best known and most widely used in the clinic, but new agents, such as PG-Taxol and ABI-007, are rapidly emerging and may possess stronger antitumor activity and/or decreased normal tissue toxicity. Of these agents, paclitaxel was first to be discovered and is a natural product originally isolated from the bark of the Pacific Yew Tree (Taxus brevifolia) (Wani et al. 1971). Docetaxel is a semi-synthetic analogue of paclitaxel prepared from needle extracts of the

Taxanes have undergone extensive laboratory and clinical testing both for their cytotoxic and antitumor efficacy (Bissery et al. 1995; Choy et al. 1994; Liebmann et al. 1994a; Li et al. 1999; Milas et al. 1995a; Milross et al. 1996; Piccart et al. 1995; Rowinsky and Donehower 1995; Singer et al. 2005; Tishler et al. 1992a). The agents exhibit cytotoxic action in vitro against various tumor cell lines (Bhalla et al. 1993; Bissery et al. 1995; Hanauske et al. 1992; Kelland and Abel 1992; Liebmann et al. 1994a; Tishler et al. 1992a), show antitumor activity against many different experimental animal tumor systems and human tumor

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xenografts (Bissery et al. 1995; Li et al. 1999; Milas et al. 1995a; Milross et al. 1996; Singer et al. 2005), and are effective in the treatment of common cancers in humans (Choy et al. 1994; Piccart et al. 1995; Rowinsky and Donehower 1995). Currently, paclitaxel and docetaxel are widely used in the clinic in combination with other chemotherapeutic agents and with radiotherapy (Chen and Okunieff 2004; Choy 2000; Figgitt and Wiseman 2000; Wani et al. 1971).

3.3 Mechanisms of Cell Cytotoxicity by Taxanes 3.3.1 Mitotic Arrest and Apoptosis Taxanes are potent mitotic spindle poisons. They block cell division by disrupting dynamics of microtubule organization. Microtubules, a complex structure composed of cellular polymers made of DE-tubulin and associated proteins, are involved in many cellular functions including intracellular transport, secretion and cell shape maintenance.

They are highly dynamic and unstable structures constantly incorporating free dimers and releasing dimers into the soluble tubulin pool (Gigorov and Lotz 2004). Taxanes bind to E-subunit of polymerized tubulins, increase tubulin polymerization, and promote microtubule assembly. Since taxanes inhibit tubulin depolymerization, the assembled microtubules remain stabilized, causing arrest of cells in the G2 and M phases of the cell cycle (Gueritte-Voegelein et al. 1991; Schiff et al. 1979; Schiff and Horwitz 1980). The formation of stable microtubule bundles is a hallmark of taxane binding to microtubules (Horwitz 2004). Disruption of microtubule organization and functioning by taxanes and consequent mitotic arrest is commonly associated with cell death, and apoptosis is considered to be the central mode of taxane cytotoxicity. Massive apoptosis after treatment with taxanes was observed both in cell cultures (Bhalla et al. 1993; Gangemi et al. 1995) and in vivo tumor systems (Mason et al. 1997; Milas et al. 1995a; Milross et al. 1996). Histological appearance of mitotically arrested and apoptotic cells in a murine carcinoma is illustrated in Figure 3.2. The data of our own study obtained in a cohort of 16 different murine tumors (Milross et al. 1996) showed

control

paclitaxel

mitosis

diameter (mm)

Mitosis and apoptosis (%)

mitosis

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Fig. 3.2 Percent mitosis (circles) or apoptosis (squares) induced in MCa-4 (lower left) and SCC-VII (lower right) tumors as a function of time after a single paclitaxel dose of 60 mg/kg. Mice bearing 8-mm tumors were injected intravenously with paclitaxel. Percentage of mitosis or apoptosis was scored from histological sections made from tumors 0–96 h after treatment. Vertical bars represent the SEM. In the insets are growth curves of untreated (circles) or paclitaxel-treated (squares) tumors. (From Milross et al. 1997). The top panel shows mitotically arrested cells and apoptotic cells (piknotic cells) in MCa-4 tumors 12 h after treatment with paclitaxel

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that apoptosis may indeed be the major mechanism underlying antitumor action of paclitaxel. While paclitaxel induced mitotic arrest in all 16 tumors, although to various degrees ranging from 7 to 26%, it caused significant apoptosis (ranging from 8 to 36%) only in 50% of these tumors. This paclitaxelinduced apoptosis, but not mitotic arrest, correlated with antitumor efficacy of paclitaxel as quantified by tumor growth delay (Fig. 3.3). Tumors which exhibited both mitotic arrest and apoptosis were responsive (sensitive) to the treatment with taxanes, whereas tumors that exhibited only the mitotic arrest remained resistant to taxanes. These results suggest that taxane-induced mitotically arrested cells may be capable of continued survival, which significantly impacts the outcome of the combined taxane plus radiation treatment of taxane-resistant tumors

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3.3.2 Other Mechanisms of Cytotoxicity by Taxanes

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(see below). An additional important finding of this study was that the pretreatment (spontaneous) level of apoptosis correlated with both paclitaxel-induced apoptosis and tumor growth delay (Milross et al. 1996); thus, both the extent of pretreatment apoptosis and the paclitaxel-induced percentage of apoptosis may be useful predictors of tumor response to the drug. In tumors treated with taxanes, time course of development of mitotic arrest differed from that of apoptosis (Mason et al. 1997; Milas et al. 1995a; Schimming 1999a). In general, mitotic arrest develops and disappears earlier than apoptosis. Observations in rodent tumors (Milas et al. 1995a; Milross et al. 1997) showed that mitotic arrest already appears within 2 h after paclitaxel administration, increases rapidly with time, and reaches a plateau between 8 and 12 h. After the peak, the percentage of cells arrested in mitosis gradually declines and disappears 1–2 days after the treatment, depending on tumor type. Apoptosis begins to increase about 6–9 h after paclitaxel administration, reaches the highest level between 12 and 24 h, and remains elevated for several hours to 2 days, depending on tumor type. Apoptosis then slowly declines to the background level within 2–3 days after paclitaxel administration. The kinetics of development of mitotic arrest and apoptosis induction in paclitaxelsensitive tumors, and the development of mitotic arrest in paclitaxel-resistant tumors, is illustrated in Figure 3.3.

0 0

4 8 12 Absolute growth delay (days)

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Fig. 3.3a,b Correlation plots of the (a) peak level of mitotic arrest and (b) peak level of apoptosis vs the absolute growth delay (in days) induced by paclitaxel (40 mg/kg i.v.) for 16 different murine tumors. Points were ﬁtted by linear regression (solid line). A: R2=0.16 (p=0.1); B: R2=0.59; p=0.001). (From Milross et al. 1996)

Taxanes can cause cell death by mechanisms other than apoptosis. We demonstrated no correlation between the ability of docetaxel to induce apoptosis and docetaxel’s antitumor efficacy (Schimming et al. 1999a), the observation opposite to that for paclitaxel activity in the same cohort of murine tumors (Milross et al. 1996). Instead, docetaxel induced profound necrosis in tumors that responded to docetaxel by tumor growth delay (Mason et al. 1997; Schimming et al. 1999a). Taxanes can cause cell death through mitotic catastrophe, which is characterized by the occurrence of aberrant mitosis, or missegregation of the chromosomes, followed by cell division (Morse et al. 2005). Nuclear envelops form around individual chromosomes or groups of chromosomes forming large nonviable cells with multiple micronuclei. Eventually, these cells undergo cell

Combinations of Taxanes and Ionizing Radiation

lysis. Whether apoptosis or other modes of cell death will prevail in individual tumors depends on the taxane used, concentration of taxane, tumor type, etc. Our own studies demonstrated that docetaxel exerted antitumor efficacy more through induction of necrotic cell death (Mason et al. 1997; Schimming et al. 1999a), whereas paclitaxel acted via preferentially inducing apoptotic cell death (Milas et al. 1995a; Milross et al. 1996). It should be noted that a number of studies, particularly those that used in vitro cell systems, showed that docetaxel was generally more cytotoxic than paclitaxel (Lavelle et al. 1995; Ringel and Horwitz 1991). This was attributed to docetaxel’s higher affinity for microtubules, higher achievable intracellular concentration, and slower cellular efflux (Lavelle et al. 1995). As will be apparent from the discussion further in the text, docetaxel seems to also be more effective in enhancing tumor radioresponse than paclitaxel. Another difference between paclitaxel and docetaxel is that while paclitaxel arrests cells in mitosis, docetaxel, in addition to arresting cells in mitosis, is cytotoxic for S-phase cells (Hennequin et al. 1995).

3.3.3 Effect of Taxanes on Molecular Signaling Taxanes have been found to affect several signaling pathways involved in cell cycle arrest and apoptotic cell death. The most notable reported effects include Bcl-2 phosphorylation (Blagosklonny et al. 1996; Haldar et al. 1996; Haldar et al. 1997), and activation of JNK/SAPK (c-Jun N-terminal kinase/stressactivated protein kinase; Lee et al. 1998; Wang et al. 1999) and Raf-kinases (Blagosklonny et al. 1996; Torres and Horwitz 1998). Members of Bcl-2 family of proteins regulate apoptosis and have been found to be dysregulated in many types of cancer. Bcl-2 inhibits apoptosis, primarily by forming heterodimers with the Bax protein, a pro-apoptotic member of the Bcl-2 family. Upon phosphorylation Bcl-2 loses its ability to form heterodimers with Bax. Taxanes phosphorylate Bcl2, which reduces the binding of Bcl-2 to Bax protein and, in turn, decreases the Bcl-2/Bax ratio, allows the pro-apoptotic activity of Bax (Haldar et al. 1997; Haldar et al. 1996). Docetaxel was more effective than paclitaxel in the induction of Bcl-2 phosphorylation and apoptosis (Haldar et al. 1997; Haldar et al. 1996). Taxanes can induce apoptosis via the involvement of Raf-1 kinase (Blagosklonny et al. 1996;

39

Wang et al. 1999) and JNK/SAPK (c-Jun N-terminal kinase/stress-activated protein kinase) kinase (Lee et al. 1998; Wang et al. 1999). Raf-kinase was found to be activated in tumor cells treated with paclitaxel and the effect was concentration dependent, being observed at paclitaxel concentrations that induce mitotic arrest (Torres and Horwitz 1998). JNK/ SAPK, a sub-family of the MAPK (mitogen-activated protein kinase) family, is involved in regulation of both cell cycle (Shim et al. 1996) and apoptosis (Xia et al. 1995), and is thought to mediate the early phase of taxane-induced apoptotic process (Wang et al. 1999). The role of the tumor suppressor p53 gene, considered the guardian of the genome, in induction of cell death by taxanes is inconclusive, although the prevailing information suggest that it may be p-53 independent. Cytotoxic agents, primarily DNA-damaging agents, initiate a signal transduction pathway that increases the levels of p53 protein (Kastan et al. 1995; Lowe et al. 1993). The activated functional (not mutant) p53 has two outcomes: either cell-cycle arrest in the G1 phase or apoptosis; which event prevails depends on activation of other downstream genes, such as p21WAF1/CIP1, GADD45, Bax, and Bcl-2, and a chain of biochemical processes (Kastan et al. 1995; Lowe et al. 1993). The cyclin inhibitor protein p21WAF1/CIP1 is a major determinant of G1 cell-cycle arrest, whereas Bax and Bcl-2 affect apoptosis. Most information available suggests that taxane-induced cytotoxicity is p53-independent; however, the results available from in vitro investigations show that the involvement of p53 in taxane-induced apoptosis depends on the cell type studied. While induction of apoptosis of NIH-3T3 fibroblasts by paclitaxel required functional p53 (Tishler et al. 1995), the loss of normal p53 function rendered fibroblasts of another cell line sensitive to paclitaxel (Wahl et al. 1996). Paclitaxel can induce both rapid and slow onset of apoptosis (Woods et al. 1995); while the rapid onset was p53-independent and occurred in cells arrested in mitosis, the slow onset was p53-dependent and occurred when cells entered G1 arrest. More recently, no relationship between paclitaxel cytotoxicity and p53 status was observed in nine different human ovarian cancer cell lines, five of which expressed wild-type p53 and four mutated p53 (Debernardis et al. 1997). Furthermore, no change in cytotoxicity to paclitaxel was observed by re-introducing p53 into p53-mutant ovarian cancer cell lines (Debernardis et al. 1997; Graniela-Sire et al. 1995). Our own in vivo studies using 15 different mouse tumors showed no correla-

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tion between p-53 functional status and antitumor efficacy of docetaxel (Schimming et al. 1999a). On the other hand, in clinical studies, p53-mutations were found to be associated with poor response in patients with non-small cell lung carcinoma treated with paclitaxel (Rosell et al. 1995). A recent review by Zhao et al. (2005) discusses in detail various molecular mechanisms involved in antitumor effects of taxanes.

Relative survival

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3.4 Interaction of Taxanes With Radiation Preclinical testing of radioenhancing properties of taxanes began in the 1990s, first in vitro and then in vivo. The original rationale for these investigations was based on the ability of taxanes to alter the cell cycle, specifically to arrest cells in G2 and M, known to be the most radiosensitive phases of the cell cycle (Sinclair and Morton 1966; Terasima and Tolmach 1963); however, during the course of preclinical investigations, it became clear that in addition to cell cycle alteration, taxanes involve a number of other mechanisms that enhance tumor radioresponse.

3.4.1 Modification of In Vitro Cellular Radiosensitivity Paclitaxel was the first taxane reported to increase radiosensitivity of cancer cells, specifically a human astrocytoma cell line (Tishler et al. 1992a). This initial study demonstrated that radiation enhancement depended on the concentration and the length of time cells were exposed to paclitaxel. Maximum radiosensitization was observed when the cells were arrested in G2 and M phases of the cell cycle, that occurred 24 h after continuous incubation of cells with paclitaxel. At this time, the radiation enhancement factor (EF) was 1.8 (Fig. 3.4). This initial investigation was followed by many subsequent studies using a variety of different cell lines of rodent and human origin to more fully define the radiomodulating potential of taxanes (Choy et al. 1993; Geard and Jones 1994; Griffon-Etienne et al. 1996; Gupta et al. 1997; Hennequin et al. 1996; Ingram and Redpath 1997; Jaakkola et al. 1996; Leonard et al. 1996; Liebmann et al. 1994a; Liebmann et al. 1994b; Liebmann et al. 1996; Lokeshwar et al. 1995;

Absorbed dose (Gy) Fig. 3.4 Survival curves of astrocytoma cells. Survival is presented at a particular radiation dose and expressed relative to nonirradiated controls with the same concentration of paclitaxel. Points are the meanrSE. Symbols represent untreated control (circles), DMSO (2)-, 1-nm paclitaxel (open triangles)-, and 10-nm paclitaxel (solid triangles)-treated cells. (From Tishler et al. 1992b with permission)

Minarik and Hall 1994; Rodriguez et al. 1995; Stromberg et al. 1995; Steren et al. 1993; Tishler et al. 1992b; Van Rijn et al. 1995; Zanelli et al. 1997). The majority of these studies used the specific taxane, paclitaxel. Treatment with paclitaxel, the most commonly used taxane for in vitro studies, did not consistently enhance cellular radioresponse. In the majority of cases paclitaxel exerted a supraadditive effect, but many cell lines responded in an additive manner, and several showed only a subadditive effect. It should be noted that in a number of cases, a single cell line displayed supra-additive, additive, or sub-additive interactions depending on experimental variables employed.

3.4.2 Supra-Additive Interactions Supra-additive paclitaxel-radiation interaction occurred predominantly when cells were incubated with the drug prior to radiation. The radiation enhancement factors (EF) ranged widely from 1.1 to 3.2 (Zanelli et al. 1997). Only a limited number of studies performed radiation-dose survival curves necessary to accurately determine EFs,

Combinations of Taxanes and Ionizing Radiation

and in these studies the highest EFs were between 1.8 and 2.0 (Liebmann et al. 1994a; Liebmann et al. 1994b; Lokeshwar et al. 1995; Tishler et al. 1992b). The degree of enhancement depended primarily on the cell line and its proliferating status, taxane concentration, and duration of exposure to the drug. Drug concentrations ranged from less than 1 to 10,000 nM (Liebmann et al. 1994a; Liebmann et al. 1996; Tishler et al. 1992b), and the incubation time ranged from less than 1 h (Choy et al. 1993; Hennequin et al. 1996) to 72 h (Liebmann et al. 1994a). In general, the presence of paclitaxel in moderate concentrations in culture medium (5 to 100 nM) for 24 h or longer resulted in higher radioenhancement (Gupta et al. 1997; Liebmann et al. 1994a; Liebmann et al. 1994b; Tishler et al. 1992b). Tissue origin of cell lines was not found to be a major determinant of the response. Enhanced radiosensitivity was consistently observed when radiation was delivered at the time of cell accumulation in G2 and M, thus supporting the original rationale that G2/ M arrest is a major mechanism for taxane-induced radioenhancement (Choy et al. 1993; Leonard et al. 1996; Liebmann et al. 1994a; Liebmann et al. 1994b; Lokeshwar et al. 1995; Tishler et al. 1992b). This finding implies that a significant proportion of taxane-induced G2/M arrested cells are capable of surviving the chemotherapeutic insult and may be more radiosensitive by virtue of being arrested in these sensitive phases of the cell cycle. Preclinical studies further showed that even nonproliferating cells in the plateau phase of cell growth could be radiosensitized, although to a lesser degree than actively proliferating cells (Steren et al. 1993). This implies that mechanisms in addition to G2/M arrest may contribute to taxane-induced radiosensitization (Ingram and Redpath 1997; Liebmann et al. 1994a). Different mechanisms may be operative for specific taxanes. For example, docetaxel was shown not only to arrest cells in radiosensitive G2 and M phases but was also toxic for radioresistant S-phase cells (Hennequin et al. 1995; Hennequin et al. 1996); therefore, at least two different cell cyclerelated mechanisms have been identified to underlie taxane-radiation interactions resulting in the supraadditive effect.

3.4.3 Additive Effect Several studies failed to demonstrate radiosensitization but reported only an additive effect when

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paclitaxel was combined with radiation (Geard and Jones 1994; Gupta et al. 1997; Hennequin et al. 1996; Jaakkola et al. 1996; Minarik and Hall 1994; Zanelli et al. 1997). In one study this occurred when the drug induced significant G2/M arrest of cells, but the arrested cells died by apoptosis without being irradiated (Minarik and Hall 1994). One study reported that paclitaxel treatment induced changes in other phases of the cell cycle, such as G1 block, whereby it created more resistant subpopulations that counteracted the radiosensitization by the G2/M arrest (Geard and Jones 1994). Additive effect was also observed under experimental conditions when drug concentrations and/or incubation periods were insufficient to exert cellular effects (Gupta et al. 1997; Hennequin et al. 1996) or when paclitaxel was added to the culture medium after irradiation (Zanelli et al. 1997), or both, before and after irradiation (Jaakkola et al. 1996).

3.4.4 Sub-Additive Interaction Sub-additive interactions between taxanes and radiation have also been reported but infrequently compared with supra-additive and additive effects (Hennequin et al. 1996; Ingram and Redpath 1997; Liebmann et al. 1996). Sub-additivity was observed when paclitaxel was added to, and maintained, in the culture medium for a prolonged period after radiation exposure (Ingram and Redpath 1997; Liebmann et al. 1996). Under these conditions, radiation alone induced both G1 and G2 cell cycle arrest (which allowed repair of sublethal damage) so that subsequently added paclitaxel could not exert further cell-cycle perturbations. This presumably reduced paclitaxel’s cytotoxicity. When radiationinduced G2/M arrest was inhibited by pentoxifylline administered after irradiation, the sub-additive effect was partially counteracted (Liebmann et al. 1996), thus supporting the above explanation for sub-additivity. A short exposure (1 h) of cells to low concentration of either paclitaxel or docetaxel was also found to reduce in vitro cell radiosensitivity, whereas the same short exposure of cells to high concentration of these drugs enhanced radiosensitivity (Hennequin et al. 1996). The general conclusion regarding in vitro interaction of taxanes and radiation is that radiosensitization by taxanes is not omnipresent. As discussed, the interaction can be supra-additive, additive, or sub-additive, depending on many factors including

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specific taxane used, dose of drug, timing of drug administration relative to radiation exposure, incubation period, and proliferation status of cells.

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3.5 In Vivo Interaction of Taxanes and Radiation

3.5.1 Enhancement of Tumor Radioresponse Milas and associates were among the first to explore in depth the effect of taxanes on radioresponse of murine tumors in vivo (Mason et al. 1997; Milas et al. 1994; Milas et al. 1995b; Milas et al. 1996; Milas et al. 1999; Milross et al. 1997). Their studies utilized both taxane-sensitive and taxane-resistant tumors. As shown in Figure 3.5, tumors of the sensitive group respond to paclitaxel alone by significant tumor growth delay, and at the cellular level, they display both mitotic arrest and apoptosis. Two mammary carcinomas (MCa-4 and MCa-29) and an ovarian carcinoma (OCa-I) were exposed to a range of single doses of radiation at different times (1–96 h) after paclitaxel administration (40 mg/kg i.v.; Milas et al. 1994; Milas et al. 1995b; Milas et al. 1996; Milross et al. 1997). Treatment efficacy was assessed by either tumor growth delay or local

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The in vitro studies showed that taxanes can interact with radiation at the cellular level, that the interaction can lead to increased cell radiosensitivity of varying magnitude and revealed major mechanisms responsible for increased cellular radiosensitivity. To further develop cancer treatment strategies that combine taxanes with radiotherapy it was necessary to undertake preclinical investigations in vivo to assess both the antitumor activity and normal tissue toxicity of this treatment combination. The in vivo studies provided more detailed insight into the radiomodulating potential of taxanes with regard to their ability to increase radiotherapeutic gain. These studies revealed that taxanes involve multiple mechanisms that directly and indirectly affect the efficacy of radiation on tumor cells and explored treatment schedules that would maximize therapeutic ratio. Taxanes were capable of enhancing radioresponse of both taxane-resistant and taxane-sensitive tumors; however, different taxanes differed in their effectiveness.

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Fig. 3.5a,b. Tumor growth of untreated 8-mm diameter MCa29 (a) or SCC-VII (b) untreated tumors (circles) and of tumors treated with paclitaxel alone (40 mg/kg i.v.; triangles), radiation alone (15 Gy for MCa-29, 45 Gy for SCC-VII; squares), or paclitaxel followed by radiation (at 24 h for MCa-29 or 9 h for SCC-VII; diamonds). The 9- and 24-h time points were selected to illustrate the ability of paclitaxel to potentiate growth delay produced by irradiation in two different tumors

tumor control. All three tumors exhibited improved radioresponse, as evidenced by more than additive increase in tumor growth delay and by increased rate of tumor cure. The radiation EFs ranged from 1.2 to > 2.0 depending on tumor type, time of radiation delivery in relation to paclitaxel administration, and tumor treatment end point (Milas et al. 1999). The most significant determinant of treatment response was the time at which radiation was given after paclitaxel administration with the highest EF obtained when tumor irradiation was delivered 2–3 days after paclitaxel. The degree of radiopotentiation declined when radiation was given at either shorter or longer inter-treatment intervals. Paclitaxel was also effec-

Combinations of Taxanes and Ionizing Radiation

Tumor cure (%)

tive in enhancing radioresponse of paclitaxel-resistant tumors, as shown in Figure 3.5 for the SCC-VII tumor. Single-dose radiation was delivered 1–24 h after injection of paclitaxel (40 mg/kg). In contrast to paclitaxel-sensitive tumors, this resistant tumor exhibited radioenhanced response only between 3 and 12 h after paclitaxel administration. The magnitude of the enhancement was lower for these tumors compared with paclitaxel-sensitive tumors, ranging from 1.1 to 1.4. Docetaxel was also evaluated for its ability to enhance tumor radioresponse of both docetaxelsensitive and docetaxel-resistant tumors (Mason et al. 1997; Mason et al. 1999; Mason et al. 2001a). Using tumor growth delay as the treatment end point, it was observed that a single i.v. dose of docetaxel of 33 mg/kg enhanced radioresponse of the docetaxel-sensitive MCa-4 carcinoma by a factor of 1.5 when given 9 h, and by a factor of 2.3 when given 48 h, before irradiation. This effect was greater than that observed for paclitaxel, although the dose of docetaxel (33 mg/kg) was slightly lower than that of paclitaxel (40 mg/kg). Docetaxel was even more effective in enhancing radioresponse of the docetaxel-sensitive mouse MCa-K mammary carcinoma, achieving radiation EF of 3.3 (Mason et al. 2001a). This effect of docetaxel on tumor radiocurability is illustrated in Figure 3.6. Docetaxel was also effective in enhancing radioresponse of docetaxel-resistant SCC-VII tumor, providing an EF of 1.58 (Mason et al. 1999). PG-TXL conjugate was recently tested for its ability to enhance radioresponse of murine tumors, and was found to be more effective than other tax-

DOC +

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Radiation dose Fig. 3.6 Radiation dose-response curves for local tumor control of MCa-K tumors in mice. (From Mason et al. 2001a)

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anes tested (Li et al. 2000a; Li et al. 2000b; Milas et al. 2003a). When a direct comparison between the efficacy of PG-TXL and paclitaxel was made, PG-TXL containing 60 mg/kg paclitaxel, given 24 h before tumor irradiation, enhanced radioresponse of the murine OCa-I carcinoma to a single dose of 15 Gy by a factor of 4.44, whereas 60 mg/kg unconjugated paclitaxel given under the same treatment conditions enhanced it by a factor of only 1.5 (Li et al. 2000a). The conjugate is also highly effective in enhancing tumor radioresponse when given after tumor irradiation, which was not the case with paclitaxel (Li et al. 2000b). Our most recently investigated taxane, ABI-OO7, also showed, in initial studies, to be highly effective in enhancing radioresponse of the OCa-I tumor when given between 9 h and 5 days before local tumor irradiation (Mason et al., in press); however, like its parent agent paclitaxel, it failed to enhance tumor radioresponse when given after irradiation. The studies described above used combination of taxanes with a range of single-dose radiation. A number of studies also combined taxanes with fractionated irradiation (Joschko et al. 1994; Lokeshwar et al. 1995; Mason et al. 1999). Paclitaxel enhanced the response of a human hypopharyngeal tumor xenograft as assessed by tumor-growth delay (Joschko et al. 1994). Radiation at a dose of 2 Gy per fraction was given twice daily for 10 days, and paclitaxel was administered either initially as a single bolus or daily for 10 days starting immediately before the first daily fraction of radiation. Another study (Lokeshwar et al. 1995), which used a rat Dunning tumor, showed only an additive effect when paclitaxel, given daily for 5 days, was combined with radiation (1.5 Gy daily for 5 days). Two studies compared the effect of taxanes (docetaxel or PG-Taxol) on both tumor and normal tissue radioresponse to establish whether or not therapeutic gain can be improved (Mason et al. 1999; Milas et al. 2003a). Details of these studies will be discussed in section 3.8.

3.6 Mechanisms of Taxane-Induced Enhanced Tumor Radioresponse Several mechanisms have been identified to be involved in enhanced tumor radioresponse by taxanes. These mechanisms include direct increase of tumor cell radiosensitivity through cell cycle redis-

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tribution, indirect increase in tumor cell radiosensitivity due to increased tumor oxygenation, and increased tumor cell destruction through inhibition of angiogenesis or participation of immune antitumor resistance mechanisms.

3.6.1 Cell Cycle Effects As already mentioned, the original rationale for testing taxanes as radioenhancing agents was based on their ability to arrest cells in the radiosensitive G2 and M phases of the cell cycle. This rationale was amply justified by the in vitro experiments discussed above. The G2M arrest is also a major mechanism by which taxanes induce in vivo enhancement of tumor response to radiation, and it dominates in tumors whose growth is not significantly affected by taxanes when applied as a single treatment (Mason et al. 1999; Milas et al. 1999; Milross et al. 1997). Although their growth is not affected, these taxaneresistant tumors still respond at the cellular level by mitotic arrest (see Fig. 3.2), which makes them more sensitive to radiation. Mitotic arrest in these tumors peaks between 6 and 12 h after taxane administration (Mason et al. 1999; Milas et al. 1999; Milross et al. 1997), a time that coincides with the highest enhancement of tumor response after the combined taxane-radiation treatment (Milross et al. 1997). One of the taxanes, notably docetaxel, was found to induce the G2/M arrest and to be toxic for radioresistant S-phase cells (Hennequin et al. 1995); therefore, this specific taxane may have another cell-cycle mechanism that enhances tumor radioresponse, i.e., elimination of the radioresistent S-phase cell population prior to radiation delivery.

3.6.2 Increased Tumor Oxygenation Hypoxic regions commonly develop in solid tumors as a result of deficient tumor vascularization, both in the number of blood vessels and their function. In these hypoxic regions tumor cells poorly proliferate, are less accessible to chemotherapeutic agents, and hypoxia makes them 2.5–3 times more resistant to radiation. Since hypoxic cell fraction in solid tumors is often high, improvement in tumor oxygenation would make tumors more responsive to radiotherapy. Our early studies on taxanes showed that these agents enhance tumor oxygenation in

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tumors sensitive to taxanes as a single treatment, which then acts as a major mechanism in enhancing tumor response to radiation (Milas et al. 1995b). In these taxane-sensitive tumors, the majority of tumor cells that become arrested in G2/M die by apoptosis or necrosis within a few days after treatment with taxanes (Mason et al. 1997; Mason et al. 1999; Milas et al. 1995b; Milas et al. 1996; Milas et al. 1999). This cell loss occurred preferentially in close vicinity to blood vessels, well-oxygenated tumor regions where tumor cells rapidly proliferate and are easily accessible to taxanes. That this taxane-induced cell loss causes significant tumor reoxygenation was demonstrated by a number of methods (Milas et al. 1995b). Using the Eppendorf pO2 histograph for direct measurements of tumor oxygenation in a murine adenocarcinoma treated with paclitaxel, it was shown that the pO2 increased from the control median value of 6.8–10.5 mmHg at 24 h and to 31.2 mmHg at 48 h after paclitaxel treatment (Milas et al. 1995b). This change in pO2 values was associated with a reduction in the percentage of hypoxic cells from 32% in untreated tumors to 4 and 2% at 24 and 48 h after paclitaxel administration, respectively (Milas et al. 1995b). The observed increase in tumor pO2 and reduction in the number of hypoxic cells within the first few days after administration of paclitaxel corresponded well with the increase in degree of taxane-induced tumor radioresponse, supporting the hypothesis we advanced (Milas et al. 1995b) that tumor reoxygenation was a major mechanism of taxane-induced enhancement of tumor radioresponse; however, the radiobiological evidence for the existence of this mechanism was provided by experiments in which tumors treated with or without paclitaxel were locally irradiated under hypoxic conditions (total hypoxia) and then assessed for tumor growth delay or cure (Milas et al. 1995b). If reoxygenation dominates as a mechanism, the enhancement of tumor radioresponse would be greatly reduced or even abolished in tumors irradiated under hypoxic conditions. Tumors were made totally hypoxic by clamping tumor-bearing legs for two minutes before and during tumor irradiation thus blocking blood flow to the tumor. As illustrated in Figure 3.7 treatment with paclitaxel enhanced tumor cure by radiation delivered under ambient (air breathing) conditions. The enhancement increased as the time interval between paclitaxel administration and irradiation was increased; however, this paclitaxel-enhancing effect was almost totally abolished when tumors were irradiated under hypoxic conditions. A simi-

Combinations of Taxanes and Ionizing Radiation

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murine tumors, with docetaxel being more effective than paclitaxel. Finally, tumor shrinkage and active migration of tumor cells bring previously hypoxic micro-regions closer to blood vessels.

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3.6.3 Inhibition of Tumor Angiogenesis

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Fig. 3.7a,b. Effect of paclitaxel on radiation dose-response curves for local tumor control of MCa-4 tumor irradiated under (a) air breathing or (b) hypoxic conditions. Horizontal lines represent 95% conﬁdence limits at the TCD50 (radiation dose yielding 50% local tumor control) level. (From Milas et al. 1995)

lar effect of hypoxic conditions was observed when tumor growth delay was the treatment end point (Milas et al. 1995b). Mechanistically, taxanes induce tumor reoxygenation by virtue of their preferential killing of oxygenated cells, which are positioned close to blood vessels. Firstly, by eliminating oxygenated cells, more oxygen becomes available to the more resistant cells that survived treatment. Secondly, this loss of cells lowers the interstitial pressure on microvessels within a tumor, reopening previously closed capillaries and increasing blood delivery to tumor cells. In support of this mechanism, Griffon-Etienne et al. (1999) reported that both paclitaxel and docetaxel reduced tumor tissue interstitial fluid pressure in

Angiogenesis, or formation of blood vessels, is a prerequisite for the growth of malignant tumors beyond small microscopic aggregates of tumor cells. Proficient vascularization appears to favor more rapid tumor growth, promotes metastatic spread, and may be related to poor patient prognosis; therefore, inhibition of tumor angiogenesis may be a promising cancer therapy approach. Increasing evidence shows that chemotherapeutic agents, including taxanes (Schimming et al. 1999b; Sweeney et al. 2001), are anti-angiogenic. For example, docetaxel was reported to suppress in vitro proliferation of endothelial cells and their ability to form capillaries, and in vivo formation of vessels in Matrigel plugs (Sweeney et al. 2001). These antiangiogenic effects of docetaxel were partly blocked by the presence of the angiogenic factors, endothelial cell growth factor (VEGF) and basic fibroblast growth factor (FGF). This protection was, however, overcome by anti-VEGF antibody or by combining docetaxel with 2-methoxyestradiol, another anti-angiogenic agent. Our group (Schimming et al. 1999b) showed that docetaxel inhibited in vivo formation of blood vessels induced in mice at the site of intradermal injection of tumor cells. This inhibition occurred when the injected cells were derived from tumors sensitive to docetaxel, but not from tumors resistant to docetaxel. This anti-angiogenic activity is likely one more mechanism by which taxanes enhance tumor response to radiation, a reasoning based on increasing preclinical data showing that inhibitors of angiogenesis increase tumor radioresponse (Mason et al. 2001b). Anti-angiogenic agents including taxanes, may increase tumor radioresponse by a number of mechanisms including inhibition of VEGF and FGF that act radioprotectively for tumor cells (Gorski et al. 1999; Haimovitz-Friedman et al. 1991). Also, since VEGF is a potent vessel permeability factor leading to fluid accumulation in extracapillary spaces with consequent impairment of blood flow and oxygen supply to tumor cells, its inhibition by taxanes will result in increased tumor oxygenation.

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46

3.6.4 Stimulation of Anti-Tumor Immune Responses Cytotoxic agents are generally known to be potent immunosuppressive drugs. Surprisingly, although taxanes are potent cytotoxic agents they can elicit or augment various facets of immune reactions that may be involved in the destruction of tumor cells. Taxanes were reported to activate macrophages, increase NK-cell-mediated cytotoxicity, stimulate production of cytokines such as tumor necrosis factor-D (TNF-D) and interferon-J (IFN-J), and induce tumor infiltration with lymphoid cells (Bogden and Ding 1992; Burkhart et al. 1994; Grunberg et al. 1998; Manthey et al. 1994; Mason et al. 2001a). Our own recent study (Mason et al. 2001a) demonstrated heavy infiltration of a murine adenocarcinoma with lymphocytes and macrophages when tumors were treated with docetaxel or with docetaxel combined with local tumor irradiation. This infiltration was associated with an increased anti-tumor efficacy of the drug when applied as a single agent or when combined with radiotherapy. This effect of docetaxel was reduced by immunosuppressive (whole-body irradiation) treatment of tumor-bearing mice. While tumor radioresponse in immunocompetent mice was enhanced by a factor of 3.3, it was enhanced in immunocompromised mice by a factor of 1.9; therefore, stimulation of anti-tumor immune responses represents an additional mechanism by which docetaxel, and likely other taxanes, enhance the efficacy of radiotherapy.

3.7 Anti-Metastatic Effects of Taxanes One of the objectives of chemo-radiotherapy is to control metastatic disease. Because of their systemic activity, chemotherapeutic agents may act on existing microscopic metastatic lesions, or by improving local tumor control they may reduce the risk of metastatic dissemination. Using a mouse mammary carcinoma, Mason et al. (2001a) demonstrated that docetaxel combined with radiation not only increased the cure rate of primary tumors but also reduced the incidence of lung metastases. Mice that received the combined treatment developed lung metastases in only 11% of cases, whereas the metastasis incidence in mice whose primary tumor was locally controlled by radiation only was 26%.

3.8 Normal Tissue Radioresponse and Therapeutic Gain Radioenhancing agents, including taxanes, must influence radioresponse of normal dose-limiting tissues less than tumor radioresponse in order to achieve an increase in therapeutic ratio. Since poisoning mitotic apparatus of cells is the hallmark of cellular action of taxanes, resulting in accumulation of cells in radiosensitive phases of the cell cycle, it is to be expected that taxanes are likely to influence radioresponse of highly proliferating normal tissues (tissues that respond to radiation acutely, i.e., several days to a few weeks from initiation of radiotherapy), but not of slowly proliferating normal tissues (tissues that respond to radiation late, i.e., months to years from initiation of radiotherapy). The effects of taxanes were tested both on acutely responding tissues, notably jejunal mucosa (Mason et al. 1997; Mason et al. 1999; Mason et al. 1995; Milas et al. 1996) and skin (Milas et al. 2003a; Milross et al. 1997), and late responding tissues such as subcutaneous tissue using the leg contracture assay (Milross et al. 1997). As single agents, both paclitaxel (Mason et al. 1999; Milas et al. 1996) and docetaxel (Mason et al. 1997) cause arrest of jejunal crypt cells in mitosis and induce their death by apoptosis. The extent of these cellular effects are similar to those in tumors; however, the effects are more rapid in jejunum; mitotic arrest peaked at 3–4 h and returned to baseline within 9–10 h after treatment with taxanes, and the apoptotic response peaked at 9–12 h and declined to the baseline within 24 h after treatment. The interaction between taxanes and radiation was tested using mouse jejunal epithelial cells in situ (microcolony assay; Withers and Elkind 1970). The results showed an increase in radiation injury occurring when radiation was delivered 4–6 h after taxane administration, when jejunal cells showed significant mitotic arrest. The magnitude of this increase was much smaller (EF <1.1) than that observed for tumors; however, no enhancement but rather a slight radioprotection was observed if radiation was delivered 1–4 days after paclitaxel or docetaxel administration. The observed increase in radiation response at the time of mitotic arrest may be attributed to the additive cytotoxicity of these drugs and radiation and/or the taxane-induced enhancement of radiation response of jejunal epithelial cells. The reasons for the observed radioprotection are also unknown but could be related to rapid regeneration of epi-

Combinations of Taxanes and Ionizing Radiation

47

thelial cells after their initial depletion by taxanes. This occurs because of a shorter cycling time of stem cells and/or recruitment of Go stem cells into the cell cycle (Mason et al. 1999), resulting in an increased cell number at risk at the time of radiation delivery. Paclitaxel had no appreciative modifying effects on either skin radioresponse or radiation-induced leg contractures (Milross et al. 1997). These experiments were performed using a range of single doses of radiation, and results clearly show that taxanes can significantly improve the therapeutic ratio of radiotherapy, as illustrated in Figure 3.8, which plots EFs for both tumors and jejunum. The taxaneinduced increase in therapeutic ratio is more profound for taxane-sensitive tumors than for resistant tumors. The therapeutic ratio for taxane-sensitive tumors changes with time. It increases as the time between administration of taxanes and radiation delivery is increased up to 3 days and declines thereafter. In contrast, the therapeutic ratio for tumors resistant to taxanes increases only during the time of peak mitotic arrest. Preclinical studies provided ample evidence that taxanes can potentiate tumor response to radiation more than they increase normal tissue radiation damage. Although taxanes are able to enhance radioresponse of both taxane-resistant and taxane sensitive tumors, the timing of administration of taxanes 2.4 2.2

MCa-4 docetaxel

Enhancement factor

2.0 MCa-29 1.8

OCa-I MCa-4

1.6 1.4

SCC-VII

1.2 1.0

Jejunum 0.8 0

20

40

60

80

100

Time between taxanes and radiation (h) Fig. 3.8 Radiation enhancement factors for various tumors and jejunum as a function of time between paclitaxel (40 mg/kg given intravenously) or docetaxel (red line; 33 mg/kg given intravenously) and irradiation. (From Milas et al. 1999)

in relation to radiation delivery was an important parameter in achieving the effect, and it differed between the two types of tumors. This suggests that the most effective treatment schedule must be based on biological effects of taxanes on both tumors and normal tissues. This guiding principle was recently tested by Mason et al. (1999) using fractionated irradiation in two murine tumors, one sensitive to taxanes (MCa-4) and one resistant to taxanes (SCCVII). Tumor response was tested using tumor growth delay and jejunal damage was used to assess normal tissue response. As shown in Table 3.1, for tumors sensitive to docetaxel the best therapeutic gain was achieved with a single bolus of drug administered one day before fractionated radiotherapy. This schedule optimized the reoxygenation of hypoxic tumor cells during the interval between drug treatment and radiation delivery. The best therapeutic gain for tumors resistant to docetaxel was achieved with intermittent multiple doses of docetaxel during the course of fractionated radiotherapy. This treatment schedule maximized the exposure of cells to radiation while they were arrested in the radiosensitive G2 and M phases of the cell cycle; however, this schedule also maximized normal tissue injury, thus reducing the overall therapeutic gain. Thus, taxanes greatly enhanced tumor response to fractionated radiotherapy, but the magnitude of therapeutic efficacy depended on drug-radiation scheduling. Based on these data, it is reasonable to suggest that the best treatment schedule for tumors sensitive to taxanes would consist of one or two doses of taxane weekly in combination with daily fractionated radiotherapy. On the other hand, a more frequent administration of taxanes may be required for the treatment of taxane-resistant tumors; however, in this case more severe toxicity is likely to be encountered. As elaborated previously, new taxane formulations are being developed to reduce normal tissue toxicity and improve tumor-specific drug delivery. One of these new taxane formulations, PG-Taxol, has been shown to remarkably enhance tumor radioresponse without an increase in normal tissue toxicity (Milas et al. 2003a). As illustrated in Figure 3.9 a single dose of PG-Taxol given 24 h before initiation of five daily fractions of radiation dramatically enhanced tumor cure rate of a murine carcinoma. PG-Taxol reduced TCD50 (radiation dose yielding 50% cure rate) of single-dose irradiation from 53.9 Gy (range 52.2– 55.5 Gy) to 7.5 Gy (range 4.5–10.7 Gy), an enhancement factor (EF) of 7.2. The drug improved the efficacy of fractionated irradiation even more, reducing the TCD50 of 66.6 Gy (62.8–90.4 Gy) total fraction-

L. Milas et al.

48 Table 3.1. Therapeutic gain factors after combining docetaxel (DOC) with fractionated irradiation. (Reprinted from Mason et al. 1999 with permission) Treatment

EFsa

DOC

XRT

MCa-4c

Singleg

FXRTh

2.02

1.58

0.99

1.02

2.04

1.55

Multii

FXRT

1.24

2.00

1.10

1.26

1.13

1.59

SCC-VIId

EFs jejunum

TGb

MCa-4e

MCa-4

SCC-VIIf

SCC-VII

aEF,

radiation EF therapeutic gain obtained by dividing EF for tumor by EF for jejunum cMCa-4, DOC-sensitive tumor dSCC-VII = DOC-resistant tumor eMCa-4 = type schedule with DOC 9 h before each radiation dose fSCC-VII = type schedule with DOC 6 h before each radiation dose gSingle dose of 33 mg/kg DOC 24 h before irradiation hFXRT, fractionated irradiation once daily for 5 days iMultiple dose of 8 mg/kg DOC 6 or 9 h before irradiation for SCC-VII and MCA-4, respectively bTG,

▲ ▲ ▲ ● ▲ ▲

100

●

●

○

△

● ▲

80 Tumor cure (%)

● △

● ▲

▲

△

○

60 ●

40 ▲ ○

20 △

0 0

○ ○ △

○ △ ○ △ ○

10

20 30 40 50 60 Total radiation dose (Gy)

70

80

Fig. 3.9 Effect of PG-Taxol on radiocurability of OCa-I tumor after single or fractionated irradiation. Mice bearing 7-mm tumors in the right hind leg were given 80 mg/kg PG-Taxol intravenously and/or local tumor irradiation with graded doses of J-rays delivered as a single dose or as daily fractions for ﬁve consecutive days. When the two agents were combined, PG-Taxol was given 24 h before the start of irradiation. Radiation dose-response curves were generated for local tumor control at 120 days after treatment with single-dose irradiation alone (open triangles), fractionated irradiation (open circles), PG-Taxol plus single-dose irradiation (solid triangles), or PGTaxol plus fractionated irradiation (solid circles). Error bars are 95% conﬁdence intervals on the TCD50. (From Milas et al. 2003a)

ated dose to only 7.9 Gy (4.3–11.5 Gy), for an EF of 8.4. In contrast, PG-Taxol did not increase acute normal tissue injury inflicted on jejunal mucosa or the skin by fractionated irradiation. Clearly, drug-polymeric macromolecule conjugates are highly promising. Their efficacy in combination with radiotherapy is still awaiting clinical assessment.

3.9 Conclusion Taxanes, a newer class of anticancer agents, of which paclitaxel and docetaxel are most known, have undergone extensive preclinical investigations for their ability to enhance antitumor efficacy of ionizing radiation and to improve therapeutic gain of radiotherapy. They affect mitotic spindle and disrupt dynamics of microtubule organization with consequent arrest of cells in G2 and mitosis, the most sensitive phases of the cell cycle. Formation of stable microtubule bundles in affected cells is considered a hallmark of taxanes’ activity, and the resulting mitotic arrest is commonly associated with cell death. Most commonly, taxane treated cells die by apoptosis, although other modes of cell death such as cell lysis and necrosis also occur. At the molecular level, taxanes affect several signaling pathways involved in cell cycle arrest and apoptotic cell death including Bcl-2 phosphorylation and activation of JNK/SAPK and Raf-kinases. Cytotoxic and antitumor actions of taxanes seem to be largely independent of p-53 status. In vivo studies with murine tumors revealed that tumors sensitive to taxanes, as measured by tumor growth delay, exhibit both mitotic arrest and apoptosis (or necrosis) at the cellular level, whereas tumors resistant to taxanes only exhibit mitotic arrest. Ample preclinical evidence obtained using paclitaxel and docetaxel shows that taxanes can enhance in vitro radiation sensitivity of tumor cells, with EFs ranging from 1.1 to more than 3. Both additive and sub-additive effects were observed. Multiple factors determine whether or not taxanes will enhance (and to which extent) cell radiosensitivity including cell

Combinations of Taxanes and Ionizing Radiation

type, cell proliferation state, drug concentration, and timing of radiation delivery in relation to drug administration. Taxanes are also able to strongly enhance in vivo tumor response to radiotherapy with EFs up to more than 8, as demonstrated by either tumor growth delay or the rate of tumor cure. Different taxanes differed in their ability to enhance tumor radioresponse; for example, PG-Taxol was found to be more effective than paclitaxel. In contrast to exerting a strong enhancement of tumor radioresponse, the ability of taxanes to modify normal tissue radiation damage, either acute or late, was much lower. This was observed both after single dose and fractionated irradiation; thus, taxanes can significantly increase therapeutic gain when combined with radiotherapy. The ability of taxanes to arrest cells in the radiosensitive G2 and M phase of the cell cycle was the original rationale for using taxanes as radiation enhancers; however, subsequent studies revealed additional mechanisms to be involved, particularly for the in vivo augmentation of tumor radioresponse. These include tumor reoxygenation, inhibition of tumor angiogenesis, and taxane-induced stimulation of antitumor immune response mechanisms. Of these mechanisms, tumor oxygenation seems to dominate in tumors that respond to taxanes by both mitotic arrest and apoptosis (or necrosis; taxane-sensitive tumors), and G2/M arrest seems to dominate in tumors that respond to taxanes only by mitotic arrest (taxane resistant tumors). These mechanisms may be decisive in designing the most effective taxane-radiation treatment schedule. There is some evidence suggesting that the best treatment schedule for tumors sensitive to taxanes would consist of one or two doses of taxane weekly in combination with daily fractionated radiotherapy. On the other hand, more frequent administration of taxanes may be required for the treatment of taxane-resistant tumors; however, in this case more severe toxicity is likely to be encountered. Overall, taxanes are highly potent chemotherapeutic agents on their own and are strong enhancers of the efficacy of radiotherapy in preclinical tumor models. The use of taxanes in combination with clinical radiotherapy is discussed in other chapters of this book.

49

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51 Sparreboom A, Scripture CD, Trieu V, et al (2005) Comparative preclinical and clinical pharmacokinetics of a cremophorfree, nanoparticle albumin-bound paclitaxel (ABI-007) and paclitaxel formulated in cremophor (Taxol). Clin Cancer Res 11:4136–4143 Steren A, Sevin BU, Perras J et al (1993) Taxol sensitizes human ovarian cancer cells to radiation. Gynecol Oncol 48:252– 258 Stromberg JS, Lee YJ, Armour EP et al (1995) Lack of radiosensitization after paclitaxel treatment of three human carcinoma cell lines. Cancer 75:2262–2268 Sweeney CJ, Miller KD, Sissons SE et al (2001) The antiangiogenic property of docetaxel is synergistic with a recombinant humanized monoclonal antibody against vascular endothelial growth factor or 2-methoxyestradiol but antagonized by endothelial growth factors. Cancer Res 61:3369-3372 Terasima T, Tolmach LJ (1963) Variations in several responses of HeLa cells to X-irradiation during the division cycle. Biophys J 3:11–33 Tishler RB, Geard CR, Hall EJ, Schiff PB (1992a) Taxol sensitizes human astrocytoma cells to radiation. Cancer Res 52:3495–3497 Tishler RB, Schiff PB, Geard CR et al (1992b) Taxol: a novel radiation sensitizer. Int J Radiat Oncol Biol Phys 22:613– 617 Tishler RB, Lampus DM, Park S et al (1995) Microtubuleactive drugs taxol, vinblastine, and nocodazole increase the level of transcriptionally active p53. Cancer Res 55:6021–6025 Torres K, Horwitz SB (1998) Mechanisms of taxol-induced cell death are concentration dependent. Cancer Res 58:3620– 3626 Van Rijn J, Van Den Berg J, Meijer OW (1995) Proliferation and clonal survival of human lung cancer cells treated with fractionated irradiation in combination with paclitaxel. Int J Radiat Oncol Biol Phys 33:635–639 Wahl AF, Donaldson KL, Fairchild C et al (1996) Loss of normal p53 function confers sensitization to taxol by increasing G2/M arrest and apoptosis. Nature Med 2:72–79 Wang T-H, Popp DM, Wang H-S et al (1999) Microtubule dysfunction induced by paclitaxel initiates apoptosis through both c-Jun N-terminal kinase (JNK)-dependent and -independent pathways in ovarian cancer cells. J Biol Chem 274:8208–8216 Wani MC, Taylor HL, Wall ME et al (1971) Plant antitumor agents. VI. The isolation and structure of taxol, a novel antileukemic and antitumor agent from Taxus brevifolia. J Am Chem Soc 93:2325–2327 Withers HR, Elkind MM (1970) Microcolony survival assay for cells of mouse intestinal mucosa exposed to radiation. Int J Radiat Biol 17:261–267 Woods CM, Zhu J, Mcqueney PA et al (1995) Taxol-induced mitotic block triggers rapid onset of a p53-independent apoptotic pathway. Mol Med 1:506–526 Xia Z, Dickens M, Raingeaud J et al (1995) Opposing effects of ERK and JNK-p38 MAP kinases on apoptosis. Scinece 270:1326–1331 Zanelli GD, Quaia M, Robieux I et al (1997) Paclitaxel as a radiosenitizer: a proposed schedule of administration based on in vitro data and pharmacokinetic calculations. Eur J Cancer 33:486–492 Zhao J, Kim JE, Reed E et al (2005) Molecular mechanism of antitumor activity of taxanes in lung cancer (Review). Int J Oncol 27:247–256

Combinations of Topoisomerase Inhibitors and Ionizing Radiation

4

53

Combinations of Topoisomerase Inhibitors and Ionizing Radiation Michael Bastasch and Hak Choy

CONTENTS 4.1 4.2 4.3 4.4 4.5 4.6 4.6.1 4.6.2 4.7 4.7.1 4.7.2 4.8 4.9 4.10

Introduction 53 Topoisomerases 53 Topoisomerase-I Inhibitors 54 Topoisomerase-II Inhibitors 54 Topoisomerase Inhibition Enhances Radiation In Vivo and In Vitro 55 Lung 56 Non-Small Cell Lung Cancer 56 Small Cell Lung Cancer 57 Gastrointestinal Tumors 58 Esophageal Cancer 58 Rectal Cancer 59 CNS Tumors 60 Head and Neck Tumors 61 Conclusion 62 References 63

4.1 Introduction Radiation has been used in the treatment of cancer since its discovery and has recently undergone significant innovations through increased technical refinements. With increased computing power, three-dimensional radiation therapy, intensitymodulated radiation therapy, tomotherapy, and stereotactic radiation have emerged as tools to increase the therapeutic ratio. While safe implementation of such programs has resulted in improvements in local control through pure dose escalation and/or alterations in fraction sizes, limitations still exist secondary to adjacent normal tissue toxicity. Furthermore, radiation has never been more than a local therapy, unable to affect disease distant to the treatment field. Chemotherapy agents, in contrast, act systemically, although they are unlikely to

M. Bastasch, MD H. Choy, MD, Professor and Chairman Department of Radiation Oncology, The University of Texas Southwestern Medical Center at Dallas, 5801 Forest Park Rd., Dallas, TX 75390-9183, USA

control completely gross solid tumors. Combining highly effective local therapy and systemic therapy might enhance the overall chance of cure, especially in disease entities known to harbor microscopic metastatic deposits frequently. Additional benefit in terms of local tumor control might be derived from an additive effect of chemotherapy; thus, cytotoxic agents might provide several advantages over radiation alone for improved local, regional, and systemic disease control.

4.2 Topoisomerases DNA topoisomerases (Topo) function to regulate the topology of DNA to ensure correct DNA metabolism. Currently five human topoisomerases for DNA have been identified, Topo1, Topo2D, Topo2E, Topo3D, and Topo3E (Wang 2002). They serve in a vital capacity for successful DNA synthesis (Wang 1985; Wang 1991). As such, DNA topoisomerases I and II (Topo I and II) are important targets for cancer chemotherapeutic agents. These nuclear enzymes are essential for DNA replication, RNA transcription, chromosomal condensation, and mitotic chromatid separation (Wang and Sinha 1996). The level of Topo I is independent of cell cycle phases, although cytotoxicity is manifested only in proliferating cells (Choy and Macrae 2001). Topo II, in contrast, is cell-cycle dependent. It increases at the onset of G2 and S phases and disappears in G0/G1 phase (Heck and Earnshaw 1986). Topoisomerases also have activity in G1 cells or cells held in plateau phase (Ng et al. 1994). The difference between Topo I and Topo II is number of DNA strands involved. The human DNA topoisomerase I is a monomeric 100 kDa protein that is able to relax supercoiled DNA. This is achieved through the introduction of a single stranded break in DNA followed by the passing of the intact strand through the break prior to religation. This activity is key in many aspects of DNA

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metabolism including transcription, replication and the regulation of DNA supercoiling, which is important in maintaining genomic stability. It is believed that the camptothecins function by stabilizing a topoisomerase I-DNA intermediate called the cleavable complex such that the 5’phosphoryl end of the DNA single-stranded break is bound covalently to a topoisomerase-I tyrosine residue (Chen et al. 1999). It is believed that collision of this drug-trapped complex with the DNA replication machinery will lead to G2 phase cell-cycle arrest and cell death (Chen and Liu 1994; Cheng et al. 1994). Topo II acts similarly, but on two strands of DNA (Wang 1985). Topo II binds covalently to double-stranded DNA, cleaves both strands, and reseals the cleaved complex. Collisions of Topo II–etoposide cleavable complexes with DNA tracking enzymes, such as polymerases or helicases, generate DNA DSBs. The resulting DNA DSBs may lead to cell death by apoptosis. Through analysis of their dysfunction in otherwise normal cells, other duties involving DNA repair have been implicated. When not performing properly, mutation (Bae et al. 1988), sister chromatid exchange (Pommier et al. 1984, 1998; Downes et al. 1991) illegitimate recombination (Bae et al. 1988), DNA fragmentation (Kaneko and Horikoshi 1987), and tumor promotion (Downes et al. 1994; Andoh et al. 1987) may occur.

4.3 Topoisomerase-I Inhibitors Camptothecin, the parent compound (see Fig, 4.1), was initially isolated from the tree, Camptotheca acuminata, and was found to have a broad spectrum of activity in a variety of solid tumors through inhibition of Topo I (Chen and Liu 1994); however, early clinical trials with the ring-open form of the drug

M. Bastasch and H. Choy

showed excessive toxicity and the trials were terminated (Muggia et al. 1972). More recently, interest has been rekindled in these drugs with the advent of derivatives that have significant antitumor activity and much less toxicity. Irinotecan, one of these derivatives, is actually a prodrug which is metabolized intracellularily into SN-38 (Takimoto et al. 1998). SN-38 is approximately a 1000 times more potent inhibitor of Topo I than irinotecan (Kawato et al. 1991). All of the camptothecins have a terminal lactone ring with can be hydrolyzed to a less active carboxylate species; however, under acidic conditions, like those expected in a tumor’s microenvironment, the active lactone species is favored (Takimoto et al. 1998). After an intravenous infusion, SN-38 can have a plasma half-life of 5.9–13.8 h and this certainly can have implications in terms of both direct cytoxicity and radiosensitization abilities. The major method of SN-38 elimination is through hepatic glucuronidation, and it is felt that a decreased ability to glucuronidate the drug correlates with increased gastrointestinal side effects (Takimoto et al. 1998). One of the major side effects of irinotecan is late onset diarrhea. This is felt to be related to the high S-phase fraction of the intestinal mucosa as well as action of intestinal flora glucoronidase in cleaving the camptothecin-glucuronidase conjugate leading to the drug’s release into the intestinal lumen (Araki et al. 1993). Other common toxicities include neutropenia, nausea, vomiting, anorexia, fatigue, asthenia, and elevation of hepatic transaminases. Currently available camptothecin drugs include irinotecan (CPT-11), topotecan (9-aminocamptothecin; Lamond et al. 1996), 7-ethyl-10-hydroxycamptothecin (Kohara et al. 2002), and 9-nitro-20(S)camptothecin (RFS-2000; Amorino et al. 2000; see Table 4.1).

4.4 Topoisomerase-II Inhibitors

Fig. 4.1. Chemical structure of camptothecin

Etoposide (VP-16) is one of the most frequently used Topo-II inhibitors with specific action in late S or early G2 phase of the cell cycle. Etoposide forms a ternary complex with Topo II and DNA (Sakamoto et al. 2001). An early change in etoposide treated cells is an interruption in the transition from S phase prior to G2 arrest. Coinciding with this S-phase delay is a selective inhibition of thymidine incorporation into DNA and a severing of DNA strands. Very low doses of etoposide can initiate DNA strand inter-

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Table 4.1. List of Topo-I and Topo-II agents used with radiation in patients. CNS central nervous system Name

Type of inhibitor

Combined use with radiation

Topotecan

Topo I

Glioma CNS metastasis Cervix Lung

Irinotecan

Topo I

Lung Esophagus Rectum

9-nitro-20(S)-camptothecin (RFS-2000)

Topo I

Pancreas

Etoposide (VP-16)

Topo II

Lung

ruption. The suggestion is that DNA strand scission is the initial event in the sequence of kinetic and biosynthetic changes leading to growth inhibition and death of etoposide treated cells (Kalwinsky et al. 1983). In vitro data indicate that cytotoxic efficacy can be increased with chronic exposure. The more frequent the exposure, the higher the cytoxic effect (Dombernowsky and Nissen 1973). Given its availability as an oral agent, etoposide may be sequenced daily. In a phase-I trial, daily administration was tolerated in refractory lymphoma patients treated days 1–21 with tolerable hematological toxicity (Hainsworth et al. 1990). Similar trials have been conducted with refractory (Einhorn et al. 1992) and untreated (Clark and Cottier 1992) small cell lung cancer (SCLC).

4.5 Topoisomerase Inhibition Enhances Radiation In Vivo and In Vitro The principle mechanism of radiation’s lethality is the creation of irreparable DNA damage. Chemotherapy that disrupts normal DNA repair may act definitively to cause cell death or serve to complete partial damage caused by ionizing radiation thereby causing cell death (Ng et al. 1994; Amorino et al. 2000; Kim et al. 2002). The DNA strand breaks are a critical pathway by which ionizing radiation exerts a lethal effect on a cell. Chemotherapeutic agents that induce or prevent repair of DNA strand breaks may act synergistically with ionizing radiation to kill cells. The DNA topoisomerases are one such class of enzymes involved in DNA strand break repair. If the DNA topoisomerase enzymes are blocked, then transient DNA breaks cannot be repaired. Cells thus affected die. The effect of combining these

agents may be supra-additive. Preclinical data show that both Topo-I and Topo-II inhibitory agents can act as radiosensitizers (Kim et al. 1992; Kirichenko et al. 1997; Takahashi et al. 2003). Topo-I inhibition has enhanced radiosensitity through in vitro experiments with camptothecin derivatives in V-79 Chinese hamster cells (Marples et al. 1996), MCF-7 breast cancer cells (Chen et al. 1997), and human U1-Mel melanoma cells (Boothman et al. 1992). This effect has been seen in further in vivo experiments in murine MCa-4 mammary tumors (Kirichenko et al. 1997) and fibrosarcoma (Kim et al. 1992). Topo-II inhibition has been seen to enhance radiosensitivity in vitro in V-79 fibroblasts (Giocanti et al. 1993; Haddock et al. 1995; Marples et al. 1996) and human breast cancer cells (Iwata and Kanematsu 1999). Human clinical studies followed these encouraging preclinical results. The exact mechanism by which topoisomerase inhibitors act to sensitize cells to ionizing radiation is unknown. Stabilization of the cleavable complex of the topoisomerase and DNA occurs with inhibition (see Fig. 4.2). The cellular apparatus geared for DNA replication encounters this complex and apparently at this junction the cell becomes more sensitive to ionizing radiation. The replication forks in the DNA and the cleavable complex lead to several interactions: (a) a double-stranded DNA break; (b) arrest of the replication fork, and (c) an aborted DNA-topoisomerase complex. This is shown in Figure 4.3. This damage can be repaired over the course of time leading to the comparison to sublethal damage repair, SLDR, a known phenomenon in radiation; therefore, combining both agents can lead to a supra-additive effect whereby SLDR from either agent is rendered impotent leading to cell death that otherwise would not occur. The DNA Topo II helps the introduction of double-stranded DNA breaks and subsequent rejoining necessary for DNA replication. Etopo-

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TOP1 Non-cleavable complex

TOP1-targeted drug TOP1 Cleavable complex DNA replication fork in S-phase

Cell death

Fig. 4.2. Formation and proposed mechanism of Topo-I cleavable complex leading to cell death

Drug-trapped TOP1 Cleavable complex

tion of metabolic byproducts consisting of reactive oxygen species and hydroxyl radicals. These species could create abasic sites, potent position-specific enhancers of DNA Topo-II cleavage (Larsen et al. 2003). Radiation is a known cause of reactive oxygen species and hydroxl radicals through which some of its cytoxic effects are exerted. Some of the synergy between these two agents can be understood through this shared biochemical pathway. Topo-II, in addition to catalyzing the unwinding of DNA for replication, also serves as a recruiter for other proteins to arrive at their specific sites in chromatin domains, e.g., MAR/SAR regions, which are located in the base of the chromatin loops. Essential, well-known proteins, including the tumor suppressor proteins Rb and p53 and the protein kinases ERK2, CK2, and Cdc2 kinase, are recruited with the assistance of Topo II (Escargueil et al. 2001). Their inhibition by etoposide could inhibit repair of DNA damage caused by radiation and, therefore, prevent sublethal damage repair to “fix” sublethal to lethal damage.

DNA replication fork in S-phase

4.6 Lung

Aported TOP1 Cleavable complex

double-stranded DNA breaks

Radiosensitization

Replication fork arrest

Cytotoxicity

Fig. 4.3. Possible mechanism of radiosensitization (RS) by Topo-I inhibitors. The drug-trapped TOP1 cleavable complex may initiate TOP1-mediated RS by „interacting“ with replication fork during active DNA synthesis. Three major biochemical events, including double-strand DNA breaks, arrest of replication fork, and an aborted „cleaved“ TOP1–DNA complex, can be generated. It is plausible that one or a combination of these three events may be responsible for the induction of TOP1-mediated RS. The current data indicate the involvement of a currently undeﬁned repair process in the induction of TOP1-mediated RS and suggest that dissociation between the pathways leads to RS and cytotoxicity

side, a member of the epipodophyllotoxin family of chemotherapeutic agents and commonly used concurrently with radiation, forms a complex with the DNA and DNA Topo II. This complex decreases DNA rejoining and causes chromosomal breakage. The breakage leads to cell death. Additional actions of the epipodophyllotoxins include intrinsic produc-

4.6.1 Non-Small Cell Lung Cancer Topo-1 inhibitors have demonstrated activity in NSCLC (Chastagner et al. 2001). Concurrent administration of chemotherapy and radiation therapy in the definitive management of locally advanced NSCLC has been shown to improve outcomes (Clamon et al. 1999). While acute toxicities are increased compared with radiation therapy alone, they are tolerable. Irinotecan has been combined with radiation in phase-I and phase-II trials with demonstrated efficacy. Takeda et al. (2001) performed a phase-I/II trial of escalated doses of irinotecan with standard radiation of 60 Gy in 30 fractions over 6 weeks. Inclusion criteria were Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1, or 2, unresectable disease, non-small cell histology. Irinotecan doses started at 30 mg/m2 IV weekly concurrent with radiation to a maximally tolerated dose of 60 mg/m2. Yamada et al. (2002) investigated the maximally tolerated dose of irinotecan when combined with carboplatin in the same group of patients (unresectable Stage IIIA/B) treated with the same radiation parameters. That phase-II trial showed the maximally toler-

Combinations of Topoisomerase Inhibitors and Ionizing Radiation

ated dose to be 60 mg/m2 weekly with carboplatin dosed daily at 20 mg/m2. Toxicities were esophagitis, pneumonitis, neutropenia, and thrombocytopenia. Serious toxicities at the maximally tolerated dose level were two grade-4 cases and one grade-5 case of pneumonitis. The authors recommended a dose of irinotecan of 50 mg/m2 when combined with daily carboplatin. An objective response was noted in 60% of the patients’ tumors. The median survival time was 14.6 months with 1- and 2-year survival rates of 52 and 32%, respectively. Similar dosing conclusions had been drawn previously by Takeda et al. (2001) with a small study of 17 patients using a minimum of two 28-day cycles of carboplatin and irinotecan. Irinotecan was delivered intravenously days 1, 8, and 15 with carboplatin at an area under the concentration–time curve dose of 5 mg/ml u min (Calvert's formula) on day 1. An overall response rate of 35% was noted with median overall survival of 10.5 months and 1-year survival rate of 35%. Dose limiting toxicities were hematologic. The MTD was 60 mg/m2. They recommended a dose of 50 mg/m 2 for future trials (Takeda et al. 2001). The radiation field size was relatively large with the primary and elective nodal basin receiving a dose of 40 Gy and the primary disease sites receiving additional dose to 60 Gy. The lateral mediastinal margin was 1.5 cm and the ipsilateral supraclavicular fossa was treated from the cricoid cartilage to the middle of the clavicle. The impact of the additional normal lung volume by elective nodal irradiation may have contributed to the grade-4 and grade-5 pneumonitis experienced at the 60 mg/m2 dose level (Takeda et al. 2001). Typical doublet chemotherapy for NSCLC consists of a platinum compound coupled with another agent. Yokoyama et al. (1998) reported the results of a phaseI/II trial of irinotecan and cisplatin for patients with unresectable stage-IIIA/B NSCLC. Thirteen patients were enrolled with 12 being available for analysis for maximum tolerated dose on a schedule of one course of chemotherapy every 4 weeks for three cycles. Standard thoracic radiation was initiated on day 2 of cycle one consisting of 60 Gy in 30 fractions over 6 weeks. Of the 6 patients in the initial cohort, only four were able to complete the scheduled courses of chemotherapy because of associated hematologic toxicities. Only 3 of 6 patients at dose level two completed all planned chemotherapy. Irinotecan doses and radiation doses were low in the two initial cohorts leading to early termination of the trial. Emerging trends in radiation therapy include the refinement of radiation fields for lung cancer. The need for extensive fields in combined treatment

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with chemotherapy has been questioned as toxicity increases with field size and subclinical disease may be addressed adequately by chemotheraphy alone. To pursue combined modality therapy with acceptable toxicity, efforts have been undertaken to limit the radiation field to the known sites of disease with modest margins. Socinski et al. (2004) took this path while escalating the radiation dose with concurrent carboplatin and paclitaxel after induction chemotherapy of carboplatin, paclitaxel, and irinotecan. Sequential treatment with irinotecan failed to show promising results in a study by Scagliotti et al. (1996), consistent with findings of Radiation Therapy Oncology Group (RTOG) study 94-10 (Curran et al. 2000). Graham et al. (1996) investigated the use of another Topo-1 inhibitor, topotecan, with concurrent thoracic radiation for inoperable NSCLC in a phase-I trial. Using standard dose radiation of 60 Gy in 30 fractions over 6 weeks with large fields, primary tumor and mediastinum, the maximum tolerated dose was 0.5mg/m2. Toxicities were primarily hematologic and gastrointestinal (esophagitis and diarrhea with the former related to the inclusion of the mediastinum into the field). No patient had a report of pneumonitis. Although it is tempting to attribute that fact to a drug difference between topotecan and irinotecan, it is important to remember that the study by Takeda et al. (2001) with irinotecan, which showed several severe cases of pneumonitis at 60 mg/m 2, had an even larger field including the ipsilateral supraclavicular fossa.

4.6.2 Small Cell Lung Cancer Etoposide, a Topo-II inhibitor, has been in routine use with radiation for SCLC for many years (Sierocki et al. 1979; Turrisi et al. 1988). The current standard consists of cisplatin and etoposide concurrent and adjuvant to thoracic radiotherapy of 45 Gy delivered 1.5 Gy b.i.d. (Turrisi et al. 1999; Takada et al. 2002). Recent trial paradigms for limited stage SCLC have begun integrating irinotecan. The RTOG initiated a phase-I trial, RTOG 0241, using a fixed dose of cisplatin 60 mg/m 2 combined with sequential increases of irinotecan 40, 50, and 60 mg/m 2. Dose escalations occur until the dose limiting toxicity is met. The chemotherapy is given every three weeks. The trial has begun to accrue with radiation either being 45 Gy b.i.d. or 70 Gy in just one fraction per day. The radiation ports are limited to areas

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of known involvement at time of diagnosis without elective nodal irradiation. Sequencing of cisplatin and etoposide was the subject of a large Canadian trial. Maksymiuk et al. (1994) found the optimal sequence to be cisplatin 30 mg/m2 i.v. bolus followed by etoposide 130 mg/m2 bolus. Phase-I data for oncedaily radiotherapy concurrent with chemotherapy (cisplatin, etoposide, and cyclophosphamide) has shown the maximally tolerated radiation dose to be 70 Gy in 35 fractions of 2 Gy/day. For b.i.d. radiation, the maximally tolerated radiation dose with identical chemotherapy proved to be 45 Gy at 1.5 Gy b.i.d. (Choi et al. 1998). The phase-I study RTOG 97-12 showed that a total dose of 61.2 Gy with b.i.d. radiation given for the last 9 days of treatment was the maximally tolerated dose (Komaki et al. 2005). Patients received four cycles of cisplatin 60 mg/m2 day 1 and etoposide either orally 240 mg/m2 or i.v. 120 mg2 days 2 and 3. Reduction in tumor volume by induction chemotherapy has been shown to be acceptable if required in rare cases. It may be necessary in situations where the volume of normal lung treated exceeds tolerance. No increase in marginal failures developed with use of two to three induction cycles in case series (Arriagada et al. 1991). Thoracic radiation should be started as soon as possible for maximal benefit (Murray et al. 1993). With the advent of Topo-I inhibitors, their use is expanding. Topo-I inhibitors have shown efficacy combined with radiation and combined with a Topo-II inhibitor in patients with extensive stage disease (Sekine et al. 2003). Phase-III data indicate a difference in efficacy favoring combination cisplatin and Topo-1 inhibition with irinotecan in the treatment of extensive stage disease compared with cisplatin and Topo-2 inhibition with etoposide (Noda et al. 2002). Kubota et al. (2005) reported on alternating chemotherapy using both Topo-1 and Topo-2 inhibitors with accelerated hyperfractionation for limited stage SCLC. Using standard radiation doses for limited SCLC, 45 Gy at 1.5 Gy b.i.d., chemotherapy was one cycle of etoposide 100 mg/m 2 on days 1–3, and cisplatin 80 mg/m2 on day 1. Radiation started on day 2 and was completed over 15 treatment days after which irinotecan and cisplatin started on day 29. Irinotecan was given at 60 mg/m2 on days 1, 8, and 15, and cisplatin 60 mg/m 2 on day 1, with three 28-day cycles. The response rate was 97% (complete response, 37%; partial response, 60%). Median overall survival was 20 months; 1-, 2-, and 3-year survival rates were 76, 41, and 38%, respectively. Of the 30 patients evaluable, 22 received multiple courses of adjuvant chemotherapy. Similarly,

Johnson et al. (2003) reported on the use of combination Topo-1 and Topo-2 inhibitors combined with b.i.d. fractionated thoracic radiotherapy to 45 Gy. This phase-I trial used alternating fixed dosing of cisplatin 20 mg/m2 day 1 and etoposide 60 mg/m 2 days 1–3 or irinotecan. Three irinotecan doses, 60, 80, or 100 mg/m2, substituted for the etoposide. Radiation was given weeks 4–6 for patients with limited SCLC while on a course of cisplatin and etoposide. Granulocyte stimulating factor was administered on days 2–5 and days 4–7 after irinotecan/cisplatin and etoposide/cisplatin, respectively. Therapy lasted a total of 12 weeks. Irinotecan toxicity was acceptable up to the third dose level of 100 mg/m 2 and is the subject of further investigation. Despite prior phase-III data and a meta-analysis, irinotecan and cisplatin have been used neoadjuvantly in a recent trial of 35 patients (Han et al. 2005). Two cycles of induction irinotectan and cisplatin were given with excellent results, 97% objective response rate. Three patients had a complete and 31 had a partial response. Following induction chemotherapy, twice-daily radiation with a cisplatin/etoposide combination similar to that of Turrisi et al. (1999) was given yielding a 100% CR rate. Toxicities were not insubstantial, however. Hematologic toxicities predominated with 68% of patients suffering grade-3 to grade-4 neutropenia during induction and 100% during radiochemotherapy. With relatively short median follow up of 26.5 months, the median progression-free survival was 13 months and median overall survival was 25 months. The 1and 2-year overall survival rates were 86 and 54%, respectively. The rates reported previously were a median overall survival of 23 months with a 2-year overall survival rate of 47% for the b.i.d group at a median follow-up of 8 years (Turrisi et al. 1999). It is unclear what improvement from neoadjuvant chemotherapy with alternating agents for overall survival might be.

4.7 Gastrointestinal Tumors 4.7.1 Esophageal Cancer Standard treatment in the United States for inoperable cancer of the esophagus is chemoradiation with cisplatin, 5-fluorouracil, and radiation to 50.4 Gy at 1.8 Gy/day (Cooper et al. 1999; Herskovic et al.

Combinations of Topoisomerase Inhibitors and Ionizing Radiation

1992). Long-term results show that at 5 years 26% of patients with non-metastatic disease at diagnosis are alive with chemoradiation but with locoregional failure remaining a significant problem. Investigators looked for additional agents that might add further radiosensitization to address persistence of local disease. Ilson et al. (1999, 2003) reported on phase-I and phase-II trials looking at cisplatin and irinotecan combined with radiation for esophageal cancer. Nineteen patients with clinical stage-II to stage-III esophageal squamous cell or adenocarcinoma were enrolled. Induction chemotherapy with weekly cisplatin 30 mg/m2 and irinotecan 65 mg/ m2 was administered for four treatments during weeks 1–5. Radiotherapy was delivered weeks 8–13 in 1.8-Gy daily fractions to a dose of 50.4 Gy. Cisplatin 30 mg/m2 and escalating-dose irinotecan (40, 50, 65, and 80 mg/m2) were administered on days 1, 8, 22, and 29 of radiotherapy. The dose-limiting toxicity was defined as a 2-week delay in radiotherapy for grade-3 to grade-4 toxicity. Minimal toxicity was observed during chemoradiotherapy, with no grade3 or grade-4 esophagitis, diarrhea, or stomatitis. Myelosuppression caused the dose-limiting toxicity in 2 of 6 patients treated at the 80 mg/m 2 dose level; thus, irinotecan 65 mg/m2 was defined as the recommended phase-II dose. Dysphagia improved or resolved after induction chemotherapy in 13 (81%) of 16 patients who reported dysphagia before therapy. Only 1 patient (5%) required a feeding tube. Six complete responses (32%) were observed, including four pathologic complete responses in 15 patients selected to undergo surgery (27%). These data were further supported by another phase-I trial that found the maximum tolerated dose of irinotecan as a single agent concurrent with 50.4 Gy at 1.8 Gy/day to be 60 mg/m2 infused over 90 min weekly starting on day 1 of radiation. In this trial patients suffered principally from hematologic grade-3 or grade-4 toxicity with non-hematologic toxicities consisting typically of gastrointestinal, nausea, vomiting, dehydration, anorexia, hypothermia, and hypotension (Komaki et al. 2000). Another approach has been investigated using preoperative induction irinotecan and cisplatin chemotherapy followed by concurrent paclitaxel and radiation (Ajani et al. 2004). Forty-three patients with endoscopically proven locally advanced esophageal or gastroesophageal junction tumors were given irinotecan 70 mg/m2 and low-dose cisplatin 20 mg/ m2 once weekly for 4 weeks (one cycle) and then repeated 2 weeks later provided all toxicities were less than or equal to grade 1. Routine i.v. hydration

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and anti-emetic prophylaxis were given before chemotherapy. At the completion of the induction chemotherapy, patients started on a course of radiation to 45 Gy at 1.8 Gy/day to standard volumes (5 cm proximal and distal to the lesion and 2 cm lateral to the lesion). Concurrent chemotherapy was administered. Patients received 5-fluoruracil at 300 mg/m2 for 5 days per week by continuous infusion typically on a Monday-to-Friday schedule. Paclitaxel was given once weekly, typically on Mondays, at 45 mg/m2 on a 3-h infusion schedule. Surgery followed in 39 patients (91%), but the exact type was not prescribed by protocol. Objective disease responses were seen in 16 of the 43 patients (37%); no changes were noted in 24 (56%); and disease progressed in 3 (7%). Responses were gauged based on barium swallows, endoscopies, or both, 4–6 weeks at the end of therapy, as positron emission tomography was not used. The overall pathologic response rate was 63% (27 of 43). A quarter of patients had a pathologic complete response and an additional 37% had pathologic partial response. Overall survival with a minimum follow up of 28 months was 37%. Patients typically died from disease progression, whereas two deaths were from myocardial infarctions in the perioperative period. Patterns of disease recurrence changed from predominately local to distant with or without local disease. Future trials will be using irinotecan concurrently with radiation.

4.7.2 Rectal Cancer Rectal cancer has been the subject of investigations combining Topo-I inhibitors with 5-fluorouracil for metastatic patients. Improvements in disease control resulted in a change in the standard of care for metastatic patients (see chapter on rectal cancer). These results began to influence chemoradiation for locally advanced patients through a series of early phase trials. Investigators from Stanford University led a phase-II trial of protracted venous infusion 5-fluorouracil, weekly CPT-11 with radiation followed by surgery in patients with endoscopic ultrasound based staging (Mehta et al. 2003). Thirtytwo patients, most of whom had uT3N0 or uT3N1, entered the trial and received 45 Gy to the draining lymphatics followed by a boost to 50.4 Gy to the primary tumor that excluded small bowel. Standard fractionation of 1.8 Gy/day with three-dimensional conformal planning was used. Starting simultaneously with radiation, irinotecan 50 mg/m2 on days 1,

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8, 15, and 22, and 5-fluorouracil 200 mg/m2 daily 7 days a week on days 1–33, were given. The type of surgery was not prescribed in the protocol. Resection occurred 6–10 weeks after the completion of therapy. Toxicity from the neoadjuvant therapy was frequent with 18 patients (56%) requiring chemotherapy dose reductions or interruptions >3 days of radiotherapy. No grade-IV toxicity was seen, but grade-III toxicity was frequently observed; diarrhea in 9 (28%), mucositis in 7 (21%), rectal sores in 7 (21%), and abdominal cramping in 3 (3%). One patient withdrew from the trial after 10 days because of grade-III toxicity consisting of diarrhea and cramping. All patients underwent surgery with 12 (37.5%) showing a pathologic complete response. Downstaging occurred in 23 (71%). These results compare favorably with conventional regimens that have noted a 27% rate of pathologic complete response. The impressive downstaging results can be attributed partially to the delay until surgery in some patients, but these results are superior to those noted in the Lyon R90-01 multicenter, randomized controlled trial (26%; Francois et al. 1999). Hofheinz et al. (2005) conducted a phase-I trial combining capecitabine with irinotecan and radiation for 19 patients with locally advanced, T3/T4 NX, rectal cancer. Irinotecan was administered weekly at 50 mg/m2 days 1, 8, 15, 22, and 29. Capecitabine was prescribed at two different dose levels daily days 1 through 38. Dose level 1 was 500 mg/m2 b.i.d., and dose level 2 was 625 mg/m2 b.i.d. Patients received 45 Gy to the lymphatics with a boost to 50.4 Gy to the primary with three-dimensional conformal radiation at 1.8 Gy/day. Dose level 1 was tolerated without any dose limiting toxicities. Dose level 2 caused grade-3 diarrhea in three of seven patients. None of the 12 patients on dose level 1 required chemotherapy dose reductions in either drug. Only one patient suffered a grade-3 or grade-4 toxicity, a grade-3 asthenia. All patients underwent an R0 resection with four (21%) showing a pathologic complete response and an additional five (26%) with microscopic disease remaining.

4.8 CNS Tumors Investigators have examined the use of the TopoI inhibitor, topotecan, in both adult and pediatric populations combined with cranial radiation in the treatment of high-grade, primary CNS malignancies.

M. Bastasch and H. Choy

The interest in topotecan was driven by intriguing in vivo data in grade-IV glioma xenograft models (Chastagner et al. 2001; Ciusani et al. 2005). Children’s Cancer Group 0952 phase-I trial data on tolerance of pediatric patients with intrinsic, diffuse pontine glioma to daily i.v. topotecan showed the mean tolerated dose to be 0.40 mg/m2 (Sanghavi et al. 2003). Topotecan was infused 30–60 min prior to radiation. Of the 17 patients enrolled, 16 were able to complete therapy to 59.4 Gy at 1.8 Gy/day. The dose limiting toxicity was grade-IV neutropenia. Phase-II data have been reported in children with various brain tumors: grade-IV glioma; anaplastic astrocytoma; ependymoma; medulloblastoma/primitive neuroectodermal tumors; and diffuse intrinsic pontine gliomas (Turner et al. 2002). No concurrent radiation was administered. The patients received three cycles of topotecan i.v.125 mg/m2 weekly for 4 weeks followed by a 2-week break. Reassessment occurred at the end of each course with contrast-enhanced magnetic resonance imaging. Remarkable response in several patients occurred. Of the total 22 patients, 2 of 4 patients with recurrent grade-IV gliomas had a complete response lasting 9 and 48+ months. One of 4 patients with newly diagnosed grade-IV glioma of the midbrain had a partial response, leading to a delay in initiation of radiation by 18 months. None of the 5 patients with diffuse, intrinsic brain-stem gliomas responded. Only one of the 5 patients with recurrent ependymoma had a partial response for 11 months. Half of the patients suffered grade-II or grade-IV myelotoxicity, typically neutropenia, leading to dose reductions in seven. Subsequent phase-II data from the National Cancer Institute failed to find any complete or partial responders with high-grade CNS malignancies though stabilization of low-grade neoplasms was noted for prolonged periods (Blaney et al. 1996). These data are also supported by a phase-II trial in recurrent, pretreated high-grade glioma patients by the National Cancer Institute of Canada that assessed response to 1.5 mg/m 2/d for 5 days every 3 weeks (Macdonald et al. 1996). The trial found only a modest benefit with two patients (6%) of 31 with a response. In adults, phase-I data also assessed topotecan and radiation for biopsy-proven grade-IV gliomas (Grabenbauer et al. 2002). Three-dimensional conformal radiation therapy was used to deliver 1.75 Gy b.i.d. to 57.75 Gy. Concurrently, topotecan was given as a continuous infusion starting at a dose of 0.30 mg/ m2. The maximum tolerated dose was 0.7 mg/m2 per day with half the cohort suffering dose limiting toxicities. Three patients suffered febrile sinusitis, bac-

Combinations of Topoisomerase Inhibitors and Ionizing Radiation

terial sepsis, and grade-IV thrombocytopenia. The recommended dosing of topotecan was 0.6 mg/m2 per day on a 21-day infusion cycle. No significant toxicity from radiation was noted. Another phase-I trial used more conventional fractionation patterns, 60 Gy at 2 Gy/day, in patients with grade-IV gliomas (Fisher et al. 2001). The maximum tolerated dose of topotecan was 1.5 mg/m2 per day intravenously for 5 days every 3 weeks. The median survival of the 47 patients was 9.7 months. This trial’s successor was the phase-II trial RTOG 9513 and enrolled 87 patients. The addition of topotecan 1.5 mg/m 2 per day intravenously for 5 days every 3 weeks for three cycles concurrent with radiation failed to improve overall survival (Fisher et al. 2002). Additional phase-II trial data, however, arrived at a different conclusion about the efficacy of the addition of topotecan 1 h prior to standard radiation, 60 Gy at 2 Gy/day, for patients with grade-IV gliomas (Gross et al. 2001). The topotecan dose was 0.5 mg (absolute dose). The median cumulative dose of topotecan was 15 mg, range 7.5–18.5 mg. All but 3 of the 60 patients completed radiotherapy. Toxicity was acceptable with six cases of grade III and three cases of grade IV. Neurotoxicity appeared in 4 patients split evenly between grades III and IV. Two patients died of sepsis believed related to corticosteriod immune suppression. The median overall survival was 15 months. Different approaches with dose and administration of topotecan might improve the therapeutic ratio compared with radiation alone for high-grade gliomas in adults. Additional investigation into possible genetic differences between responders and nonresponders, especially in children, might elucidate the different results. This selection might improve outcomes in future trials. Further accumulation of data in children is warranted.

4.9 Head and Neck Tumors Local failure remains a problem in the control of head and neck cancers despite the integration of chemotherapy with radiation or alterations in fractionation. Cisplatin-based regimens have emerged as the standard (Fu et al. 1996). This drug is often combined with 5-fluorouracil, which independently can cause severe mucositis. Its use was tested in a phase-III randomized, controlled trial and found to improve local control but without additional benefit to overall survival (Jacobs et al. 1992). Altered

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fractionation also improves local control (Fu et al. 2000). Use of altered fractionation and cisplatin alone is being explored in an effort to improve local control (Ang et al. 2005). Improvements have been noted in the postoperative setting for locally advanced patients treated with radiation and cisplatin alone (Al-Sarraf et al. 1997; Cooper et al. 2004; Bernier et al. 2005). The addition of agents which do not cause mucositis but also exhibit activity against squamous cell cancers of the head and neck may result in further therapeutic gain with acceptable toxicity. Irinotecan has known activity as a single agent for recurrent squamous cell cancers of the head and neck, unlike topotecan or 9-nitro-20(S)-camptothecin (RFS-2000; Murphy et al. 2001). Its activity was modest exhibiting an overall response rate of 21%. Patients treated with it as a single agent had a median survival of 7 months and a 1-year survival rate of 30%. With results as modest as this, irinotecan would be considered as a single agent with radiation, but might become part of a doublet chemotherapy (Salama et al. 2005). Two early trials have assessed the impact of irinotecan combined with a second chemotherapy agent with radiation in the primary treatment of locally advanced head and neck cancer. Humerickhouse et al. (2000). elected to combine irinotecan with 5-fluorouracil and hydroxyurea with radiation in a phase-I trial in 16 patients. Patients either had recurrent or inoperable disease. The radiation schedule was hyperfractionated split course at 1.5 Gy b.i.d. for 2 weeks for four or five courses. The radiation fractionation schedule would not be considered standard today off protocol. Irinitotecan was given intravenously days 1–5 with radiation. The 5-fluorouracil was given as a continuous infusion days 1–5 along with hydroxyurea orally days 0–5 with each cycle of radiation. The maximum tolerated dose of irinotecan given daily with radiation and these other agents was 15 mg/m2. Only 14 patients were assessable for toxicity and eight for response out of the 16 enrolled. The grade-III to grade-IV mucositis rate was 10 of 14 (71%) patients. The grade-III to grade-IV dermatitis rate was 8 of 14 (57%) patients by third to fifth cycle. Of the patients available for assessment of response, only two had a complete response (25%); four had a partial response (50%); one had stable disease (12.5%); and one progressed (12.5%). Another preliminary trial of 12 patients investigated the use of irinotecan combined with docetaxel (Koukourakis et al. 1999). These patients had not

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been previously treated and had locally advanced primary tumors. All patients were stage IVA, T3N2/3, or T4N0. In contrast to the prior trial, standard radiation schedule and fractionation were used. The total dose ranged from 66 to 70 Gy in 33–35 fractions treated once daily without planned breaks. Both agents had planned escalations until dose limiting toxicities were reached. The maximum tolerated doses of docetaxel and irinotecan were 20 and 40 mg/m2, respectively, after two dose escalations of irinotecan. Eight patients successfully completed treatment with docetaxel 20 mg/m 2 and either 25 or 40 mg/m2, the initial two dose levels. Docetaxel dosing was not increased. Seven of the eight patients had a complete response and the other patient had a partial response. The results for the third dose escalation in which all four patients had such severe mucositis that a prolonged treatment break in radiation occurred were inferior. Two patients had a complete response, and two had a partial response. These results underscore the critical importance of duration of radiation in the successful management of rapidly dividing tumors. Some combination of altered fractionation and chemotherapy may become the standard of care for unresectable or locally advanced squamous cell cancers of the head and neck (Budach et al. 2005). Successful regimens likely need to contain a platinum agent and a second agent, perhaps initiated late in the course of therapy concurrent with radiation. As tumors are exposed to radiation, resistant clones begin to proliferate at the end of therapy. This fact makes overall treatment time an important variable in head and neck squamous cell cancer control. Optimized sequencing might help minimize treatment breaks from toxicity and aid in controlling accelerated repopulation of resistant clonogens.

4.10 Conclusion Evidence in multiple tumor types exists for enhanced radiosensitivity and supra-additive cell killing with the combination of topoisomerase inhibitors and ionizing radiation. Combinations of topoisomerase inhibitors have been shown to be additive for cell killing in a sequence dependent manner. An effective combination sequence was Topo-I inhibition followed by Topo-II inhibition in V79 Chinese hamster lung fibroblast lines (Bonner and Kozelsky

M. Bastasch and H. Choy

1996). Further work has shown this combination to be more efficacious when given simultaneously with radiation. Comparing the Topo-I inhibitor 9-nitro20(S)-camptothecin (RFS-2000) or etoposide alone with radiation or combined with radiation, Kim et al. (2002) noted increased radiosensitivity with the combination in human lung cancer lines. Given the synergism noted through the simultaneous suppression of both Topo I and II with radiation (Kim et al. 2002), intriguing combinations of oral agents, such as etoposide, 9-nitro-20(S)-camptothecin or oral irinotecan, capecitabine, and satraplatin, are possible. The ease of administration, decreased expense associated with oral agents, favorable toxicity profiles, and possibility for daily use with radiation as radiosensitizers argue for further studies of oral chemotherapy. A permutation in the use of conventional agents, such as intravenous irinotecan, might yield improvements. The Children’s Oncology Group recently opened ADVL0414, a phase-I study of temozolomide, oral irinotecan, and vincristine for children with refractory solid tumors (see Fig. 4.4). Should encouraging results be noted, continuation of this paradigm combined with radiation might be feasible and logical. Sequence might prove to be important with combination inhibition. Administration of Topo I followed by Topo II does not always provide synergism. Antagonism has been reported when topotecan was followed by etoposide in glial and medulloblastoma cell lines in vitro (Janss et al. 1998). These data were obtained with chemotherapy alone. Similar findings were noted in IL-60 human progranulocytic leukemia cells incubated in etoposide and then treated with a Topo-I inhibitor (Kaufmann 1991). In fact, simultaneous exposure resulted in 30-fold survival compared with treatment with etoposide alone. This inhibition extended to structurally unrelated TopoII inhibitors. By contrast, simultaneous administration of Topo-I and Topo-II inhibitors in human glial lines acted synergistically, even in cells that individually were resistant to both agents in vitro (Ciesielski and Fenstermaker 1999). With prolonged exposure to topotecan the timing of the administration of a Topo-II inhibitor failed to influence significantly the synergism. No radiation was given in this experiment with V79 cells (Cheng et al. 1994). Other data seem to indicate that such a sequence is logical. After administration of a TopoI inhibitor, levels of Topo IID rise (Whitacre et al. 1997). Based in part on this finding, lung cancer cells were treated sequentially with irinotecan or 9nitro-20(S)-camptothecin (RFS-2000) followed by

Combinations of Topoisomerase Inhibitors and Ionizing Radiation

Week

1

Day

1 T I V

63

2 2 T I

3 T I

4 T I

5 T I

3

8

9

10

11

12

I V

I

I

I

I

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Ceﬁxime will be started 5 days before week 1 day 1. and continued daily while on study Chemotherapy dose escalation scheme: Irinotecan

Temozolomide

Vincristine*

Dose level 1

30 mg/m2/day

100 mg/m2/day

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/day

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mg/m2/day

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100

2

100 mg/m /day

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* maximum dose 2 mg Fig. 4.4. Treatment scheme for Cooperative Oncology Group (COG) phase-I trial of oral irinotecan, temozolomide and vincristine, and ADVL 0414

radiation followed by etoposide (Kim et al. 2002). Antagonism was not demonstrated; instead, synergism was found. Dose enhancement ratios of 1.63 and 1.65 resulted with this sequence with irinotecan and 9-nitro-20(S)-camptothecin (RFS-2000), respectively. A small series of adult patients with a variety of refractory solid tumors received combination Topo-I and Topo-II inhibitory therapy. Relatively low efficacy was noted. Interestingly, biopsies of accessible tumors did not substantiate the purported upregulation of Topo II after Topo-I administration, nor did Topo-I levels fall as expected after Topo-I administration (Hammond et al. 1998). Variations based on the cell lines investigated and the effect of radiation might help to explain these contradictory findings. Future investigations looking at these variables will be needed prior to implementation into clinical trials to determine for each type of tumor the optimal integration of multiple topoisomerase inhibitors and radiation.

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M. Bastasch and H. Choy non-small-cell lung cancer: a dose-escalation phase-I trial. J Clin Oncol 22:4341–4350 Takada M, Fukuoka M, Kawahara M et al (2002) Phase III study of concurrent versus sequential thoracic radiotherapy in combination with cisplatin and etoposide for limited-stage small-cell lung cancer: results of the Japan Clinical Oncolo Gy Group Study 9104. J Clin Oncol 20:3054–3060 Takahashi T, Mitsuhashi N, Akimoto T et al (2003) Interaction of radiation and etoposide on two cell lines with different radiosensitivities in vitro. Anticancer Res 23:3459–3464 Takeda K, Negoro S, Takifuji N et al (2001) Dose escalation study of irinotecan combined with carboplatin for advanced non-small-cell lung cancer. Cancer Chemother Pharmacol 48:104–108 Takimoto CH, Wright J, Arbuck SG (1998) Clinical applications of the camptothecins. Biochim Biophys Acta 1400:107–119 Turner CD, Gururangan S, Eastwood J et al (2002) Phase II study of irinotecan (CPT-11) in children with high-risk malignant brain tumors: the Duke experience. Neurooncolo Gy 4:102–108 Turrisi AT, Glover DJ, Mason BA (1988) Concurrent twice-daily radiotherapy plus platinum-etoposide chemotherapy for the treatment of limited small cell lung cancer: a preliminary report. Antibiot Chemother 41:109–114 Turrisi AT, Kim K, Blum R et al (1999) Twice-daily compared with once-daily thoracic radiotherapy in limited small-cell lung cancer treated concurrently with cisplatin and etoposide. N Engl J Med 340:265–271 Wang JC (1985) DNA topoisomerases. Annu Rev Biochem 54:665–697 Wang JC (1991) DNA topoisomerases: why so many? J Biol Chem 266:6659–6662 Wang JC (2002) Cellular roles of DNA topoisomerases: a molecular perspective. Nat Rev Mol Cell Biol 3:430–440 Wang Z, Sinha BK (1996) Interleukin-1 alpha-induced modulation of topoisomerase I activity and DNA damage: implications in the mechanisms of syner Gy with camptothecins in vitro and in vivo. Mol Pharmacol 49:269–275 Whitacre CM, Zborowska E, Gordon NH et al (1997) Topotecan increases topoisomerase II alpha levels and sensitivity to treatment with etoposide in schedule-dependent process. Cancer Res 57:1425–1428 Yamada M, Kudoh S, Fukuda H et al (2002) Dose-escalation study of weekly irinotecan and daily carboplatin with concurrent thoracic radiotherapy for unresectable stage III non-small cell lung cancer. Br J Cancer 87:258–263 Yokoyama A, Kurita Y, Saijo N et al (1998) Dose-finding study of irinotecan and cisplatin plus concurrent radiotherapy for unresectable stage III non-small-cell lung cancer. Br J Cancer 78:257–262

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5

67

Combinations of Hypoxia-Targeting Compounds and Radiation-Activated Prodrugs with Ionizing Radiation G-One Ahn and J. Martin Brown

CONTENTS 5.1 5.2 5.3 5.3.1 5.3.2 5.3.3 5.3.4 5.4 5.4.1 5.4.2 5.4.3 5.4.4 5.4.4.1 5.4.4.2 5.4.4.3 5.4.5 5.4.5.1 5.4.5.2 5.4.5.3 5.4.6 5.4.7 5.4.7.1 5.4.7.2 5.5 5.5.1 5.5.2 5.5.3 5.5.4 5.6 5.6.1 5.6.2 5.6.3 5.7

Targeting Tumor Hypoxia 67 Oxygen-Level Enhancers 68 Hypoxia-Selective Radiosensitizers 69 Nitroimidazoles 69 Mixed-Function Radiosensitizers 69 DNA-Affinic Radiosensitizers 71 Limitations of HSR 71 Hypoxic Cytotoxins 72 Introduction 72 Combination of Hypoxic Cytotoxins with Ionizing Radiation 72 Nitroimidazoles 73 Other Nitroaromatics 73 CB 1954 73 SN 23862 and PR-104 74 RSU 1069 and RB 6145 74 Quinones 75 Mitomycin C 75 Porfiromycin 75 EO9 75 Benzotriene di-N-Oxides 76 Tertiary Amine N-Oxides 78 Nitracrine N-Oxides 78 AQ4N 79 Combination of Radiation-Activated Prodrugs with Ionizing Radiation 79 Concepts of RAP 79 Nitro(Hetero)Cyclic Methylquarternary Ammonium Salts 79 5-Fluorouracil (5-FU)-Releasing Prodrugs 81 Transition Metal Complexes 81 Other Hypoxia-Targeting Strategies 82 GDEPT Targeting Tumor Hypoxia 82 Clostridia-Directed Enzyme Prodrug Therapy 82 Targeting HIF-1 83 Conclusion 83 References 83

G. Ahn, PhD J. M. Brown, PhD Division of Radiation and Cancer Biology, Department of Radiation Oncology, Stanford School of Medicine, 269 Campus Drive, Center for Clinical Science and Research, Rm 1255, Stanford, CA 94305-5152, USA

5.1 Targeting Tumor Hypoxia Tumor hypoxia was first postulated from histological studies of human lung adenocarcinomas by Thomlinson and Gray (1955). They reasoned that, because of unrestrained growth, tumor cells are forced away from blood vessels beyond the effective diffusion distance of oxygen (O2) in respiring tissues, hence becoming hypoxic and eventually necrotic (Fig. 5.1a). Given the typical values for intracapillary O2 tensions and consumption rates, they calculated that O2 diffusion distances would be approximately 150 Pm and this was consistent with their histological observations (Thomlinson and Gray 1955). This type of hypoxia has come to be termed “chronic,” or “diffusion-limited,” hypoxia. Acute hypoxia also develops in tumors through temporal (reversible) cessation or reduction of tumor blood flow resulting from highly disorganized tumor vasculature (Fig. 5.1b; Brown 1979). Definitive evidence for acute hypoxia and fluctuating blood flow has been demonstrated in transplanted tumors in mice injected at some time apart with two different diffusion limited fluorescent dyes showing mismatch of labeled cells (Chaplin et al. 1986; Trotter et al. 1989); however, acute and chronic hypoxia are in fact the two ends of a continuum with fluctuations in blood flow without total occlusion, which are common in both experimental (Kimura et al. 1996) and human tumors (Hill et al. 1996), producing a dynamic situation with fluctuating oxygen diffusion distances in many parts of tumors. Tumor hypoxia is a major factor contributing to the failure of radiotherapy (Fig. 5.2). This is largely because DNA damage produced by ionizing radiation, which would otherwise become fixed and lethal to cells by reacting with O2 under well oxygenated conditions, can be restored to its undamaged form under hypoxic conditions (Brown and Wilson 2004). Clinically hypoxia predicts poor local control and survival of patients undergoing radiotherapy

G. Ahn and J. M. Brown

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a

b Fig. 5.1. a A diagram of a tumor capillary and surrounding tumor cells at decreasing oxygen concentrations (in the direction of arrows). Cells become hypoxic (green) and eventually necrotic (blue); chronic hypoxia. Cellular proliferation and chemotherapeutic drug concentration are also decreasing in the same direction, as a function of distance from the capillary. (From Brown 1999). b A diagram of normal (left) and tumor (right) blood vasculature. The tumor vasculature is highly disorganized resulting in acutely hypoxic regions in the tumor. (From Brown and Giaccia 1998)

Fig. 5.2. A Kaplan-Meier plot of overall survival of patients with head and neck carcinoma undergoing radiotherapy. Well-oxygenated tumors (pO2 >10 mmHg; dotted line) showed better prognosis than poorly oxygenated (pO2 <10 mmHg; solid line) tumors. (From Brizel et al. 1997)

teins, such as vascular endothelial growth factor (VEGF), are increased under hypoxic conditions, potentially resulting in increased tumor angiogenesis (Shweiki et al. 1992; Fang et al. 2001). Thus, there is substantial evidence that hypoxia both interferes with the effective therapy of solid tumors and contributes to a more malignant phenotype; however, hypoxia may also prove to be a therapeutic advantage: because it is virtually unique to tumor cells, therapies that target hypoxic regions may have the potential to kill malignant cells while leaving nonmalignant cells relatively untouched. This chapter discusses some examples of hypoxia targeting compounds and approaches for combination with ionizing radiation in experimental or clinical settings.

5.2 Oxygen-Level Enhancers for carcinoma of the head and neck (Nordsmark et al. 1996; Brizel et al. 1997), and cancer of the cervix (Hockel et al. 1993; Fyles et al. 1998). Hypoxia further complicates cancer management by limiting the access of conventional chemotherapeutic drugs (Fig. 5.1a; Brown and Wilson 2004). Hypoxia also increases genomic instability by increasing mutation frequency (Reynolds et al. 1996) or selecting for cells expressing an anti-apoptotic phenotype such as mutated p53 (Graeber et al. 1996). This leads to a more metastatic phenotype as has been observed clinically (reviewed by Rofstad 2000). In addition, expression of proangiogenic pro-

One of the earliest attempts to overcome the problem of the resistance of hypoxic cells in tumors to radiotherapy was to increase O2 levels in the blood stream, thereby increasing the diffusion distance of O2. A number of trials were performed with patients breathing 100% O2 at a pressure of 3 atmospheres, but the results were mixed (Watson et al. 1978; Dische et al. 1983; Henk 1986). One potential reason for such failures is that increasing the diffusion distance of O2 would not be expected to reduce the levels of acute hypoxia. In some systems, the use of carbogen (95% O2/5% CO2) appears to have

Combinations of Hypoxia-Targeting Compounds and Radiation-Activated Prodrugs with Ionizing Radiation

greater effect than 100% O2 in increasing O2 level in the blood stream (Rockwell 1997) possibly by preventing the vasoconstriction caused by high partial pressures of O2. Other potential approaches to overcome hypoxia include the use of nicotinamide (Horsman et al. 1987; Chaplin et al. 1991; Kjellen et al. 1991) in conjunction with carbogen (Corry and Rischin 2004), agents to increase tumor blood flow such as flunarizine (Jirtle 1988), artificial blood substitutes carrying increased levels of O2 (Teicher and Rose 1984; Rockwell et al. 1986), drugs to reduce the affinity of hemoglobin for O2 (Hirst and Wood 1989), blood transfusion (Bush et al. 1978), and hyperthermia (Song et al. 2001). Recently, RSR13, a drug reducing hemoglobin O2-binding affinity, has been claim to benefit non-small cell lung cancer patients receiving radiotherapy in phase-II trials (Choy et al. 2005).

5.3 Hypoxia-Selective Radiosensitizers In the 1960s Adams and Cooke (1969) proposed that electron-affinic drugs might act like O2, a potent electron-affinic molecule, to sensitize hypoxic tumor cells. These agents (hypoxia-selective radiosensitizers (HSR) mimic O2 by reacting with the short-lived DNA free radicals generated by ionizing radiation; however, unlike O2, HSR are not rapidly metabolized by the cells through which they penetrate and are thus able to reach areas beyond the O2 diffusion distance. Some examples of HSR are discussed below.

Metronidazole

Misonidazole

Pimonidazole

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5.3.1 Nitroimidazoles Metromidazole and misonidazole (Fig. 5.3) are the prototype members of this class. They were administered to patients in the 1970s. Disappointingly, they showed very little efficacy sensitizing tumors but a high incidence of peripheral neuropathy (Urtasun et al. 1976; Dische et al. 1977). With the limited dose of misonidazole that can be administered to patients, almost all of the clinical trials of radiotherapy combined with misonidazole were negative (Dische 1985); however, a meta-analysis of 50 randomized trials later showed a small but significant benefit of misonidazole and other hypoxic radiosensitizers when added to radiotherapy in head and neck cancers (Overgaard 1994). Attempts to produce superior drugs to misonidazole resulted in the development of etanidazole (Fig. 5.3; Brown et al. 1981), pimonidazole (Fig. 5.3; Smithen et al. 1980), and nimorazole (Fig. 5.3; Dische 1985); of these, nimorazole showed a significant benefit of loco-regional control when given in conjunction with radiotherapy to patients with invasive carcinoma of larynx and pharynx (Overgaard et al. 1998; Overgaard et al. 2005) and is now given as part of the standard of care for radiotherapy of head and neck cancer patients in Denmark (Table 5.1).

5.3.2 Mixed-Function Radiosensitizers The neurotoxicity of misonidazole stimulated the search for drugs not only with less toxicity, but also with increased efficiency as radiosensitizers on a

Etanidazole

Nimorazole

Fig. 5.3. Examples of nitroimidazole compounds as hypoxia-selective radiosensitizers (HSR)

Radical radiotherapy Split-course radiotherapy Conventional fractionation radiotherapy

Carcinoma of the cervix Invasive carcinoma of larynx and pharynx Advanced head and neck cancer

Conventional radiotherapy

Head and neck

Phase III

HSR

HSR, hypoxia-selective radiosensitizers

Head and neck

Phase II

HSR

Nimorazole

Carcinoma of the uterine cervix

Phase III

Conventional radiotherapy

422

61

183

Conventional radiotherapy

Continuous hyperfractionated accelerated radiation therapy (CHART)

521, 374

Conventional radiotherapy

Small-cell lung cancer Head and neck carcinoma

30

External beam radiation

Locally advanced prostate cancer 58, 39

523

626

73

331, 120

Conventional radiotherapy

Carcinoma of the uterine cervix

No. of patients 239

Type of radiotherapy

Locally advanced non- Conventional radiotherapy small cell lung cancer

Type of cancer

Pimonidazole HSR

Phase III

Phase II

HSR

Etanidazole

Type of trial

Phase III

Drug evaluation category

Misonidazole HSR

Name of drug

Table 5.1. Examples of nitroimidazole radiosensitizers and results from the clinical trials

Positive effect (better locoregional control rate and cancerrelated death)

Overgaard et al. (1998)

Henk et al. (2003)

Dische et al. (1993)

No signiﬁcant beneﬁt; unusually good response in the control arm Positive effect compared with previous CHART study

Lee et al. (1995); Eschwege et al. (1997)

Urtasun et al. (1998)

Beard et al. (1994); Lawton et al. (1996)

No signiﬁcant beneﬁt

No signiﬁcant beneﬁt

No signiﬁcant beneﬁt

Van Den Bogaert et al. (1995)

Overgaard et al. (1989b)

No signiﬁcant beneﬁt No signiﬁcant beneﬁt

Chan et al. (2004)

No signiﬁcant beneﬁt

Overgaard et al. (1989a); Grigsby et al. (1999)

Simpson et al. (1989)

No signiﬁcant beneﬁt No signiﬁcant beneﬁt

Reference

Outcome

70 G. Ahn and J. M. Brown

Combinations of Hypoxia-Targeting Compounds and Radiation-Activated Prodrugs with Ionizing Radiation

dosage basis. The latter strategy has been achieved by incorporating other functional moieties in the drug molecule. CB 1954 (2,4-dinitro-5-aziridinylbenzamide; Fig. 5.4) is an HSR-bearing DNA alkylating moiety

CB 1954

RSU 1069

Fig. 5.4. Examples of mixed-function compounds as HSR

of aziridine, which showed more efficient radiosensitization than misonidazole (Chapman et al. 1979). Similarly, RSU 1069 (1(2-nitro-1-imidazolyl)3aziridinyl-2-propanol; Fig. 5.4), the second generation of CB 1954, showed in vitro radiosensitization potency tenfold greater than misonidazole at equimolar doses (Stratford 1982; Adams et al. 1984); however, it appears that the more effective sensitizing ability of RSU 1069 is due to a greater degree of hypoxic cell cytotoxicity rather than to enhanced radiosensitizing ability (Hill et al. 1986). Both CB 1954 and RSU 1069 are discussed further as hypoxic cytotoxins in section 5.4.4.

5.3.3 DNA-Affinic Radiosensitizers This class of HSR incorporates a DNA-affinic moiety thereby attracting the drug molecule closer to DNA where they exert their radiosensitizing effect. Nitracrine, 1-nitroacridine derivative (1-nitro-9-(dime thylaminopropylamino)acridine; Fig. 5.5) showed 1700 times more efficient in vitro radiosensitization than misonidazole (Roberts et al. 1987); however the development of nitracrines as HSR was limited

Nitracrine

2-NLP-3 (n=3) or 2-NLP-4 (n=4)

Fig. 5.5. Examples of DNA afﬁnic compounds as HSR

71

by cellular metabolism occurring at 37qC (Roberts et al. 1987) and poor extravascular penetration through tumor cell layers (Wilson et al. 1986). 2-NLP-3 (5-[3-(2-nitro-1-imidazolyl)-propyl]-phenanthridinium bromide; Figure 5.5) and 2-NLP-4 (5-[3-(2-nitro-1-imidazolyl)-butyl]-phenanthridinium bromide; Fig. 5.5) are 2-nitroimidazoles attached to the DNA intercalator phenanthridine. They were shown to be 10–100 times more efficient as HSR than misonidazole both in vitro and in vivo (Cowan et al. 1991). The structurally similar compound, NLA-1 (9-[3-(2-nitro-1-imidazolyl) propylamino]acridine hydrochloride; Fig. 5.5) is a DNA-targeted acridine-linked 2-nitroimidazole (Papadopoulou et al. 1992). Although NLA-1 is a potent HSR in vitro, it lacked in vivo activity (Denny et al. 1992).

5.3.4 Limitations of HSR The major drawback of HSR is that the radiosensitization efficacy of HSR to tumors decreases at the radiation doses used in clinically relevant fractionated irradiation. Experimental results showed that 2–3 Gy fractionated irradiation resulted in lower enhancement ratios than single large doses for misonidazole (Denekamp and Stewart 1978; Hill and Bush 1978; Sheldon and Fowler (1978) or etanidazole (Brown and Yu 1984). One explanation for the lack of radiosensitization at fractionated low doses could be reoxygenation occurring between each fraction (Brown and Yu 1984); however, an equally likely reason is that it is not the cells at maximum radiation resistance, but those at intermediate oxygenation and intermediate radioresistance that dominate the response to fractionated irradiation (Wouters and Brown 1997). Though hypoxic cell radiosensitizers at clinically realistic doses can sensitize the maximally hypoxic cells to radiation killing, they have little effect on the radiosensitivity of the cells at intermediate hypoxia and radiosen-

NLA-1

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sitivity. This is a consequence of the logarithmic nature of the curve of radiosensitization vs dose: as cell sensitivity increases it takes geometrically more drug to increase their radiosensitivity still further; thus, a hypoxic cell partially sensitized by some oxygen takes much more drug to increase its sensitivity by a given amount compared with a fully hypoxic cell. It thus seems unlikely that hypoxic cell radiosensitizers – even newer ones with greater potency – have a major influence on the outcome of fractionated radiotherapy. They may, however, play a role – or probably should play a role – in those situations where large, single doses of radiation are given such as with stereotactic radiotherapy of brain tumors.

Selectivity for hypoxia is usually a result of a futile redox cycling in which the presence of O2 reoxidizes the one-electron reduced intermediate thereby regenerating the parent drug (Fig. 5.6a; Mason and Holtzman 1975). Superoxide anion (O2x-), a major by-product of this reaction, is capable of producing DNA strand breaks and other oxidative damage, but can be detoxified by superoxide dismutase and catalase (Biaglow et al. 1982). Hypoxia selective cytotoxicity therefore occurs when the reduction of the hypoxic cytotoxin produces a more toxic intermediate than the O2x- radical (Wardman et al. 1995; Wardman 2001).

5.4 Hypoxic Cytotoxins

Hypoxic cytotoxins are the ideal drug to combine with ionizing radiation because they produce a profile of cytotoxicity as a function of distance from blood vessels in tumors that are the opposite to that produced by ionizing radiation (Fig. 5.6b; Brown 1999). In other words, hypoxic cytotoxins kill the tumor cells that are resistant to ionizing radiation. In addition, hypoxic cytotoxins may release stable and diffusible cytotoxins capable of killing the surrounding tumor cells at relatively higher O2 concentrations, producing a so-called bystander effect (Denny and Wilson 1993). Unlike HSR, the efficacy of hypoxic cytotoxins is independent of the dose of radiation because there is no interaction between the two agents; hence, the benefit of adding a hypoxic cytotoxin to fractionated irradiation increases with the number of times the drug is administered and can produce greater benefit than if all of the tumor

5.4.1 Introduction An alternative strategy to overcome the problem of hypoxic tumor cells is to selectively kill them by using hypoxic cytotoxins. Typically these are prodrugs of very low cytotoxicity that are reduced by enzyme(s) in hypoxic tumor cells. This results in conversion to potent cytotoxins killing the activating cell and, in some cases, the surrounding cells. The development of hypoxic cytotoxins was originally stimulated by the findings that nitroimidazoles were more toxic to hypoxic than oxic tumor cells even without irradiation (Sutherland 1974; Hall and Roizon-Towle 1975).

5.4.2 Combination of Hypoxic Cytotoxins with Ionizing Radiation

a

Fig. 5.6. a The concept of hypoxic cytotoxins (indicated as D). Hypoxia selectivity is achieved by the futile cycle by oxygen converting the reduced intermediate (D•-) back to its nontoxic prodrug form (D). b The prediction of tumor cell killing by a hypoxic cytotoxin or radiation and most anticancer drugs as a function of the distance from the capillary. Note the opposite proﬁle in cytotoxicity towards tumor cells; the combination of the two should yield complementary cell killing and is shown as a dashed line. (From Brown 1999)

b

Combinations of Hypoxia-Targeting Compounds and Radiation-Activated Prodrugs with Ionizing Radiation

were fully oxygenated as shown in the theoretical study by Brown and Koong (1991).

5.4.3 Nitroimidazoles A general scheme (Fig. 5.7) for nitroheterocycle reduction is that the addition of an odd number of electrons (1, 3, 5) leads to radical intermediates, while an even number of electrons (2, 4, 6) leads to the nitroso (R-NO), hydroxylamine (R-NHOH), and amine reductants (R-NH2), respectively (Mason and Holtzman 1975; Perez-Reyez et al. 1980). Oxygen is able to reverse or inhibit reduction at the one-electron radical anion, although it could in principle act at various stages (Wardman and Clarke 1976). In the absence of O2, further reduction occurs primarily via disproportionation reactions of R-NO2x-, ultimately leading to the fragmentation of the imidazole ring (Varghese et al. 1976; Flockhart et al. 1978). Two- and four-electron reduced derivatives may have different stabilities and reactivities depending upon the nature of the aromatic ring and its substituents (McClelland et al. 1984). Some examples of this class of hypoxic cytotoxins are metronidazole, misonidazole (Fig. 5.8; Rauth et al. 1984), bis-nitroimidazole (Fig. 5.8; Hay et al. 1994;

73

Moselen et al. 1995), and NLCQ-1 (Papadopoulou et al. 2000). NLCQ-1 is a nitroimidazole-linked chloroquinoline (4-[3-(2-nitro-1-imidazolyl)-propylamino]-7-chloroquinone hydrochloride; Fig. 5.8), a member of NLP-1/NLA-1/THNLA-1 series, which is also an efficient HSR (Papadopoulou et al. 1994; Papadopoulou et al. 1996). It shows time-dependent increase in hypoxic cytotoxicity in vitro and is currently under preclinical evaluation (Papadopoulou et al. 2000; Squillace et al. 2000). In mammalian cells, aldehyde oxidase, DTdiaphorase, xanthine oxidase, NADPH:cytochrome P450 reductase, cytochrome b5 reductase, NADHdehydrogenase, and succinate dehydrogenase (Heimbrook and Sartorelli 1986; Walton and Workman 1987; Hodgkiss 1998) have been reported as nitroreductases.

5.4.4 Other Nitroaromatics 5.4.4.1 CB 1954

Though not strictly a hypoxic selective cytotoxin, CB1954 has been an important lead for the development of such agents. CB 1954 (Fig. 5.9) is a mono-

Fig. 5.7. The reduction of nitroimidazole hypoxic cytotoxins. R generalized nitroimidazole ring

Metronidazole

Bis-nitroimidazole

Misonidazole

NLCQ-1

Fig. 5.8. Examples of nitroimidazole compounds as hypoxic cytotoxins

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RSU 1069

CB 1954

SN 23862 RB 6145

Fig. 5.9. Examples of nitroaromatic hypoxic cytotoxins

functional alkylating agent that can be enzymatically activated to a potent difunctional alkylating agent which crosslinks DNA (Knox et al. 1988a; Knox et al. 1988b; Brown and Wilson 2004). Reduction of CB 1954 produces the potent cytotoxic metabolites, the 4-hydroxylamine, and 2-amine (Helsby et al. 2004). The activation of CB 1954 also occurs through a second activation step by a non-enzymatic reaction with a thioester (such as acetyl CoA) to form the final DNA reactive species, which is presumably 4-(N-acetoxy)-5-(aziridin-1-yl)-2-nitrobenzamide (Knox et al. 1991). The reduction of CB 1954 has been shown to proceed at about equal rates under aerobic and hypoxic conditions, presumably because the two-electron reduction by DT-diaphorase is not inhibited by O2. Currently, there is interest in CB 1954 in gene-directed enzyme-prodrug therapy (GDEPT) using Escherichia coli B. nitroreductase (Bridgewater et al. 1995; Green et al. 1997), and is in currently phase-I clinical trials (Chung-Faye et al. 2001; Dachs et al. 2005). 5.4.4.2 SN 23862 and PR-104

Structurally similar to CB 1954, a nitrogen mustard compound, SN 23862 (5-[N,N-bis(2chloroethyl)amino]-2,4-dinitrobenzamide; Fig. 5.9) exploits the nitro-group as an electronic switch in that nitro-to-amine conversion shifts electron density modifying the reactivity of a drug molecule (Siim et al. 1997; Helsby et al. 2003). The chemical reduction of each of the 2-nitro and the 4-nitro group of SN 23862 showed an increase in cytotoxicity by 160- and 9-fold in AA8 cell line, and by 4400and 83-fold in UV 4 cell line, respectively, and that the reduction of both nitro groups led to further increase in cytotoxicity (Palmer et al. 1995; Helsby

et al. 2003). Good bystander effect in both in vitro and in vivo systems together with substrate specificity to Escherichia coli B nitroreductase warrants development of SN 23862 for GDEPT (Anlezark et al. 1995; Wilson et al. 2002). PR-104 is a phosphate pre-prodrug of the dinitrobenzamide mustard PR-104A that is activated in hypoxia to become a potent bifunctional alkylating agent producing DNA interstrand crosslinks (Douglas et al. 2005). In addition, PR-104 has demonstrated substantial bystander effect killing aerobic as well as hypoxic cells in solid tumors (Wilson et al. 2005). Because of this ability to kill both aerobic and hypoxic cells in tumors PR-104 shows significant antitumor activity as a single agent alone. It is also superior to tirapazamine in combination with fractionated irradiation in preclinical models (Dorie et al., unpublished data). PR-104 entered clinical phase-1 trials in December 2005. 5.4.4.3 RSU 1069 and RB 6145

RSU 1069 (Fig. 5.9) is bioreductively activated by NADPH-cytochrome P450 reductase forming a bifunctional crosslinking agent (Stratford et al. 1986; Whitmore and Gulyas 1986). In air, RSU 1069 functions as a monofunctional alkylating agent due to the presence of the aziridine group (Stratford et al. 1986). It shows in vivo antitumor activity against KHT sarcoma and RIF-1 tumor when given before or after irradiation (Hill et al. 1986). The bromoethylamine derivative RB 6145 (Fig. 5.9) was developed as a prodrug of RSU 1069 because of irreversible gastrotoxicity observed in early phase-I trials of RSU 1069 (Horwich et al. 1986). RB 6145 showed slightly less hypoxia selective cytotoxicity than RSU 1069 in vitro (Jenkins

Combinations of Hypoxia-Targeting Compounds and Radiation-Activated Prodrugs with Ionizing Radiation

et al. 1990) but was active against hypoxic cells in vivo with lowered toxicity compared with RSU 1069 (Jenkins et al. 1990; Cole et al. 1990); however, further development of this compound was stopped because preclinical studies showed irreversible cytotoxicity toward retinal cells in mice (Parker et al. 1996; Breider et al. 1998).

5.4.5 Quinones 5.4.5.1 Mitomycin C

Mitomycin C (Fig. 5.10), isolated from Streptomyces caespitosus, was introduced into the clinic in 1958, and was subsequently shown to have a moderate in vitro hypoxia selective cytotoxicity [hypoxic cytotoxicity ratio (concentration of drug in air divided by concentration of drug in hypoxia to produce the same level of cell killing; Brown 1993) of about 1–5; Rockwell et al. 1982; Fracasso and Sartorelli 1986]. The cytotoxicity of mitomycin C is associated with formation of monofunctional alkylation and more potently with intra- and inter-strand crosslinks of DNA, all of which require bioreductive activation (Iyer and Szybalski 1963; Tomasz et al. 1987; Volpato et al. 2005). The one-electron reduction of mitomycin C results in a semiquinone, which under hypoxic conditions activates the aziridine ring and results in binding of the drug to DNA (Pan et al. 1984). Following the initial covalent attachment of mitomycin C to DNA, the drug can undergo further reductive activation to form a second alkylating site (Pan et al. 1984). The one-electron reduction pathway can be catalysed by any of several enzymes including NADPH:cytochrome P450 reductase (Pan et al. 1984; Keyes et al. 1984) and xanthine oxidase (Pan et al. 1984), in a process that can be reversed by O2 (Bachur et al. 1978; Bachur et al. 1979; Pritsos and Sartorelli

Mitomycin C Fig. 5.10. Examples of quinones

Porﬁromycin

75

1986). Mitomycin C can also be reductively activated via two-electron reducing DT-diaphorase generating an O2-insensitive hydroquinone (Iyanagi and Yamazaki 1970; Keyes et al. 1984). Despite variable results in hypoxia selective cytotoxicity observed in preclinical studies (Rockwell and Kennedy 1979; Rockwell et al. 1982; Keyes et al. 1984), clinical trials have reported that mitomycin C in combination with radiation shows a significant benefit in local regional control rates for patients with head and neck cancer (Weissberg et al. 1989; Haffty et al. 1993; Haffty et al. 1997), squamous cell carcinoma of the cervix (Roberts et al. 2000), and laryngeal and hypopharyngeal cancer (Saarilahti et al. 2004) (Table 5.2). 5.4.5.2 Porfiromycin

Porfiromycin (Fig. 5.10), a second-generation version of mitomycin C, showed superior in vitro hypoxic selectivity over mitomycin C as a result of lowered aerobic cytotoxicity (Fracasso and Sartorelli 1986; Rockwell et al. 1988) and an improved in vivo therapeutic index as a result of higher LD50 (the dosage required to kill 50% of the treated population) in mice (Keyes et al. 1985). Although a phase-I trial showed an acceptable toxicity profile, a recent phase-III randomized trial showed that porfiromycin was inferior to mitomycin C as an adjunct to radiotherapy in squamous cell cancer of the head and neck (Haffty et al. 2005). For this and other reasons (Brown (1999), it therefore seems unlikely that the clinical activity of mitomycin C is the result of its (modest) selectivity as a hypoxic cytotoxin. 5.4.5.3 EO9

EO9 ([3-hydroxymethyl-5-aziridinyl-2-methyl-2(H-indole-4,7-indione)-propenol]; Fig. 5.10) was originally developed as a synthetic analog of mito-

EO9

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5.4.6 Benzotriene di-N-Oxides Tirapazamine (SR 4233; Fig. 5.11a) is the prototype of this class of hypoxic cytotoxins. Under hypoxic conditions, tirapazamine is reduced to an O2-sensitive tirapazamine radical (Lloyd et al. 1991). The tirapazamine radical then eliminates a water molecule to form a nitrogen-centered oxidant, benzo-

a

Fig. 5.11. a Chemical structure of tirapazamine. b Synergistic activity of tirapazamine in killing SCCVII tumors in vivo when combined with fractionated irradiation (ﬁlled circles), determined by clonogenic cell survival. Tirapazamine alone and radiation alone (2.5 Gy per fraction) are shown as open circles and dots, respectively. From Brown and Lemmon (1990)

triazinyl radical, which can mediate the initial cytotoxic process by abstracting a hydrogen atom from the deoxyribose backbone of DNA (Anderson et al. 2003). The tirapazamine radical may also lead to the formation of the two-electron reduced product, SR 4317, a major non-toxic metabolite detected in cultured hypoxic cells (Baker et al. 1988; Hicks et al. 2003), in the mouse (Walton and Workman (1993), and in humans (Grahams et al. 1997). Formation of SR 4317 can occur by a number of different routes, including the direct two-electron reduction of tirapazamine by DT-diaphorase (Riley and Workman 1992), by radical disproportionation reaction, or by hydrogen abstraction from macromolecules other than DNA (Brown and Wang 1998). Tirapazamine has a unique O2 concentration dependency such that its cytotoxicity does not level off at high concentrations, but gradually decreases as the O2 concentration increases (Koch 1993; Hicks et al. 2004). Tirapazamine shows hypoxic cytotoxicity ratios of up to 200 in murine and 50 in human cell lines (Zeman et al. 1986). The hypoxic cytotoxicity of tirapazamine is due to the formation of DNA strand breaks resulting in chromosome aberrations (Beidermann et al. 1991; Wang et al. 1992; Siim et al. 1996). The chromosome breaks produced by tirapazamine were shown to be less easily repaired than those produced by X-rays, and this has been suggested to be a result of probable metabolism by reductases located close to DNA (Wang et al. 1992). Although a large proportion of tirapazamine is metabolized in the cytoplasm by enzymes, such as cytochrome P450 (Walton et al. 1992; Wang et al. 1993; Riley et al. 1993), NADPH cytochrome P450 reductase (Cahill and White

Relative clonogenic cells/tumor

mycin C (Oostveen and Speckamp 1987). The reductive bioactivation of EO9 occurs in a similar fashion to mitomycin C such that one- and twoelectron reduction processes yield the corresponding semiquinone and hydroquinone, respectively (Maliepaard et al. 1995). The semiquinone is believed to be more cytotoxic than the hydroquinone based on its ability to produce DNA interstrand crosslinks and strand breaks (Bailey et al. 1993; Plumb et al. 1994; Maliepaard et al. 1995). Although partial responses were observed in a small number of patients in phase-I trials (Schellens et al. 1994), no apparent antitumor activity by EO9 alone was demonstrated in phaseII studies in patients with advanced breast, gastric, pancreatic, and colorectal carcinoma (Dirix et al. 1996); however, some concerns about the design of the trials were raised in that enzymatic activity in patients’ tumors was not measured routinely (Phillips 1996) and that hypoxic cytotoxins, such as EO9, should be combined with other treatment modalities, such as radiotherapy or chemotherapy, to demonstrate detectable clinical responses (Workman and Stratford 1993).

Number of fractions

b

HSR and BEP

HSR and BEP

HSR and BEP

BEP

RSU-1069

RB-6145

NLCQ-1

Tirapazamine

RT, radiotherapy

BEP

AQ4N

Clinical Phase-II randomized trial

Phase I

Preclinical In vivo

Preclinical In vivo

Preclinical In vivo

Preclinical In vivo

Phase III

Locally advanced head and neck cancer

U251 human glioma xenograft

KHT sarcoma

Positive effect Positive effect (3-year failurefree survival rates; 3-year locoregional failure-free rates)

122 patients, deﬁnitive RT

No signiﬁcant beneﬁt Fractionated RT (4u1 Gy) 16 patients with conventionally fractionated RT

Additive effect

Additive effect

Additive effect

5-Gy single-dose RT

10-Gy single-dose RT

10-Gy single-dose RT

KHT sarcoma

Additive effect

Additive effect

Fractionated RT (5u3 Gy) Fractionated RT (5u3 Gy)

Additive effect

12-Gy single-dose RT

FSaIIC murine ﬁbrosarcoma

T50/80 murine mammary carcinoma

182 patients with conventional RT

120 patients with conventional RT

Rischin (2005)

Rischin et al. (2001)

Papadopoulou et al. (2005)

Cole et al. (1990)

Cole et al. (1990)

Teicher et al. (1991)

McKeown et al. (1995)

Positive effect (5-year disease-free Weissberg et al. (1989) survival and local recurrence free survival) Haffty et al. (1993)

Widder et al. (2004)

Saarilahti et al. (2004)

Reference

Squamous cell carcinoma of the head and neck

Positive effect

Positive effect

Outcome

Positive effect (4-year disease-free Roberts et al. (2000) survival)

21 patients with accelerated hyperfractionated RT

No. of patients and/or type of RT

Advanced squa160 patients with mous-cell carcinoma radical RT of the cervix

Advanced head and neck cancer

Advanced laryngeal and hypopharyngeal cancer

Phase II

BEP

Mitomycin C

Clinical

Type of cancer/ tumor evaluated

Name of drug Drug evaluation Evaluation Type of trial/ evaluation system category

Table 5.2. Potential candidates of hypoxic cytotoxins and their recent clinical/preclinical evaluation data

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78

1990; Lloyd et al. 1991; Walton et al. 1992; Wang et al. 1993; Patterson et al. 1995; Patterson et al. 1997), xanthine oxidase (Laderoute et al. 1988), and DT-diaphorase (Riley and Workman 1992; Wang et al. 1993), it is the nuclear metabolism of tirapazamine (ca. 20% of the overall cellular metabolism) that accounts for essentially all of the tirapazamine-induced DNA damage under hypoxic conditions (Evans et al. 1998; Delahoussaye et al. 2001). Recently, tirapazamine in hypoxic conditions has also shown to markedly inhibit DNA replication (Peters et al. 2001) and to poison topoisomerase-II activity (Peters and Brown 2002) in vitro leading to the suggestion that the DNA double-strand breaks produced by tirapazamine result from its poisoning topoisomerase II (Peters and Brown 2002). Tirapazamine potentiates cell killing with fractionated irradiation in mouse tumors (Fig. 5.11b; Brown and Lemmon 1990), and with cisplatin in a highly schedule-dependent manner (Dorie and Brown 1993). Tirapazamine is currently in phaseIII evaluation and appears particularly effective in combination with cisplatin (Rodriguez et al. 1996; Miller 1997; Treat 1998; von Powel 2000) or as an adjunct to cisplatin/radiotherapy treatment (Rischin et al. 2001; Rischin et al. 2005).

Nitracrine N-oxide a

b

5.4.7 Tertiary Amine N-Oxides 5.4.7.1 Nitracrine N-Oxides

Nitracrine N-oxide (Fig. 5.12a) was developed as a prodrug of nitracrine, a hypoxia cytotoxin whose cytotoxicity is due to nitroreduction that is inhibited by O2 (Wilson et al. 1986). While nitracrine showed the degree of hypoxic selectivity similar to misonidazole (ca. tenfold) in vitro, its metabolism was too rapid to provide selective killing of hypoxic cells in vivo (Wilson et al. 1986). Derivatization with tertiary amine N-oxide lowered DNA binding (15-fold), cell uptake, and aerobic cytotoxicity compared with nitracrine, while its hypoxic selectivity was greatly increased (1000- to 1500-fold; Wilson et al. 1992). The very high hypoxia selectivity was suggested to be due to a requirement for both the nitro and Noxide moieties for full activation in an O2 inhibitable manner (Wilson et al. 1992). Despite some improvement of extravascular diffusion properties observed in vitro (Wilson et al. 1992), in vivo activity against KHT tumors was only observed at doses lethal to the host (Lee et al. 1996).

AQ4N

Fig. 5.12. a Examples of tertiary amine N-oxide compounds. b Tumor growth delay of T50/80 in BDF mice treated with AQ4N. Combination with a single dose radiation (ﬁlled squares) produced a signiﬁcantly greater antitumor activity compared with AQ4N alone (open squares). (From McKeown et al. 1996)

Combinations of Hypoxia-Targeting Compounds and Radiation-Activated Prodrugs with Ionizing Radiation

5.4.7.2 AQ4N

AQ4N (1,4-bis-{[2-(dimethylamino-N-oxide)ethyl] amino}5,8-dihydrox yant hracene-9,10 -dione; Fig. 5.12a) is a prodrug designed to be prevented from binding to DNA (Patterson 1993; Smith et al. 1997b) until metabolized in hypoxic cells to give AQ4, a stable, oxygen insensitive metabolite (Smith et al. 1997a). AQ4 is a DNA intercalator and potent inhibitor of DNA topoisomerase II (Patterson 1993; Patterson et al. 1994; Smith et al. 1997b). Early development of AQ4N has been confounded by the lack of hypoxia selective activity in several cell lines; however, a large (>100-fold) increase in cytotoxicity of AQ4N was observed when cells were incubated under hypoxic conditions with liver microsomes (Patterson 1993). It was later shown that AQ4N is not activated by NAD(P)H-dependent cytochrome P450 reductase per se (Patterson et al. 1999), but by cytochrome P450 (CYP) isoforms. Several studies have shown that the metabolism of AQ4N correlates with levels of CYP1A1, 2B6, and 3A in humans (Patterson and McKeown 2000), 3A in mice (Patterson et al. 2000), and 2B and 2E in rats (Raleigh et al. 1999). Reduction of the two N-oxide functionalities of AQ4N has been suggested to be involved in an oxygen atom transfer from the N-oxide side chains in a process that is O2 sensitive (Patterson and McKeown 2000). Moreover, hemecontaining systems other than CYP, such as nitric oxide synthase, have also shown to mediate AQ4N reduction (Raleigh et al. 1998). AQ4N has shown in vivo antitumor activity when combined with radiation (Fig. 5.12b; McKeown et al. 1995), McKeown et al. 1996) or when combined with a range of methods inducing additional tumor hypoxia, e.g., hydralazine (Patterson et al. 2000), dimethylxanthenone acetic acid (Wilson et al. 1996), or clamping (Patterson et al. 2000). It is currently in phase-I clinical trials.

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prodrugs (RAP) are reduced by eaq- (aquated/ hydrated electron) generated from the radiolysis of water, offering two distinct mechanisms strongly inhibited by O2. These mechanisms involve either back-oxidization of the one-electron reduction intermediate of RAP (RAPx-) or to scavenge eaq- at diffusion controlled rate (Fig. 5.13; Other primary radicals formed by radiolysis of water (OHx and Hx) are expected to be scavenged at very high rates by other biomolecules. Some of the resulting organic radicals also have reducing properties so might make a further contribution to prodrug reduction. The RAP approach offers a number of potential advantages such as selective activation within the radiation field (tumor bearing volume); exploitation of necrotic hypoxic regions lacking reductase activity through release of a stable cytotoxin with a good bystander effect, no requirement for expression of specific reductase(s); lack of two-electron activation; and improved extravascular transport by allowing design of prodrugs that are not substrates for metabolism in tumors (Wilson et al. 1998). Some of the main classes of the compounds that have been considered as candidates for RAP are discussed below.

Fig. 5.13. The concept of radiation-activated prodrugs (RAP). Hypoxia selectivity occurs by the futile cycling of oxygen reverting the reduced intermediate of RAP (RAP•-) or scavenging hydrated electron (eaq-) generated from the radiolysis of water

5.5.2 Nitro(Hetero)Cyclic Methylquarternary Ammonium Salts

5.5 Combination of Radiation-Activated Prodrugs with Ionizing Radiation 5.5.1 Concepts of RAP Another way to target hypoxic tumor cells is to use ionizing radiation, rather than enzymes, to effect the reduction of the prodrug. Radiation-activated

NMQ ammonium salts such as 4-nitroimidazole (SN 25341; N,N-bis(2-chloroethyl)-N-methyl-N-[(1methyl-4-nitro-5-imidazolyl)methyl]ammonium chloride; 4-NIQ-HN2; Fig. 5.14a) and 5-nitropyrrole (N,N-bis(2-chloroethyl)-N-methyl-N-[(1-methyl5-nitro-1-pyrrolyl)methyl]ammonium chloride; 5NPQ-HN2; Fig. 5.14a) that were originally developed as hypoxic cytotoxins (Tercel et al. 2001), have also been reported as RAP that are reduced with

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80

SN 25341

a

b

4-NBQ-AMAC

5-NPQ-HN2

4-NIQ-AMAC

5-NPQ-AMAC

Fig. 5.14. a Examples of NMQ compounds as RAP. b Radiolytic activation of 4-NIQ-HN2 in human plasma determined as apparent IC50 against UV4 cells. Oxic (95% O2 and 5% CO2) and anoxic (95% N2 and 5% CO2) are shown in open and ﬁlled circles, respectively. The IC50 for authentic HN2 is also shown (ﬁlled square) with an arrow

one-electron stoichiometry by pulse and steadystate radiolysis (Anderson et al. 1997; Wilson et al. 1998). Irradiating 4-NIQ-HN2 in anoxic human plasma, followed by exposure to UV4 cells showed that IC50 (concentration of a compound giving 50% growth inhibition relative to the control cells) was markedly decreased with radiation, approaching a value equal to that of the cytotoxin, mechlorethamine (HN2), itself after ca. 20 Gy (Fig. 5.14b; Wilson et al. 1998); however, a relatively high one-electron

reduction potential of the prodrug (therefore susceptible for enzymatic reduction) and only modest cytotoxicity of HN2 limited their utility to that of only model compounds. In order to incorporate a more potent cytotoxin within the prodrug system, 4-NBQ-AMAC (Fig. 5.14a), 4-NIQ-AMAC (Fig. 5.14a), and 5-NPQAMAC (Fig. 5.14a) were synthesized. These prodrugs were two orders of magnitude less cytotoxic than the released cytotoxin (AMAC) against a panel of tumor

Combinations of Hypoxia-Targeting Compounds and Radiation-Activated Prodrugs with Ionizing Radiation

cell lines (Wilson et al. 1998). Irradiation in anoxic culture medium followed by exposure to UV4 cells showed significant activation of 4-NIQ-AMAC and 5-NPQ-AMAC at 2 Gy, although the yield of AMAC was lower than that for the HN2 analogs (Wilson et al. 1998). The AMAC prodrugs showed appreciable enzymatic reduction in hypoxic cell cultures, and convulsion in mice by a mechanism unrelated to the cytotoxin release (Wilson et al. 1998), suggesting that they are not likely to be useful as RAP prodrugs.

81

OFU001 (1-(2’-oxopropyl)-5-fluorouracil; Fig. 5.15) and OFU101 (Fig. 5.15) have been reported to release 5-FU and 5-fluoro-2’deoxyuridine (FdUrd), respectively, with higher efficiency (two-electron stoichiometry) in anoxic buffer upon irradiation (Shibamoto et al. 2000; Shibamoto et al. 2004). The mechanism proposed is that attachment of eaq-, generated by radiolysis of water, weakens the N(1)C(1’) bond that links 5-FU or FdUrd to the oxoalkyl side chain. Although these compounds showed cell killing after hypoxic irradiation, they failed to demonstrate any significant antitumor activity in vivo (Shibamoto et al. 2000, 2001, 2004).

5.5.3 5-Fluorouracil (5-FU)-Releasing Prodrugs Nishimoto et al. (1992) first reported that the N(1)-C(5)-linked dimer of 5-FU (1-(5’-fluoro-6’hydroxy-5’,6’-dihydrouracil-5’-yl)-5-fluorouracil) releases 5-FU with ca. three-electron stoichiometry by irradiation in anoxic aqueous buffer and some indication of antitumor effect in combination with radiation in mice bearing SCCVII tumors. Recently,

OFU001

OFU001

Fig. 5.15. Chemical structures of 5-FU prodrugs of RAP

Co(III) complex

5.5.4 Transition Metal Complexes A number of transition metal complexes, such as those of cobalt (III) (Co(III) (Fig. 5.16; Wilson et al. 1994; Ahn et al. 2004b) and copper (II) (Cu(II) (Fig. 5.16; Parker et al. 2004; Torre et al. 2005), have been reported as hypoxia-selective prodrugs. In particular, Co(III) complexes are kinetically inert when not reduced; however, when reduced radiolytically by eaq-, the inert d6 electron spin state of Co(III) becomes labile d7, which dramatically weakens the coordination bond hence releasing the cytotoxin (Fig. 5.17; Ware et al. 1993). A Co(III) complex bearing a very potent DNA minor groove alkylator cyclopropylindoline (Fig. 5.17) has demonstrated a number of attractive features as a RAP such as: a good masking of the cytotoxicity of cyclopropylindoline in the intact Co(III) complex; an efficient release of the cytotoxin with clinically relevant radiation dose of 2 Gy in anoxic human plasma

Cu(II) complex

Fig. 5.16. Chemical structures of Co(III) and Cu(II) complexes of hypoxic prodrugs

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82

Inactive

IR

eaq–

+

DNA alkylation Fig. 5.17. A Co(III) complex of cyclopropylindoline releasing its cytotoxin upon ionizing radiation (IR)

or buffer; cell exclusion property of the complex enhancing extravascular transport through multicellular tumor layers; a HCR of up to 20 in human colorectal HT29 cells (Ahn et al. 2002; Ahn 2003); however, further development of this Co(III) complex as a RAP has failed due to the lack of efficacy in RIF-1 bearing mice when combined with ionizing radiation (Ahn 2003).

5.6 Other Hypoxia-Targeting Strategies 5.6.1 GDEPT Targeting Tumor Hypoxia As discussed in section 5.1, many genes supporting anaerobic metabolism and angiogenesis are upregulated under hypoxic conditions by the transcription factor, hypoxia-inducible factor-1 (HIF-1). Specifically, HIF-1, once it heterodimerizes with D and E subunits, binds to a common hypoxia-responsive element (HRE) found in the enhancer region of all HIF-1 responsive genes (Semenza 2001). One GDEPT approach targeting tumor hypoxia aims to express an exogenous therapeutic gene by introduc-

ing an HRE sequence into an appropriate expression cassette (Dachs et al. 1997). With this system, studies have shown that in transfected tumor cells, NADPH:cytochrome P450 reductase enhances the antitumor efficacy of RSU 1069 or tirapazamine in combination with ionizing radiation (Patterson et al. 2002; Cowen et al. 2004). Another approach has shown antitumor activity with HRE driven nitroreductase enhancing the activity of CB1954 (Shibata et al. 2002). Dual responsive promoters have also been developed whose expression is driven not only by HRE but also by radiation-responsive promoter sequence such as the early growth response-1 (Egr-1) to enhance the reporter gene expression in response to hypoxia in conjunction with low dose of radiation (Greco et al. 2002; Chadderton et al. 2005).

5.6.2 Clostridia-Directed Enzyme Prodrug Therapy The above-mentioned GDEPT systems have the major drawback of utilizing ex vivo manipulated (transfected) tumor cell lines implying that their clinical applicability may be difficult. To overcome this limitation Brown and colleagues have exploited the

Combinations of Hypoxia-Targeting Compounds and Radiation-Activated Prodrugs with Ionizing Radiation

necrotic regions as a target for cancer therapy using a non-pathogenic strain of the bacterial genus Clostridium, an obligate anaerobe (Lemmon et al. 1994; Fox et al. 1996). This Gram-positive, spore-forming bacteria becomes vegetative and grows only in the absence or at very low levels of oxygen (Brown and Wilson 2004). Clinical studies in 1970s already have proven the safety of Clostridium and its tumor-specific germination (Carey et al. 1967; Heppner and Mose 1978; Heppner et al. 1983). Recently, genetically engineered Clostridium expressing E. coli enzyme cytosine deaminase showed tumor-specific delivery of the enzyme and the consequent antitumor activity upon 5-fluorocytosine (5-FC) prodrug administration (Liu et al. 2002; Ahn (2004a). The combination of CDEPT with ionizing radiation is expected to result in enhanced antitumor activity because of ionizing radiation killing well-oxygenated tumor cells and/or the radiosensitizing abilities of 5-FC and 5-FU.

5.6.3 Targeting HIF-1 In addition to its role in hypoxic conditions, HIF-1 can be upregulated in the tumor in an O2-independent manner. Oncogenic mutations and lossof-function mutations in tumor-suppressor genes have been shown to be associated with the increased activity of HIF-1 (Semenza 2003; Li et al. 2005). Evidence for HIF-1 serving as a potential target for cancer therapy is substantial and extensively reviewed elsewhere (Semenza 2003; Giaccia et al. 2003). For example, HIF-1D (the O2 sensitive HIF-1 subunit) expression has been shown to be a poor prognostic factor in a number of cancers including bladder cancer (Nakanishi et al. 2005; Theodoropoulos et al. 2004), pancreatic cancer (Shibaji et al. 2003), and breast carcinoma (Bos et al. 2003). HIF-1 is also reported to promote tumor growth in many studies (Ryan et al. 1998; Carmeliet et al. 1998; Chen et al. 2003; Stoeltzing et al. 2004). Some recent approaches targeting HIF-1 include using small molecule inhibitors blocking transcriptional activity of HIF-1 (Kung 2004; Kong et al. 2005) or those blocking HIF-1D protein synthesis (Tan et al. 2005), inhibitors of HIF-1 downstream target (Majumder et al. 2004; Zhong et al. 2004; Fang et al. 2005), enhancement of HIF-1D protein degradation (Li et al. 2004), and antisense (Sun et al. 2005) or RNA interference against HIF-1D (Li et al. 2005).

83

Interestingly, ionizing radiation has been recently shown to upregulate HIF-1 activity in tumors (Moeller et al. 2004); however, the effect of HIF-1 on the radiosensitivity of the tumor is controversial. Moeller et al. (2005) showed that functional HIF-1 enhances tumor radiosensitivity by promoting ATP metabolism, cell proliferation, and p53 activation, whereas others have reported that it is the deficiency in HIF-1 that increases tumor radiosensitivity, independent of p53 function (Unruh et al. 2003; Williams et al. 2005). The reason for this discrepancy is yet to be determined, but the difference in experiment systems (RNA interference vs cell lines deficient for either HIF-1D or -E) could have contributed.

5.7 Conclusion The potential clinical benefit of exploiting tumor hypoxia by combining a hypoxia activated drug with conventional cancer therapy has yet to be realized in routine clinical practice. Despite this, the positive clinical results with the combination of the hypoxic cytotoxin tirapazamine with cisplatin in advanced non-small cell lung cancer and with chemoradiotherapy with advanced head and neck cancer demonstrate the potential of this approach. There is a good reason to expect that future drugs or strategies will do better: indeed advances made in experimental models identifying the determinants of the efficacy of these hypoxia-targeting compounds, together with other strategies to exploit tumor hypoxia, auger well for the future of this field.

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Combinations of Platinum Compounds and Ionizing Radiation

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Combinations of Platinum Compounds and Ionizing Radiation Carsten Nieder and Florian Lordick

CONTENTS 6.1 6.2 6.2.1 6.2.2 6.2.3 6.2.4 6.3 6.4 6.5 6.6

Introduction 93 Cisplatin 93 Mechanisms of Action 94 Combinations with Ionizing Radiation 94 Perspectives for Cisplatin Combinations with Ionizing Radiation 95 Toxicity and Normal Tissue Data 96 Carboplatin 96 Oxaliplatin 97 Addition of Other Drugs to Platinum/Ionizing Radiation Regimens 98 Conclusion 99 References 99

6.1 Introduction The contemporary clinical concepts of multimodal oncology include combined administration of ionizing radiation and three different platinum compounds (cisplatin, carboplatin and oxaliplatin) in a variety of common solid tumors. Examples are sites such as head and neck, esophagus, lung, cervix uteri, rectum, and bladder. All these platinum drugs have demonstrated efficacy against a variety of cell lines, tumor xenografts, and human tumors. Yet, their effects vary with several molecular features of the cells, e.g., p53 status and expression of drug resistance proteins (Blumenthal et al. 2003, Weaver et al. 2005). Resistance also results from increased expression of the ERCC1 gene (excision repair crosscomplementing 1), which is involved in nucleotide

C. Nieder, MD Department of Radiation Oncology, Klinikum rechts der Isar der Technischen Universität München, Ismaninger Strasse 22, 81675 Munich, Germany F. Lordick, MD Third Department of Internal Medicine (Hematology/ Medical Oncology), Klinikum rechts der Isar der Technischen Universität München, Ismaninger Strasse 22, 81675 Munich, Germany

excision repair and the removal of DNA interstrand crosslinks, and other repair genes (Altaha et al. 2004). Both intrinsic and acquired drug resistance have been described. The simultaneous administration of platinum agents can be used to enhance the effects of radiation treatment, aiming either at additive cell kill or true radiosensitization (“radiopotentiation”) within the target volume, or to treat distant, out-of-field tumor sites based on the principle of spatial cooperation. Thereby, it is hoped to achieve a therapeutic gain. This chapter covers a broad range of mature and emerging data, published over several decades. Over time, our knowledge about cellular and molecular tumor biology and radiobiology has increased tremendously. Many of the methods used presently were not available at the time when early studies of platinum compounds took place. It should also be noted that this chapter does not contain any further discussion of platinum compounds that are clinically unavailable. Data on such agents is given by the following: Skov and MacPhail 1991; Monk et al. 1998; and Wang and Lippard 2005.

6.2 Cisplatin Discovered 40 years ago and initially recognized for its bacteriostatic effects (Rosenberg et al. 1965), cisdichlorodiammine-platinum(II) or cisplatin was found in 1969 to cause antitumor effects. In 1971, the drug was, for the first time, combined with irradiation in mice (Zak and Drobnik 1971) and subsequently was the first platinum-based drug entering the clinical practice of radiation oncology. Clinical reports date back to as early as 1981 (Creagan et al. 1981). The first randomized trial involved patients with bladder cancer, had an unusual design and a small number of patients, and compared intravesical cisplatin to combined cisplatin and radiotherapy (Hemstreet et al. 1984). Subsequently, positive ran-

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domized trials were published for cervical cancer and non-small cell lung cancer (NSCLC; Choo et al. 1986, Schaake-Koning et al. 1990). The latter three-arm phase-II study suggested that daily administration of cisplatin is superior to once a week application. Presently, a large variety of administration schedules are in clinical use, including daily dosing with 6 mg/m2, 20 mg/m2 day -1 on days 1–5 and 29–33 of fractionated radiotherapy, 40 mg/m2 day -1 on days 1, 8, 15, 22, 29, and 36, 100 mg/m 2 day -1 on days 1, 22, and 43, etc. Examples of such regimens are given in the organ-specific chapters of this book. Figure 6.1 shows the structure and molecular weight of cisplatin. As for all drugs, tissue concentration varies with blood perfusion. Heterogeneity of

Fig. 6.1. Structure and molecular weight of cisplatin

tissue concentration has been examined in various tumor models, e.g., in mouse B16 melanoma, human NSCLC xenografts (Zamboni et al. 2002), and the human prostate cancer cell line PC-3 M grown in nude mice, where the tumor concentrations ranged from 478 to 937 ppb (Coughlin et al. 1994). In the same article heating is shown to increase the amount of platinum uptake in dog prostate, possibly as a result of better perfusion. Another group examined the levels of platinum in murine mammary adenocarcinoma after intraperitoneal injection of 20 mg/ kg body weight cisplatin by atomic absorption spectrometry (Douple et al. 1988). The highest levels were found after 15 min, however, and at 30 min the concentration was still of the magnitude that produced potentiation of cell killing in those authors’ experience. The next prerequisite for drug efficacy is cellular uptake and avoidance of either efflux or inactivation, e.g., by glutathione or other sulphurcontaining molecules.

C. Nieder and F. Lordick

take place by passive diffusion, the chloride ligands are replaced by hydroxyl groups. This aquated, reactive form of the drug reacts with several proteins and DNA binding sites, as reviewed by Dewit (1987), and causes DNA-protein linkage and DNA interstrand and intrastrand crosslinks interfering with DNA replication and repair, including repair of doublestrand breaks (Taylor et al. 1976; Richmond and Powers 1976; Begg 1990; Amorino et al. 1999). The cellular responses include replication arrest, transcription inhibition, cell-cycle arrest and DNA repair via several signal transduction pathways (AKT, p53, MAPK/JNK/ERK, etc.) reviewed, for example, by (Wang and Lippard 2005). Cisplatin adducts might be removed by nucleotide excision repair mechanisms, following first-order kinetics. In cell culture, knockout of the nonhomologous end-joining (NHEJ) repair pathway did not change the response to cisplatin, whereas mutation of the homologous recombination repair pathway through XRCC3 resulted in increased radiation and cisplatin sensitivity (Raaphorst et al. 2005). Other data also demonstrate that yeast mutants in double-strandbreak repair by NHEJ and mutants in base excision repair showed no sensitivity to cis- or oxaliplatin (Wu et al. 2004). Recent work suggests that the cellular responses to cisplatin depend on DNA-activated protein kinase and DNA polymerase eta (Turchi et al. 1997; Albertella et al. 2005). It has been postulated that the loss of DNA mismatch repair is linked to the failure in detecting the DNA damage caused by cisplatin and to the lack of signal triggering the cell-death mechanisms (Fink et al. 1996). Putative defective repair of oxidative damage also resulted in sensitivity to cis- and oxaliplatin in yeast (Wu et al. 2004). Cell killing after higher drug doses appears apoptosis related, whereas after lower drug doses failure to overcome a G2 block is more important (Ormerod et al. 1994). In p53-mutated 9L rat gliosarcoma, intraperitoneal cisplatin (1 mg/kg) led to an increase in micronuclei formation, most likely indicating induction of mitotic catastrophe, but produced little or no apotosis (Driessens et al. 2003). The drug is not cell-cycle specific.

6.2.2 Combinations with Ionizing Radiation 6.2.1 Mechanisms of Action After transport into the cell, which appears to be linked to the copper metabolic pathway, but can also

If cisplatin is not given concomitant to radiotherapy, in vivo data from R1H rhabdomyosarcoma of the rat treated with 30 fractions of 2 Gy over either 6 or 3 weeks indicate that intraperitoneal drug admin-

Combinations of Platinum Compounds and Ionizing Radiation

istration (single dose of 5 mg/kg) 3 days after the end of irradiation is superior to cisplatin 3 days before the start of irradiation (Würschmidt and Beck-Bornholdt 1995); however, most experiments addressed simultaneous radiochemotherapy. Concomitant application might reduce the likelihood of acquired resistance compared with induction chemotherapy (Jackel et al. 1994) and reduces the overall time from initiation of any treatment to completion of local radiotherapy. In early experiments, cisplatin reduced the repair of sublethal radiation-induced damage, as defined by split-dose recovery, in exponentially growing rat hepatoma cells. In plateau phase, radiation sensitization was found (Carde and Laval 1981). Later, Dolling et al. (1998) reported inhibition of DNA double-strand-break repair when cisplatin was administered prior to radiation. In H460 human lung carcinoma cells, dose enhancement ratios of 1.2–1.4 were found for cis- and carboplatin (Amorino et al. 1999). Comparable figures were reported for RIF1 tumor cells (Begg et al. 1986), different lung cancer cells (Groen et al. 1995) and prostate cancer cells, again for cis- and carboplatin (Geldof and Slotman 1996). Some authors suggested that similar effects were observed in well-oxygenated and hypoxic cells (Skov and MacPhail 1991). When cis- or carboplatin were present at the time of irradiation, higher enhancement ratios were observed compared with administration 24 h prior to or 3 h after irradiation (Schwachöfer et al. 1991). As seen in some of the in vitro studies, results of animal tumor models were also heterogenous. An example where only additive effects were seen is the SSK2 fibrosarcoma of the mouse (Höglmeier et al. 1985). Overgaard and Khan examined mouse mammary tumors exposed to radiotherapy with or without 6 mg/kg cisplatin administered intraperitoneally 30 min before irradiation (Overgaard and Khan 1981). The dose modification factor in these TCD50 experiments was 1.8, compared with 1.3 if the drug was given 30 min or 4 h after irradiation. Kallman (1994) reported a large set of animal experiments where fractionated radiotherapy was combined with cisplatin. Tumor growth inhibition (RIF-1 and SCCVII tumors) and three normal tissue end points (duodenal crypt cell survival, lung toxicity after 5 and 10 months, respectively) were assessed. With few exceptions, the greatest therapeutic gain was achieved with multiple doses of cisplatin administered simultaneously with five daily fractions of radiotherapy. Joschko et al. (1997) studied FaDu squamous cell carcinoma in nude mice treated

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with twice-daily 2-Gy fractions, applied 6 h apart over 2 weeks, 5 days a week. Cisplatin was given at maximally tolerated doses either as a single bolus, a daily bolus 30 min before the first fraction of that day, or as a continuous subcutaneous infusion. The end point was tumor growth delay. In contrast to the additive effect of single bolus dosing, daily bolus and continuous infusion resulted in greater than additive effects. Greater than additive effects of cisplatin and radiation are seen in tumor models most reliably when fractionated irradiation regimens are tested (Douple et al. 1977; Bartelink et al. 1986; Tanabe et al. 1987). Most likely, this reflects the platinum interaction with sublethal damage repair (Carde and Laval 1981; Begg et al. 1987). Fractionated irradiation of tumor cells in vitro might induce resistance to cisplatin (Hill et al. 1990). In cultured glioma cells, this effect was independent of p53 function (Yount et al. 1998). Whether this would decrease cell killing at the end of a fractionated treatment regimen with multiple cisplatin administrations over several weeks or would interfere with the effectiveness of post-radiation adjuvant chemotherapy remains unanswered because of a lack of systematic experiments on this subject. Some reports suggest that cisplatin-resistant cells are also resistant against ionizing radiation (De Pooter et al. 1991; Twentyman et al. 1991); however, contradictory in vitro data on this hypothesis have also been published (Oshita et al. 1992; Caney et al. 2004).

6.2.3 Perspectives for Cisplatin Combinations with Ionizing Radiation Recently, the combination of cisplatin with monochromatic synchrotron irradiation at 78.8 keV was studied (Biston et al. 2004). This treatment just above the 78.4 keV platinum absorption Kedge leads to an enhanced photoelectric effect and caused an extra number of more slowly repaired double-strand breaks in F98 glioma cells. Treatment of glioma-bearing rats resulted in encouraging survival. Another preclinical development is treatment with radioactive (191)Pt-cisplatin, which was shown to induce a more pronounced growth delay of human squamous cell carcinoma in nude mice than cisplatin (Areberg et al. 2001). Intratumoral pre-irradiation delivery of cisplatin is effective in animal models, but might be difficult to achieve in the clinic (Yapp et al. 1998; Ning et al. 1999). Sup-

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pression of repair gene expression, such as ERCC1, by small interfering RNAs (siRNAs) might enhance the sensitivity of tumor cells to cisplatin (Chang et al. 2005). Prediction of individual tumor sensitivity, e.g., by uncovering genetic polymorphisms of DNA repair genes, has not yet entered clinical routine. Preliminary, retrospective clinical data suggest that polymorphisms, e.g., of XRCC1, may also be important prognostic factors for patients treated with platinum-based regimens (Gurubhagavatula et al. 2004).

6.2.4 Toxicity and Normal Tissue Data The major side effects of cisplatin include emetogenicity, nephrotoxicity, ototoxicity, and neurotoxicity. The need for hydration excludes patients with moderate to severe cardiac insufficiency from treatment. Several authors examined the effects of cisplatin plus ionizing radiation on normal tissues. Systematic experiments in rat kidneys indicated that single bolus injection of maximum tolerated dose cisplatin 1 day or 1 week before single-dose irradiation results in increased damage with a dose modification factor of 1.6 (Van Rongen et al. 1994). The same effect was observed for fractionated irradiation. However, the fractionation sensitivity of the kidney remained unchanged; thus, administration before fractionated radiotherapy is not expected to result in extra kidney toxicity. In human fetal lung fibroblasts cisplatin plus irradiation did not result in more than additive toxic effects (Basham et al. 1989). Yet, the same observations were made in HeLa and human melanoma cells by this group.

6.3 Carboplatin In chronological order, cis-diammine (1,1-cyclobut anedicarboxylate)platinum(II) (carboplatin, Fig. 6.2) was the second compound that became part of clinical treatment protocols, although carboplatin often exhibits cross-resistance with cisplatin (Table 6.1). In 20 cervical cancer cell lines, 30% of the tumors resistant to cisplatin were also resistant to carboplatin (Monk et al. 1998); however, the toxicity profile is advantageous. Carboplatin has greater chemical stability than cisplatin and longer half-lives of ultrafilterable platinum (23 and 120 min vs 6 and 36 min

C. Nieder and F. Lordick Cis-diammine (1,1-cyclobutanedicarboxylate) platinum(II) (carboplatin) Molecular weight 371

1,2-diaminocyclohexaneoxalatoplatinum(II) (oxaliplatin) Molecular weight 397

Fig. 6.2. Structure and molecular weight of carbo- and oxaliplatin

for distribution and initial elimination half-lives, respectively; Van der Vijgh 1991). The terminal halflives are comparable (5–6 days). It forms a similar spectrum of DNA adducts as cisplatin with slightly different sequence preferences (Blommaert et al. 1995). In order to obtain equivalent DNA platination levels, higher concentrations of carboplatin are needed. The sensitivity of squamous cell carcinoma cell lines to carboplatin differs at least by a factor of 4 (Pekkola-Heino et al. 1992). In these experiments, no cross-resistance was observed between inherent radiosensitivity and chemosensitivity. When administered 1 h before irradiation to carboplatin-sensitive cell lines, additive effects were observed. It has also been suggested that increasing radiation doses enhance intracellular carboplatin concentrations and, specifically under hypoxic conditions, the binding of the drug to DNA double strands (Yang et al. 1995b). Radiation-induced free radicals might also enhance the formation of toxic derivatives of cisplatin (Richmond and Mahtani 1991). Carboplatin enhances the production and persistence of radiation-induced DNA single-strand breaks (Yang et al. 1995a) and reduces cell survival after radiation treatment measured by clonogenic assays (supra-additive effect; Scalliet et al. 1999). In two cell lines proficient in both excision repair and DNA

Combinations of Platinum Compounds and Ionizing Radiation

double-strand break repair, and in a cell line deficient in nucleotide excision repair, carboplatin before and during irradiation enhanced radiation-induced cell killing (Yang et al. 1995c). In air and under hypoxic conditions, the enhancement was characterized as both a reduction in the shoulder region of the survival curves (reduced Dq) and a reduction in D0 in the terminal region of the survival curves. Only the latter effect was observed in a cell line deficient in DNA double-strand-break repair. Enhancement ratios ranged from 1.3 to 1.7, irrespective of oxygenation. Drug levels sufficient to produce cytotoxicity by themselves were required for the effect of radiation enhancement. In the extreme case, only 1 of 30 of the drug concentration required for other cell lines produced enhanced cell killing, as seen in the intrinsically sensitive UV41 cells. In a mouse model of Ehrlich ascites tumors, combined treatment was compared with a single dose of carboplatin alone and a single dose of radiation alone. Tumor growth delay was better with simultaneous combined treatment than each modality alone (Aratani et al. 1997). In vivo studies of human small cell lung cancer tumors transplanted into rats suggest that carboplatin administered 24 h before irradiation may be effective also in cisplatinresistant tumor cells (Fokkema et al. 2003). The most common dose-limiting side effect of carboplatin is myelosuppression. Compared with cisplatin, there is less need for hydration. In rat kidneys, maximum tolerated dose carboplatin showed a maximum dose modification factor of 1.1 when given with single fraction radiotherapy (van Rongen et al. 1994). No enhancement was seen with fractionated radiotherapy. In addition, there was no

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change of the alpha/beta ratio, suggesting that carboplatin can safely be administered in conjunction with fractionated radiotherapy when the kidney is close to the radiation portals. In mouse lip mucosa there was also no influence of carboplatin on the response to single dose irradiation, the capacity to repair sublethal radiation damage, and the ability to repopulate (Landuyt et al. 1987).

6.4 Oxaliplatin Oxaliplatin (1,2-diaminocyclohexaneoxalato platinum (II)), a third-generation lipophil platinum drug, contains a 1,2-diaminocyclohexane ring in its structure (Table 6.1). This drug has less hematologic toxicity and lacks nephrotoxicity (Raymond et al. 1998). The dose-limiting side effect is peripheral neurotoxicity. The parent compound undergoes hydrolysis to form the effective reactive species. The distribution half-life of ultrafiltrated plasma platinum ranges from 10 to 25 min and its terminal elimination half-life determined by flameless atomic absorption is 26 h (Levi et al. 2000). Cisplatinresistant cell lines tend not to be resistant to oxaliplatin. Furthermore, oxaliplatin was more effective in several animal tumor models. Despite the fact that oxaliplatin forms covalent adducts with DNA that have sequence and region specificity similar to those formed by cisplatin, they are more cytotoxic (Pendyala and Creaven 1993; Woynarowski et al. 1998). It has recently been shown that cellular proteins, e.g., mismatch repair proteins, recognize

Table 6.1. Examples of in vitro results with different platinum compounds. IC50 inhibitory concentration at 50% survival, DER dose enhancement ratio, 5-FU 5-ﬂuorouracil Reference

Cell line

Drug

Mean IC50

Radiation DER

Amorino et al. (1999)

H460 lung carcinoma

Cisplatin

7 PM

1.31

Amorino et al. (1999)

H460 lung carcinoma

Carboplatin

110 PM

1.20

Monk et al. (1998)

Cervical cancer cells from 20 patients

Cisplatin

0.73 Pg/ml

Not tested

Monk et al. (1998)

Cervical cancer cells from 20 patients

Carboplatin

18.6 Pg/ml

Not tested

Rixe et al. (1996)

Human cervix cancer KB 3-1, cisplatin resistant

Oxaliplatin

2.3 PM

Not tested

Raymond et al. (1997)

Human colon cancer HT29, 5-FU resistant

Oxaliplatin

1.7 PM

Not tested

Raymond et al. (1997)

Human breast cancer MCF-7, doxorubicin resistant

Oxaliplatin

12.2 PM

Not tested

C. Nieder and F. Lordick

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oxaliplatin adducts differentially (Chaney et al. 2005) and that the effects of oxaliplatin when compared with cisplatin are less dependent on intact mismatch repair (Raymond et al. 2002). Further differences exist regarding postreplicative bypass mechanisms. DNA polymerase beta and eta catalyze translesion synthesis past certain oxaliplatin adducts with greater efficiency than past cisplatin adducts. Like cisplatin, interstrand crosslinks appear to be important toxic lesions caused by oxaliplatin (Wu et al. 2004). Oxaliplatin showed synergistic effects with 5fluorouracil (5-FU) as well as radiosensitization in human colon cancer cells (Kjellstrom et al. 2005). Additional data suggest that these effects might vary with p53 status of the colon cancer cell line (Magne et al. 2003). In p53 wild type SW403 cells, additive-synergistic effects were observed when the best sequence was administered, i.e., irradiation 2 h before or at mid-drug application. Oxaliplatin was given over 2 h followed by 5-FU/folinic acid over 24 h. In p53 mutated WiDr cells, additive-antagonistic effects were seen, irrespective of sequence. Radiosensitization was also found in head and neck cancer cell lines (Espinosa et al. 2005). In vivo data generated with transplanted mammary adenocarcinoma, but with the disputable end point of tumor growth delay rather than cure, suggest that sequence and time interval of radiation treatment and oxaliplatin do not influence the results for single-dose treatments (10 Gy and 6 or 10 mg/kg; Cividalli et al. 2002). With ten daily fractions of 2 Gy, however, the drug increased the efficacy of radiation treatment better when administered only twice during the treatment course as compared with daily.

6.5 Addition of Other Drugs to Platinum/ Ionizing Radiation Regimens The potential of adding other drugs, such as 5-FU, to combined radiation plus cisplatin was demonstrated already more than 20 years ago (Dionet and Verrelle 1984). Based on their mode of action, cross-resistance, cell cycle specificity, and role in cell cycle arrest, rational combinations of platinum drugs with other compounds were found to display additive or synergistic effects, reviewed by Raymond et al. 2002, and entered preclinical testing, usually without administration of ionizing radiation (Table 6.2). Most of these were optimized in sequential clinical trials and are now in routine use in many countries. Considering the widespread use of ionizing radiation with drug combination regimens that have evolved based on clinical studies, the question needs to be addressed of whether experimental data support and reflect the theoretical basis for administration of these combinations. Surprisingly, there is only a limited set of experimental data available, e.g., for cisplatin and 5FU in mouse lymphoma cells (Nagy et al. 2002) and cis- and carboplatin with 5-FU in an in vivo mouse leukemia model (Dionet et al. 2002). It is hoped to further increase the therapeutic efficacy of radiotherapy plus cisplatin/5-FU by adding, for example, antiangiogenic agents. In a recent experiment in mice bearing Lewis lung carcinoma, this approach was successfully studied, although it is noteworthy that no TCD50 end points are available (McDonnell et al. 2004). It has been demonstrated that the hypoxic cytotoxin tirapazamine can preferentially sensitize solid tumors to cisplatin both in preclinical models

Table 6.2. List of other chemotherapeutic agents that are commonly combined with platinum drugs Compound

Mode of action

Irinotecan

Topoisomerase-I inhibitor

Etoposide

Topoisomerase-II inhibitor

Taxanes (Paclitaxel, Docetaxel)

Microtubule inhibitors, disruption of the centrosome network, inhibition of mitotic spindle formation

Vinblastine, Vincristine, Vinorelbine

Tubuling-binding vinca alkaloids, inhibition of mitosis

5-Fluorouracil, Capecitabine, Gemcitabine

Affect DNA synthesis, nucleoside, and nucleotide metabolism deplete the deoxynucleoside triphosphate pool (5-FU: inhibition of thymidilate synthase; Capecitabine: oral prodrug, converted to FU by thymidine phosphorylase; Gemcitabine diphosphate inhibits ribonucleotide reductase inducing a depletion of cellular deoxynucleotides (dNTP)

Mitomycin C

Affects DNA synthesis in hypoxic cells through formation of adducts and crosslinks

Tirapazamine

Affects hypoxic cells through intracellular reduction resulting in a highly reactive radical capable of causing DNA strand breaks

Combinations of Platinum Compounds and Ionizing Radiation

(Dorie and Brown 1993), and in a randomized clinical trial with NSCLC patients (von Pawel et al. 2000). Recent results with the addition of tirapazamine to cisplatin and radiation of head and neck cancer are also promising (Rischin et al. 2005).

6.6 Conclusion The use of platinum compounds concomitant to radiotherapy is based on sound rationales and has resulted in development of several clinically successful combined modality regimens. Optimization of such regimens was accomplished mainly in clinical trials. Systematic work in a broader panel of preclinical tumor models suggests that more than additive effects can be obtained with fractionated radiotherapy when the drug is given shortly before radiation. Importantly, normal tissues do not exhibit the same degree of sensitization. With the advent of improved molecular characterization of tumor and host factors, it is hoped to identify the most suitable regimen for each individual patient. Nevertheless, it is emphasized that within a heterogeneous tumor (different molecular features of the cells, different perfusion, different drug sensitivity, changes of such factors over time) heterogenous drug concentrations and treatment effects have to be anticipated, which are very difficult to model or predict. In addition, each component of the treatment protocol might influence both the microenvironment of the tumor and the sensitivity to the other components, as exemplified by radiationinduced cisplatin resistance. These factors complicate the comparison and optimization of different drug administration protocols. The problems of drug access to the tumor cells, efflux, inactivation, toxicity, etc., are being addressed by advances in pharmacogenetics, delivery routes, development of new generation platinum compounds, and modifiers of metabolism and damage repair.

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C. Nieder and F. Lordick Höglmeier F, Kummermehr J, Trott KR (1985) Effect of a combined therapy of cis-platinum and local irradiation on a fibrosarcoma in the mouse (German). Strahlentherapie 161:362–366 Jackel M, Tausch-Treml R, Kopf-Maier P (1994) Effect of acquired cisplatin resistance on the response of a xenografted human hypopharynx carcinoma to concurrent radiochemotherapy with cisplatin. Laryngoscope 104:329–334 Joschko MA, Webster LK, Bishop JF et al (1997) Radioenhancement by cisplatin with accelerated fractionated radiotherapy in a human tumour xenograft. Cancer Chemother Pharmacol 40:534–539 Kallman RF (1994) The importance of schedule and drug dose intensity in combinations of modalities. Int J Radiat Oncol Biol Phys 28:761–771 Kjellstrom J, Kjellen E, Johnsson A (2005) In vitro radiosensitization by oxaliplatin and 5-fluorouracil in a human colon cancer cell line. Acta Oncol 44:687–693 Landuyt W, Keizer J, Chin A et al (1987) Evaluation of mouse lip mucosa reactions after combinations of cis-diammine1,1-cyclobutanedicarboxylate platinum (II) (CBDCA) and irradiation: single and fractionated treatments. Int J Radiat Oncol Biol Phys 13:1367–1370 Levi F, Metzger G, Massari C et al (2000) Oxaliplatin: pharmacokinetics and chronopharmacological aspects. Clin Pharmacokinet 38:1–21 Magne N, Fischel JL, Formento P et al (2003) Oxaliplatin-5fluorouracil and ionizing radiation. Importance of the sequence and influence of p53 status. Oncology 64:280– 287 McDonnell CO, Holden G, Sheridan ME et al (2004) Improvement of efficacy in chemoradiotherapy by addition of an antiangiogenic agent in a murine tumor model. J Surg Res 116:19–23 Monk BJ, Alberts DS, Burger RA et al (1998) In vitro phase II comparison of the cytotoxicity of a novel platinum analog, nedaplatin (254-S), with that of cisplatin and carboplatin against fresh, human cervical cancers. Gynecol Oncol 71:308–312 Nagy B, Mucsi I, Molnar J et al (2002) Combined effect of cisplatin and 5-fluorouracil with irradiation on tumor cells in vitro. Anticancer Res 22:135–138 Ning S, Yu N, Brown DM et al (1999) Radiosensitization by intratumoral admimistration of cisplatin in a sustainedrelease drug delivery system. Radiother Oncol 50:215–223 Ormerod MG, Orr RM, Peacock JH (1994) The role of apoptosis in cell killing by cisplatin: a flow cytometric study. Br J Cancer 69:93–100 Oshita F, Fujiwara Y, Saijo N (1992) Radiation sensitivities in various anticancer-drug-resistant human lung cancer cell lines and mechanism of radiation cross-resistance in a cisplatin-resistant cell line. J Cancer Res Clin Oncol 119:28–34 Overgaard J, Khan AR (1981) Selective enhancement of radiation response in a C3H mammary carcinoma by cisplatin. Cancer Treatm Rep 65:501–503 Pekkola-Heino K, Kulmala J, Grenman R (1992) Carboplatinradiation interaction in squamous cell carcinoma cell lines. Arch Otolaryngol Head Neck Surg 118:1312–1315 Pendyala L, Creaven PJ (1993) In vitro cytotoxicity, protein binding, red blood cell partitioning, and biotransformation of oxaliplatin. Cancer Res 53:5970–5976

Combinations of Platinum Compounds and Ionizing Radiation Pawel J von, Roemeling R von, Gatzemeier U et al (2000) Tirapazamine plus cisplatin versus cisplatin in advanced non-small-cell lung cancer: a report of the international CATAPULT I study group. J Clin Oncol 18:1351–1359 Raaphorst GP, Leblanc M, Li LF (2005) A comparison of response to cisplatin, radiation and combined treatment for cells deficient in recombination repair pathways. Anticancer Res 25:53–58 Raymond E, Buduet-Fagot O, Djelloul S et al (1997) Antitumor activity of oxaliplatin in combination with 5-fluorouracil and the thymidilate synthase inhibitor AG337 in human colon, breast and ovarian cancers. Anticancer Drugs 8:876– 885 Raymond E, Faivre S, Woynarowski JM et al (1998) Oxaliplatin: mechanisms of action and antineoplatic activity. Semin Oncol 25 (Suppl) 5:4–12 Raymond E, Faivre S, Chaney S et al (2002) Cellular and molecular pharmacology of oxaliplatin. Mol Cancer Ther 1:227–235 Richmond RC, Powers EL (1976) Radiation sensitization of bacterial spores by cis-dichlorodaimmineplatinum (II). Radiat Res 68:251 Richmond RC, Mahtani HK (1991) An interrelatedness of the potentiation of radiation-induced bacterial cell killing by cisplatin and binuclear rhodium carboxylates. Radiat Res 127:36–44 Rischin D, Peters L, Fisher R et al (2005) Tirapazamine, cisplatin and radiation versus fluorouracil, cisplatin and radiation in patients with locally advanced head and neck cancer: a randomized phase II trial of the Trans-Tasman Radiation Oncology Group (TROG 98.02). J Clin Oncol 23:79–87 Rixe O, Ortuzar W, Alvarez M et al (1996) Oxaliplatin, tetraplatin, cisplatin, and carboplatin: spectrum of activity in drug-resistant cell lines of the National Cancer Institute’s Anticancer Drug Screen panel. Biochem Pharmacol 52:1855–1865 Rosenberg B, van Camp L, Krigas T (1965) Inhibition of cell division in Escherichia coli by electrolysis products from a platinum electrode. Nature 205:698–699 Scalliet P, De Pooter C, Hellemans PW et al (1999) Interactions of carboplatin, cisplatin, and ionizing radiation on a human cell line of ovarian cancer. Cancer Radiother 3:30–38 [in French] Schaake-Koning C, Maat B, van Houtte P et al (1990) Radiotherapy combined with low-dose cis-diamminedichloroplatinum (II) for inoperable nonmetastatic non-small cell lung cancer (NSCLC): a three arm phase II study of the EORTC Lung Cancer and Radiotherapy group. Int J Radiat Oncol Biol Phys 19:967–972 Schwachöfer JHM, Crooijmans RP, Hoogenhout J et al (1991) Effectiveness in inhibition of recovery of cell survival by cisplatin and carboplatin: influence of treatment sequence. Int J Radiat Oncol Biol Phys 20:1235–1241 Skov K, MacPhail S (1991) Interaction of platinum drugs with clinically relevant X-ray doses in mammalian cells: a comparison of cisplatin, carboplatin, iproplatin, and tetraplatin. Int J Radiat Oncol Biol Phys 20:221–225 Tanabe M, Godat D, Kallman RF (1987) Effects of fractionated schedules of irradiation combined with cis-diaminedichloroplatinum II on the SCCVII/ST tumor and normal

101 tissues of the C3H/KM mouse. Int J Radiat Oncol Biol Phys 13:1523–1532 Taylor DM, Tew KD, Jones JD (1976) Effects of cis-dichlorodiammine platinum (II) on DNA synthesis in kidney and other tissues of normal and tumoour-bearing rats. Eur J Cancer 12:249–254 Turchi JJ, Patrick SM, Henkels KM (1997) Mechanism of DNA-dependent protein kinase inhibition by cis-diamminedichloro-platinum(II)-damaged DNA. Biochemistry 36:7586–7593 Twentyman PR, Wright KA, Rhodes T (1991) Radiation response of human lung cancer cells with inherent and acquired resistance to cisplatin. Int J Radiat Oncol Biol Phys 20:217–220 Van der Vijgh WJ (1991) Clinical pharmacokinetics of carboplatin. Clin Pharmacokinet 21:242–261 Van Rongen E, Kuijpers WC, Baten-Wittwer A (1994) The influence of platinum drugs on the radiation response of rat kidneys. Radiother Oncol 31:138–150 Wang D, Lippard SJ (2005) Cellular processing of platinum anticancer drugs. Nat Rev Drug Discov 4:307–320 Weaver DA, Crawford EL, Warner KA et al (2005) ABCC5, ERCC2, XPA and XRCC1 transcript abundance levels correlate with cisplatin chemoresistance in non-small cell lung cancer cell lines. Mol Cancer 4:18 Woynarowski JM, Chapman WG, Napier C et al (1998) Sequence- and region-specificity of oxaliplatin adducts in naked and cellular DNA. Mol Pharmacol 54:770–777 Wu HI, Brown JA, Dorie MJ et al (2004) Genome-wide identification of genes conferring resistance to the anticancer agents cisplatin, oxaliplatin, and mitomycin C. Cancer Res 64:3940–3948 Würschmidt F, Beck-Bornholdt HP (1995) Combined modality treatment of the rhabdomyosarcoma R1H of the rat: tumor and normal tissue response after cisplatin and conventional or accelerated irradiation treatment. Int J Radiat Oncol Biol Phys 32:391–394 Yang LX, Douple EB et al (1995a) Carboplatin enhances the production and persistence of radiation-induced DNA single-strand breaks. Radiat Res 143:302–308 Yang LX, Douple EB et al (1995b) Irradiation enhances cellular uptake of carboplatin. Int J Radiat Oncol Biol Phys 33:641–646 Yang L, Douple EB, O’Hara JA et al (1995c) Enhanced radiation-induced cell killing by carboplatin in cells of repairproficient and repair-deficient cell lines. Radiat Res 144:230–236 Yapp DT, Lloyd DK, Zhu J et al (1998) The potentiation of the effect of radiation treatment by intratumoral delivery of cisplatin. Int J Radiat Oncol Biol Phys 42:413-420 Yount GL, Haas-Kogan DA, Levine KS et al (1998) Ionizing radiation inhibits chemotherapy-induced apoptosis in cultured glioma cells: implications for combined modality therapy. Cancer Res 58:3819–3825 Zak M, Drobnik J (1971) Effects of cis-dichlorodiammineplatinum (II) on the post irradiation lethality in mice after irradiation with X-rays. Strahlentherapie 142:112–115 Zamboni WC, Gervais AC, Egorin MJ et al (2002) Inter- and intratumoral disposition of platinum in solid tumors after administration of cisplatin. Clin Cancer Res 8:2992–2999

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7

103

Combinations of Cytotoxic Drugs, Ionizing Radiation, and Angiogenesis Inhibitors Carsten Nieder and Nicolaus H. Andratschke

CONTENTS 7.1 7.2 7.3 7.4 7.4.1 7.4.2

7.4.3 7.4.4 7.4.5 7.5 7.6

Introduction 103 VEGFs in Tumor Angiogenesis 104 VEGF Inhibition Strategies 105 Combination of VEGF Inhibition with Radiotherapy 106 Tumor Models 106 Mechanisms Underlying the Enhanced Effect of Anti-VEGF Agents when Combined with Irradiation 108 Impact of Anti-VEGF Strategies on Radiobiological Hypoxia 108 Sequencing of Anti-VEGF Strategies Combined with Radiotherapy 109 Side Effects of Anti-VEGF Compounds Combined with Radiotherapy 109 Trimodal Treatment with Anti-Angiogenic Agents, Radiotherapy, and Chemotherapy 110 Conclusion 110 References 111

7.1 Introduction Many years after the fundamental hypotheses about delivery of oxygen and nutrients to malignant tumors via formation of new blood vessels (angiogenesis) were published, drugs developed to inhibit angiogenesis have now entered routine clinical practice, after landmark randomized trials have identified suitable combination regimens in metastatic colorectal cancer and advanced nonsquamous non-small cell lung cancer (Table 7.1). Previously, monotherapy, e.g., with matrix metalloproteinase inhibitors, failed to improve the results. The fundamental principles of anti-angiogenic approaches and their consequences for the devel-

C. Nieder, MD N. H. Andratschke, MD Department of Radiation Oncology, Klinikum rechts der Isar der Technischen Universität München, Ismaninger Strasse 22, 81675 München, Germany

opment and growth of solid tumors were published by Folkman (1971, 1986, 1995). Tumor angiogenesis results from imbalance between pro-angiogenic factors, e.g., vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF) and platelet-derived growth factor (PDGF), and endogenous anti-angiogenic factors such as angiostatin and endostatin (Folkman 1995; O’Reilly et al. 1996, 1997; Endrich and Vaupel 1998; Ferrara and Alitalo 1999; Kerbel 2000; Carmeliet and Jain 2000; Yancopoulos et al. 2000). A large body of experimental data indicate that application of either inhibitors of pro-angiogenic factors or administration of anti-angiogenic factors reduce the formation of new blood vessels. As a result, tumors grow at a slower rate or even decrease their size. However, in most cases no permanent tumor control can be achieved; therefore, the combination of anti-angiogenic strategies with cytotoxic agents such as chemotherapy, ionizing radiation, or both represents a promising approach to increase the cure rates of solid tumors (Folkman 1971; Teicher et al. 1992; Denekamp 1993; Folkman 1995; Siemann et al. 2000; Koukourakis 2001; Rosen 2002; Kal et al. 2004; Jain 2005; Xu et al. 2005). This chapter is focused on the VEGF pathways as an illustrative example of the therapeutic principles and efficacy. Further data can be found in the disease-specific chapters such as 15.6.4 (pancreatic cancer) and 20.4.3 (gynecological cancers). Angiogenesis is not restricted to tumors but can also be found in many other physiological and pathological conditions, e.g., normal growth, wound healing, proliferative retinopathies, rheumatoid arthritis, and inflammation (for review see Folkman 1995; Carmeliet and Jain 2000); hence, inhibition of angiogenesis combined with other treatment may be associated with increased normal tissue reactions. In addition, several angiogenic growth factors were shown to reduce radiation-induced long-term toxicity, e.g., in the spinal cord and parotid glands (Andratschke et al. 2004, 2005; Thula et al. 2005); therefore, the therapeutic ratio of anti-angiogenic

C. Nieder and N. H. Andratschke

104 Table 7.1. Randomized clinical trials of chemotherapy plus/minus anti-angiogenic agents Reference

Compound

Tumor

Patient no. Results

Leighl et al. (2005)

Paclitaxel/carboplatin plus BMS-275291 (MMPI) or placebo

NSCLC stage IIIB/IV

774

Outcome not improved, toxicity increased

Bissett et al. (2005)

Cisplatin/gemcitabine plus prinomastat (MMPI) or placebo

NSCLC stage IIIB/IV or recurrent

362

Outcome not improved, more treatment interruption

Sparano et al. (2004)

Marimastat (MMPI) or placebo after ﬁrst-line chemotherapy

Metastatic breast cancer

179

Outcome not improved, toxicity increased

Bramhall et al. (2002a)

Gemcitabine plus marimastat or placebo

Unresectable pancreatic cancer

239

Outcome not improved, well tolerated

Bramhall et al. (2002b)

Maintenance marimastat vs placebo after max. 1 5-FU-based chemotherapy regimen

Non-resectable gastric and gastro-esophageal cancer

369

2-year survival 3 vs 9% in favor of marimastat (p=0.07), PFS sign. Longer

Stadler et al. (2004)

SU 5416 plus dexamethasone vs dexamethasone

Hormone-refractory prostate cancer

36

Outcome not improved

Szczylik et al. (2005)

Sorafenib vs best supportive care

Advanced renal cell carcinoma

769

PFS sign. improved (interim analysis)

Miller et al. (2005)

Capecitabine plus/minus bevacizumab

Metastatic breast cancer

462

Sign. higher response rate (20 vs 9%), PFS, and OS not improved

Sandler et al. (2005)

Paclitaxel/carboplatin plus/minus bevacizumab

Non-squamous NSCLC stage IIIB/IV

878

Sign. improvement in response rate, PFS and OS

Kabbinavar et al. (2005)

5-FU/LV plus bevacizumab or placebo

Metastatic colorectal cancer

209

PFS sign. better, OS better but not signiﬁcant

Hurwitz et al. (2004)

5-FU/LV/irinotecan plus placebo vs bevacizumab

Metastatic colorectal cancer

813

Sign. improvement in OS, PFS, and response (ﬁrst line)

Giantonio et al. (2005)

5-FU/LV/oxaliplatin (FOLFOX4) vs FOLFOX4 plus bevacizumab vs bevacizumab alone

Previously treated advanced colorectal cancer

829

Sign. improvement in PFS and OS

MMPI matrix metalloproteinase inhibitor, NSCLC non-small cell lung cancer, 5-FU 5-ﬂuorouracil, LV leucovorin, PFS progression-free survival, OS overall survival

strategies in combination with radiotherapy needs to be thoroughly determined for safe translation of this approach into clinical practice.

7.2 VEGFs in Tumor Angiogenesis VEGFs are potent mitogenes for endothelial cells and key mediators of tumor angiogenesis (for review see Dvorak et al. 1995; Kerbel et al. 1998; Ferrara 1999; Carmeliet 2000; Carmeliet and Collen 2000; Carmeliet and Jain 2000; Karkkainen and Petrova 2000; Kerbel 2000; Veikkola et al. 2000; Yancopoulos et al. 2000; Byrne et al. 2005). The VEGFs represent a family of distinct proteins, e.g., VEGF (VEGF-A), VEGF-B, VEGF-C, VEGF-D, VEGF-E, and isoforms (e.g., VEGF121 and VEGF165).

Some family members are involved in lymphangiogenesis (VEGF-C and VEGF-D). Down-regulation of VEGF-C, e.g., by endostatin, might therefore inhibit lymph node metastasis (Fukumoto et al. 2005). The VEGF expression can be demonstrated in the vast majority of tumors and is usually elevated above normal tissue levels. Until tumors reach a volume of about 1 mm3, tumor cells are supplied by diffusion from the surrounding tissues (Folkman 1971; Ausprunk and Folkman 1977; Folkman 1986). At larger volumes, impaired supply with oxygen and nutrients and accumulation of metabolites occur in the tumor. This is accompanied by important changes in the tumor microenvironment, e.g., hypoxia, hypoglycemia, and acidosis, which result in up-regulated production and release of HIF-1D, VEGF, and other angiogenic factors by the tumor cells (angiogenic switch, see Chap. 20.3.1 for further details). These factors represent potential targets

Combinations of Cytotoxic Drugs, Ionizing Radiation, and Angiogenesis Inhibitors

for anti-cancer treatment (Abdollahi et al. 2005; Diaz-Gonzalez et al. 2005). In addition to environmental factors, other triggers, such as mechanical stress, immune/inflammatory responses, and genetic alterations (e.g., activation of oncogenes or deletion of tumor-suppressor genes that control production of angiogenesis regulators), may influence the expression of VEGF (Kerbel et al. 1998; Okada et al. 1998; Carmeliet and Jain 2000). Secreted VEGFs bind to specific receptors (VEGFR-1/Flt-1, VEGFR-2/KDR, VEGFR-3/Flt-4), which are almost exclusively expressed on the surface of endothelial cells (Jakeman et al. 1992; Veikkola et al. 2000; Yancopoulos et al. 2000). Within the families of VEGFs and VEGFRs ligand affinity and receptor properties are variable. The VEGFRs consist of distinct structural elements, most importantly an extracellular immunoglobulin-like binding domain and an intracellular tyrosine kinase domain. Binding of VEGF is followed by receptor dimerization, tyrosine kinase activation, autophosphorylation, and eventually activation of a complex cascade of intracellular pathways (Guo et al. 1995; Abedi and Zachary 1997; Karkkainen and Petrova 2000;

105

Veikkola et al. 2000; Stoletov et al. 2001). The activation of endothelial cells results in vasorelaxation, increased vascular permeability, endothelial cell migration, proliferation, and survival. New blood vessels originating from surrounding, preexisting normal vessels generate a tumor neovasculature that allows further tumor growth, tumor progression, and development of metastasis; however, important differences in vessel structure and organization exist, such as irregular leaky basement membranes (Di Tomaso et al. 2005).

7.3 VEGF Inhibition Strategies Based on the molecular mechanisms underlying the biological effects of the VEGFs and their receptors, various rationally designed strategies to inhibit VEGF-dependent angiogenesis have been developed (Table 7.2). The best investigated approaches include antibodies against VEGF or VEGFR and VEGF receptor tyrosine kinase inhibitors (RTKI).

Table 7.2. Strategies to enhance the efﬁcacy of radiotherapy by inhibitors of angiogenesis Target

Mechanism

Reference

VEGF ligand

Neutralizing monoclonal antibodies

Kim et al. (1993), Asano et al. (1995), Borgström et al. (1996), Presta et al. (1997)

Neutralizing chimeric proteins

Aiello et al. (1995)

Soluble VEGFR-1

Lin et al. (1998), Goldman et al. (1998), Davidoff et al. (2001)

Antisense oligonucleotides

Bell et al. (1999), Im et al. (1999)

Neutralizing monoclonal antibodies

Prewett et al. (1999), Fenton et al. (2004), Li et al. (2005)

VEGF receptor

Others

Mutant VEGF receptor 2 (VEGFR-2)

Machein et al. (1999)

Ribozyme targeted to mRNA

Parry et al. (1999)

Antisense oligonucleotides

Rockwell et al. (1997)

Tyrosine kinase inhibitors

Fong et al. (1999), Laird et al. (2000), Wood et al. (2000), Wedge et al. (2000), Zips et al. (2005)

Multitargeted kinase inhibitors, e.g., ZD6474 and SU11657

Williams et al. (2004), Damiano et al. (2005), Huber et al. (2005), Frederick et al. (2006)

Multitargeted growth factor-binding molecules

Sun et al. (2005)

Inhibitors of mTOR

Shinohara et al. (2005; for further references see Chap. 9.4)

Agents disrupting the tubulin cytoskeleton, e.g., ZD6126

Siemann and Rojiani (2005), Wachsberger et al. (2005)

Thalidomide

Ansiaux et al. (2005)

HIV protease inhibitor ritonavir

Maggiorella et al. (2005)

MN-029

Shi and Siemann (2005)

AMCA (lysine analog interfering with lysine binding sites of plasminogen)

Kal et al. (2004)

Metronomic chemotherapy

Kerbel and Kamen (2004)

C. Nieder and N. H. Andratschke

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Neutralizing antibodies against VEGF or VEGFR2 can reduce the growth rate of tumors and metastases in experimental animals (Kim et al. 1993; Asano et al. 1995; Borgström et al. 1996; Presta et al. 1997; Prewett et al. 1999; Gorski et al. 1999; Bruns et al. 2000; Lee et al. 2000; Kozin et al. 2001; Gupta et al. 2002; Winkler et al. 2004); however, considerable heterogeneity in response to anti-VEGF or anti-VEGFR antibodies has been observed. In some tumors treated with anti-VEGF antibodies a nearly complete inhibition of angiogenesis, a decline in vessel permeability, and a decrease in vascular density compared with control tumors has been demonstrated by intravital microscopy and histology (Borgström et al. 1996; Yuan et al. 1996). Recent data suggest that VEGFR2 blockade increases tumor oxygenation, pericyte coverage of brain tumor blood vessels, and degradation of their pathologically thick basement membrane (Winkler et al. 2004). To generate VEGF antibodies suitable for clinical trials, mouse monoclonal antibodies were humanized in order to combine high affinity to human VEGF with little or no immunogenicity (Presta et al. 1997; Ferrara and Alitalo 1999). In a phase-I clinical trial including 25 patients with advanced solid tumors no dose-limiting toxicity up to the highest dose of recombinant human anti-VEGF monoclonal antibody (bevacizumab, 10 mg/kg body weight) was observed (Gordon et al. 2001); however, in this trial three episodes of tumor bleeding were noted. In two additional patients with known pulmonary metastasis minor hemoptysis occurred. It was not possible to discriminate whether these bleedings were caused by the treatment or by the underlying disease. In combination with chemotherapy rhumabVEGF (3 mg/kg body weight) was safely administered without hemorrhagic complications (Margolin et al. 2001). In a multicenter trial 99 patients with advanced non-small cell lung cancer were randomized to standard chemotherapy or standard chemotherapy plus rhumabVEGF (DeVore et al. 2000). Response rate and time to progression were increased after combined treatment. In six patients, four of them with a central tumor location, severe tumor bleeding occurred, which was fatal in four patients. VEGF-dependent angiogenesis can also be suppressed by RTKIs. Agents such as SU5416, ZD4190, and PTK787/ZK222584, competitively inhibit ATPdependent phosphorylation of tyrosine residues of the VEGF receptor resulting in a decrease in proliferation and survival of endothelial cells in vitro, angiogenesis in vivo, growth rate of tumor, and metastasis (Fong et al. 1999; Shaheen et al. 1999; Drevs et al. 2000; Laird et al. 2000; Mendel et al. 2000; Wedge

et al. 2000; Wood et al. 2000; Schuuring et al. 2005). Although these compounds were designed to inhibit VEGFR2, some of them show also activity against other receptors involved in angiogenesis (Laird et al. 2000). In a clinical phase-I study on single-agent SU5416 treatment in patients with advanced malignant disease, the dose-limiting toxicity was vomiting, nausea, and severe headache (Cropp et al. 1999; Rosen et al. 1999; Stopeck 2000). In a subsequent phase-I clinical trial SU5416 combined with cisplatin and gemcitabine in a total of 19 patients with solid tumors, an unexpectedly high rate of thrombembolic events was observed (Kuenen et al. 2002). These discouraging results may be a consequence of the specific regimen of chemotherapy applied. This illustrates the importance of further, detailed investigations of interactions and optimal scheduling of administration (Marx et al. 2002). Of special importance in this context are pre-clinical investigations into normal tissue effects of combined approaches, exploiting suitable animal models.

7.4 Combination of VEGF Inhibition with Radiotherapy 7.4.1 Tumor Models Whether anti-VEGF strategies in combination with radiotherapy can be used to improve tumor response was investigated in a number of experimental models (Table 7.3). In these studies different human and murine tumors, grown in experimental animals, were treated with various anti-VEGF compounds combined with single-dose or fractionated irradiation. Although VEGF inhibition alone had only a modest or no significant impact on tumor growth, the combination with irradiation consistently resulted in improved outcome. For example, in the study published by Gorski et al. (1999) anti-VEGF165 antibody alone did not reduce tumor growth rate in U87 human glioblastoma xenografts, whereas the combination of 40 Gy given in eight fractions with anti-VEGF165 antibody 3 h before each fraction increased tumor growth delay compared with irradiation alone. In another study performed by Kozin and colleagues (2001) two different human xenograft tumors were treated with an anti-VEGFR2 antibody combined with fractionated irradiation. In both tumor models the combined treatment resulted

Combinations of Cytotoxic Drugs, Ionizing Radiation, and Angiogenesis Inhibitors

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Table 7.3. Pre-clinical in vivo studies testing anti-VEGF strategies in combination with radiotherapy. (Modiﬁed from Zips and Baumann 2003) Compound

Mechanism of VEGF inhibition

Tumor

Treatment schedule

End point

SU5416

RTKIa

Murine SCC VIIb

5u2 Gy plus concomitant SU5416

Growth delay

+c

Ning et al. (2002)

SU6668

RTKI

Murine SCC VII

5u2 Gy plus concomitant SU6668

Growth delay

+

Ning et al. (2002)

SU6668

RTKI

Human mammary carcinoma SCK

Two applications of SU6668 prior to irradiation with a single dose of 15 Gy

Growth delay

+

Grifﬁn et al. (2002)

SU5416

RTKI

Murine maligant glioma GL261

Six fractions of 3 Gy with concomitant SU5416

Growth delay

+

Geng et al. (2001)

ZK 222584/ PTK 787

RTKI

Human SW480 colon carcinoma

12 Gy in four fractions with concomitant ZK222584/ PTK787

Growth delay

+

Hess et al. (2001)

A.4.6.1

Anti-VEGF antibody

Human glioblastoma U87, human colon adenocarcinoma LS174T

Single dose under normoxic or hypoxic conditions after antibody treatment

Growth delay

+

Lee et al. (2000)

DC101

AntiVEGFR2 antibody

Human small cell lung Five fractions in 5 days with cancer 54A, human six applications of DC101 glioblastoma U87 every third day

Growth delay, + tumor control rate

Kozin et al. (2001)

DC101

AntiVEGFR2 antibody

Human SCC-1 or SCC-6 carcinoma

3 Gy twice weekly for 3.5 weeks with twice weekly DC101 for 3 weeks

Growth delay

+

Li et al. (2005)

DC101

AntiVEGFR2 antibody

Mca-4 and Mca-35 mammary adenocarcinoma

Five fractions of 6 Gy with DC101

Growth delay

+

Fenton et al. (2004)

Human SCC SQ20B, Seg-1 human adenocarcinoma, human glioblastoma U87

Anti-VEGF165 prior to irradia- Growth delay tion with four or eight fractions

+

Gorski et al. (1999)

Anti-VEGF165 Anti-murine Murine Lewis lung VEGF165 carcinoma antibody

40 Gy in two fractions with Growth delay anti-VEGF165 prior to irradiation

+

Gorski et al. (1999)

Anti-VEGF165 Anti-human VEGF165 antibody

Growth delay Anti-VEGF165 plus 20 Gy in four fractions (Seg-1) or 40 Gy in eight fractions (U87)

+

Gupta et al. (2002)

Anti-VEGF165 Anti-human VEGF165 antibody

Seg-1 human adenocarcinoma, human glioblastoma U87

Reference

a

RTKI receptor tyrosine kinase inhibitor. Squamous cell carcinoma. c Better outcome with combined treatment compared to control tumor. b

in a statistically significant decrease of the dose necessary for permanent local tumor control compared with tumors that were only irradiated. This result demonstrates that anti-VEGFR antibody treatment increases the inactivation of clonogenic tumor cells and supports the hypothesis that anti-VEGF strategies may improve the outcome of curative radiotherapy; however, in the majority of the experiments listed in Table 7.3, tumor growth delay was

the experimental end point. Importantly, total dose, dose per fraction, overall treatment time, and the sequence of the modalities in combined treatment may impact on the outcome of combination treatment; hence, further pre-clinical studies in relevant animals models addressing these parameters need to be conducted to investigate whether the benefit of the combined therapy holds true for clinically relevant irradiation schedules.

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7.4.2 Mechanisms Underlying the Enhanced Effect of Anti-VEGF Agents when Combined with Irradiation The observation that anti-VEGF compounds alone only modestly impact tumor growth rate while in combination with irradiation anti-VEGF agents consistently improve the response of tumors, suggests a radiosensitizing effect. This might be restricted to endothelial cells, because VEGF receptors are almost exclusively expressed on this cell type (Jakeman et al. 1992; Ning et al. 2002). This notion is supported by the fact that neither unirradiated nor irradiated tumor cells were affected by anti-angiogenic compounds (Gorski et al. 1999; Hess et al. 2001; Gupta et al. 2002; Dings et al. 2005). The VEGFs are potent mitogens and survival factors for endothelial cells (see section 7.2). Irradiation of endothelial cells in vitro results in decreased proliferation and decreased clonogenic survival (De Gowin et al. 1974; Hei et al. 1987; Haimovitz-Friedman et al. 1991; Fuks et al. 1994; Gorski et al. 1999; Hess et al. 2001; Kermani et al. 2001; Gupta et al. 2002; Brieger et al. 2005). When VEGF is added to culture media, the effects of irradiation on proliferation and survival of endothelial cells were attenuated. On the other hand, VEGF inhibitors reduce these effects of VEGF on irradiated endothelial cells (Gorski et al. 1999; Hess et al. 2001; Gupta et al. 2002). In studies using another angiogenic growth factor, bFGF, increased clonogenic survival of irradiated bovine aortic endothelial cells was observed (Haimovitz-Friedman et al. 1991; Fuks et al. 1994). In these studies the slope of the dose–survival curves was not significantly different between endothelial cells incubated with or without bFGF; however, the shoulder region of the dose effect curve was almost completely eliminated when no bFGF was added to culture media. An interesting hypothesis of the mechanism of anti-VEGF combined with irradiation was proposed by Gorski and colleagues (1999) based on the fact that many cell types, including tumor cells, respond to irradiation with an increased release of growth factors such as VEGF or bFGF. These growth factors may in an autocrine and/or paracrine manner increase endothelial cell survival after irradiation (Witte et al. 1989; Haimovitz-Friedman et al. 1991; Gorski et al. 1999; Gupta et al. 2002). The authors hypothesized that the inhibition of VEGF can abrogate the effects of radiation-induced VEGF on irradiated endothelial cells in tumors. This may result in increased radiation-induced endothelial cell kill which even-

C. Nieder and N. H. Andratschke

tually leads to impaired tumor vascularization. As a result, the tumor cell production rate decreases and/or the tumor cell loss increases which may result in improved tumor response after irradiation. Further experimental studies are required to elucidate the complex interactions of the endothelial cell and the tumor cell compartment after a combination of anti-angiogenic compounds with irradiation.

7.4.3 Impact of Anti-VEGF Strategies on Radiobiological Hypoxia Theoretically, anti-angiogenic agents might increase tumor hypoxia. Anoxic cells are less sensitive to irradiation compared with normoxic cells by a factor of about three (Gray et al. 1953; Wright and HowardFlanders 1957); thus, inhibitors of angiogenesis, by decreasing vessel density or vessel function, might increase the proportion of poorly oxygenated clonogenic tumor cells and thereby decrease the efficacy of irradiation. A negative effect of anti-angiogenic agents on the results of irradiation was observed in an experiment by Murata and colleagues (1997). The authors investigated the effect of TNP-470 on local tumor control after single-dose and fractionated irradiation of murine mammary carcinoma in C3H/He mice. The radiobiological hypoxic fraction of clonogenic tumor cells, as determined from the tumor control data after single-dose irradiation, was not affected significantly by TNP-470; however, for fractionated irradiation under normal blood flow conditions, tumors treated with TNP-470 were more resistant compared with control tumors. In contrast, no differences were observed for fractionated irradiation under clamp hypoxia. The authors concluded that inhibition of angiogenesis by TNP-470 impairs reoxygenation during fractionated irradiation and thus increases radioresistance of tumors. In a study on human colon carcinoma growing in nude mice, another anti-angiogenic compound, suramine, was also found to increase radiobiological hypoxia (Leith et al. 1992). Yet, both TNP-470 (Zhang et al. 2000) and suramine do not specifically inhibit VEGF or VEGFR but decrease angiogenesis at least in part by other mechanisms. Whether anti-VEGF drugs similarly increase radiobiological hypoxia was addressed in two experimental studies using antiVEGF and anti-VEGFR antibodies (Lee et al. 2000; Kozin et al. 2001). Tumor growth delay after graded single radiation doses given under normal blood flow conditions was compared with tumor growth delay

Combinations of Cytotoxic Drugs, Ionizing Radiation, and Angiogenesis Inhibitors

after irradiations applied under clamp hypoxia. In both studies anti-VEGF and anti-VEGFR antibodies increased tumor growth delay compared with control tumors irrespective of the tumor oyxgenation status at the time of irradiation. These results suggest that VEGF inhibition does not increase the radiobiological hypoxic cell fraction in tumors. The discrepancy of reduced vessel density on the one hand but lack of increase in hypoxia, on the other hand, may be attributed to an impact on the quality of vascular organization by selective ablation of immature tumor blood vessels, a decrease in the number of oxygen consuming cells, and a decrease in vessel permeability (Benjamin et al. 1999; Lee et al. 2000). Examination of FSAII tumors grown in mice demonstrated that anti-angiogenic treatment with thalidomide caused reoxygenation within 2 days, accompanied by a reduction of interstitial fluid pressure and increase in perfusion (Ansiaux et al. 2005).

7.4.4 Sequencing of Anti-VEGF Strategies Combined with Radiotherapy The VEGF inhibitors can be administrated before (neoadjuvant), during (simultaneous) and/or after (adjuvant) a course of fractionated radiotherapy. No conclusion on the optimal sequence can be drawn from the studies listed in Table 7.3. Current data indicate that VEGF inhibitors have only minor effect on tumor volume when given alone. Neoadjuvant application should have only little effect on the number of clonogenic tumor cells that need to be killed by irradiation; thus, a substantial improvement of the results of radiotherapy by neoadjuvant VEGF inhibition can only be expected from different mechanisms such as more functional vascularization and abrogation of resistance-inducing microenvironmental parameters. Table 7.3 shows that simultaneous application of VEGF inhibitors with fractionated irradiation improved the radiation response of several tumor models. These results might be caused by abrogation of the radioprotective effects of radiation-induced VEGF on endothelial cells. So far, the experimental results do not support that neoadjuvant or simultaneous application of VEGF inhibitors increases tumor hypoxia. To circumvent the possibility of increased hypoxia, anti-angiogenic agents may be applied after the end of fractionated irradiation. In a study by Murata and colleagues (1997) TNP-470 applied after a course of ten fractions in 2 weeks significantly increased tumor growth delay

109

compared with irradiation alone. In experiments by Zips et al. (2005), different combination schedules of a VEGFR tyrosine kinase inhibitor with fractionated irradiation of human squamous cell carcinomas in nude mice were compared. Short-term neoadjuvant and simultaneous administration showed no effect on tumor growth delay, whereas long-term adjuvant treatment resulted in prolonged tumor growth delay (but not increased cure rates). Arguments for adjuvant administration of VEGF inhibitors include the following: tumors may shrink after irradiation and smaller tumors are more likely to respond to antiangiogenic compounds than larger tumors (Griffin et al. 2002). Irradiated vessels appear to be more sensitive to VEGF inhibition, which is supported by the observation that in vitro irradiated endothelial cells show an increased VEGFR2 expression (Kermani et al. 2001). An obvious disadvantage of the adjuvant sequence is that the radioprotective effect of VEGF on endothelial cells will not be counteracted. Certainly, further studies to determine the optimal sequence of VEGF inhibition in combination with fractionated irradiation are needed.

7.4.5 Side Effects of Anti-VEGF Compounds Combined with Radiotherapy In most of the studies listed in Table 7.3 the combination with irradiation was well tolerated. Skin reactions after irradiation of the subcutaneously growing experimental tumors on the hind leg or flank of the animals were not increased; however, after wholebody irradiation in combination with anti-VEGFR2 antibody DC101 40% of 54A tumor-bearing mice developed ascites and half of them died (Kozin et al. 2001). Histology revealed focal segmental glomerulonecrosis associated with increased expression of VEGFR2 on the surface of glomerular endothelial cells in the kidneys (Kozin et al. 2002). This indicates that, although angiogenesis in adult organisms is almost exclusively confined to tumor tissue, inhibition of VEGF-dependent processes may result in increased normal tissue reactions after irradiation. This might be explained by the fact that VEGF does not only stimulate angiogenesis but is also important for survival and maintenance of normal function of endothelial cells. Such results underline the importance of further studies of normal tissue reactions, particularly those dominated by a long-term vascular component, after combined anti-VEGF strategies with radiotherapy.

C. Nieder and N. H. Andratschke

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7.5 Trimodal Treatment with Anti-Angiogenic Agents, Radiotherapy, and Chemotherapy Kumar et al. (2005) reported that combination treatment with low doses of the phosphatidyl-inositol 3-kinase (PI3K) inhibitor LY294002, cisplatin, and irradiation resulted in significantly higher endothelial cell death as compared with each agent used alone. This combination treatment was equally effective in inducing tumor cell death. Combination treatment also significantly inhibited endothelial cell tube formation in Matrigel as compared with each of the agents used alone. In an in vivo severe combined immunodeficient mouse model, combination treatment with low doses of LY294002, cisplatin, and irradiation significantly inhibited the growth of human oral squamous carcinoma (OSCC-3) as well as prostate cancer (LnCap). The combination therapy was also effective in inhibiting tumor angiogenesis where it showed a greater than 90% decrease in neovascularization. In contrast, combination treatment showed only a 29% inhibition of physiological angiogenesis. Another group treated mice bearing Lewis lung carcinoma with combinations of intraperitoneal cisplatin, 5-fluorouracil, and the antiangiogenic agent genistein, together with 10 or 20 Gy of external beam radiotherapy (McDonnell et al. 2004). Animals were sacrificed at day 6 when tumor volume, microvessel density, and serum VEGF were determined. Mean tumor volume in the chemoradiotherapy group was 35% larger than in the chemoradiotherapy plus genistein group (p=0.04). The addition of genistein produced a significant reduction in tumor microvessel density as well as serum VEGF levels compared with those animals receiving chemoradiation alone. Huber et al. (2005) found that in vitro and in vivo, the anti-endothelial and anti-tumor effects of the triple therapy combination consisting of SU11657 (a multitargeted small molecule inhibitor of VEGF and PDGF receptor tyrosine kinases), pemetrexed (a multitargeted folate antimetabolite), and ionizing radiation were superior to all single and dual combinations. The superior effects in human umbilical vein endothelial cells and tumor cells (A431) were evident in cell proliferation, migration, tube formation, clonogenic survival, and apoptosis assays. Triple therapy induced greater tumor growth delay than all other therapy regimens without increasing apparent toxicity. When testing different treatment schedules for the A431 tumor, these authors

found that the regimen with radiotherapy (7.5 Gy single dose), given after the institution of SU11657 treatment, was more effective than radiotherapy preceding SU11657 treatment. The SU11657 markedly reduced intratumoral interstitial fluid pressure after 1 day. Among the multiple pathways altered by epidermal growth factor receptor (EGFR) inhibitors, angiogenesis appears to play an important role. Data on combined treatment with radiotherapy, chemotherapy, and EGFR inhibitors are reviewed in Chapter 8.6.1.

7.6 Conclusion Pre-clinical experiments in a variety of tumor models indicate that inhibition of angiogenic growth factors or growth factor receptors in combination with irradiation is a promising concept for the improvement of the radiation response of tumors, although most data relate to tumor growth delay rather than cure. The mechanisms underlying this approach are not fully understood to date. Both, radiosensitization of endothelial cells by VEGF inhibition as well as sensitization of endothelial cells against anti-angiogenic agents by irradiation appear to play an important role. In addition to approaches targeting VEGF and its pathways, a variety of other strategies are under investigation. Recently, evaluation of trimodal combinations has started, because simultaneous radiochemotherapy is now standard treatment for many types of cancer. Whether such strategies improve the therapeutic window remains to be determined. So far, systematic data on long-term toxicity in many critical organs are lacking. Future research must include investigations of the efficacy of angiogenesis inhibition (and normalization of the microenvironment) in combination with irradiation and cytotoxic drugs with regard to dose-fractionation parameters, optimization of the dosing and sequence, identification of predictive factors for response, and studies on normal tissue toxicity in relevant experimental animal tumor and normal tissue models as well as early clinical trials. Examples of such trials in gastrointestinal tumors are discussed in more detail in Chapter 15.6.4. In brief, preliminary experience suggests that changes in tumor perfusion and interstitial intratumor pressure occur, and that acute toxicity of bevacizumab plus radiotherapy is acceptable. Further data have been published for

Combinations of Cytotoxic Drugs, Ionizing Radiation, and Angiogenesis Inhibitors

the combination of radiotherapy and temozolomide with thalidomide evaluated in a phase-II trial Chang et al. (2004). This regimen was administered to 67 patients with newly diagnosed glioblastoma. It was relatively well tolerated and showed a median survival of more than 16 months. Whether this represents an improvement over trials without thalidomide (median survival 1316 months) requires prospective confirmation.

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114 Schuuring J, Bussink J, Bernsen H et al (2005) Irradiation combined with SU5416: microvascular changes and growth delay in a human xenograft glioblastoma tumor line. Int J Radiat Oncol Biol Phys 61:529–534 Shaheen RM, Davis DW, Liu W et al (1999) Antiangiogenic therapy targeting the tyrosine kinase receptor for vascular endothelial growth factor receptor inhibits the growth of colon cancer liver metastasis and induces tumor and endothelial cell apoptosis. Cancer Res 59:5412–5416 Shi W, Siemann DW (2005) Preclinical studies of the novel vascular disrupting agent MN-029. Anticancer Res 25:3899– 3904 Shinohara ET, Cao C, Niermann K et al (2005) Enhanced radiation damage of tumor vasculature by mTOR inhibitors. Oncogene 24:5414–5422 Siemann DW, Rojiani AM (2005) The vascular disrupting agent ZD6126 shows increased antitumor efficacy and enhanced radiation response in large, advanced tumors. Int J Radiat Oncol Biol Phys 62:846–853 Siemann DW, Warrington KH, Horsman MR (2000) Targeting tumor blood vessels: an adjuvant strategy for radiation therapy. Radiother Oncol 57:5–12 Sparano JA, Bernardo P, Stephenson P et al (2004) Randomized phase III trial of marimastat versus placebo in patients with metastatic breast cancer who have responding or stable disease after first-line chemotherapy: Eastern Cooperative Oncology Group trial E2196. J Clin Oncol 22:4683–4690 Stadler WM, Cao D, Vogelzang NJ et al (2004) A randomized phase II trial of the antiangiogenic agent SU5416 in hormone-refractory prostate cancer. Clin Cancer Res 10:3365– 3370 Stoletov KV, Ratcliffe KE, Spring SC, Terman BI (2001) NCK and PAK participate in the signaling pathway by which vascular endothelial growth factor stimulates the assembly of focal adhesions. J Biol Chem 276:22748–22755 Stopeck A (2000) Results of a phase I dose-escalating study of the antiangiogenic agent, SU5416, in patients with advanced malignancies. Proc Am Soc Clin Oncol 19:206a, abstract 802 Sun J, Wang DA, Jain RK et al (2005) Inhibiting angiogenesis and tumorigenesis by a synthetic molecule that blocks binding of both VEGF and PDGF to their receptors. Oncogene 24:4701–4709 Szczylik C, Eisen T, Stadler WM et al (2005) Randomized phase III trial of the Raf kinase and VEGFR inhibitor sorafenib (BAY 43-9006) in patients with advanced renal cell carcinoma (Abstract). J Clin Oncol 23:1093s Teicher BA, Sotomayor EA, Huang ZD (1992) Antiangiogenic agents potentiate cytotoxic cancer therapies against primary and metastatic disease. Cancer Res 52:6702–6704 Thula TT, Schultz G, Tran-Son-Tay R, Batich C (2005) Effects of EGF and bFGF on irradiated parotid glands. Ann Biomed Eng 33:685–695 Tomaso E di, Capen D, Haskell A et al (2005) Mosaic tumor vessels: cellular basis and ultrastructure of focal regions lacking endothelial cell markers. Cancer Res 65:5740–5749

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Combinations of Cytotoxic Drugs, Ionizing Radiation and EGFR Inhibitors Guido Lammering

CONTENTS 8.1 8.1.1 8.1.2 8.2 8.3 8.4 8.4.1 8.4.2 8.5 8.6 8.6.1 8.7

The EGFR (ErbB) Family of Receptors in Cancer 115 EGFR 115 EGFR Variations 116 EGFR and Treatment Resistance 116 EGFR and Irradiation 117 Approaches to Inhibit EGFR During Irradiation 118 The Antibody and Dominant-Negative Approach 118 The Small Molecule Approach 118 Combination of EGFR Inhibitors and Irradiation 119 Combinations of Cytotoxic Drugs, Irradiation and EGFR Inhibitors 121 C225 or EGFR Tyrosine Kinase Inhibitors and Radiochemotherapy 121 Conclusion 122 References 123

8.1 The EGFR (ErbB) Family of Receptors in Cancer Growth factors and their receptors play a key role in the development and progression of human cancers. They are overexpressed or aberrantly expressed in many cancers, which results in unregulated cell signalling, dysregulation of growth, tumour initiation or promotion, and invasion and metastasis, thus contributing to at least four of the six hallmarks of cancer (Hanahan and Weinberg 2000). Within the growth factor receptors, the ErbB family of receptor tyrosine kinases and related plasma membrane receptors has been identified as critical components facilitating autocrine growth regulation that are typically the result of coordinated co-expression of growth factors and G. Lammering, MD, PhD Department of Radiation Oncology and Laboratory of Experimental Radiation Oncology, University of Maastricht, 6401 CX Heerlem, The Netherlands

their receptors (Weinberg 1989; Baselga and Mendelsohn 1994). Although the plasma membrane components share important similarities as 170- to 200-kD transmembrane glycoproteins, each ErbB species carries a specific function within the ErbB-receptor Tyr kinase response network (Riese and Stern 1998). ErbB 1 (EGFR) and ErbB 4 are complete receptors with growth factor binding sites in the extracellular NH2-portion and a Tyr kinase domain in the cytoplasmic COOH-terminal portion of the molecule. ErbB 2 represents a constitutively active receptor without a ligand binding domain, and ErbB3 shares ligand specificities with ErbB4 but lacks Tyr kinase activity; therefore, ErbB 2 and ErbB 3 represent important modulators of cellular response to growth factors through heterodimerisation with ErbB 1 and ErbB 4 (Riese and Stern 1998; Earp et al. 1995). These different properties of ErbB receptor tyrosine kinases determine the nature of their interactions with defined homo- and heterodimerisation hierarchies and result in receptor activation. The ErbB receptors mediate their proliferative signals through a major cytoprotective signalling pathway involving the adapter proteins (i.e. GrB2 and SHC), GTP exchange factors, such as SOS, phospholipase CJ (PLCJ), Ras, protein kinase C (PKC), Raf, MAPK and PI-3-kinase-dependent pathways. These signalling pathways directly or indirectly affect cellcycle control and transcription regulation initiating the biosynthetic machinery and cell proliferation (Schmidt-Ullrich et al. 1999).

8.1.1 EGFR All cells of epithelial origin as well as many cells from mesenchymal derivation express the EGFR. A primary function of the EGFR revolves around its capacity to influence cellular growth, proliferation and differentiation. In recent years, many reports have confirmed an overexpression of EGFR in epi-

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thelial tumours. As is the case with other growth factor receptors, increased EGFR activation can result from higher levels of ligand (such as EGF), EGFR gene amplification, increased transcription or mutations that cause unregulated receptor signalling. A correlation between EGFR overexpression and disease stage, disease progression, patient survival and response to therapy has been put forth for a variety of the most common human malignancies (Wells 2000). Although this correlation between EGFR overexpression and poor clinical outcome appears convincing, a direct cause and effect relationship has yet to be firmly established. It is certainly possible that the specific reliance of a particular cell type or tissue on the EGFR pathway for growth is more important than the arithmetic quantification of EGFR.

8.1.2 EGFR Variations Overexpression of EGFR is sometimes associated with the expression of mutated species. One mutant EGFR, named EGFRvIII, lacks a portion of the extracellular ligand-binding domain, leading to a constantly active tyrosine kinase (Huang et al. 1997). EGFRvIII is not found in normal tissues but is expressed on the cell membrane in certain tumours including gliomas, prostate, breast, non-small cell lung, colorectal and ovarian cancers (Moscatello et al. 1995). Mutations of the EGFR kinase domain have also been reported, and recent studies indicate that its frequency is rare in most types of human cancer apart from that of lung adenocarcinoma (Sihto et al. 2005). Studies of a large number of lung tumour patients identified a frequency of 24% for EGFR mutations in the tyrosine kinase domain (exons 18–21) with a higher incidence for female, young, non-smoking patients. Importantly, these mutations seem to identify distinct subsets of lung cancer patients with an increased response to an EGFR-inhibiting drug called gefitinib (Pao et al. 2004).

8.2 EGFR and Treatment Resistance Alterations in chemosensitivity have been noted in preclinical studies of EGFR-overexpressing tumour cell lines. Indeed, higher levels of expres-

G. Lammering

sion of drug-resistance-related proteins, such as topoisomerase II and p-glycoprotein, are found in untreated EGFR-positive renal tumours. Ogawa et al. (1993) measured EGFR expression and cisplatin sensitivity in tumour tissues from 84 patients with lung cancer. The EGFR expression was significantly higher in tumours that were resistant to cisplatin compared with cisplatin-sensitive tumours (Ogawa et al. 1993). Similarly, patients with ovarian cancer who have EGFR-positive tumours or increased transforming growth factor (TGF)-D expression have a lower rate of response to chemotherapy with cisplatin compounds compared with patients with lower EGFR levels (Fischer-Colbrie et al. 1997). Santini et al. (1991) reported that patients with head and neck tumours in which EGFR expression levels were >100 fmol/mg protein had a lower probability of response to chemotherapy than did patients with EGFR levels <100 fmol/mg protein. Furthermore, an association between EGFR expression and clinical radioresistance has been reported in patients with cancer. Ang et al. (2004) and Giralt et al. (2002) reported a correlation between EGFR overexpression and response to radiotherapy in human head and neck cancers or rectal cancer, respectively. The EGFR expression was a significant and independent prognostic indicator for overall survival and recurrence-free survival after radiation therapy in patients with astrocytic gliomas (Zhu et al. 1996). Pillai et al. (1998) noted that patients who had residual or recurrent disease after radiotherapy for cervical cancer had more EGFR expression than those patients who were diseasefree. Other authors found an inverse correlation between EGFR expression and radiocurability in murine carcinomas (Akimoto et al. 1999). Treatment of EGF protected cells against radiation in culture, whereas treatment with an antibody against EGFR induced radiosensitisation (Balaban et al. 1996). While preclinical studies indicate that EGFR inhibition can sensitise many tumour cells to ionizing radiation, in vitro sensitisation with cell lines may not reflect the prognostic implications of EGFR overexpression in vivo. Together, the currently available data suggest that higher levels of EGFR may be associated with chemo- and/or radioresistance in some tumours. These findings therefore stimulated the research of targeted modulation of EGFR function as a new therapeutic strategy; however, the current data are insufficient to suggest using EGFR expression as a predictor of response to chemo- and/ or radiotherapy in general. It is probably more valuable to con-

Combinations of Cytotoxic Drugs, Ionizing Radiation and EGFR Inhibitors

sider modifying EGFR activity to enhance chemoand/or radiotherapy.

8.3 EGFR and Irradiation Over the past decade, molecular biological approaches applied to radiobiological questions have uncovered several mechanisms by which cells respond to ionizing radiation (Schmidt-Ullrich et al. 2003). The DNA damage responses are arguably the most critical, although it is unclear if they can account for the variability in response observed between different tumours and patients. Radiation effects on protein expression and activation of cellular signalling are also important. Three principal consequences of EGFR activation have been shown to be important for tumours and radiation response: 1. Proliferation and cell cycle effects. The inﬂuence of EGFR on tumour cell proliferation has been mainly established by studies investigating the capacity of anti-EGFR agents to slow tumour proliferation and modulate cell cycle phase distribution (Huang et al. 1999, 2002). 2. Anti-apoptosis and survival. The EGF has been demonstrated in some cell lines to prevent apoptosis or promote survival in cells that overexpress EGFR (Rodeck et al. 1997). Many studies on inhibition of EGFR stimulation suggest that activation of growth factor receptors, such as EGFR, may have a role in promoting cell survival in some tumours (Modjtahedi et al. 1998). 3. Angiogenesis. Several oncogenic growth factors and their receptors, including EGF and EGFR, are thought to play a role in tumour angiogenesis as evidenced by numerous studies (Fox et al. 1996). The EGFR activation has been shown to upregulate VEGF production, whereas EGFR inhibition signiﬁcantly effects tumour angiogenesis and reduces VEGF expression (Huang and Harari 2000). The exact mechanisms by which the EGFR family pathway mediates resistance to radiation have been investigated over the past years. Recent studies have been able to demonstrate that irradiation of tumour cells at clinically relevant dose levels can result in an immediate activation of the EGFR family of receptors, and that repeated radiation exposures of 2 Gy lead to an increased expression of EGFR (Schmidt-

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Ullrich et al. 1994, 1996). The underlying molecular mechanisms of the radiation-induced activation of EGFR remain to be understood. First studies indicate, however, that reactive oxygen species after ionizing radiation inhibit protein-tyrosine phosphatases, such as SHP-2, which then specifically phosphorylate the Tyr-992 residue of EGFR (Sturla et al. 2005). The radiation-induced activation of EGFR is defined by a several-fold increase in the tyrosine phosphorylation with a secondary activation of existing signalling transduction cascades. These pathways, which mainly include protein kinases, induce cytoprotective and cytotoxic responses from cell survival to cell death. Cytoprotective responses include signalling cascades of the mitogen-activated protein kinase (MAPK) and the phosphatidyl-inositol-3 phosphate kinase (PI3K), which activate the biosynthetic cascade and therefore possibly stimulate cell proliferation. Considering the increased biosynthetic activity of rapidly proliferating tumour cells, it can be assumed that this will improve the capacity for DNA damage repair. Interestingly, emerging data suggest a novel mechanism by which EGFR after irradiation might improve the capacity for DNA repair. Ionizing radiation, but not EGF, induces the import of EGFR into the nucleus. In the nucleus, EGFR then activates the DNA-dependent kinase (DNA-PK) to improve the DNA repair capacity (Dittmann et al. 2005). The radiation-induced activation of the EGFR family of receptors leads to a dose-dependent proliferative response, which can be observed after single, as well as repeated, radiation exposures (Contessa et al. 1999; Reardon et al. 1999). This cellular proliferative response after repeated radiation exposures leads to increased renewal of tumour clonogens (Withers et al. 1988; Fowler 1991). It has therefore been concluded that the radiation-induced activation of EGFR is involved in the mechanism of accelerated proliferation or repopulation. Because the radiation-induced proliferative, as well as the improved DNA repair responses of tumour cells, counteract the toxic effects of radiotherapy, they are defined as the EGFR-family-induced cytoprotective responses of tumour cells. Taken together, the radiation-induced cytoprotective responses of tumour cells might potentially be induced at the level of the cell membrane through activation of the EGFR family and other involved molecules (Fig. 8.1); therefore, the blockade of EGFR function could result in radiosensitisation in tumour cells.

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Radiation activation

Fig. 8.1. Model of the radiation-induced EGFR-family-mediated pro-proliferative and cytoprotective responses to irradiation

8.4 Approaches to Inhibit EGFR During Irradiation Since EGFR and the other ErbB receptors have emerged as promising targets in radiotherapy, extensive research activity explores potential procedures to target EGFR, the other ErbB receptors and/or its downstream pathways for radiotherapy to enhance radiation action in human carcinomas and malignant gliomas. Over the past several years, it has been recognised that antibodies, small-molecule inhibitors and genetic modulation can be used therapeutically to disturb EGFR and/or ErbB signalling at the cellular level during irradiation. These approaches include monoclonal antibodies and dominant-negative EGFR directed against the receptors and synthetic tyrosine kinase inhibitors that act directly on the cytoplasmic domain of EGFR and/or other ErbB molecules.

8.4.1 The Antibody and Dominant-Negative Approach A number of antibodies have been generated against EGFR. Among the most promising is IMC-

225 (Cetuximab), a humanised M225, which has a higher affinity for EGFR with a longer half-life (Mendelsohn 1997; Goldstein et al. 1995). C225 was found to compete with EGF binding, inhibit EGF-induced tyrosine kinase-dependent phosphorylation, and downregulate EGFR expression by inducing receptor internalisation. Another monoclonal antibody 806 is a novel EGFR antibody with significant antitumour activity that recognises the mutant EGFRvIII and a subset of EGFR found in cells that overexpress EGFR (Perera et al. 2005). Another approach currently in preclinical and clinical development is the functional inhibition of the ErbB-receptor tyrosine kinase network through gene therapeutic expression of a dominant-negative EGFR mutant called EGFR-CD533. EGFR-CD533, a mutant of EGFR, lacks the entire cytoplasmic domain of 533 amino acids and confers no transformation or proliferation-promoting activity (Kashles et al. 1991; Redemann et al. 1992). This dominant-negative EGFR exerts its effect at the protein level through the formation of non-functional receptor complexes with the ErbB-receptor tyrosine kinase family (Kashles et al. 1991; Lammering et al. 2001).

8.4.2 The Small Molecule Approach There exist a growing number of EGFR/ErbB inhibitory small molecule compounds in various stages of preclinical and already clinical development. For tyrosine kinase inhibitors to be used therapeutically, they must be highly specific. The inhibitors studied to date have varying levels of specificity. Several quinazoline derivates have been developed that are more selective for EGFR than for other tyrosine kinase receptors. They act by competitively inhibiting ATP binding (Fry et al. 1994). ZD1839 (Gefitinib, Iressa) is an anilinoquinazoline with an IC50 of 20 nM for the EGFR tyrosine kinase. It binds reversibly to EGFR tyrosine kinase, whereas EKB-569 is an irreversible inhibitor of EGFR. OSI774 (Erlotinib, Tarceva) is a quinazoline analogue with a nanomolar IC50 for reversible inhibition of EGFR activity and high specificity for the receptor (Woodburn 1999). Besides these selective approaches to target EGFR only, several dual inhibitors have also been developed. CI-1033 (Canertinib) is a quinazoline that irreversibly inhibits EGFR and ErbB-2 tyrosine kinases. PKI-166 and GW-572016 (Lapatinib)

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Table 8.1. EGFR/ErbB inhibitory small molecule compounds. TKI tyrosine kinase inhibitors Target

Action

Tested with radiotherapy

ZD1839 (geﬁnitib)

EGFR

Competitive ATP

In vitro/in vivo Antiproliferation, DNA Solomon et al. (2003); damage, apoptosis, Williams et al (2002); antivascular Tanaka (2005)

OSI774 (erlotinib)

EGFR

Competitive ATP

In vitro/in vivo Cell cycle, apoptosis, repopulation, DNA damage

Chinnaiyan et al. (2005)

EKB569

EGFR

Irreversible (Cys 773)

−

−

−

PKI-166

EGFR, ErbB 2

Competitive ATP

−

−

−

GW-572016 (lapatinib)

EGFR, ErbB 2

Competitive ATP

In vitro

Radiosensitisation

Zhou et al. (2004)

Irreversible (Cys 773)

In vitro/in vivo Radiosensitisation

Rao et al. (2000); Nyati et al. (2004)

In vitro/in vivo Antiproliferation, tumour perfusion, antiangiogenesis

Damiano et al. (2001); Williams et al. (2004)

CI-1033 (canertinib) EGFR, ErbB 2 ZD6474 (zactima)

EGFR, Competitive ATP VEGFR2

represent potent pyrrolopyrimidines competitively reversibly binding to the ATP binding site of EGFR and ErbB-2 tyrosine kinases. The compound ZD 6474, on the other hand, is a potent VEGF receptor2 tyrosine kinase inhibitor with additional activity against the EGFR (Table 8.1).

8.5 Combination of EGFR Inhibitors and Irradiation Studies using A431 human carcinoma xenografts in nude mice, combining C225 with local tumour radiation, demonstrated enhanced tumour radioresponse by a factor of 1.6 when a single dose of C225 was used and 3.6 when three doses of C225 were used (Milas et al. 2000). Other groups confirmed the significantly enhanced clinical response in a wide spectrum of epithelial human tumour xenografts that received the combination of radiation plus C225 (Huang et al. 1999; Saleh et al. 1999). Other authors recently demonstrated encouraging effectiveness of C225 when administered systemically in an intracranial model of an EGFR-amplified glioblastoma. The median survival of these animals increased by at least 900% (Eller et al. 2005). Interestingly, the interactions of C225 and radiation in general were more profound in vivo than initially predicted by in vitro studies, suggesting that mechanisms beyond simple prolifera-

Reported mechanisms of enhanced radiation response

Reference

TKI compounds

tive growth inhibition act in the in vivo setting (Harari and Huang 2001). Multiple mechanisms seem to underlie the enhancement of tumour response to radiation by C225 involving both direct and indirect interaction with tumour cells. They may include C225-induced inhibition of DNA damage repair, enhanced radiosensitivity originating from specific disturbances in cell-cycle phase distribution, enhancement of radiation-induced apoptosis, inhibition of tumour angiogenesis and effects on tumour cell migration and invasion capacity (Harari and Huang 2002). Huang and Harari (2000) reported that treatment with C225 could cause redistribution of DNA-PK from the nucleus to the cytosol resulting in reduced radiation-induced DNA damage repair. C225 significantly inhibits formation of new vessels, suggesting a direct inhibitory effect of C225 on tumour angiogenesis possibly through inhibition of mRNA and protein production of angiogenic factors (Milas et al. 2000; Perrotte et al. 1999). In contrast, the mechanisms by which C225 inhibits EGFR at the protein level are not fully understood. For example, it has not been investigated whether the radiosensitising effects of C225 might also be explained by the blockade of EGFR heterodimers formation and receptor crosstalk, which would support a critical involvement of other EGFR family members and other growth factors and their receptors in the enhanced radiosensitivity. Functional inhibition of the ErbB-receptor tyrosine kinases through dominant-negative EGFR (DN-

120

EGFR) has also been shown to significantly sensitise a broad spectrum of tumour cells independent of the varying ErbB-receptor expression levels. The further developed approach of DN-EGFR application in human xenograft tumours also effectively induced tumour radiosensitisation, providing further proof of the promise of EGFR inhibition to enhance radiosensitivity in human tumours (Lammering et al. 2001). Just as with C225, there is solid preclinical data regarding the capacity of ZD1839 and CI-1033 to enhance radiation efficacy in both in vitro and in vivo model systems (Huang et al. 2002; Raben et al. 2001; Rao et al. 2000; Williams et al. 2002). ZD1839 has been proven to enhance the cytotoxicity of radiation across a spectrum of human cancer cell lines including lung, pancreas, malignant glioma, colon and head and neck (Stea et al. 2003; Solomon et al. 2003; Baumann et al. 2003). In a more recent publication, however, ZD1839 failed to act as a radiosensitiser in vitro in concomitant association with radiation. The drug brought about additive to subadditive interaction with radiation with regard to growth inhibition, clonogenic death and induction of apoptosis, but it did not hinder the rejoining of radiation-induced DNA doublestrand breaks in any cell line tested (Giocanti et al. 2004). This finding is in contrast to another more recent presentation at the Annual Meeting of the American Association for Cancer Research 2005, strongly supporting the inhibitory effect of ZD1839 on the repair of double-strand breaks after ionizing radiation in two non-small cell lung cancer (NSCLC) cell lines (Tanaka 2005). These conflicting data highlight the growing body of evidence of the different efficacy of anti-EGFR strategies on different cellular characteristics. It could well be that successful modulation of radiosensitivity through inhibition of DNA repair with the help of anti-EGFR approaches depends on specific molecular characteristics such as the ras genotype (Toulany et al. 2005). For human colon carcinoma xenografts, the combination of ZD1839 with radiation enhanced the therapeutic effect compared with radiation alone by a factor of 1.6 (Williams et al. 2002). Growth delay assays with ZD1839 in combination with radiation for human squamous cell carcinomas revealed a significant synergistic tumour growth inhibition effect (Huang et al. 2002). In line with these data on ZD1839 and radiotherapy, Baumann et al. (2003) also found improvement of growth delay with BIBX1382BS, which is an

G. Lammering

inhibitor like ZD1839 in combination with radiation for FaDu human squamous cell carcinoma; however, they could also clearly demonstrate that despite the antiproliferative activity in these rapidly repopulating FaDu cells and the significantly increased tumour growth delay, local tumour control was not improved. These findings highlight that significant effects on tumour growth delay do not necessarily reflect the efficacy of anti-EGFR small molecule inhibitors in combination with radiation on curative potential (Krause et al. 2005). Furthermore, the efficacy of this combination on tumour cell radiosensitisation might not only purely be dependent on the presence of EGFR, but also on other cellular molecular characteristics, which are not easily understood at present (Toulany et al. 2005). Preclinical studies in ErbB-overexpressing human breast cancer cells identified a supraadditive effect of CI-1033 with fractionated radiation (Rao et al. 2000). Besides the mechanism of inhibition of EGFR-induced cancer cell proliferation, small molecule tyrosine kinase inhibitors also seem to potentiate the antitumour activity of radiation in part by effects on cellular apoptosis and angiogenesis (Huang et al. 2002). This demonstrated inhibition of neoangiogenesis in human tumour xenografts may result in improved blood supply to the tumour, leading to reoxygenation and increased radiosensitivity, thereby improving radiocurability. In contrast to C225, small-molecule tyrosine kinase inhibitors of EGFR might also be active against the naturally occurring mutant EGFRvIII, since EGFRvIII has an intact, intracellular kinase domain. This is particularly relevant because of the emerging importance of EGFRvIII in several human carcinomas and malignant gliomas (Moscatello et al. 1995; Wikstrand et al. 1997). Taken together, the currently available data regarding the combination of EGFR inhibitors and irradiation have convincingly shown that both the antibody and the small molecule approach to target EGFR are able to afford potentiation of radiotherapy through inhibition of tumour repopulation, DNA damage repair, cell cycle kinetics, antiapoptosis and angiogenesis. The individual response of anti-EGFR strategies in combination with radiotherapy, however, may be explained by complex specific molecular and cellular characteristics, which include mutations at the level of EGFR itself or at the level of downstream effectors.

Combinations of Cytotoxic Drugs, Ionizing Radiation and EGFR Inhibitors

121

Table 8.2. Preclinical results of EGFR-dependent enhanced radiation responses. DER dose enhancement ratio Approach

Fractionation

In vitro assay DER In vivo assay DER

Reference

DN EGFR

Single

1.4−1.6

1.6−1.9

Lammering et al. (2001)

Multiple

1.4−1.8

1.8−3.8

Single

1.2−1.3a

Multiple

1.3a

>4.0

Single/multiple

1.2−1.4a

1.6−3.6

Milas et al. (2000)

Single

<1.0

1.5; 1.6

Multiple

1.2

3.3a; 4.0

Giocanti et al. (2004); Solomon et al. (2003); Williams et al. (2004)

Single

1.3−1.5a

2.0−3.8a

Chinnaiyan et al. (2005) Rao et al. (2000)

C225

ZD1839

OSI-774

Huang et al. (1999) Huang and Harari (2000)

Multiple CI-1033 ZD6474

Single

1.7a

1.4

Multiple

1.0−1.4

>4.0a

Single

a

1.8−3.0

Multiple GW572016 Single aEstimated

1.2−1.3a

2.4

Nyati et al. (2004)

a

Damiano et al. (2005)

1.3−1.5 concurrent, 1.6 sequential

Williams et al. (2004)

−

Zhou et al. (2004)

from data. Method: in vitro, D37 or D10; in vivo, ex vivo clonogen or growth delay

8.6 Combinations of Cytotoxic Drugs, Irradiation and EGFR Inhibitors The significant interest and investigation of EGFR as a molecular target for radiotherapy or chemotherapy and the translation of discoveries in molecular biology into clinically relevant therapies has led to further preclinical investigations of the efficacy of combining anti-EGFR approaches, not only with radiotherapy, but also with radiochemotherapy, since radiochemotherapy is already considered the standard therapy for many epithelial tumours in the clinic. The mode of combining chemotherapeutic drugs with radiation takes advantage mainly of the sensitising effects of drugs on cell kill by radiation. The additional use of agents that counteract molecular determinants or processes responsible for resistance of cancer cells to radiation or chemotherapeutic drugs, however, might further improve efficacy without the expense of an increased normal tissue toxicity; therefore, first investigations have been undertaken to combine anti-EGFR agents with radiochemotherapy regimen. These investigations not only help us to better characterise the synergistic possibilities of anti-EGFR approaches with the combination of chemotherapy and radiotherapy, they also identify insufficient and antagonistic combination treat-

ments, which should be avoided. Most preclinical data on the combined use of anti-EGFR, chemotherapy and radiotherapy are currently only available for C225 and ZD1839, which are also the most clinically developed of the compounds described.

8.6.1 C225 or EGFR Tyrosine Kinase Inhibitors and Radiochemotherapy In both in vitro and in vivo preclinical studies, C225 was shown to enhance the antitumour effects of the chemotherapeutic drugs doxorubicin, cisplatin, paclitaxel, topotecan and gemcitabine (Mendelsohn and Fan 1997; Ciardiello et al. 1999; Inoue et al. 2000). Interactions between C225 and chemotherapy may be based on comparable mechanisms, as described for radiotherapy, such as inhibition of DNA repair mechanisms, alteration in growth factor production, promotion of apoptotic cell death and anti-angiogenesis. Based on these previous studies and the known radiosensitising effect of C225 as well, Buchsbaum et al. (2002) hypothesised that the combination of C225 with gemcitabine, which also represents a known radiosensitiser, and radiotherapy against human pancreatic cancer cells and tumour xenografts, would provide greater efficacy than either treatment alone or any combination of two treatments. The results

G. Lammering

122

indeed identified a significantly greater efficacy for the triple combination treatment. The in vitro results indicated a significant inhibition of cell proliferation and induction of apoptosis. The xenograft tumours showed a remarkable growth inhibition with a 100% regression for MiaPaCa-2 tumours for more than 250 days and the greatest growth inhibition for BxPC-3 tumours compared with any single or dual treatment. The differences in the magnitude of response between the two cell lines again could relate to differences in molecular characteristics, such as growth factor receptors, and angiogenic factors, such as VEGF. In another study combining C225 with cisplatin and radiotherapy in NSCLC, however, the triple therapy yielded only a nonsignificant advantage in tumour growth control over doublet combinations. In fact, cisplatin in combination with radiotherapy resulted in more comparable growth delay than cetuximab in combination with radiotherapy; thus, this study provided no rationale for the combined treatment of C225 and cisplatin during radiotherapy in NSCLC (Raben et al. 2005). In another study on the combined use of C225 with radiochemotherapy, Nakata et al. (2004) provided strong evidence for the potent enhancement of tumour response of C225 to docetaxel when combined with radiation. These in vivo growth delay assays were performed with a breast cancer cell line MDA468 and a squamous carcinoma cell line A431. The addition of C225 to the treatment of docetaxel and radiation (1u10 Gy) in A431 increased the growth delay enhancement factor from 1.94 with docetaxel alone during radiation to an enhancement factor of 3.98. For MDA468 tumours, the enhancement in growth delay through docetaxel during single dose or fractionated radiation reached enhancement factors of 1.3 and 1.9, respectively. The additional application of C225 improved the enhancement in growth delay to factors of 5.2 and 3.2 for single dose or fractionated radiation; thus, docetaxel seems to represent an ideal cytotoxic drug to be used in combination with C225 to achieve further enhancement of tumour radioresponse. The mechanisms are multiple and include direct effects on the tumour cells or indirect effects through affecting tumour angiogenesis or tumour microenvironment. Docetaxel has been shown to enhance tumour oxygenation and mitotic arrest, whereas C225 interferes with cellular repair processes, inhibits the production of important angiogenic factors and improves endothelial cell damage; thus, C225 and docetaxel might synergistically contribute to the radiation-induced damage at the level of the tumour as well as the endothelial cell.

There rarely exist any data on the preclinical evaluation of the synergistic enhancement of radiosensitivity through the combined use of EGFRtyrosine kinase inhibitors and chemotherapeutic agents. Although the rationale for combining EGFR tyrosine kinase inhibitors with radiochemotherapy seems convincing, no studies have yet preclinically defined the best sequence and the best combination cytotoxic drugs for the triple treatment. In vitro data suggest the application of EGFR tyrosine kinase inhibitors to being given before and during cytotoxic drug exposure, which was also the case for the combination with radiation (Magne et al. 2002); therefore, the overall recommendation exists that EGFR tyrosine kinase inhibitors be applied before and during radiochemotherapy. Phase-II and phaseIII trials have already been started mainly in head and neck and lung cancer patients with ZD1839 or OSI-774 and chemotherapy plus fractionated radiotherapy, without awaiting further preclinical investigations regarding optimised combinations and optimised sequencing. One remaining concern of all triple-treatment combinations is the lack of knowledge of a further increase in normal tissue toxicity, a major limitation of concurrent radiochemotherapy; thus, studies on the effect of EGFR inhibitors on radiochemotherapyinduced normal tissue injury are urgently needed.

8.7 Conclusion The rationale for targeting the EGFR family in combination with radiotherapy and/or chemotherapy has been established and clinical trials are already in progress. The mechanisms by which the EGFR family mediates resistance to radiotherapy are multiple and complex and include proliferative, antiapoptotic and pro-angiogenic responses as well as an enhancement in the cellular capacity for DNA repair. Importantly, ionizing radiation activates the EGFR family, which leads to an increased activation of the existing downstream signalling pathways, like the MAPK and the PI3K pathway, thereby contributing to the onset of radioresistance. Although both approaches to target EGFR, the anti-EGFR antibody (C225) and the EGFR tyrosine kinase inhibitors confer a significant improvement in the radiosensitivity of human tumour cells in vitro as well as in vivo, the antibody approach seems to provide a more profound enhancement of the tumour response to

Combinations of Cytotoxic Drugs, Ionizing Radiation and EGFR Inhibitors

radiation. This suggests that other mechanisms of C225, which modulate the microenvironment in vivo, e.g. inhibition of tumour angiogenesis and induced reoxygenation, also significantly contribute to the effects of the enhanced radiosensitivity induced by C225 in vivo (Krause et al. 2005). Promising in vivo data provide first evidence that C225 and chemotherapeutic drugs, such as docetaxel and gemcitabine, might synergistically attribute to the radiation-induced damage in tumours. In general, however, conflicting data continue to exist regarding the varying efficacy of the different anti-EGFR strategies in combination with radiation and/or chemotherapy. One important explanation is that some approaches depend on specific molecular and cellular characteristics in order to successfully modulate radiosensitivity. Specific mutations, either at the level of EGFR or at the level of downstream effectors, might correlate to the individual response and the large variety of response depending on the cancer cell line. In this regard, the PI3K/Akt pathway may represent the most important mediator of the cytoprotective responses induced by EGFR. More investigations at all levels of cellular responses to radiation are necessary in order to better understand the variation in the effectiveness of responses to antiEGFR strategies in combination with radiation. This will also provide more insight into the molecular characteristics, which could predict effectiveness of the anti-EGFR approach to radiosensitisation. It is also still unclear if it is necessary to achieve complete EGFR blockade or significant inhibition of downstream effector kinases, such as Akt or MAPK, and if other ErbB receptors, or even other receptor families, might counteract the radiosensitisation induced by EGFR blockade due to possible compensatory mechanisms in fractionated radiation regimens. There is also a need for a better understanding of the optimal combinations, the best sequence and the normal tissue toxicity of EGFR modulators together with radiation and/or chemotherapy. In addition, emerging opportunities for pharmacological manipulation of other attractive molecular targets, such as the PI3K pathway in the radiation treatment of cancer, are pending and may also ultimately prove efficacious in combination with EGFR inhibition during radiotherapy. The challenge in future research development will be to identify the appropriate inhibitor for the specific individual tumour. This also needs further studies at all levels of translational research and genome-wide screening to identify predictive markers of response for the appropriate inhibitor.

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Sihto H, Puputti M, Pulli L, Tynninen O, Koskinen W, Aaltonen LM, Tanner M, Bohling T, Visakorpi T, Butzow R, Knuuttila A, Nupponen NN, Joensuu H (2005) Epidermal growth factor receptor domain II, IV, and kinase domain mutations in human solid tumours. J Mol Med epub Solomon B, Hagekyriakou J, Trivett MK, Stacker SA, McArthur GA, Cullinane C (2003) EGFR blockade with ZD1839 (“Iressa”) potentiates the antitumour effects of single and multiple fractions of ionizing radiation in human A431 squamous cell carcinoma. Int J Radiat Oncol Biol Phys 55:713–723 Stea B, Falsey R, Kislin K, Patel J, Glanzberg H, Carey S, Ambrad AA, Meuillet EJ, Martinez JD (2003) Time and dose-dependent radiosensitization of the glioblastoma multiforme U251 cells by the EGF receptor tyrosine kinase inhibitor ZD1839 (“Iressa”). Cancer Lett 202:43–51 Sturla LM, Amorino G, Alexander MS, Mikkelsen RB, Valerie K, Schmidt-Ullrich RK (2005) Requirement of Tyr-992 and Tyr-1173 in phosphorylation of the epidermal growth factor receptor by ionizing radiation and modulation by SHP2. J Biol Chem 280:14597–14604 Tanaka T (2005) Inhibition of DNA repair in the radiosensitization of NSCLC cells by gefitinib, a specific EGFR-inhibitor. Proc Am Assoc Cancer Res 46:abstract 1994 Toulany M, Dittmann K, Kruger M, Baumann M, Rodemann HP (2005) Radioresistance of K-Ras mutated human tumour cells is mediated through EGFR-dependent activation of PI3K-AKT pathway. Radiother Oncol 76:143–150 Weinberg RA (1989) Oncogenes and the molecular origin of cancer. Cold Spring Harbor Laboratory, Cold Spring Harbor, New York, pp 54–62 Wells A (2000) The epidermal growth factor receptor (EGFR): a new target in cancer therapy. Signal 1:4–11 Wikstrand CJ, McLendon RE, Friedman AH, Bigner AD (1997) Cell surface localization and density of the tumour-associated variant of the epidermal growth factor receptor, EGFRvIII. Cancer Res 57:4130–4140 Williams KJ, Telfer BA, Stratford IJ, Wedge S (2002) ZD1839 (“Iressa”), a specific oral epidermal growth factor receptor-tyrosine kinase inhibitor, potentiates radiotherapy in a human colorectal cancer xenograft model. Br J Cancer 86:1157–1161 Williams KJ, Telfer BA, Brave S, Kendrew J, Whittaker L, Stratford IJ, Wedge SR (2004) ZD6474, a potent inhibitor of vascular endothelial growth factor signaling, combined with radiotherapy: schedule-dependent enhancement of antitumour activity. Clin Cancer Res 10:8587–8593 Withers HR, Taylor JMG, Maciejewski B (1988) The hazard of accelerated tumour clonogen repopulation during radiotherapy. Acta Oncol 27:131–146 Woodburn JR (1999) The epidermal growth factor receptor and its inhibition in cancer therapy. Pharmacol Ther 82:241–250 Zhou H, Kim YS, Peletier A, McCall W, Earp HS, Sartor CI (2004) Effects of the EGFR/HER2 kinase inhibitor GW572016 on EGFR- and HER2-overexpressing breast cancer cell line proliferation, radiosensitization, and resistance. Int J Radiat Oncol Biol Phys 58:344–352 Zhu A, Shaeffer J, Leslie S, Kolm P, El-Mahdi AM (1996) Epidermal growth factor receptor: an independent predictor of survival in astrocytic tumours given definitive irradiation. Int J Radiat Oncol Biol Phys 34:809–815

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Combinations of Cytotoxic Drugs, Ionizing Radiation, and Mammalian Target of Rapamycin (mTOR) Inhibitors Jann N. Sarkaria

CONTENTS 9.1 9.2 9.3 9.3.1 9.3.2 9.3.3 9.4 9.5 9.6 9.7

Introduction 127 Biology of mTOR 128 mTOR-Dependent Signaling Pathways 129 p70S6K 129 4EBP1 130 HIF-1 130 Anti-Tumor Effects of mTOR Inhibition 131 Clinical Experience with mTOR-Inhibitor Monotherapy 132 Combination Therapies with mTOR Inhibitors Conclusion 134 References 134

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9.1 Introduction Rapamycin and its analogs are novel, molecularly targeted drugs that are being developed as anticancer agents. The parent compound, rapamycin (Sirolimus, Rapamune, Wyeth, Madison NJ, USA) is approved by the Food and Drug Administration (FDA) for the prevention of allograft rejection following renal transplantation, and for incorporation into drug-eluting stents to prevent re-stenosis following coronary angioplasty. Experience in the transplant setting suggests that long-term use of this agent is safe and well tolerated. Rapamycin analogs with more favorable pharmacokinetic properties are currently being developed as anti-cancer drugs (Fig. 9.1). CCI-779 (Temsirolimus, Wyeth Pharmaceuticals) is an ester of rapamycin, with superior

J. N. Sarkaria, MD Assistant Professor, Department of Oncology, Mayo Clinic College of Medicine, 200 First Street SW, Rochester, MN 55905, USA

oral bioavailability compared with the parent compound rapamycin. This drug is available in oral and intravenous formulations, and clinical development of this drug is well underway with several phaseII and phase-III trials being conducted. RAD001 (Everolimus, Novartis International AG, Basel, Switzerland) is an orally available hydroxyethyl derivative of rapamycin developed for applications in the transplant, cardiovascular, and oncological settings, and clinical testing for all these indications is ongoing. The newest mammalian target of rapamycin (mTOR) inhibitor to be developed for clinical use is AP23573 (Ariad Pharmaceuticals, Inc., Cambridge, Massachusetts, USA). Early phase-I clinical trials with this agent, which is also an analog of rapamycin, are now underway. Rapamycin and its analogs inhibit the signaling activity of the serine-threonine protein kinase mTOR. mTOR functions downstream from multiple growth factor receptor tyrosine kinases to promote cell growth and proliferation. Key downstream targets of mTOR include p70S6 kinase and eukaryotic initiation factor 4E-binding protein (4EBP1), which modulate the translation of select mRNA transcripts that ultimately impact on cell growth and cell cycle progression. More recent data have linked mTOR signaling with the cellular response to hypoxia and the expression of vascular endothelial growth factor (VEGF), which suggests that mTOR may be an important mediator of tumor angiogenesis. In tumors that are reliant on mTOR signaling, disruption of these key signaling pathways by rapamycin results in cell cycle arrest and inhibition of angiogenesis, and these effects may account for the anti-neoplastic activities of mTOR inhibitors seen in multiple tumor types. Based on promising preclinical studies, rapamycin and its analogs currently are being tested as anti-neoplastic agents, both given alone or in combination with conventional cancer therapies. In this chapter, the biology of mTOR signaling and the cellular pharmacology of mTOR inhibitor monotherapy and combination therapy are reviewed.

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R Rapamycin, R =

RAD001, R =

OH

OH O O

CCI-779, R = OH

O OH

Fig. 9.1. Structure of rapamycin and rapamycin derivatives

9.2 Biology of mTOR mTOR is a serine-threonine-directed kinase that belongs to the family of phosphatidyl-inositol 3-kinase-related kinases (PIKK). Members of this PIKK family all contain a C-terminal kinase domain that shares significant homology with that of the phosphatidyl-inositol 3-kinase (PI3K). Other members of this family include ataxia telangiectasia mutated (ATM), ATM and Rad3-related (ATR) and DNA-dependent protein kinase (DNA-PK; Abraham 2001; Durocher and Jackson 2001). These latter three kinases play key roles in orchestrating DNA damage checkpoint responses and DNA repair (Zhou and Elledge 2000). In contrast, mTOR monitors intracellular nutrient and energy availability and promotes cell growth and proliferation following mitogenic stimuli, dependent upon the availability of requisite nutrients (Raught et al. 2001). Rapamycin is a highly specific inhibitor of mTOR function. Rapamycin is unable to bind directly to mTOR but forms a complex with the immunophilin, 12 kDa FK506-binding protein (FKBP12; FK-506 is an unrelated immunosuppressant). It is this drugprotein complex that binds to mTOR through an FKBP12-rapamycin binding (FRB) domain (Cutler et al. 1999). The FRB domain is adjacent to the kinase domain in mTOR and formation of this tri-molecular complex markedly attenuates downstream signaling from mTOR. Interestingly, rapamycin treat-

ment does not inhibit mTOR catalytic kinase activity directly, since autophosphorylation of mTOR is unaffected by rapamycin treatment. Instead, binding of the FKBP12/rapamycin complex is thought to prevent interaction of mTOR with its kinase substrates and thus prevent downstream signaling (Edinger et al. 2003). The interaction of the rapamycin/FKBP12 complex with mTOR is highly specific and is so stable that inhibition of mTOR by rapamycin is essentially irreversible. The cellular and biochemical effects of rapamycin are generally believed to result exclusively from inhibition of mTOR signaling (Brown et al. 1994; Sabatini et al. 1994). The mTOR signaling network (Fig. 9.2) is important for driving cell growth and proliferation in multiple tumor types. Several receptor tyrosine kinases (RTKs), including the epidermal growth factor receptor (EGFR), platelet-derived growth factor receptor (PDGFR), and insulin-like growth factor receptor (IGFR), can activate PI-3 kinase activity, which, in turn, phosphorylates phosphatidylinositol (PI) on the D-3 position (Grant et al. 2002). The resulting accumulation of phosphatidylinositol-3, 4, 5-triphosphate on the cytoplasmic surface of the plasma membrane leads to activation of a number of kinase-signaling pathways including that regulated by protein kinase B (PKB, Akt). Akt stimulates mTOR function both through direct phosphorylation of a negative regulatory domain within mTOR (Sekulic et al. 2000) as well as through its effects on the tuberous sclerosis complex-2 (TSC2) protein (Dan et al. 2002; Inoki et al. 2002; Potter et al. 2002; Tee et

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al. 2002). TSC2, in a complex with tuberous sclerosis complex-1 (TSC1) protein, functions as a GTPaseactivating protein towards the Rheb1 GTPase. Akt-mediated phosphorylation of TSC2 disrupts the TSC1/TSC2 complex and relieves inhibition of Rheb1 activity; activated Rheb1 then can stimulate mTOR phosphorylation and signaling (see Fig. 9.2; Castro et al. 2003; Garami et al. 2003; Inoki et al. 2003; Saucedo et al. 2003). The inhibitory effects of TSC2 on mTOR activity are stimulated in nutrientdeprived conditions by activation of LKB-1, which signals through AMP-activated protein kinase (AMPK) to enhance TSC2 activity (Corradetti et al. 2004; Shaw et al. 2004). Signaling from mTOR also is regulated by association with either Rictor or Raptor, which function as scaffolding proteins to promote selective association and phosphorylation of downstream targets (Hara et al. 2002; Kim Do et al. 2002). Collectively, these data highlight the idea that mTOR functions within a molecular complex of multiple proteins that regulate its activity. PI3K-mediated activation of Akt is normally opposed by the lipid phosphatase PTEN (phosphatase and tensin analog), which dephosphorylates phosphatidylinositol at the D-3 position. Deletion or mutation of the gene encoding this tumor suppressor protein commonly occurs in multiple tumor types and results in constitutive activation of PI3Kdependent signaling pathways that include Akt and

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activated Ras as signaling mediators. Consistent with the potential role of the Akt/mTOR signaling pathway in tumorigenesis, overexpression of activated Akt and activated Ras in glial progenitor cells leads to formation of glioblastoma-like tumors in a transgenic mouse model (Holland et al. 2000), and these tumors are exquisitely sensitive to treatment with rapamycin. Germ-line inherited deficiencies in PTEN, TSC, or LKB-1 result in Cowden’s disease, tuberous sclerosis, and Peutz-Jeghers syndrome, respectively, which are all characterized by the development of multiple benign hamartomas. Loss of function in any one of these three proteins results in hyperactivation of mTOR signaling, and this presumably accounts for the development of the characteristic hamartomatous lesions; thus, constitutive activation of mTOR signaling can be an important contributor to tumorigenesis in both benign and malignant tumors.

9.3 mTOR-Dependent Signaling Pathways mTOR signals downstream to multiple protein targets including but not limited to p70 S6 kinase (p70S6K), initiation factor 4E binding protein (4EBP1), and the hypoxia-inducible transcription factor, HIF-1D. These three well-characterized downstream signaling targets have been implicated in control of hypoxia- and mitogen-induced tumor proliferation, and disruption of these pathways may play an important role in the anti-tumor effects of rapamycin. In the sections below, we describe the potential links between the anti-tumor effects of mTOR inhibitors and disruption of downstream signaling to p70S6K, 4EBP1, and HIF1 in more detail.

9.3.1 p70S6K

Raptor mTOR

p70S6K

4E-BP1

HIF-1α

Ribosomal S6

eIF4E

VEGF, other hypoxia genes

Fig. 9.2. The mTOR signaling network

mTOR regulates translation of select mRNA transcripts containing 5’-terminal oligopyrimidine (5’TOP) tracts through phosphorylation of p70S6K. Following PI3K-dependent phosphorylation of residues within an auto-inhibitory domain, mTOR regulates the phosphorylation of Thr-389 (Volarevic and Thomas 2001). Modification of this residue is essential for subsequent phosphorylation of other residues within the activation loop of the kinase domain, which allows for full catalytic activity.

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After mitogen stimulation, activated p70S6K phosphorylates the S6 component of the 40S ribosomal subunit, and this promotes translation of mRNA containing 5’TOP (Jefferies et al. 1997). Because transcripts for many ribosomal proteins and translation elongation factors contain this 5’TOP motif, rapamycin-mediated suppression of p70S6K activity may inhibit cell growth and proliferation by limiting ribosomal biogenesis and restricting protein synthesis capacity.

9.3.2 4EBP1 mTOR modulates protein translation initiation by regulating the assembly of the eukaryotic initiation factor 4F (eIF4F) complex on the 5’-methyl-GTP cap of mRNA transcripts. The eIF4F complex is a heterotrimer composed of the mRNA cap-binding protein eIF4E, a scaffolding protein eIF4G, and a helicase eIF4A (reviewed by Raught et al. 2001). This tripartite complex regulates the rate of capdependent protein translation by mediating the rate-limiting step of mRNA loading onto the small 40S ribosomal subunit. Formation of a functional eIF4F complex is controlled by the phosphorylation status of an eIF4E binding protein (4E-BP1). In nutrient- or growth-factor-deprived cells, the association of hypophosphorylated 4E-BP1 with eIF4E blocks binding of eIF4G to the cap structure and inhibits cap-dependent translation. In contrast, nutrient- or mitogen-induced phosphorylation of 4E-BP1 disrupts association with eIF4E and allows formation of a functional eIF4F complex (Gingras et al. 1998; Herbert et al. 2002). 4E-BP1 is phosphorylated on at least five serine or threonine sites, and these mitogen-induced modifications are regulated, in part, by mTOR. Several studies have suggested that mTOR directly phosphorylates all five sites on 4EBP1 (Brunn et al. 1997; Mothe-Satney et al. 2000), whereas others have argued that direct mTOR phosphorylation of two of the sites (Thr-37 and Thr-46) serves as a priming event that allows subsequent phosphorylation of the other sites (Ser-65, Thr-70, and Ser-83) by other signaling pathways (Gingras et al. 1999). Rapamycin diminishes 4E-BP1 phosphorylation, prevents dissociation of 4E-BP1 from eIF4E, and results in inhibition of cap-dependent translation. Because translation is less efficient for transcripts with complex secondary structures, rapamycin preferentially inhibits translation of mRNA transcripts containing complex 5’ untranslated

regions (UTR; De Benedetti and Harris 1999). Transcripts with complex 5’UTRs whose translation is inhibited by rapamycin include key proteins involved in cell proliferation and angiogenesis, such as cyclin D1, ornithine decarboxylase, and VEGF.

9.3.3 HIF-1α Hypoxia induces the expression of multiple genes containing hypoxia response elements (HREs), and transcription from this response element is regulated primarily by the HIF-1 transcription factor. HIF-1 is a heterodimer composed of HIF-1D and HIF-1E. Under normoxic conditions, HIF-1 heterodimer levels are undetectable due to rapid degradation of HIF-1D subunit. The stability of HIF-1D is regulated through post-translational modification of an oxygen-dependent degradation (ODD) domain. In the presence of oxygen, prolyl hydroxylases modify two conserved proline residues (Pro402 and Pro-564) within the ODD (Jaakkola et al. 2001). Hydroxylation of these residues promotes HIF-1D association with the von Hippel Lindaucontaining ubiquitin ligase complex and subsequent (Yu et al. 2001) ubiquitin-mediated proteosomal degradation. Because molecular oxygen is required for catalysis of this reaction, hypoxic conditions prevent hydroxylation of the ODD, which results in stabilization of HIF-1D. Other transactivating post-translational modifications and dimerization with the HIF-1E subunit result in formation of an active HIF-1 transcriptional complex. HIF-1 drives expression of genes, such as VEGF, which contain HREs within their promoter region. The repertoire of hypoxia-inducible genes enables tumor or normal tissues to adapt to low oxygen environments and include genes involved in oxygen and glucose transport, glycolysis, growth-factor signaling, immortalization, genetic instability, invasion and metastasis, apoptosis, and pH regulation (Harris 2002). Signaling through the PI3K/mTOR pathway regulates HIF-1D expression and activity (Abraham 2004). The link between PI3K signaling and HIF-1D activity was first established in Ras-transformed cells, where hypoxia-induced signaling to HIF-1 was blocked by genetic or pharmacological inhibition of PI3K activity (Mazure et al. 1997). Subsequent studies have demonstrated that restoration of wild-type PTEN function, expression of a dominant-negative Akt construct, or treatment with rapamycin blocks hypoxia and mitogen-induced HIF-1 signaling

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(Zhong et al. 2000; Zundel et al. 2000; Laughner et al. 2001). Moreover, a recent study demonstrated that rapamycin blocks both hypoxia-induced HIF1D accumulation and transactivation, and that this effect of rapamycin is specifically due to pharmacological inhibition of mTOR (Hudson et al. 2002). Collectively, these data suggest the existence of a PI3K/Akt/mTOR signaling pathway that regulates HIF-1D expression, stability, or activation.

9.4 Anti-Tumor Effects of mTOR Inhibition The central role for mTOR in modulating cell proliferation in both tumor and normal cells and the importance of mTOR signaling for the hypoxic response suggests that rapamycin-based therapies may exert anti-tumor effects primarily through either inhibition of tumor cell proliferation or suppression of angiogenesis. Preclinical and early clinical results demonstrate that only a subset of tumors respond to rapamycin-based therapies. In the following sections, we review the preclinical data and the evidence supporting the anti-angiogenic and cytostatic properties of rapamycin. Preclinical studies have demonstrated efficacy of rapamycin analogs and the parent compound in multiple tumor types. In the National Cancer Institute (NCI) 60 tumor cell line panel, both rapamycin (NSC 226080) and CCI-779 (NSC 683864) demonstrated growth inhibitory activity against a broad spectrum of tumors with a subset of leukemia, lung, brain, prostate, breast, as well as renal and melanoma tumor cell lines being inhibited at low nanomolar concentrations (http://dtp.nci.nih.gov/). Early animal studies at the NCI and at Ayerst Research Laboratories demonstrated modest growth inhibitory properties of rapamycin in murine tumor models of B16 melanoma, P388 lymphocytic leukemia, EM ependymoblastoma, CD8F1 breast carcinoma, Colon 38, CX-1, and 11/A colon cancer models (Eng et al. 1984). Subsequently published studies have documented significant tumor growth inhibition with rapamycin or CCI-779 treatment of DAOY medulloblastoma, U251 or SF295 glioma, PC-3, DU-145, LAPC4, or LAPC9 prostate carcinoma, and Rh-18 rhabdomyosarcoma human tumor xenografts (Houchens et al. 1983; Dudkin et al. 2001; Geoerger et al. 2001; Neshat et al. 2001). These data have provided the impetus for development of mTOR inhibitor therapy in a variety of tumor types.

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Treatment of tumor cells in vitro with rapamycin results in an accumulation of cells in the G1 phase of the cell cycle. Similarly, rapamycin treatment in tumor-bearing animals results in decreased tumor cell proliferation as indicated by bromodeoxyuridine (BrdU) labeling index (Eshleman et al. 2002). At the molecular level, this drug-induced cell cycle arrest is associated with an accumulation of the cyclin-dependent kinase inhibitor, p27kip1, decreased expression of cyclinD1, and a corresponding decrease in phosphorylation of the retinoblastoma protein. CyclinD1 mRNA contains a complex 5’UTR, and reduction in cyclinD1 levels presumably results from rapamycin-mediated inhibition of 4EBP1 phosphorylation and the resulting inhibition of eIF4F function. Likewise, the mRNA encoding for multiple oncogenes or proteins involved in DNA metabolism and S-phase progression contain complex 5’UTRs and are regulated by mTOR (Kozak 1991). Although rapamycin can induce apoptosis in select tumor models, rapamycin treatment typically slows tumor growth but does not induce tumor regression, suggesting that increased tumor cell loss through apoptosis or other mechanisms of cell death likely are not major contributors to drug effect in most tumors. Collectively, these data support the idea that rapamycin exerts a cytostatic effect on tumor cell growth. Rapamycin also has cytostatic effects on normal and tumor vasculature. As discussed previously, mTOR plays an important role in modulating the cellular response to hypoxia through stabilization and activation of HIF-1D±HIF-1 and drives expression of hypoxia-responsive genes, and these genes include those such as VEGF that are important for tumor angiogenesis. Translation of VEGF mRNA also is regulated in an mTOR-dependent manner via its complex 5’UTR. Consistent with these mechanisms of regulation, treatment of tumor-bearing animals with rapamycin results in decreased expression of VEGF mRNA in tumors (Luan et al. 2003) and decreased circulating levels of VEGF protein (Guba et al. 2002). The VEGF drives endothelial proliferation through interaction with its cognate receptor tyrosine kinases, VEGF receptors 1 and 2, and these receptors can signal downstream through the PI3K/Akt pathway to mTOR; thus, proliferation of smooth muscle and endothelial cells is inhibited by mTOR inhibition (Vinals et al. 1999; Mayerhofer et al. 2002), and this effect is likely related to the efficacy of rapamycin-eluting stents in preventing vascular re-occlusion. In animal models, rapamycin inhibits tumor growth and neo-vascularization of CT-26 colon tumors grown in a dorsal skinfold model and suppresses serum levels of VEGF in

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tumor-bearing animals (Guba et al. 2002); thus, the anti-angiogenic effects may contribute to the efficacy of mTOR inhibitors in cancer therapy.

9.5 Clinical Experience with mTOR-Inhibitor Monotherapy Clinical efficacy of mTOR inhibitors has been evaluated in patients with a variety of tumor types. Although three distinct mTOR inhibitors (CCI-779, RAD001, and AP23573) are being evaluated in clinical trials, mature published phase-II study results are only available for CCI-779. In renal cell cancer, 111 patients were randomized to receive weekly IV infusions of 25, 75, or 250 mg (Atkins et al. 2004). One patient achieved a complete response, and 7 patients had partial responses with >50% reduction in tumor size. Approximately half of patients had at least stabilization of disease for >24 weeks. Based on these data, a phase-III study in renal cell cancer is now underway. Promising results also have been seen in mantle cell lymphoma, where 13 of 34 patients had either a complete (1 patient) or partial response (12 patients) with single agent weekly treatment and modest hematological toxicities (Witzig et al. 2005). Two clinical trials have evaluated the efficacy of CCI-779 in recurrent malignant glioma. In a study by the North American Brain Tumor Consortium, partial responses were observed in 2 of 43 patients and disease stabilization was observed in another 50% of patients (Chang et al. 2005). Similar results were observed in a clinical trial run by the North Central Cancer Treatment Group (NCCTG), where 20 of 65 patients had evidence of reduced T2 signal abnormality on magnetic resonance imaging (MRI) and this response correlated with a time to progression of 5.4 months relative to 1.9 months for non-responders (Galanis et al. 2005). In contrast, monotherapy with CCI-779 in patients with metastatic melanoma did not significantly affect disease progression (Margolin et al. 2005). In addition to the trials discussed here, several phase-II clinical trials using CCI-779 and RAD001 are currently ongoing in a variety of tumor types (reviewed by Rao et al. 2004). Collectively, this early clinical experience suggests that mTOR inhibitors may be useful therapeutic agents for specific tumor types. The anti-tumor effects of rapamycin therapies are likely secondary to both inhibition of tumor cell proliferation and inhibition of tumor angiogenesis.

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The relative contribution of these two effects in any given tumor may be difficult to delineate; however, preclinical and clinical data suggest that only a subset of tumors respond to rapamycin. This observation has spurred investigations into the combinations of mTOR inhibitors with conventional and molecular targeted chemotherapeutic agents.

9.6 Combination Therapies with mTOR Inhibitors Angiogenesis and tumor cell proliferation have been implicated as important mediators that can influence the efficacy of traditional cytotoxic cancer therapies; therefore, much research effort has focused on the evaluation of combinations of mTOR inhibitors with standard cancer therapies. Rapamycin potentiates cisplatin-induced apoptosis in multiple cell lines including HL-60 leukemia cells and SKOV3 ovarian cancer cells (Shi et al. 1995). Likewise, IGF-induced resistance to cisplatin in Rh30 rhabdomyosarcoma cells can be reversed by rapamycin treatment (Wan and Helman 2002). Geoerger et al. (2001) demonstrated that combinations of rapamycin with either cisplatin or camptothecin provides additive growth inhibition in the rapamycin-sensitive DAOY medulloblastoma cell line but not in the rapamycinresistant D283 cell line. Consistent with this in vitro data, CCI-779 therapy provides for additive tumor growth inhibition in animals when combined with doxorubicin, mitoxantrone, docetaxel, or cisplatin in prostate cancer and medulloblastoma xenografts (Geoerger et al. 2001; Wu et al. 2005). Several other investigators have confirmed the in vitro effect of rapamycin on sensitizing cancer cells to chemotherapeutic agents such as adriamycin, VP-16, and cisplatin. While the mechanism(s) of these effects are not fully understood, in one study inhibition of mTOR signaling blocked the cytoprotective effects of IGF-II overexpression in rhabdomyosarcoma cells (Wan and Helman 2002). Similarly, in another study, RAD001-dependent inhibition of translation blocked p53-induced accumulation of p21cip1 in response to cisplatin treatment, and the failure of this anti-apoptotic molecule to accumulate resulted in increased apoptosis (Beuvink et al. 2005); thus, the increased efficacy of chemotherapies with concomitant mTOR inhibition is likely due to disruption of key survival signaling pathways leading to increased cell killing.

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the related ATM, ATR, and DNA-PKcs kinases, rapamycin had no effect on the in vitro radiation sensitivity of several glioma cell lines including U87 cells. In contrast, intermittent dosing with rapamycin throughout a fractionated course of radiation significantly enhanced the efficacy of treatment in radioresistant U87 xenografts (Fig. 9.3). Although the mechanism of this effect is not entirely understood, a recent study demonstrated that the mTOR inhibitor RAD001 can sensitize endothelial cells to radiation and that GL261 xenografts treated with both radiation and RAD001 have delayed tumor regrowth associated with reduced tumor blood flow (Shinohara et al. 2005). While the molecular mechanisms involved in increased endothelial cell death are unclear, these two studies suggest that novel combinations of mTOR inhibitors with radiation would be interesting to evaluate in clinical trials. Given the promising responses seen in the NCCTG trial in recurrent glioma, we are now initiating a clinical trial evaluating the addition of CCI-779 to standard therapy with high-dose radiation and temozolomide in newly diagnosed glioblastoma multiforme. A network of parallel signaling pathways often contributes to resistance to mTOR inhibitors or other signal transduction inhibitors, and this realization has led to increasing interest in simultaneous inhi6 5 Relative volume

PI3K/Akt/mTOR-dependent signaling is important in the development of hormonally responsive cancers involving breast and prostate, and preclinical studies suggest that combinations of mTOR inhibitors with hormonal therapies may be worth evaluating in the clinic. In keeping with the importance of the PI3K/Akt/mTOR signaling axis, transgenic overexpression of Akt in the ventral lobe of the prostate results in development of prostatic intraepithelial neoplasia (PIN), and this PIN phenotype is completely reversed with RAD001 treatment (Majumder et al. 2004). These effects were associated with an increase in apoptosis and suppression of HIF-1D signaling. In tumor models of prostate cancer progression, hormone-refractory states are associated with activation of p70S6 kinase downstream from mTOR, upregulation of genes known to be regulated by the Akt/mTOR pathway, and increased sensitivity to mTOR inhibition (Mousses et al. 2001; Ghosh et al. 2005). These observations have prompted the evaluation of mTOR inhibitors in hormone-refractory prostate cancer, and it would be interesting to evaluate whether mTOR inhibitor therapy would prevent or delay the development of a hormone-refractory state in up-front therapy of metastatic prostate cancer. Combinations of mTOR inhibitors with hormonal therapies are also promising in breast cancer models. Hyper-activation of Akt signaling is associated with an adverse prognosis in breast cancer and has been implicated in the development of a hormone-refractory state (Kirkegaard et al. 2005). In cell culture, tamoxifen resistance can be induced by over-expression of constitutively active Akt, and sensitivity to tamoxifen can be restored by concurrent treatment with rapamycin or CCI-779 (De Graffenried et al. 2004). Similarly, others have demonstrated that the combination of RAD001 with letrazole, an aromatase inhibitor, results in synergistic anti-tumor effects (Boulay et al. 2005). Collectively, these studies support the concept of combining conventional hormonal therapies with mTOR inhibitors in breast and prostate cancers. Rapamycin also can enhance the efficacy of radiation therapy. Based on significant preclinical and clinical data demonstrating that tumor proliferation during fractionated radiotherapy contributes to clinical radiation resistance (Fowler 2001; Bentzen 2003), we hypothesized that rapamycin-mediated inhibition of tumor proliferation during radiotherapy would enhance the efficacy of radiation. Consistent with the idea that mTOR is not involved in DNA damage responses, unlike

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Fig. 9.3. Rapamycin enhances the efﬁcacy of radiation in U87 xenografts. Nude mice with established U87 ﬂank xenografts were randomized into four treatment groups: (a) placebo; (b) radiation only (4 Gy u 4); (c) rapamycin only (1 mg/kg); or (d) radiation and rapamycin. The tumor regrowth for each treatment group is shown. Data points represent the mean relative tumor volumerSE. Treatment was initiated on day 0 with the ﬁrst injection of rapamycin (Rap). The schedule for Rap and radiation (RT) treatments is depicted below the x-axis. Highly similar results were obtained in two independent experiments. (From Eshleman et al. 2002)

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bition of multiple targets within the mTOR signaling pathway. This approach is best highlighted by the example of chronic myelogenous leukemia (CML). The CML is caused by a chromosomal translocation which leads to an oncogenic chimeric BCR-Abl gene product. The resulting constitutively active kinase drives leukemia proliferation and survival and can be selectively inhibited by the kinase inhibitor imatinib. Imatinib treatment is highly effective in CML, but chronic therapy invariably leads to imatinib resistance through mutation of the BCR-Abl kinase domain, amplification of the BCR-Abl gene product, or other mechanisms. Imatinib treatment in naive CML leads to compensatory hyper-activation of Akt/ mTOR signaling (Burchert et al. 2005), and several groups have demonstrated that combined inhibition of mTOR and BCR-Abl leads to synergistic cell killing (Ly et al. 2003; Mohi et al. 2004; Dengler et al. 2005), which suggests that the hyperactive mTOR signaling is an important survival mechanism in this disease. Moreover, chronic Akt/mTOR signaling has been implicated in the ultimate development of imatinib resistance, since combined treatment with rapamycin and imatinib blocks development of imatinib resistance (Burchert et al. 2005). These data suggest that simultaneous mTOR/BCR-Abl inhibition in CML may improve the anti-tumor effects of therapy and also delay the induction of resistance to BCR-Abl inhibitors. Compensatory feedback mechanisms also can lead to relative resistance to molecularly targeted therapeutics. As mentioned previously, mTOR can be targeted to specific substrates by association with either Rictor or Raptor, and rapamycins specifically inhibit the mTOR/raptor complex. This leads to a shift in signaling to the mTOR/Rictor complex, and one substrate for this rapamycininsensitive mTOR/Rictor is a key regulatory residue (Ser-473) on Akt (Sarbassov et al. 2005); thus, mTOR inhibitor-induced up-regulation of Akt signaling (Sun et al. 2005) may actually promote survival, and conversely, simultaneous inhibition of mTOR and Akt could lead to enhanced cell killing. In support of this hypothesis, a recent study demonstrated that combined inhibition of mTOR with either PI3K or Akt inhibitors leads to synergistic anti-tumor effects (Takeuchi et al. 2005). Similarly, we have demonstrated that EGFR inhibitor therapy also can block rapamycin-mediated upregulation of Akt phosphorylation, and that combined EGFR/mTOR inhibition is significantly more effective than either therapy alone in glioma cell lines (Rao et al. 2005). Similar results have

been reported by others in a glioma (Goudar et al. 2005) and renal cell cancer models (Gemmill et al. 2005). The Ras signaling pathway also is important for promoting survival, and in leukemia cells, combined inhibition of mTOR and MEK resulted in significant synergistic interactions (Bertrand et al. 2005). Combinations of mTOR inhibitors with relatively non-specific kinase inhibitors, such as 7-hydroxystaurosporine, also have provided interesting results (Hahn et al. 2005; Takeuchi et al. 2005). With the numerous signal transduction inhibitors currently in development for clinical use, the results summarized here represent just the beginning of what are likely to be a multitude of studies evaluating mTOR inhibitors in combination with other targeted therapies.

9.7 Conclusion Rapamycin and its analogs are versatile drugs with proven efficacy in cardiovascular and transplant medicine and with promising results in early cancer clinical trials. In specific tumor types, a select minority of patients likely will benefit from monotherapy. The challenge for the future will be to dissect further the molecular signaling pathways modulated by rapamycin in order to appreciate fully the molecular mechanisms underpinning sensitivity or resistance to mTOR inhibition. This understanding will provide insight into rational combinations of mTOR inhibitors with classic cytotoxic agents, radiation, and other molecularly targeted therapies.

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136 Hudson CC, Liu M, Chiang GG et al (2002) Regulation of hypoxia-inducible factor 1alpha expression and function by the mammalian target of rapamycin. Mol Cell Biol 22:7004–7014 Inoki K, Li Y, Zhu T et al (2002) TSC2 is phosphorylated and inhibited by Akt and suppresses mTOR signalling. Nature Cell Biol 4:648–657 Inoki K, Li Y, Xu T et al (2003) Rheb GTPase is a direct target of TSC2 GAP activity and regulates mTOR signaling. Genes Dev 17:1829–1834 Jaakkola P, Mole DR, Tian YM et al (2001) Targeting of HIFalpha to the von Hippel-Lindau ubiquitylation complex by O2-regulated prolyl hydroxylation. Science 292:468–472 Jefferies HB, Fumagalli S, Dennis PB et al (1997) Rapamycin suppresses 5’TOP mRNA translation through inhibition of p70s6k. EMBO J 16:3693–3704 Kim Do H, Sarbassov D, Ali SM et al (2002) mTOR interacts with raptor to form a nutrient-sensitive complex that signals to the cell growth machinery. Cell 110:163–175 Kirkegaard T, Witton CJ, McGlynn LM et al (2005) AKT activation predicts outcome in breast cancer patients treated with tamoxifen. J Pathol 207:139–146 Kozak M (1991) An analysis of vertebrate mRNA sequences: intimations of translational control. J Cell Biol 115:887–903 Laughner E, Taghavi P, Chiles K et al (2001) HER2 (neu) signaling increases the rate of hypoxia-inducible factor 1alpha (HIF-1alpha) synthesis: novel mechanism for HIF-1-mediated vascular endothelial growth factor expression. Mol Cell Biol 21:3995–4004 Luan FL, Ding R, Sharma VK et al (2003) Rapamycin is an effective inhibitor of human renal cancer metastasis. Kidney Int 63:917–926 Ly C, Arechiga AF, Melo JV et al (2003) Bcr-Abl kinase modulates the translation regulators ribosomal protein S6 and 4E-BP1 in chronic myelogenous leukemia cells via the mammalian target of rapamycin. Cancer Res 63:5716–5722 Majumder PK, Febbo PG, Bikoff R et al (2004) mTOR inhibition reverses Akt-dependent prostate intraepithelial neoplasia through regulation of apoptotic and HIF-1-dependent pathways. Nature Med 10:594–601 Margolin K, Longmate J, BarattamT et al (2005) CCI-779 in metastatic melanoma: a phase II trial of the California Cancer Consortium. Cancer 104:1045–1048 Mayerhofer M, Valent P, Sperr WR et al (2002) BCR/ABL induces expression of vascular endothelial growth factor and its transcriptional activator, hypoxia inducible factor1alpha, through a pathway involving phosphoinositide 3-kinase and the mammalian target of rapamycin. Blood 100:3767–3775 Mazure NM, Chen EY, Laderoute KR et al (1997) Induction of vascular endothelial growth factor by hypoxia is modulated by a phosphatidylinositol 3-kinase/Akt signaling pathway in Ha-ras-transformed cells through a hypoxia inducible factor-1 transcriptional element. Blood 90:3322–3331 Mohi MG, Boulton C, Gu TL et al (2004) Combination of rapamycin and protein tyrosine kinase (PTK) inhibitors for the treatment of leukemias caused by oncogenic PTKs. Proc Natl Acad Sci USA 101:3130–3135 Mothe-Satney I, Brunn GJ, McMahon LP et al (2000) Mammalian target of rapamycin-dependent phosphorylation of PHAS-I in four (S/T)P sites detected by phospho-specific antibodies. J Biol Chem 275:33836–33843 Mousses S, Wagner U, Chen Y et al (2001) Failure of hormone

J. N. Sarkaria therapy in prostate cancer involves systematic restoration of androgen responsive genes and activation of rapamycin sensitive signaling. Oncogene 20:6718–6723 Neshat MS, Mellinghoff IK, Tran C et al (2001) Enhanced sensitivity of PTEN-deficient tumors to inhibition of FRAP/ mTOR. PNAS 98:10314–10319 Potter CJ, Pedraza LG, Xu T (2002) Akt regulates growth by directly phosphorylating Tsc2. Nature Cell Biol 4:658–665 Rao RD, Buckner JC, Sarkaria JN (2004) Mammalian target of rapamycin (mTOR) inhibitors as anti-cancer agents. Curr Cancer Drug Targets 4:621–635 Rao RD, Mladek AC, Lamont JD et al (2005) Disruption of parallel and converging signaling pathways contribute to the synergistic anti-tumor effects of simultaneous mTOR and EGFR inhibition in GBM cells. Neoplasia 7, epub Raught B, Gingras AC, Sonenberg N (2001) The target of rapamycin (TOR) proteins. Proc Natl Acad Sci USA 98:7037–7044 Sabatini DM, Erdjument-Bromage H, Lui M et al (1994) RAFT1: a mammalian protein that binds to FKBP12 in a rapamycin-dependent fashion and is homologous to yeast TORs. Cell 78:35–43 Sarbassov DD, Guertin DA, Ali SM et al (2005) Phosphorylation and regulation of Akt/PKB by the Rictor-mTOR complex. Science 307:1098–1101 Saucedo LJ, Gao X, Chiarelli DA et al (2003) Rheb promotes cell growth as a component of the insulin/TOR signalling network. (Erratum in Nat Cell Biol 2003 5:680). Nature Cell Biol 5:566–571 Sekulic A, Hudson CC, Homme JL et al (2000) A direct linkage between the phosphoinositide 3-kinase-AKT signaling pathway and the mammalian target of rapamycin in mitogen-stimulated and transformed cells. Cancer Res 60:3504–3513 Shaw RJ, Bardeesy N, Manning BD et al (2004) The LKB1 tumor suppressor negatively regulates mTOR signaling. Cancer Cell 6:91–99 Shi Y, Frankel A, Radvanyi LG et al (1995) Rapamycin enhances apoptosis and increases sensitivity to cisplatin in vitro. Cancer Res 55:1982–1988 Shinohara ET, Cao C, Niermann K et al (2005) Enhanced radiation damage of tumor vasculature by mTOR inhibitors. Oncogene 24:5414–5422 Sun SY, Rosenberg LM, Wang X et al (2005) Activation of Akt and eIF4E survival pathways by rapamycin-mediated mammalian target of rapamycin inhibition. Cancer Res 65:7052–7058 Takeuchi H, Kondo Y, Fujiwara K et al (2005) Synergistic augmentation of rapamycin-induced autophagy in malignant glioma cells by phosphatidylinositol 3-kinase/protein kinase B inhibitors. Cancer Res 65:3336–3346 Tee AR, Fingar DC, Manning BD et al (2002) Tuberous sclerosis complex-1 and -2 gene products function together to inhibit mammalian target of rapamycin (mTOR)-mediated downstream signaling. Proc Natl Acad Sci USA 99:13571– 13576 Vinals F, Chambard JC, Pouyssegur J (1999) p70 S6 kinasemediated protein synthesis is a critical step for vascular endothelial cell proliferation. J Biol Chem 274:26776– 26782 Volarevic S, Thomas G (2001) Role of S6 phosphorylation and S6 kinase in cell growth. Prog Nucleic Acid Res Molec Biol 65:101–127

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10 Combinations of Ionizing Radiation and Other Sensitizing Agents Minesh P. Mehta

CONTENTS 10.1 10.2 10.2.1 10.2.2 10.2.3 10.2.4 10.2.5 10.2.6 10.3 10.3.1 10.3.2 10.3.3 10.3.4 10.3.5

Introduction 139 Motexafin–Gadolinium 140 Structure and Chemistry 140 Imaging Properties 140 Phase-I Results 140 Phase-II Results 141 Phase-III Results 141 Conclusion 143 Temozolomide 143 Structure and Chemistry 143 Mechanism of Action 143 Brain Metastases 144 Glioblastoma Multiforme 145 Conclusion 146 References 147

10.1 Introduction Several chapters in this book cover broad classes of radiosensitizing agents. Two specific agents, recently used as “radiation enhancers,” are addressed in the present chapter. They include the redox modulator motexafin-gadolinium (MGd), and the alkylating agent temozolomide. Each of these agents came to clinical testing through the recognition of unique preclinical radiosensitizing mechanisms and data that suggest enhancement of radiation cytotoxicity; they share the common theme of having been

M. P. Mehta, MD Department of Human Oncology, University of Wisconsin Hospital Medical School, 600 Highland Avenue, K4 312-3684, Madison, WI 53792, USA

clinically tested primarily in tumors of the central nervous system (CNS), in a series of recent clinical trials, primarily because although radiation therapy (RT) has a central role in managing the majority of primary and secondary CNS neoplasms, outcomes for most patients afflicted by these tumors remain poor, and furthermore, these neoplasms, in many ways, present an ideal opportunity for enhancing the efficacy of RT in combination with radiosensitizers (Patel et al. 2004). The major reasons for considering these neoplasms as candidates for radiosensitization are as follows: 1. The majority of CNS neoplasms cause death due to local progression, thereby underscoring the need for local control (Wallner et al. 1989). 2. Evidence exists that improving local control improves survival (Patchell et al. 1990; Noordijk et al. 1994; Mintz et al. 1996; Andrews et al. 2004). 3. A dose-response relationship for RT has been established (Walker et al. 1979). 4. These neoplasms reﬂect a rapidly growing population with high cell turnover in a milieu of slowly proliferating cells, thereby affording an opportunity for tumor-selective localization of several radiosensitizers (McGinn et al. 1996). 5. Linear (dose escalation linked to lengthening of treatment duration) radiation dose-escalation strategies have been limited by late normal tissue toxicity (Lee et al. 1999). Historically, several classes of radiation sensitizers, including S-phase halogenated pyrimidines (Phillips et al. 1995; Prados et al. 1999), oxygen mimetics (Evans et al. 1990), and others (Mehta et al. 2001a), have been tested without clear evidence of clinical beneﬁt. Recently, agents with very different mechanisms of action have gained attention and are in clinical trials (Abraham et al. 1992; Rodrigus 2003; Mehta and Suh 2004). These agents, MGd, a redox modulator, and temozolomide, a DNA alkylator, are the focus of this chapter and each is addressed in sequence.

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10.2 Motexafin–Gadolinium

10.2.2 Imaging Properties

10.2.1 Structure and Chemistry

It has been demonstrated that substitution of Gd by other lanthanides abrogates the radiation-sensitizing properties of MGd (Rockwell et al. 2002). The presence of trace amounts of Gd in this molecule [in significantly lower concentrations than the amount of Gd in magnetic resonance imaging (MRI) contrast agents] permits visualization of the drug on MRI, thus providing tumor-specific kinetic information (Fig. 10.2). Several preclinical (Woodburn 2001; De Stasio 2001) and clinical (Kesslering et al. 1998; Ford et al. 2003; Mehta et al. 2004) data have now confirmed this tumor-specific intracellular localization and visualization phenomenon. Ford et al. (2003) have effectively demonstrated the impact of dose and cumulative dose in this context through a phase-I trial in which intra-tumor Gd was estimated by co-imaging control vials containing known concentrations of Gd and verifying these data by obtaining tissue specimens for actual measurements.

Motexafin-gadolinium (MGd) is an expanded metalloporphyrin, generally included in the family of compounds referred to as the texaphyrins (Fig. 10.1), and was previously referred to as gadolinium-texaphyrin. Motexafin-gadolinium, a redox active drug, specifically targets tumor cells and enhances the radiation response in several preclinical models (Xu et al. 2001; Magda et al. 2001; Biaglow and Miller 2005). As an avid electron acceptor, it catalyzes the oxidation of key intracellular reducing metabolites. These compounds, including glutathione, ascorbate, dihydrolipoate, protein thiols, and others, are necessary to maintain intracellular energy balance and play a key role in repairing cellular radiation injury. Irreversible oxidation of these reducing metabolites diminishes the cellular capacity for radiationinduced DNA damage. Furthermore, MGd inhibits thioredoxin reductase, a key enzyme in restoring the intracellular pools of these reducing agents. The oxidation of these compounds by MGd not only causes intracellular bioenergetic disruption, but also generates reactive oxygen species, a process known as futile redox cycling (Miller et al. 1999). As a consequence, cells irradiated in the presence of MGd are unable to adequately repair radiation damage, and cell death ensues (Donnelly et al. 1986).

O

OAc

AcO N N

N G d N N

O

O

O

O

O

O

OC3 H OCH 3

O Fig. 10.1. Structure of motexaﬁn–gadolinium (MGd)

10.2.3 Phase-I Results An initial single-dose phase-I trial established the maximum tolerated dose (MTD) to be 22.3 mg/kg with reversible acute renal failure as the dose-limiting toxicity (DLT) at 29.6 mg/kg (Rosenthal et al. 2000). A subsequent multicenter phase-IB/II trial tested ten daily MGd injections with cranial RT in patients with brain metastases. This study established the MTD to be 6.3 mg/kg day -1 for 10 days with reversible hepatic transaminitis as the DLT at 8.4 mg/kg day -1 for 10 days (Carde et al. 2001). Subsequent testing of this regimen identified 5.5 mg/ kg day -1 as the dose level associated with the least clinical toxicity and thus was established as the standard for further testing in the phase-II and phaseIII setting using the 10-day regimen (Mehta et al. 2002). A biodistribution study of C14-labeled MGd in SMTF tumor-bearing mice injected with 10 mmol/ kg of drug demonstrated significant tumor uptake within 1 h, at which time the blood:tumor ratio is almost unity (Rodrigus 2003). Rapid and substantial blood/plasma washout follows, but MGd is retained in tumors at high levels t5 h, thereby substantially improving the tumor:blood ratio; therefore, the 2- to 5-h window following MGd administration is generally recommended for RT delivery.

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Fig. 10.2. The tumor speciﬁcity and MR imaging capabilities of MGd in a patient with brain metastases. Both scans are non-contrast MR images. The image on the left is obtained prior to administration of MGd and the image on the right is post-MGd

More prolonged schedules have also been tested. A 22-dose (in 6 weeks) regimen in glioblastoma multiforme (GBM) patients also receiving concurrent RT established the MTD at 5 mg/kg per day using a fivetimes-per-week schedule in weeks 1 and 2 and three times per week in weeks 3–6 (110 mg/kg cumulative dose; Mehta et al. 1999). The Childrens’ Oncology Group completed a phase-I trial in children with intrinsic pontine glioma testing up to 9.2 mg/ kg day -1 for a total of 30 fractions over 6 weeks with concurrent RT with the maximum safe dose for phase-II testing being 4.4 mg/kg day -1u30 (Mehta et al. 2001b). The dose-limiting toxicities at higher doses were transaminitis, hypertension, and rash. The estimated median survival in the 44 enrolled patients is 313 days, with 95% confidence interval of 248–389 days. Redox modulation can also affect the effectiveness of chemotherapy and MGd synergy with several cytotoxic agents including bleomycin, doxorubicin, temozolomide, taxanes, platinoids, etc., as has been demonstrated in preclinical models (Miller et al. 2001). Clinical trials to determine the MTDs of these combinations are underway.

10.2.4 Phase-II Results The most extensive phase-II data are available in brain-metastases patients receiving 10 doses of MGd at 5.5 mg/kg day -1 with cranial RT (3 Gyu10=30 Gy) (Carde et al. 1998). Sixty-one patients with brain metastases from various histologic types of primary

tumors were enrolled to this phase-Ib/II trial. In the evaluable patients, the overall response rate was 77%. The median survival was compared with a 528-patient database from Germany and a casematched comparison was performed with the Radiation Therapy Oncology Group (RTOG) database. In both instances, a favorable survival trend for MGdtreated patients was noticed, and these data were utilized to estimate a potential clinical benefit in order to appropriately power a phase-III trial. The other phase-II data come from an analysis of this agent in GBM. Two trials, one a study from the University of California at Los Angeles (UCLA), and the other, a multi-institutional trial, have now been conducted in this context (Suh et al. 2002; Manon et al. 2004). The most mature data are available from the UCLA trial, and in this 33-patient case-matched comparison study, a potential median survival gain of almost 6 months was identified.

10.2.5 Phase-III Results Based on the results of the phase-II trial, a multicenter phase-III trial of cranial RT (30 Gy/10 fractions) for brain metastases with or without daily MGd (5.5 mg/kg day -1) was recently completed. Four hundred one patients, 251 with non-small cell lung cancer (NSCLC) and 75 with breast cancer, were enrolled. The study was conducted with two primary co end points, overall survival, and time to neurologic progression. The latter end point, measured

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both by the investigator and by a blinded eventsreview committee (ERC), reflects one of the most unique aspects of this trial. In addition, prospective and ongoing assessment of neurocognitive function was carried out by a blinded consultant using a validated clinical battery designed to assess various neurocognitive functional domains. Although no significant differences were noted in overall survival, both the investigator and the ERC assessment demonstrated significantly larger neurologic progression free survival for the MGd-treated patients with NSCLC (Fig. 10.3; Mehta et al. 2003). This trial also provided a large database to analyze the safety spectrum of MGd. Overall, the drug was extremely well tolerated and permitted the delivery of 96% of all intended RT fractions. The vast majority of toxicities were grade 1 or 2 in severity, and the most common was skin discoloration, consistent with the color of the drug. The most common grade-3 or greater toxicity was transient hypertension (in <6% of patients, although an additional approximately 27% of patients also experienced grade-1 or grade-2 hypertension). This transient hypertension occurred during or within 1 h of MGd administration, and was in almost all cases self-limiting. In the majority of instances, no intervention was required. It did not preclude drug or radiation administration in the majority of patients. Although the first phase-III trial demonstrated improved neurologic progression-free survival in

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NSCLC patients, this was not a pre-planned analysis and therefore was insufficient for regulatory approval. Consequently, a follow-up phase-III trial enrolling only NSCLC patients was recently completed, enrolling just over 550 patients. The results of this trial were just becoming available at the time of this writing, and as per the formal corporate announcement, the primary end point of improvement in time to neurologic deterioration was not reached. The median time to neurologic progression, as assessed by the ERC, was 10 months with whole-brain RT and 15.4 months with MGd added to whole-brain RT (p=0.122). Although this difference appears to be clinically important, it did not reach statistical significance, as the number of patients alive and evaluable for neurologic progression was small by 10 months; furthermore, as per the corporate announcement, when patients from France were excluded, for the remaining 348 patients, the median time to neurologic progression was 8.8 vs 24.2 months (p=0.004). The precise explanation for this geographic variance has not yet been provided. Whereas the bulk of the clinical results available to date are from patients with brain metastases, MGd is being evaluated in several other diseases including GBM, primary NSCLC, cancer of the pancreas, head and neck malignancies, pediatric pontine glioma, etc. At the Annual Meeting of the American Society of Clinical Oncology (ASCO) in 2003, Ford et al. (2003) presented survival data from

Fig. 10.3. The KaplanMeier neurologic progression-free survival curve from the pre-speciﬁed stratum of 251 patients with brain metastases from non-small cell lung cancer treated with MGd (solid upper line) or control (dotted lower line). D days, HR hazard ratio, M months, MGd motexaﬁn gadolinium, NR not reached, WBRT whole-brain radiation therapy. (From Mehta et al. 2003)

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their phase-I/II GBM trial and compared these with a case-matched cohort from the RTOG database. The database median survival was 12 months, and the observed median survival on the UCLA MGd cohort was 17.6 months, with a hazard ratio of 2.0. These encouraging results have prompted the RTOG to pursue additional phase-II testing of this agent in GBM, in combination with temozolomide. The combination of MGd with other cytocidal agents represents a novel research direction. Phase-I studies are currently underway, and the recent observation of synergy between temozolomide and MGd, both of which cross the blood-brain barrier and therefore could be combined in the treatment of brain tumors, is very exciting. A "cutting-edge" application of MGd lies in its potential as an agent for gadolinium-neutron capture therapy (GdNCT). Historically, boron-neutron capture therapy (BNCT) has been investigated in CNS tumors, with modest efficacy, limited in large part by the lack of significant tumor specificity of most boronated compounds. The cross-sectional area of interaction for neutrons with Gd is significantly greater than for boron, and recent work has demonstrated that >90% of the nuclei of GBM cells in culture localize MGd in the nucleus (De Stasio et al. 2005). Because the neutron-capture reaction produces Auger electrons with very limited path lengths, such extensive intranuclear localization is a prerequisite for further evaluation of GdNCT.

10.2.6 Conclusion Motexafin-gadolinium represents one of the novel radiosensitizers that have undergone recent clinical evaluation. It has shown early, but tentative, promise, and some benefit in subset analysis. This agent is continuing to be evaluated very actively in the clinic, and its precise roles remain to be adequately defined.

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hydrolyzed to its active metabolite, 5-(3-methyltriazen-1yl)imidazole-4-carboximide (MTIC), under normal physiologic conditions, and has nearly 100% bioavailability, which can be slightly reduced by concomitant meals. It readily crosses the bloodbrain barrier, producing cerebrospinal fluid concentrations that are approximately 30% of plasma concentrations (Reid et al. 1997; Patel et al. 2003).

10.3.2 Mechanism of Action The primary cytotoxicity of temozolomide results from its ability to methylate DNA bases. Although several bases can and are methylated, the most ubiquitous methylation events involve guanine at the N-7 and O-6 positions and adenine at the N-3 position. Methylation of the O-6 position of guanine accounts for approximately 5–6% of the total methylation events but is believed to represent the primary mechanism of cytotoxicity (Fig. 10.4; Ludlum 1990; Denny et al. 1994). Under normal circumstances, O-6 methylation is repaired by the enzyme methyl-guanine methyl transferase (MGMT), which demethylates guanine by accepting the methyl group onto itself, rendering the enzyme inactive (Fig. 10.5; Pegg et al. 1983; Pieper 1997). Repair of further methylation events requires de novo synthesis of additional MGMT. Recent data suggest that in several tumors there is epigenetic silencing of MGMT through promoter region methylation, thus resulting in sensitivity to temozolomide (Qian and Brent 1997; Watts et al. 1997; Jaeckle et al. 1998; Estellar et al. 1999; Silber et al. 1999; Esteller et al. 2000; Hegi et al. 2004; Paz et al. 2004; Esteller N3 adenine 9%

Other sites 16%

O6 g u a ni ne 5%*

10.3 Temozolomide 10.3.1 Structure and Chemistry Temozolomide, 3,4-dihydro-3-methyl-4-oxoimidazole [5,1-D-as-tetrazine-8-caroxamide] is a second-generation oral alkylating prodrug that is spontaneously

N7 guanine 70%

Position/base total adducts (%)

Fig. 10.4. Distribution of DNA-methylation events from temozolomide by site

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putative “radiation enhancer” and RT, with the bulk of the experience coming from brain tumors. In this chapter, we focus on the data primarily as they relate to the combination of temozolomide with concurrent RT.

10.3.3 Brain Metastases

Fig. 10.5. Proposed mechanism of action of temozolomide. The primary cytotoxic injury results from an inability to remove the methyl adduct from the O-6 position of guanine, persistence of which leads to futile DNA repair through an intact mismatch repair and possible apoptotic death through wild-type p53

and Herman 2004). Repetitive drug administration would therefore likely result in MGMT exhaustion, and potentially sensitize the tumor to cytotoxicity from temozolomide (Tolcher et al. 2003). Additional mechanisms to enhance the effect of temozolomide cytotoxicity have focused on the specific inhibition of MGMT, using the experimental agent O-6 benzylguanine, which appeared promising in preclinical studies, but produced unacceptable clinical toxicity, thereby resulting in drastic dose reduction of temozolomide, and effectively abolishing the therapeutic gain (Dolan et al. 1990; Schold et al. 2004; Wedge et al. 1996a,b; Chinnasamy et al. 1997). It is also becoming apparent that MGMT is not the only step in the repair/death process following temozolomide exposure, and the mismatch repair system, as well as the p53 mutation status, may be significant (Karran and Marinus 1982; Liu et al. 1996; Friedman et al. 1998; Tentori et al. 2001; Srivenugopal et al. 2001; Roos et al. 2004). In limited preclinical studies, some synergy between temozolomide and radiation has been demonstrated, but the precise mechanisms for this have not yet been elucidated (Wedge et al. 1997; Van Rijn et al. 2000). Another study demonstrated that temozolomide has the capacity to inhibit the invasiveness of glioma cells in combination with RT. Radiation enhances the alpha-v/beta-3 integrin expression, which intensifies the invasiveness and migration of glioma cells. Temozolomide is able to inhibit these effects by promoting the cleavage of focal adhesion kinase (Wick et al. 2002). The clinical ability to dose temozolomide in a repetitive daily fashion has led to the testing of several combinations of the drug as a

In a randomized phase-II trial of 52 patients, Antonadou et al. (2002a) compared WBRT (40 Gy in 20 fractions) alone or with concomitant temozolomide (75 mg/m2 day -1) followed by six cycles of temozolomide (200 mg/m2 day -1 for 5 days every 28 days). The primary end points were radiologic response and neurologic functional status. The secondary end points were overall survival, safety, and tolerability. The addition of temozolomide improved the response rate (96 vs 67%; p=0.017). The proportion of patients with improved function was greater in the group receiving temozolomide. The drug was well tolerated, with a significant increase in nausea and vomiting, but no difference in the rates of headache or fatigue. No grade-3 or grade-4 myleosuppression occurred. Overall survival with the addition of temozolomide was not significantly improved. Another phase-II study randomized 82 patients to WBRT (30 Gy in ten fractions) alone or with concomitant temozolomide (75 mg/m2 day -1) followed by two cycles of temozolomide (200 mg/m2 day -1 for 5 days every 28 days) beginning 4 weeks after WBRT (Verger et al. 2003). Temozolomide was well tolerated with no acute neurologic toxicity. No significant difference in radiologic response was found between the two arms. Progression-free survival at 90 days was significantly greater in those receiving temozolomide (72 vs 54%; p=0.03). The rate of neurologic death was also significantly lower in the experimental arm (41 vs 69%; p=0.029), but there was no difference in overall survival. There has been one phase-III study, randomizing 134 patients (82% with lung primaries) to WBRT (30 Gy in ten fractions) alone or with concomitant temozolomide (75 mg/m2 day -1) followed by six cycles of temozolomide (200 mg/m2 day -1 for 5 days every 28 days) beginning 4 weeks after WBRT. Patients treated with temozolomide had a significantly greater response rate (53.4 vs 33.3%; p=0.039). This improvement in response with temozolomide was even more pronounced in patients <60 years of age (76.7 vs 37.0%; p=0.003) as well as those with a

Combinations of Ionizing Radiation and Other Sensitizing Agents

KPS t90 (70.6 vs 32.4%; p=0.003). There was no significant difference in overall survival (Antonadou et al. 2002b).

10.3.4 Glioblastoma Multiforme In a phase-II study, Stupp and colleagues (2002) administered temozolomide with concomitant RT, followed by adjuvant single-agent temozolomide, to 64 patients with newly diagnosed GBM. The RT consisted of 2 Gy fractions administered for 5 days each week for 6 weeks, for a total dose of 60 Gy. In combination with RT, temozolomide was given at a dose of 75 mg/m2 day -1. As adjuvant therapy, patients received six cycles of temozolomide 200 mg/m2 day -1 for 5 days every 4 weeks. Toxicities were mild, with grade-4 neutropenia occurring in <5% of patients during the induction (n=62) or adjuvant (n=49) phases. The median overall survival was 16 months, and the 2-year survival rate was 31%, suggesting an improvement over historical survival data. Although the study size was small, these impressive results prompted a phase-III evaluation of temozolomide and concurrent RT. The randomized phase-III trial was carried out by the European Organization for Research and Treatment of Cancer (EORTC) and the National Cancer Institute of Canada (NCIC) and is described in detail in Chapter 12. An overview is shown in Figure 10.6. The study enrolled 573 patients from 15 countries, with a median age of 56 years. Patient

145

characteristics were well balanced between the two study arms (Stupp et al. 2005). With median followup of 28 months, the hazard ratio (HR) for death was 0.63 in favor of the chemoradiation therapy group, representing a 37% relative reduction in the risk of death (Table 10.1). The 2-year survival rates were 26.5 and 10%, respectively. A subset analysis demonstrated a significant benefit from the addition of temozolomide in GBM patients in most patient subgroups, with the exception of patients who had a performance status of two and those who underwent biopsy only vs resection. Table 10.1. The EORTC/NCIC phase-III trial of radiation therapy with or without temozolomide in glioblastoma: survival results and toxicity RT+temozolomide

RT

Efﬁcacy

n=287

n=286

Median overall survival

14.6 months

12.1 months

Hazard ratio

0.63 (p<0.001)

Two-year overall survival

26.5%

10%

Median progression-free survival

6.9 months

5.0 months

Hazard ratio

0.54 (p<0.0001)

Grade-3/4 toxicity Neutropenia

7%

0

Thrombocytopenia

12%

0

Rash

2%

0

Infection

3%

2%

Fatigue/constitutional

8%

6%

RT radiation therapy

RT 2 Gy/day days 1-5 for 6 weeks* Temozolomide 75 mg/m2/day days 1-7 for 6 weeks R A N D O M I Z E

Grade 4 astrocytoma with or without surgical resection

followed 4 weeks later by: Temozolomide 150-200 mg/m2/day days 1-5 q 4 weeks x 6 cycles

RT 2 Gy/day days 1-5 for 6 weeks

n = 573 *Total dose: 60 Gy Abbreviations: RT = radiation therapy

Fig. 10.6. The EORTC/NCIC phase-III trial of radiation therapy with or without temozolomide in glioblastoma multiforme: treatment scheme

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Toxicity was higher with temozolomide, as expected, but both regimens were well tolerated (Table 10.1). There were no grade-3/4 hematologic toxicities in the RT-only group. In 284 patients who received temozolomide, the following grade-3/4 hematologic toxicities were observed: neutropenia in 21 patients (7%); leukopenia in 20 patients (7%); and thrombocytopenia in 33 patients (12%). During RT, 6 patients (2%) in the radiation therapy group and 9 patients (3%) in the combination group experienced severe infection. Moderate to severe fatigue was experienced by approximately 30% of the patients in both groups. The addition of temozolomide during RT did not appear to increase the rate of grade-3/4 rash (d1% in each group). During adjuvant therapy, 5 patients (2%; all from the temozolomide group) experienced grade-3/4 rash. Two subsequent trials, one a phase-III study from Greece, and a second phase-II trial from Germany (Athanassiou et al. 2005; Combs et al. 2004), further corroborated these results, and in March 2005, the U.S. Food and Drug Administration granted approval to temozolomide for the first-line treatment of GBM in combination with RT. From a radiation-sensitizing perspective, the phase-II German trial is of particular interest, as it utilized a lower dose of temozolomide (50 mg/m2 day -1) during RT, without any adjuvant drug, and achieved comparable survival outcome, thereby leading to several questions specific to drug dose and scheduling. Although the findings of EORTC/NCIC trial 22981/26981 showed an increase in survival in patients receiving concomitant and adjuvant temozolomide for GBM, a large proportion of these patients only marginally benefited from this regimen. This observation might be explained by the role of MGMT. The gene that encodes for MGMT is located on chromosome 10q26. The loss of function of this gene is most often due to epigenetic changes, specifically promoter-region methylation, leading to lack of MGMT expression. Epigenetic silencing of the MGMT gene through promoter methylation has been found to lead to increased overall survival and better response to treatment with temozolomide and BCNU in patients with gliomas (Silber et al. 1999; Esteller et al. 2000). To determine if MGMT gene promoter methylation status had an impact on survival in the patients enrolled in EORTC 22981/26981, Hegi et al. (2005) evaluated the methylation status of the MGMT gene promoter region in patients with available and adequate specimens. Methylation status was assessed for 206 of the 573 original

patients (36%) through methylation-specific polymerase chain reaction (PCR). The MGMT promoter methylation was found in 45% of assessable patients. Both treatment arms, RT alone and RT plus temozolomide, were equally represented in this sample population. Median overall survival, irrespective of treatment assignment, was increased in patients with methylated MGMT promoter regions compared with those with unmethylated MGMT promoter regions. When treatment assignment was considered with MGMT promoter methylation status, a survival benefit from the addition of temozolomide to RT was seen only in patients with MGMT promoter methylation (Table 10.2). Table 10.2. Impact of MGMT promoter region methylation status on survival by treatment arm in the EORTC/NCIC phase-III trial TMZ+RT RT

Signiﬁcance (p)

Overall MS (months)

14.6

12.1

<0.001

MS of methylated GBM

21.7

15.3

0.007

MS of unmethylated GBM

12.7

11.8

0.06

MGMT methyl-guanine methyl transferase, TMZ temozolomide, RT radiation therapy, MS median survival, GBM glioblastoma multiforme

A further research direction with significant implications on radiosensitization comes from the recognition that the cytotoxicity of temozolomide can be enhanced through inhibition of the enzyme poly-ADP-ribose polymerase 1 (PARP-1), and initial preclinical and clinical studies are showing promising results. Furthermore, inhibition of PARP-1 also leads to radiosensitization, thereby creating an opportunity for three-way synergy (Tentori et al. 2002; Curtin et al. 2004; Calabrese et al. 2004; Lapidus et al. 2005; Plummer et al. 2005).

10.3.5 Conclusion Temozolomide has demonstrated modest activity in patients with recurrent or newly diagnosed brain metastases from various malignancies. Recent trials of temozolomide with RT suggest a significant increase in response rates, especially for metastases from lung cancer. Histology appears to have a bearing on the effect of temozolomide, as well as when it is used with RT. For example, in a phase-II study of dose-intense alternating weekly regimen

Combinations of Ionizing Radiation and Other Sensitizing Agents

of temozolomide, the response rate was 24% for NSCLC, 19% for breast cancer, and 40% for melanoma (Siena et al. 2003). This differential activity could putatively be associated with methylation of the promoter region of the MGMT gene which synthesizes MGMT, the enzyme responsible for repairing the lethal methylation lesion produced by temozolomide. It is therefore possible to consider a future treatment strategy with temozolomide, based on the MGMT promoter-region methylation status of the tumor. The frequency of this finding ranges from 36 to 42% in squamous and adenocarcinoma (of the lung), respectively (Furonaka et al. 2005). In GBM, the concurrent administration of temozolomide and RT has improved survival, with a large increase in patients with MGMT promoter-region methylation. Consequently, its role in other gliomas, both low grade and anaplastic, is actively being explored.

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Combinations of Ionizing Radiation and Other Sensitizing Agents Rosenthal DI, Becerra CR, Toto RD et al (2000) Reversible renal toxicity resulting from high single doses of the new radiosensitizer gadolinium texaphyrin. Am J Clin Oncol 23:593–598 Schold SC Jr, Kokkinakis DM, Chang SM et al (2004) O6-benzylguanine suppression of O6-alkylguanine-DNA alkyltransferase in anaplastic gliomas. Neuro-Oncol 6:28–32 Siena S, Landonio G, Baietta E et al (2003) Multicenter phase II study of temozolomide therapy for brain metastasis in patients with malignant melanoma, breast cancer, and non-small cell lung cancer (Abstract). Proc Am Soc Clin Oncol:102 Silber JR, Blank A, Bobola MS et al (1999) O6-methylguanineDNA methyltransferase-deficient phenotype in human gliomas: frequency and time to tumor progression after alkylating agent-based chemotherapy. Clin Cancer Res 5:807–814 Srivenugopal KS, Shou J, Mullapudi SR et al (2001) Enforced expression of wild-type p53 curtails the transcription of the O(6)-methylguanine-DNA methyltransferase gene in human tumor cells and enhances their sensitivity to alkylating agents. Clin Cancer Res 7:1398–1409 Stasio G de, Casalbore P, Gilbert B et al (2001) Gadolinium in human glioblastoma cells for gadolinium neutron capture therapy (GdNCT). Cancer Res 61:4272–4277 Stasio G de, Rajesh D, Casalbore P et al (2005) Are gadolinium contrast agents suitable for gadolinium neutron capture therapy? Neuro Res 27:387–398 Stupp R, Dietrich PY, Ostermann Kraljevic S et al (2002) Promising survival for patients with newly diagnosed glioblastoma multiforme treated with concomitant radiation plus temozolomide followed by adjuvant temozolomide. J Clin Oncol 20:1375–1382 Stupp R, Mason WP, van den Bent MJ et al (2005) Radiotherapy plus concomitant and adjuvant temozolomide for glioblastoma. N Engl J Med 352:987–996 Suh J, Chang E, Timmerman R et al (2002) Phase II trial of motexafin gadolinium (MGd, Xcytrin) and cranial radiation in newly diagnosed glioblastoma multiforme (Abstract). Proc Am Soc Clin Oncol 21:74b Tentori L, Portarena I, Bonmassar E, Graziani G (2001) Combined effects of adenovirus-mediated wild-type p53 transduction, temozolomide and poly (ADP-ribose) polymerase inhibitor in mismatch repair deficient and non-proliferating tumor cells. Cell Death Differ 8:457–469 Tentori L, Portarena I, Graziani G (2002) Potential clinical applications of poly(ADP-ribose) polymerase (PARP) inhibitors. Pharmacol Res 45:73–85

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Tolcher AW, Gerson SL, Denis et al (2003) Marked inactivation of O6-alkylguanineDNA alkyltransferase activity with protracted temozolomide schedules. Br J Cancer 88:1004– 1011 van Rijn J, Heimans JJ, van den Berg J et al (2000) Survival of human glioma cells treated with various combination of temozolomide and X-rays. Int J Radiat Oncol Biol Phys 47:779–784 Verger E, Gil M, Yaya R et al (2003) Concomitant temozolomide and whole brain radiotherapy in patients with brain metastases: randomized multicentric phase II study (Abstract). Proc Am Soc Clin Oncol 22:101 Walker MD, Strike TA, Sheline GE (1979) An analysis of doseeffect relationship in the radiotherapy of malignant gliomas. Int J Radiat Oncol Biol Phys 5:1725–1731 Wallner KE, Galicich JH, Krol G et al (1989) Patterns of failure following treatment for glioblastoma multiforme and anaplastic astrocytoma. Int J Radiat Oncol Biol Phys 16:1405–1409 Watts GS, Pieper RO, Costello JF et al (1997) Methylation of discrete regions of the O6-methylguanine DNA methyltransferase (MGMT) CpG island is associated with heterochromatinization of the MGMT transcription start site and silencing of the gene. Mol Cell Biol 17:5612–5619 Wedge SR, Porteous JK, May BL, Newlands ES (1996a) Potentiation of temozolomide and BCNU cytotoxicity by O(6)benzylguanine: a comparative study in vitro. Br J Cancer 73:482–490 Wedge SR, Porteous JK, Newlands ES (1996b) 3-aminobenzamide and/or O6-benzylguanine evaluated as an adjuvant to temozolomide or BCNU treatment in cell lines of variable mismatch repair status and O6-alkylguanine-DNA alkyltransferase activity. Br J Cancer 74:1030–1036 Wedge SR, Porteous JK, Glaser MG et al (1997) In vitro evaluation of temozolomide combined with X-irradiation. Anticancer Drugs 8:92–97 Wick W, Wick A, Schulz JB et al (2002) Prevention of irradiation-induced glioma cell invasion by temozolomide involves caspase 3 activity and cleavage of focal adhesion kinase. Cancer Res 62:1915–1919 Woodburn KW (2001) Intracellular localization of the radiation enhancer motexafin gadolinium using interferometric Fourier fluorescence microscopy. J Pharmacol Exp Ther 297:888–894 Xu S, Zakian K, Thaler H et al (2001) Effects of motexafin gadolinium on tumor metabolism and radiation sensitivity. Int J Radiat Oncol Biol Phys 49:1381–1390

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11 Radiotherapy and Tumor-Targeted Drug Delivery Zhaozhong Han, Ghazal Hariri, and Dennis E. Hallahan

CONTENTS 11.1 11.2 11.3 11.3.1 11.3.2 11.3.3 11.4 11.5 11.6

Introduction 151 Radiation-Induced Neoantigens on Tumor Endothelium as Targets for Drug Delivery 152 Approaches for Discovery of Inducible Neoantigens 153 Gene-Based Approaches 153 Proteomics-Based Approaches 154 Bioinformatics and Other Approaches 155 Display Technologies for Isolation of Targeting Ligands 156 Delivery Vehicles: from Liposome to Nanoparticle 157 Conclusions and Perspectives 159 References 160

11.1 Introduction Unlike heat, sonication, ultraviolet light, and photodynamic therapy (PDT), ionizing radiation has

advantages that include deep tissue penetration and minimal scatter to adjacent tissues. Moreover, stereotactic radiosurgery and high dose rate brachytherapy further improve the precision of radiation dose distribution because of abrupt fall-off of dose away from tumor tissue. Ionizing radiation can therefore activate or guide drug delivery to neoplasms with greater precision compared with other forms of energy deposition into tissue. Table 11.1 lists the mechanisms by which ionizing radiation can either guide or activate drug delivery within cancer. The first general principle is the use of monochromatic X-rays to induce auger electron emission from gold or platinum. Cisplatin (CDDP) binds to DNA and auger electrons cause DNA double strand breaks adjacent to the cisplatin conjugation to DNA (Borjesson et al. 1993; Biston et al. 2004; Hainfeld et al. 2004). The second general principle is the use of radiation to induce the expression of therapeutic genes using a radiation-inducible promoter (Weichselbaum et al. 1994; Hallahan et al. 1995). This method exploits radiation inducible

Table 11.1. Radiation-directed drug delivery to tumor Concept

Principle

Reference

Auger electron

Monochromatic X-ray activation of auger electron emission

Borjesson et al. (1993), Biston et al. (2004), Hainfeld et al. (2004)

Radiation-inducible gene therapy

Radiation-induced activation of the therapeutic gene expression

Weichselbaum et al. (1994), Hallahan et al. (1995)

Radiation regulation of viral proliferation

Radiation induced increase in proliferation of oncolytic viruses

Advani et al. (1998)

X-ray-guided drug delivery

Radiation-induced neoantigens targeted by antibodies or ligands

Hallahan et al. (2003), Geng et al. (2004)

Activation of proteolysis

Radiation activation of proteases

Demetriou et al. (2004), Winkler et al. (2004), Van Valckenborgh et al. (2005)

Z. Han, PhD, G. Hariri, MD Department of Radiation Oncology, School of Medicine, Vanderbilt University, 1161 21st Avenue South, Nashville, TN 37232-5671, USA D. E. Hallahan, MD B-902 Vanderbilt Clinic, Vanderbilt University, 1301 22nd Avenue South, Nashville, TN 37232-5671, USA

promoters that cause an increased expression of the therapeutic gene within irradiated tumors. The third general principle is the use of radiation to increase proliferation of a therapeutic virus. This technique has been used to increase the efficacy of oncolytic herpes simplex virus (HSV) within irradiated neo-

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plasms (Advani et al. 1998). Radiation can also be used to activate the expression of antigens within neoplasms. Although this approach can be used to increase antigen expression in cancer cells, stroma, and epithelium, the host component (blood vessels) are most attractive for both drug delivery and stability among all neoplasms. Using this approach, antibodies or ligands bind to receptors that are present only after irradiation of tumors. Proteases are activated within irradiated stroma and cancers (Demetriou et al. 2004; Winkler et al. 2004; Van Valckenborgh et al. 2005); therefore, radiationactivated proteases can cleave a therapeutic agent from a pro-drug. This chapter focuses primarily on drug delivery targeting at radiation-induced neoantigens.

11.2 Radiation-Induced Neoantigens on Tumor Endothelium as Targets for Drug Delivery The first concept of using radiation-induced neoantigens as targets for drug delivery was developed and proved several years ago (Hallahan et al. 2001). It was found that blood vessels express a number of cell adhesion molecules and receptors that participate in homeostasis when they are treated with ionizing radiation. Examples of radiation-induced molecules in blood vessels include intercellular adhesion molecule (ICAM)-1, E-selectin, P-selectin, and the E3 integrin. It was also observed that the endothelium and blood components respond to oxidative stress in a similar, if not identical, manner in all tumor models. This observation suggested that targeting drug delivery to these tumor endothelium-associated, radiation-inducible neoantigens might represent a common drug delivery route for a variety

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of tumors. Integrin E3-binding proteins (peptides and antibodies) conjugated to fluorochromes were located within the lumen of blood vessels immediately following irradiation as revealed by immunofluorescent and immunohistochemical staining. The peptide led conjugated radionuclides to irradiated tumors in animal models and clinical trials (Fig. 11.1). It is well recognized that therapy of cancer is still challenging because of the nature of cancer itself. The microenvironment of solid tumor prevents the therapeutic gene product diffusion to tumor cells. Adaptive resistance arising from genomic instability in cancer is another obstacle that attenuates drug efficacy. Compared with tumor cells, the tumorsupporting tissues, such as tumor-related blood vessels, are composed of “normal” cells and would be more reluctant to be adapted with treatments. Direct contact with circulating drugs adds another benefit for tumor blood vessels as a therapeutic target. The importance of tumor-related blood vessels for tumor development, growth and metastasis has been clarified in the last few decades. Extensive research indicates that neoplasms require a functioning vascular network to provide tumor cells with oxygen and other nutrients and also to remove toxic waste products associated with cellular metabolism. For continued growth and development, tumors must generate their own networks of microvessels through the process of neovascularization (Folkman 1971). In fact, it is widely accepted that no solid tumor can grow larger than a critical size of a1 mm3 without developing a vascular network (Cox et al. 2004). The importance of blood vessels for tumor development, growth, and metastasis supports the concept of targeting tumor-related blood vessels for tumor control. Two related, but strategically different, approaches have been developed to test this hypothesis (Bisacchi et al. 2003; Sridhar and Shepherd 2003; Thorpe

Fig. 11.1. Radiation-guided drug delivery of 99mTc-labeled biapcitide by use of an external radiation beam. The 99mTc-labeled biapcitide binding in a breast cancer brain metastasis after treatment with radiosurgery (20 Gy) is shown (arrow)

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2004; Mousa and Mousa 2004). The first approach aims to inhibit the tumor-initiated angiogenic process. Strategies that have been tested include the use of agents that interfere with the delivery or export of angiogenic stimuli (Zhang et al. 2004); antibodies that inhibit or inactivate angiogenic factors after their release (Fernando and Hurwitz 2003); and blockades for signaling pathways, such as inhibitors of receptor kinase activity, tumor invasion, or endothelial cell proliferation (Augustin 2003; Isayeva et al. 2004; Mousa and Mousa 2004). The alternative approach involves the use of therapeutic agents to preferentially destroy established tumor vessel networks, for example, by tumor vessels-targeted delivery of cytotoxic agents. These vascular-disrupting agents (VDAs) differ from antiangiogenic agents not only in their mode of action but also in their therapeutic application. Whereas VDAs are used in intermittent doses, antiangiogenic treatment is administered continually over months or years. This obvious advantage in drug administration makes the second approach more attractive for clinical settings. Nevertheless, an increasing number of agents have been created and tested in preclinical and clinical settings (for a full list, see www.cancer.gov/cancertopics/factsheet/Therapy/angiogenesis-inhibitors). As revealed with doxorubicin (Sengupta et al. 2005) and cisplatin (Geng et al. 2004), most of these tumor vessel-destroying agents would be more efficient for tumor control and less toxic to normal tissues, if tumor-targeted drug delivery was achieved. Targeting to tumor-related endothelium might encounter less drug resistance compared with that found in tumor-specific targeting strategies. So far, diverse approaches have been employed to survey gene expression patterns at various levels, such as mRNA, protein and post-translational modification, and ligand binding properties.

11.3 Approaches for Discovery of Inducible Neoantigens Tumor-associated endothelium is supported by growth factors secreted by tumor and stromal cells. As a result, the fast-growing neovasculature in tumors differs greatly from what is found in most normal adult tissue (Kerbel 2000). The structures in tumor endothelium which can be targeted for drug delivery include elevated “epitope” expression on endothelial surface resulted from increased gene

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transcription, improved stability and accumulation, altered 3D conformation from modification and complex formation, as well as intracellular and intercellular translocation; therefore, various approaches have been employed to discover the tumor-specific, especially radiation-inducible, neoantigens.

11.3.1 Gene-Based Approaches Compared with normal endothelial cells, tumorassociated endothelial cells are more active in DNA replication, transcription, and translation, to keep up with its higher proliferation rate; thus, genes with elevated transcription level have been considered as biomarkers which could be used to distinguish tumor from normal endothelium. Various genebased experimental approaches have been employed in vigorous efforts of tumor endothelium-specific biomarker discovery. DNA array is still the most commonly used method to identify differences at mRNA level (Kim et al. 2005). Probes for thousands of transcripts have been immobilized onto tiny chips that makes it possible to monitor gene expression. In order to increase accuracy and completeness of expression profiling, chips have been made to include synthetic oligoes which cover more than one protein-encoding region of any possible open reading frames (ORF) in whole genome. Alternatively, complementary DNA (cDNA) products have been used as probes with high specificity and fidelity. This approach has been employed to profile gene transcription in tumor-associated endothelial cells, by using endothelial cells co-cultured with tumor in vitro (Khodarev et al. 2003), extracted and purified from fresh tumor tissues (Terashima et al. 2005), and micro-sectioned from paraffin-fixed biopsies (Bibikova et al. 2004). Other similar approaches, such as serial analysis of gene expression (SAGE; St. Croix et al. 2000), polymerase chain reaction (PCR) differential display (Pang et al. 2004), and subtractive hybridization techniques (Nakshatri et al. 1996) have also been used to identify differences at gene transcription level. Potential biomarkers identified by these approaches can be validated by quantitative real time-PCR and antibody staining. Some recently identified tumor endothelial biomarkers are listed in Table 11.2. Among those recently identified biomarkers, several tumor endothelial markers (TEM) were reported by St. Croix and colleagues (2000) who isolated tumor endothelial cells by fluorescence-activated cell sorting, and conducted SAGE

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154 Table 11.2. Biomarkers recently identiﬁed on tumor-associated endothelial cells (EC) Marker

Tissue speciﬁcity

Novel functions

Identiﬁcation methods

Reference

Clusterin

Proliferate EC

Apoptosis

Micro-array proﬁling

Hardwick et al. (2005)

Endoglin (CD 105)

Mainly on EC, over-expressed on tumor-associated vascular endothelium

An accessory component of the TGF–beta receptor complex and is involved in vascular development and remodeling

HP59 (sp55)

Tumor vasculature human fetal lung

Receptor for CM101 (a bacterial lipid)

KIT

Angiosarcomas, fetal EC

Tyrosine kinase growth factor receptor for stem cell factor

MSTP032 Hepatocellular carcinoma, EC

Fonsatti et al. (2003)

Drug screening, target identiﬁcation by cDNA library screening

Fu et al. (2001)

Miettinen et al. (2005)

Micro-array proﬁling

Chen et al. (2004)

TEM7, TEM7R

Blood vessels of human solid tumors (colorectum, breast, lung, and brain tumors)

Glycosylated in splicing variants (intracellular, secreted, and membraneattached), containing single hydrophobic domain, binds to cortactin via 9 a.a. epitope; unknown physiological function

Serial analysis of gene St. Croix et al. (2000), expression (SAGE) on Nanda and St. Croix (2004), endothelial cells isolated Davies et al. (2004) from human normal or malignant colorectal tissues

TEM8

Colorectal, bladder, esophageal and lung cancer (endothelium)

Glycosylated, binds to COOH terminus of collagen 3(VI); receptor of anthrax toxin

SAGE

Thy-1

Adult EC with injury, tumor EC

Involved in cell growth and differentiation

Lee et al. (1998) Firstly identiﬁed as biomarker for thymocyte differentiation in mice, then documented with high expression in neuronal cells; variable expression was reported in other cell types, including EC

Embryogenesis, developmental angiogenesis, tumor invasion and metastasis (?)

Conﬁrmed by tissue staining of tumors with different origins

Plexin D1 Tumor cells and tumor vasculature, neuronal cells

to identify genes expressed in the tumor but not in a normal endothelium. As reported by the group and other investigators, several TEMs have been identified as specifically expressed in tumor endothelium (Carson-Walter et al. 2001; Nanda and St. Croix 2004). Some experiments have documented that expression pattern of some of these identified TEMs correlates with tube formation (Rmali et al. 2005), tumor progress, recurrence (Davies et al. 2004), and potential of metastasis. One group isolated antibodies against TEM-1 (Marty et al. 2005), and one antibody fragment expressed nice tumortargeting effect in drug delivery experiment.

St. Croix et al. (2000), Nanda and St. Croix (2004), Rmali et al. (2005)

Roodink et al. (2003)

11.3.2 Proteomics-Based Approaches Although the genomic analysis achieved discovery of potential biomarkers, the nature of the technology makes it impossible to detect any molecular anatomical variations generated by processes after gene transcription step, such as protein translation, posttranslational modification, intracellular and intercellular translocation, and conformational changes. Proteomic approaches, which rely on component fractionation and identification, can be employed for profiling alterations in proteins. Traditionally,

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samples were fractionated by two-dimensional PAGE (2D PAGE), which separates molecules by molecular size and charges, and comparison of samples from different gels revealed different “spots” which were then extracted for mass spectrometry identification (Wulfkuhle et al. 2003). This approach was limited with moderate sensitivity and obvious variations between gels, as well as incapability in analysis of molecules with extreme molecular size, charge, and solubility. Two-dimensional difference gel electrophoresis and mass spectrometry (DIGE/ MS; Friedman et al. 2004) was developed to label samples with different fluorescent dyes, to separate samples on the same gel, to detect abundance of molecules based on fluorescent signals, and to normalize samples by incorporated inner markers. This modification improves sensitivity (because of fluorescence-based protein detection) and reliability (because of reduced gel-between variations) of this approach. In order to analyze molecules with extreme size, charge, and solubility, fractionating methods other than gel-based separation, such as multidimensional liquid chromatographytandem mass spectrometry (Mcdonald and Yates 2002), have been used to benefit high flexibility of solvents used for separation and high detection sensitivity of chromatographic methods. Improved component fractionating methods can be used to reduce contents in samples, especially removing abundant components, which makes it easier and more efficient to identify a needle from huddles. Fractionation of biological complex, prior to separations at molecular level, has been employed to simplify the profiling by reducing contents (Shin et al. 2003). For some rare and insoluble molecules, such as membrane-associated proteins, tagging with biotin for avidin-based enrichment, and fragmentation with enzymatic digestion for higher solubility, helped elucidation of several protein markers on cells and in tissues (Shin et al. 2003; Peirce et al. 2004; Rybak et al. 2005).

11.3.3 Bioinformatics and Other Approaches Gene expression profiling conducted in the past few years has yielded data on gene expression patterns under various physiological and pathological conditions. While considering similarities between tumor-initiated angiogenesis and other physiological and pathological angiogenesis processes, such as wound healing and embryo development, it is reasonable to hypothesize that some molecules and

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pathways might be common in all these processes. This bioinformatic data-mining approach, assisted with in vitro and in vivo verification methods, is increasingly employed to explore the expanding databases with gene-based and proteomics-based expression profiling data. Examples for radiationinduced neoantigens discovered with this approach include cell adhesive molecules involved in inflammation, such as P-selectin (CD62P), E-selectin, ICAM-1, and integrins. These inflammation-related molecules can be induced on site at transcription level, recruited from circulation or translocated from intracellular storage reservoirs. These molecules are involved in the initiation of leukocyte adhesion and extravasations at the vascular endothelium, platelet aggregation, and inflammatory cell activation (Carlos and Harlan 1994; Wu et al. 1994; Kimura et al. 1995; Ebnet and Vestweber 1999; Molla et al. 1999). These radiation-induced receptors have been used to target drug and gene therapies to tumors after irradiation (Wickham et al. 1995; Hallahan et al. 2001; Yuan et al. 2003). Understanding of overlapped pathways of angiogenesis and axon guidance in nerve development leads to identification of several axon guidance-related molecules in the process of angiogenesis (Neufeld et al. 2002; Neufeld et al. 2005; Davy and Soriano 2005; Wang et al. 2005; Klagsbrun and Eichmann 2005), and some of them could be explored as targets for tumor endothelium-targeted drug delivery. Another approach to identify novel tumor endothelial surface proteins is phage display, which is discussed below. Actually, phage-displayed combinatorial libraries have been successfully used to profile organ- and tumor-specific endothelium (Joyce et al. 2003; Laakkonen et al. 2004). The random peptides displayed on phage surface can be “biopanned” on cells and tissues in vitro and in vivo for cell- or tissue-specific peptide sequences. Since great diversity (billions of peptides in one library) has been achieved with chemical and biological approaches, it is possible that any molecule in nature could match up with one or more specific peptide sequences with reasonable affinity and specificity. The enrichment generated by affinity “purification” and biological replication of the “purified” phages make it assumable to have specific peptides binding with any molecular targets, including the rare ones. Once the affinity reagents are in hand, the corresponding interacting molecules or “receptors” in the biological samples can be further isolated and identified by using bioinformatics approach (Arap et al. 2002), affinity-based separation (Christian

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et al. 2003), and expression cloning (Zhang et al. 2005) methods. Compared with its extraordinary success in affinity-ligand discovery, phage display technology has not achieved its inherited potential in identification of neoantigens, partially because of relatively low affinity and specificity of the short peptides for putative receptors that complicate the identification of the corresponding putative receptor. Larger structural entities, such as engineered antibody fragments and other scaffold proteins (Holt et al. 2003; Schlehuber and Skerra 2005; Boulter and Jakobsen 2005), might be alternative sources of combinatorial diversified sequences for profiling the differences among tissues. More stable structures in these larger entities would ensure higher specificity. Larger interaction surfaces provided by these scaffolds would also contribute more energy and thus higher affinity to the molecular interactions.

11.4 Display Technologies for Isolation of Targeting Ligands With neoantigens in hand, the next question is how to isolate affinity ligands for ligand-guided drug delivery. The targeting ligands could be natural or artificial peptides (Ruoslahti 2000), monoclonized

Displayed Entity

antibodies (Kortt et al. 2001), or non-proteinous structures (Geng et al. 2004). Display technologies, with phage display as an outstanding representative, enable isolation and optimization of engineered peptides, proteins, and antibodies for drug delivery in a cost- and effort-efficient way. Display technologies, firstly developed in concept and implemented with filamentous bacteriophage by Smith (1985) and Scott and Smith (1990), utilize physical linkage between the displayed entity (phenotype) and its genetic code (genotype), as shown in Figure 11.2, to permit selection of ligands with desired affinity to targets from a large collection of diversities and fast decoding the sequence information of the isolated peptides or proteins. In the first proof-of-concept experiment, gene fragmentencoding restriction enzyme, EcoR I, was incorporated into filamentous bacteriophage genome as fusion at downstream of phage coat proteins III. As a result, the phages expressing EcoR I enzyme on its surface was efficiently enriched on enzyme-specific antibody-coated solid matrix from a pool with nonrecombinant phage particles through rounds of a process called “biopanning.” This experiment leads to the idea to clone genes from an expression library by isolating proteins by phenotype (affinity to baiting molecule) and decoding amino-acid sequence information from the associated DNA. Since its first implantation for biological research, platforms for displaying moieties have been expanded to in vivo

Linker

Code

Protein on RNA/DNA

Protein/peptide

DNA/RNA binding

DNA/RNA

Viral display

Protein/peptide

Viral capsid

DNA

Cell based display

Protein/peptide

Prokarytic or eukaryotic cells

DNA

Protein/peptide/ other compounds

Physical attachment

DNA/spatial address/ chromatographic property

Nonbiological display

Fig. 11.2. Display modules showing physical linkage of genotype (structure-encoding information) and phenotype (target-binding entity). (From Li et al. 2000)

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self-replicating bacteriophages M13 (Markland et al. 1991), fd (Smith 1985), lambda (Mikawa et al. 1996), and T7 (Yamamoto et al. 1999); and eukaryotic viruses (Muller et al. 2003), bacterium (Rode et al. 1996; Georgiou et al. 1997), yeast (Boder and Wittrup 1997), and in vitro cell-free biological complex such as ribosome (Hanes et al. 1998) and mRNA (Roberts and Szostak 1997). The displayed moieties include short peptides encoded by randomized DNA fragments, cDNA products from mRNA pools, engineered proteins and antibody fragments (Cesareni et al. 1999; Sidhu 2000; Dani 2001; Pini et al. 2004), and non-natural amino acids or other building blocks (Frankel et al. 2003). Library diversity has expanded from original millions of members to extremely high number (1014) achieved in the mRNA display system. With high diversity of library, in addition to high throughput technologyenabled target protein preparation, screening, and validation, it is now possible to have affinity reagents in a very cost- and effort-efficient way in a short time (Hallborn and Carlsson 2002). Other than purified homogenous targets, more sophisticated targets, such as molecular complex, cells, and organs have been successfully used for in vitro and in vivo “biopanning” (Pasqualini and Ruoslahti 1996; Arap et al. 1998; Ruoslahti 2004). Because the whole-cell or tissue biopanning bypasses the time- and costconsuming purification of the target protein, this method is attractive for developing affinity reagents against targets that are unknown or hard to purify, such as membrane proteins in tumor blood vessels. In vivo selection simultaneously provides positive and subtractive screens because organs and tissues, such as tumors, are spatially separated. Comprehensive reviews of isolation of tumor-targeted peptides have been published recently (Zurita et al. 2003; Ruoslahti 2004). Selective tumor-targeted drug deliveries were achieved by using these peptide ligands (Arap et al. 1998).

11.5 Delivery Vehicles: from Liposome to Nanoparticle Drug can be directly conjugated to a targeting agent for targeted delivery. Vehicled delivery resulted in improved therapeutic efficacy because of increased bioavailability of drugs to the targeted cells. Engineered cells, bacteria, as well as natural and artificial molecular scaffolds, have been used as vehicles for

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drug delivery. Among the developed drug-delivery vehicles, nanoparticles are attracting more enthusiasm because of their ability to meet requirements for drug-delivery vehicles in size, stability, solubility, and targeting properties (Ferrari 2005; Mcneil 2005; Lee et al. 2005). Nanoparticles refer to particles with size scale of 1–100 nm which are created by controlled array of building blocks at atomic, molecular, or macromolecular scale. As illustrated in Figure 11.3a, nanoparticles are of the same basic size as biological entities, such as enzymes and hemoglobins, that enable nanoparticles to behave as biological macromolecules. Nanoparticles smaller than 20 nm can transit through blood vessel walls and penetrate the bloodbrain barrier or the stomach epithelium (Vinogradov et al. 2004), while avoiding rapid filtration by the spleen and liver (Moghimi et al. 2001). Ligand-conjugated quantum dots were demonstrated with capability of receptor-mediated endocytosis (Osaki et al. 2004). Nanoparticles can interact readily with biomolecules on the cell surface and within the cell, often in ways of the natural binding ligands or interacting counterparts of the biomolecules, to modulate signal transduction pathways and other biological processes. Current nanoparticles are divided mainly into synthetic and natural categories based on their components. Particles composed of natural or nonsynthetic moieties are represented with liposomes, micelles, and chitosan-based particles. Compared with the synthetic methods described below, this approach is more likely to mimic the phospholipid bilayer naturally present on the outer surface of cells to exhibit biocompatibility. Liposomes are composed of a lipid bilayer separating an aqueous internal compartment from the bulk aqueous phase. Micelles are closed lipid monolayers with a fatty acid core and polar surface; both have been used for the past decade as carriers of various anticancer drugs such as anthracyclines, platinum compounds, cytarabine, paclitaxel, camptothecin, and vincristine. Encapsulating anticancer drugs in liposomes typically improves the pharmacokinetic profile of the drug and results in reduced systemic toxicity (Hofheinz et al. 2005). Drug release can be slow at tumor sites, and chemical instability issues must often be addressed when preparing liposomes. Chitosan is a polysaccharide similar in structure to cellulose. Its primary amine groups, positive charge, and mucoadhesivity make it attractive for drug-delivery applications. Chitosanbased nanoparticles have been used as carriers for doxorubicin to tumors. Mitra et al. (2001) encap-

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a

Fig. 11.3a,b. Nano-sized particles with potential in drug delivery. a relative size of nanoparticles. (From McNeil 2005). b Multi-functional nanoparticle composed of targeting regions, functional moiety, and core scaffold. (From Ferrari 2005)

b

sulated doxorubicin–dextran conjugate into long circulating chitosan nanoparticles and showed that the system not only reduced toxic side effects, but also improved the therapeutic efficacy of doxorubicin in the treatment of solid tumors. Even though chitosan-based nanoparticles are suitable for controlled release and targeting of drugs to tumor sites, most studies performed to date have been in in vitro models, and more work must be done to establish in vivo efficacy. Chemical modifications of chitosan-based nanoparticles are also needed to get the desired physicochemical properties such as solubility and hydrophilicity (Agnihotri et al. 2004). Alternatively, nanoparticles can also be created from many biologically compatible polymers such as

polyglycolic acid (PGA), polylactic acid (PLA), polylacticglycolic acid (PLGA) copolymer, and polyethylene glycol (PEG), among many others. Various factors, such as the molecular weight, chain length, and degree of branching of the polymers, can alter the properties of the polymer. Frequently, a combination of polymers is used such as in co-polymer blends and tri-block polymers. The PLGA is an example of a co-polymer commonly used in nanoparticle applications. When combinations of polymers are used, the ratios of each polymer along with the arrangement of each within the polymer unit can be modified to obtain different properties in the polymer. Nanoparticles made with a core-shell structure have been produced using PLA as a core polymer

Radiotherapy and Tumor-Targeted Drug Delivery

and PEG as a coating. The PEG molecules are typically used in nanoparticle applications as coatings to delay degradation of the molecule, increase circulation time, and improve bioavailability. Studies have shown that PLA-PEG and PLGA-PEG nanoparticles exhibit prolonged blood circulation following intravenous administration to animals (Avgoustakis 2004). Such nanoparticles have been used to carry drugs such as paclitaxel and doxorubicin. Feng et al. (2004) showed that encapsulation efficiency of paclitaxel in PLGA nanoparticles can be achieved as high as 100%. In vitro experiments done by this group on HT-29 cancer cells showed that after 24 h of incubation, the cell mortality caused by the drug administered by such nanoparticle formulation could be more than 13 times higher than that caused by the free drug under similar conditions. The PLGA nanoparticles loaded with doxorubicin were examined by Yoo et al. (2000) and found to be useful for targeting of cancer cells as well as sustained drug release at the site. The main advantage of using synthetic polymers for nanoparticles lies in their ability to be designed to accommodate particular applications. This “tunability” exploits the different properties of polymers and polymer combinations to produce nanoparticles with certain properties. Examples of properties that can be “tuned” include the particle size, chain length, molecular weight, surface charge, hydrophobicity, surface morphology, and surface chemistry. Depending on the particular drug, dosage, and treatment schedule, nanoparticle materials can be modified to provide the desired characteristics; these might include encapsulation of hydrophobic drugs, various administration methods, biodegradeability, controlled release, sustained release, and localized delivery of drug to maximize the therapeutic index and minimize systemic toxicity. Problems that have been encountered with some polymeric nanoparticles include potential chemical instability, limited bioavailability, and lack of site specificity. These problems are often addressed by modifying the polymer composition and incorporation of surface groups such as PEG and specific targeting agents. Another polymer-based type of nanoparticle is the dendrimer (Lee et al. 2005). Unlike other polymers, dendrimers have a narrow molecular weight distribution, specific size and shape characteristics, high degree of molecular uniformity, and a highly functionalized terminal surface. They are typically made of polymeric materials such as polyamidoamine (PAMAM). Dendrimers are good candidates for drug-delivery applications because of their mod-

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ifiable surface functionalities along with their highly defined size and structure. Drug delivery can be achieved by binding a drug to polymer through one of two approaches. Hydrophobic drugs can be complexed within the hydrophobic dendrimer interior to make them water soluble, or drugs can be covalently coupled onto the surface of the dendrimer. Patri et al. (2005) conjugated methotrexate to PAMAM dendrimer in both ways and demonstrated that, while drug as a dendrimer inclusion complex is readily released and active in vitro, covalently conjugated drug to dendrimer is better suited for specifically targeted drug delivery. Tumor-targeted delivery of PAMAM dendrimeric conjugates with methotrexate was reported with increased antitumor activity and markedly decreased toxicity, compared with therapeutic responses not possible with the free drug (Kukowska-Latallo et al. 2005). Dendrimers are advantageous due to their biocompatibility and nonimmunogenic nature. This allows them to provide a unique method for delivery of a variety of therapeutic agents, targeting agents, and imaging agents.

11.6 Conclusions and Perspectives Radiation is used in the majority of cancer patients. Technological and scientific advances ensure precise and efficient delivery of radiation to tumor sites. Low-dose radiation has been reported to enhance drug delivery by inducing higher drug diffusion in solid tumors (Joiner et al. 2001). It has also been demonstrated with invaluable potential in inducing tumor-specific neoantigen expression for targeted drug delivery. Given the progress in targeting ligand discovery, as well as development in nano-sized vehicles for drug delivery and improved conjugating methods (Kovar et al. 2002), it is possible to design and create multifunctional nanoparticles (as shown in Fig. 11.3b) for tumor-targeted drug delivery. The multifunctional particles could be composed of therapeutic genes and drugs or imaging agents for therapeutic or diagnostic purposes, some modification groups, such as PEG, for better solubility and bioavailability, and targeting reagents such as peptides or antibody fragments. Having all the components embedded in a core structure, bioavailability can be improved with targeted delivery and tens of thousands of small molecular drugs on the surface of one particle. As illustrated with combination of chemotherapy with tumor neovasculature-targeted

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delivery of antiangiogenic drug, which resulted in significantly improved therapeutic index with reduced toxicity (Sengupta et al. 2005), combining tumor-targeted drug delivery with radiotherapy could lead to improved tumor control.

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II. Clinical Part

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12 Applications in Malignant Brain Tumors Carsten Nieder and Mark R. Gilbert

CONTENTS 12.1 12.2 12.2.1 12.2.2 12.2.3 12.2.4 12.2.5 12.2.6 12.2.7 12.3 12.4 12.5 12.6 12.7

Introduction 165 Astrocytoma 166 Histology and Prognosis 166 Surgical Resection and Supportive Measures 167 Postoperative Radiotherapy 167 Postoperative Chemotherapy 168 Potential New Strategies 174 Recurrent Tumors 176 Perspectives 177 Oligodendroglioma 178 Ependymoma 178 Medulloblastoma 179 Meningioma 180 Brain Metastases 180 References 181

12.1 Introduction Primary brain tumors are a very heterogeneous group of diseases arising from different cells of origin showing characteristic age distributions. The World Health Organization (WHO) has recently published an updated classification system, reviewed, for example, by (Fuller and Perry 2001). Virtually all of these tumors represent <2% of all cancers in most western countries. The treatment recommendations take into account the differences between pediatric and adult patients, and, when applicable, the different grades of the disease. One has to discriminate, for example, between histological tumor types

C. Nieder, MD Department of Radiation Oncology, Klinikum Rechts der Isar der Technischen Universität München, Ismaninger Strasse 22, 81675 Munich, Germany M. R. Gilbert, MD Department of Neuro-Oncology, The University of Texas M.D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030, USA

that arise localized and unifocal, types that might present as either unifocal or multifocal central nervous system (CNS) disease, and types that are rarely limited to just one site. In contrast, tumor presentation outside of the CNS is exceedingly uncommon, even in the presence of cerebrospinal fluid (CSF) dissemination; therefore, based on the pattern of spread, the treatment volume might vary from the primary site alone to the whole cranio-spinal axis. Chemotherapy with different sequentially or simultaneously administered agents can be used to enhance the effect of local treatment aiming either at additive cell kill or true radiosensitization, to defer intense, potentially toxic local treatment in vulnerable subgroups, or to treat distant tumor sites based on the principle of spatial cooperation. In general, primary brain tumors are not curable by chemotherapy alone; however, certain histological groups with better response to chemotherapy as well as radiotherapy have been defined, e.g., medulloblastoma. The main prerequisites of successful chemotherapy are sensitivity of the tumor cells to the mechanisms of the drug and sufficient drug exposure. The key issues of tumor heterogeneity with primary and acquired resistance as well as pharmacokinetics, pharmacodynamics, and tumor microenvironment deserve particular attention because of several facts that are specific for CNS tumors. First of all, the intact blood-brain barrier (BBB) prevents access to the brain for several compounds. Even in areas of BBB disturbance, as present, for example, in high-grade glioma, the effects of contemporary drug treatment are not fully satisfactory; thus, achieving therapeutic concentrations in distal, seemingly intact areas that also are known to contain infiltrating tumor cells remains an enormous challenge. Various strategies of modified application or increased dose have been explored, including intraarterial, intrathecal, and intratumoral delivery as well as disruption of the BBB. Furthermore, many patients with brain tumors are able to metabolize chemotherapy drugs and receptor tyrosine kinase (RTK) inhibitors more rapidly than other tumor

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patients because of concomitant enzyme-inducing medications that are necessary to treat or prevent seizures. Phenytoin, carbamazepine, and phenobarbital induce hepatic cytochrome P450 enzymes, resulting, e.g., in higher maximum tolerated drug doses. Decreased drug effectiveness has been postulated from corticosteroid treatment. Radiological assessment of the effectiveness of chemotherapy might be difficult, especially in high-grade glioma after intensive pre-treatment (Vos et al. 2003). Many groups combine radiological with clinical findings, as published by (McDonald et al. 1990). The need for chemotherapy administration is less obvious when local control rates are very high and toxicity from local treatment is uncommon as is, for example, the case in stereotactic radiosurgery (SRS) for WHO grade-II meningioma; however, in diffusely infiltrating high-grade glioma, combined modality treatment has gained increasing acceptance because intensified radiotherapy approaches are limited by normal tissue complications and have not resulted in satisfactory long-term control rates to date. In summary, brain tumors, especially those with high-grade histological features, present unique therapeutic challenges because of their location, aggressive biological behavior, and diffuse, infiltrative growth. Both the tumor and its treatment often result in profound changes in quality of life. Failure of local treatment is still the most common feature in several disease types; thus, improvement of long-term survival rates likely requires substantial refinements of combined-modality therapy.

12.2 Astrocytoma 12.2.1 Histology and Prognosis Astrocytic neoplasms can be classified as low-grade (II) or high-grade (tIII) tumors. Further local progression or high-grade transformation is common. The most malignant type, glioblastoma multiforme (GBM), or WHO grade-IV glioma, tends to occur in 50- to 70-year-old patients, whereas the less malignant forms develop at least a decade earlier. The different types of astrocytoma can also be found in children. Pediatric patients are best treated in the context of appropriate cooperative group trials. (A detailed description of their treatment protocols is beyond the scope of this chapter.) Median survival

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time is limited to approximately 10–15 months for GBM and up to 30–50 months for anaplastic astrocytoma (AA) or WHO grade-III astrocytoma. Anaplastic astrocytoma is histologically characterized by its increased cellularity and mitotic activity, whereas GBM shows additional necrosis or endothelial proliferation. Mixed anaplastic oligoastrocytoma (MOA) and particularly pure anaplastic oligodendroglioma (AOD) represent more favorable histological groups with better response to chemotherapy as well as radiotherapy. Survival after relapse and second-line treatment of high-grade astrocytoma is usually in the range of 6–8 months while median time to further progression was 14 weeks in over 1400 patients treated with different regimens (Huncharek and Muscat 1998). Whereas the prognosis of low-grade pilocytic astrocytoma is favorable after surgical resection alone, most WHO grade-II infiltrating astrocytomas will eventually fail and require radiotherapy. Tumor suppressor gene inactivation and oncogene activation and overexpression play a part, along with alterations in cell-cycle progression, abnormalities in signal transduction pathways, glial cell invasion, and angiogenesis, in the development of glioma. Prognosis is determined by several patient-associated factors (age, performance status, neurological function, symptom indices, and duration), tumor location and grade, as well as treatment-related factors such as surgical resectability or residual tumor volume (Laws et al. 2003). Less consistently reported factors include necessity for corticosteroids (or dose), duration of symptoms, or tumor side (frontal more favorable; Curran et al. 1993; Simpson et al. 1993). Curran et al. (1993) analyzed the survival of more than 1500 patients with high-grade glioma in the Radiation Therapy Oncology Group (RTOG) database and found that five variables (duration of symptoms, mental status, age at diagnosis, tumor grade, and postoperative performance status) defined six patient subgroups with distinct prognoses (median overall survival (OS) from 5 to 59 months. Proliferative activity measured, for example, by variants of the Ki-67 antibody was found to correlate to WHO grade, but not to OS, in multivariate analysis adjusted for the clinically established prognostic variables (reviewed by Stemmer-Rachamimov and Louis 1997). The same holds true for p53 immunostaining or presence of p53 gene mutations (Nieder et al. 2000a). Expression of PAI1, p27Kip1(a cell-cycle regulator), alterations in the MMAC/PTEN gene, and epidermal growth factor receptor (EGFR) amplification in GBM have been

Applications in Malignant Brain Tumors

examined with mixed results and are not standard assessments yet (Shih et al. 2005; Quan et al. 2005). Given the complexity of assessment of a large set of potential prognosticators, it would be interesting to determine whether gene-array technology will result in clinically implementable prognostic information. Recent data suggest that class prediction models, based on defined molecular profiles, classify diagnostically challenging high-grade glioma in a manner that correlates with clinical outcome better than standard pathology (Nutt et al. 2003; Shai et al. 2003). It might therefore be expected that better prognostic models will be available in the future.

12.2.2 Surgical Resection and Supportive Measures Surgical resection remains the initial treatment of choice. Besides establishing a tissue diagnosis, resection might lead to rapid improvement of symptoms, e.g., from mass effects, hydrocephalus, etc., and reduction of steroid doses. Despite the inability to cure high-grade glioma by surgery, the macroscopic completeness of a “T1 resection” (referring to the removal of all MR-visible enhancing tumor) is related to survival (Keles et al. 1999; LaCroix et al. 2001). The amount of residual tumor should therefore be quantified by early postoperative magnetic resonance imaging (ideally within the first 24 h after surgery). Detailed descriptions of technical surgical improvements, e.g., use of functional imaging, neuronavigation, intraoperative mapping, microsurgery, use of fluorescent tissue markers, etc., are given in recent reviews (e.g., Schiff and Shaffrey 2003). Medical treatment aims at counteracting peritumoral edema with corticosteroids and preventing seizures with anticonvulsants. Many phase-I, phaseII, and pharmacokinetic studies confirm significant alterations of several chemotherapeutic agents (i.e., paclitaxel, CPT-11) and signal transduction modulators (i.e., gefitinib, imatinib) by hepatic cytochrome p450-inducing anticonvulsants.

12.2.3 Postoperative Radiotherapy In low-grade tumors immediate postoperative radiotherapy with 5054 Gy improves progressionfree survival (PFS); however, when compared with deferred salvage radiotherapy, OS is not increased (Karim et al. 1996; Shaw et al. 2002). The situation

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is different in high-grade tumors. Historically, early recurrences after resection prompted investigators to study immediate postoperative radiotherapy (Walker et al. 1978). It was found that local fields (tumor with or without edema with safety margins) are as appropriate as whole-brain radiotherapy (WBRT), and that 60 Gy are better than lower doses (Walker et al. 1979; Bleehen and Stenning 1991). Presently, this postoperative regimen still remains an important and effective way to increase the time to progression, although it does not lead to cure in the majority of patients. Delaying the start of radiotherapy beyond 46 weeks appears to hamper its effectiveness. Intensification of external beam radiotherapy beyond a standard course of 60 Gy over 6 weeks has been extensively investigated. Methods included the use of altered fractionation, i.e., application of more than one fraction per day. Our group has recently summarized the results of trials published between 1997 and 2002 (Nieder et al. 2004). We identified 1414 patients from 21 studies; 2 of these were randomized phase-III studies. In 7 studies involving 658 patients, chemotherapy or radiosensitizers were not administered in addition to radiotherapy. None of the 21 studies reported a significantly improved OS by altered fractionation in comparison with either institutional historical controls or their respective randomized control arm. Doses of 60–70 Gy did not appear to improve OS compared with 5060 Gy. Median OS was 10 months after altered-fractionation radiotherapy alone (658 patients) and 11 months after combined treatment (756 patients). Regarding 2-year survival rates, radiotherapy alone resulted in 13%, and combined chemoradiation or use of sensitizers in 23% (p<0.0001); however, prognostic factors, such as tumor histology, were not equally distributed and favored the combined treatment group. The median OS of 571 patients in six studies of conventional radiotherapy alone was 10.8 months, and the 2-year survival was 15%. In comparison, the median OS of 1115 patients treated with conventional radiotherapy plus chemotherapy or sensitizers was 11 months, with a 2-year survival rate of 18.5%. In the absence of unequivocal evidence from randomized trials, significant external beam dose escalation to 90 Gy, as investigated by different groups, remains a highly controversial issue. Randomized studies which achieved intensification by SRS, stereotactic fractionated radiotherapy (SFRT), or brachytherapy, rather than conventional external beam treatment, also failed to define a new standard of care (Laperriere et al. 1998; Selker et al. 2002;

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Souhami et al. 2004). Local and marginal disease progression continued to be the most common pattern of failure. Neither addition of radiosensitizers or enzyme inactivators, such as misonidazole, etanidazole, tirapazamine, bromodeoxyuridine, D-difluromethylornithine (DFMO), or hyperbaric oxygen, have resulted in significant gains (Shafman and Loeffler 1999; Prados et al. 2001; Nieder et al. 2004). Currently, newly developed radiosensitizers, e.g., motexafingadolinium (a tumor-selective redox-active porphyrin) and RSR13 (an allosteric effector of hemoglobin) are under prospective clinical investigation. For patients in unfavorable prognostic groups, hypofractionated treatment to doses of 3045 Gy over 2–3 weeks is a reasonable alternative to standard conventional radiotherapy due to increased patient convenience and better cost-effectiveness (Roa et al. 2004).

12.2.4 Postoperative Chemotherapy In low-grade tumors chemotherapy does not have an established role but is being investigated for very young children (carboplatin, vincristine, temozolomide or 6-thioguanine, procarbazine, CCNU, vincristine) or tumors that recur despite extensive local treatment. In the context of clinical trials, different approaches with the drugs that are used for highgrade tumors and cross the BBB have been examined. With temozolomide, 47% of adult patients with low-grade gliomas responded according to criteria of McDonald et al. (1990), median duration of response was 10 months, and PFS was 39% at 12 months (Pace et al. 2003). The study included 43 patients with different low-grade histologies, including oligodendroglial or mixed tumors (n=14), and pre-treatment (70% radiotherapy, 37% chemotherapy). In high-grade astrocytoma many cytotoxic drugs, most often nitrosoureas and other alkylating agents, have been added to surgery and radiotherapy since the 1970s. They were usually administered after completion of local treatment. A metaanalysis of 16 randomized clinical trials from a 17-year period suggested a moderate increase of survival of 8.6% at 2 years by adding systemic chemotherapy. Median survival increased from 9.4 to 12 months (Fine et al. 1993). Interestingly, the most recent second metaanalysis of 3004 patients from 12 randomized controlled trials also suggested a small but statistically

C. Nieder and M. R. Gilbert

significant improvement of survival from chemotherapy (Stewart 2002). The largest randomized trial for patients with newly diagnosed malignant gliomas (grades III and IV) was performed by the Medical Research Counsel in the United Kingdom. This study, which compared radiation therapy alone with radiation treatment followed by adjuvant chemotherapy using procarbazine, CCNU, and vincristine, showed no statistical benefit with the addition of chemotherapy to radiation treatment. Pre-radiation chemotherapy has resulted in disappointing results if given to adult patients with AA (Rao et al. 2005) or GBM (Raymond et al. 2003; Mane et al. 2004), possibly with the exception of temozolomide plus cisplatin (Balana et al. 2004). In the latter trial, 45% objective responses according to McDonald’s criteria were noted prior to radiotherapy. Similarly, a multicenter study (Gilbert et al. 2002) which treated patients with grades III and IV gliomas with pre-radiation temozolomide demonstrated a high objective response rate in both GBM and AA (40% in each group); however, the responses were not durable and overall survival was not increased compared with historic controls. A recently completed phase-III trial by the German Neuro-Oncology Working Group (NOA-4) has investigated the possibility of deferred radiotherapy in adults with AA and AOD. In one arm of the study postoperative radiotherapy was administered, whereas in the other two arms radiotherapy was deferred and patients were randomized to receive either temozolomide or PCV (procarbazine, CCNU, vincristine) with defined crossover options in case of progression. The results of this trial await publication. Currently, a trend can be seen towards concomitant application of chemo- and radiotherapy. Certain drugs were found to sensitize glioma cells in vitro and in vivo (Van Rijn et al. 2000). In general, the optimal drug or drug combination is still a matter of debate. Tables 12.1 and 12.2 provide an overview of the most relevant trials. Further activity data are provided in Table 12.3 (summary of chemotherapy for recurrent glioma). The results of several studies do not convincingly demonstrate superiority of polychemotherapy or additional biologics such as interferon vs single-agent nitrosoureas alone (Buckner et al. 2001). These studies include a phase-III trial comparing carmustine (BCNU) plus procarbazine or BCNU plus hydroxyurea, procarbazine and teniposide to single agent BCNU (Shapiro et al. 1989), a trial of carboplatin/etoposide followed by BCNU (Brandes et al. 1998) and a recent phase III study of BCNU vs continuous infusion BCNU plus cisplatin

Applications in Malignant Brain Tumors

(Grossman et al. 2003). Several other studies of cisplatin or carboplatin also did not report improved results (Jeremic et al. 2001; Levin et al. 2002). The practice of routine use of adjuvant PCV chemotherapy for patients with AA by some neurooncologists was based largely on a post hoc analysis of an otherwise negative trial (Levin et al. 1990). Later, a comparison of AA patients treated in different RTOG studies either with PCV or BCNU showed no relevant difference (Prados et al. 1999); however, further studies of PCV administration have been published. A recent phase-III trial comparing adjuvant PCV with PCV plus DFMO in anaplastic glioma (Levin et al. 2003) showed a slight survival difference favoring PCV-DFMO, limited to the first 2 years of follow-up. Median survival was 76 vs 61 months. In a recent randomized trial of ACNU plus teniposide vs ACNU plus cytarabine no significant survival difference was observed for the complete group of patients with different types of high-grade glioma or any subpopulation (Weller et al. 2003). Median survival was 60 and 62.5 months for AA, comparable to that of PCV trials. Thus far, superiority of combination PCV or BCNU-PV has not been confirmed in a prospective study designed specifically to address this issue. In the absence of any clear survival difference between different regimens, other considerations, such as toxicity, oral application, and cost of treatment, might guide the choice (Table 12.4). Several possible strategies might increase the effectiveness of chemotherapy by administering higher doses of otherwise moderately effective drugs. Intra-arterial chemotherapy, e.g., with BCNU, was comprehensively evaluated but found to be more toxic and no more effective than intravenous administration and, thus, did not offer a therapeutic gain; the latter appears to be the case for highdose chemotherapy regimens with autologous bone marrow or peripheral blood stem cell support too (Durando et al. 2003). Results reported so far are less encouraging than anticipated. Although a high response rate was reported, the responses were not durable and treatment-related mortality was as high as 10–15%. Biodegradable polymers may be impregnated with cytotoxic chemotherapeutic drugs, such as BCNU, and the polymer wafers placed into the tumor bed during surgery, possibly exposing tumor cells to higher drug concentrations. A randomized trial of BCNU vs placebo wafers demonstrated a statistically significant increase in median survival (13.9 vs 11.6 months) for the BCNU wafer-group; however, the “wafer” trials have never directly compared the active wafer against conventionally

169

administered chemotherapy (Westphal et al. 2003). Furthermore, when the survival analysis included only patients with GBM, statistical significance was not reached. Other compounds, such as bucladesine and 5-fluorouracil, are also under investigation for local delivery. Convection-enhanced delivery (CED) can be used to perfuse regions of the brain with therapeutic agents in a manner that bypasses the BBB. In animal studies, encouraging results have been obtained. Clinical trials of CED are underway, also for studies of toxin-conjugates (composed, for example, of interleukin-13 plus Pseudomonas exotoxin or transferrin plus diphteria toxin). Newer drugs, such as paclitaxel, topotecan, irinotecan, and temozolomide, are being evaluated singly or in combination (Tables 12.1, 12.2). A large randomized phase-III and a smaller randomized phase-II trial of different temozolomide schedules in addition to radiotherapy have been published (Stupp et al. 2005; Athanassiou et al. 2005). These trials were conducted after encouraging survival data (median 16 months for patients with newly diagnosed GBM) were observed in a phase-II study of radiotherapy with 60 Gy and both concomitant and adjuvant temozolomide (Stupp et al. 2002). After oral administration, temozolomide crosses the BBB. The compound needs conversion into its active form to methylate the O6 and N7 positions of guanine bases. The study by Stupp et al. (2005) represented the collaborative effort of the EORTC and the NCIC. Five hundred seventy-three patients were randomized to either external beam radiotherapy or concurrent temozolomide with radiation followed by six cycles of adjuvant temozolomide. This study confirmed the survival benefit of the combination regimen (12.1 vs 14.6 months) and 2-year survival rate (10 vs 26%). Discontinuation of temozolomide for toxicity reasons was recorded in 13%. The median number of postradiation cycles was 3. No significant survival improvement was found in patients with biopsy only and in patients with poor performance status (WHO II). An ongoing phaseIII trial, the collaborative effort of the RTOG and EORTC, will further explore optimizing the dose of temozolomide. Resistance of tumor cells to cytotoxic drugs is a major problem. Possible resistance mechanisms include the cell membrane protein P-glycoprotein (PGP), an energy-dependent drug efflux pump removing a wide range of lipophilic chemotherapy agents. The PGP expression has been described in tumor blood vessels as well as neoplastic cells of both low- and high-grade glioma (von Bossanyi

57 93

Median 80 Median PS 1 t90 in 83%

46 53

0 69 58 67 94

18

16

33

Rajkumar et al. Single inst. phase I (1999)

Rajkumar et al. Single inst. phase I (1998)

Single inst. phase II

Multi-center 339 335 phase III

Tanaka et al. (2001)

MRC (2001)

77 None, all anaplastic

14

79

90

21

Single inst. phase II

Single inst. phase II

Single inst. phase II

Single inst. phase II

Peterson et al. (2001)

Jeremic et al. (2001)

Levin et al. (2002)

Weller et al. (2001)

71 72 ?

t70 in 85% t90 in 84% All t 70

57 37 56

43

87

63

66

Median 80

51

52

All ECOG 0-1

All ECOG 0-1

ECOG 0-1 in 81% 76

59.4–60

55–60

60

60

57

45 or 60

60

48

48

64.8

60 vs 60 plus SRS

11

28

14

9

11

9.5 vs 10

21

14

14

13 vs 12

13.5 vs 13.6

?

65

33

?

12

15 vs 17

24 (GBM), 70 (AA)

?

22

21 each

19 vs 21

Two-year Survival (%)

Gemcitabine

Carboplatin plus PCV

Carboplatin plus etoposide

Carboplatin

BrdU plus PCV

None vs PCV

ACNU and VP-16

BCNU, cisplatin, and etoposide

BCNU plus cisplatin

BCNU vs BCNU plus interferon-D

BCNU

Chemotherapy

BCNU carmustine, PCV procarbazine, CCNU, vincristine, GBM glioblastoma multiforme, KPS Karnofsky performance status, ECOG Eastern Cooperative Oncology Group, SRS stereotactic radiosurgery, ? Data could not be extracted from original publication.

100

64

88

Single inst. phase II

Groves et al. (1999)

49

48

57

?

80

Median 90

Multi-center 275 phase III

56

Buckner et al. (2001)

100 d40 mm

203

RTOG phase III

Souhami et al. (2004)

Resection Total dose Median survival (months) (Gy) (%)

Number

Study type

Reference

Histology GBM Median age KPS (years) (%)

Table 12.1. Overview of recent, combined modality studies

170 C. Nieder and M. R. Gilbert

92 93

100 68 100 100 100

56

287

286

64

69

61

67

40

Single inst. phase I/II

Multi-center phase III

Multi-center phase II

Two centers phase II

Single inst. phase II

Single inst. phase II

Single inst. phase II

Multi-center phase II

Schuck et al. (2002)

Stupp et al. (2005)

Athanassiou et al. (2005)

Stupp et al. (2002)

Kocher et al. (2005)

Butowski et al. (2005)

Chang et al. (2004a)

Balana et al. (2004)

58

51

54

52

Median 80

Median 90

Median 90

Median 80

90–100 in 64% 60

60

60

60

60

63

80

84

60

60

60

60 67 (complete)

76

58

51% > 80

? 52

58

84

30% > 80

87% WHO 0/1

57

83

?

86% WHO 0/1

60

70

All t60

60 60

92

60

12.5

17

13

15 (GBM)

16

8

13

12

15

12

10

15

9

Total dose Median survival (months) (Gy)

Median 80 or 90 75

Median 90

Median 80 or 90 71

56

51

?

57

?

Resection (%)

11

27

20

24 (GBM)

31

?

16

10

27

5 (GBM) 32 (WHO III)

?

?

11

Two-year survival (%)

GBM glioblastoma multiforme, KPS Karnofsky performance status, ? data could not be extracted from original publication a 75 mg/m2 day-1 during radiotherapy and 150–200 mg/m2 day-1 for 5 days every 4 weeks for six cycles b 75 mg/m2 day-1 during radiotherapy and 150 mg/m2 day-1 on days 15 and 1519 every 4 weeks for six cycles c 75 mg/m2 day-1 during radiotherapy and 200 mg/m2 day-1 for 5 days every 4 weeks for six cycles d 75 mg/m2 day-1 with weekend break during radiotherapy only e 75 mg/m2 day-1 during radiotherapy and 150–200 mg/m2 day-1 for 5 days every 4 weeks for up to 1 year, depending on toxicity and local control f 150–200 mg/m2 day-1 for 5 days every 4 weeks starting on the ﬁrst day of radiotherapy for up to 1 year, depending on toxicity and local control g 200 mg/m2 day-1 for 5 days every 4 weeks, plus cisplatin 100 mg/m2 on day 1 for three cycles before radiotherapy

100

61

61

Multi-center phase II

Langer et al. (2001)

53

100

60

Multi-center phase II

Gross et al. (2001)

100

100

87

Multi-center phase II

Fisher et al. (2002)

57

100

Number

Study type

Reference

Histology GBM Median age KPS (years) (%)

Table 12.2. Overview of recent, combined modality studies

Temozolomideg and cisplatin

Temozolomidef plus thalidomide

Temozolomidee plus cis-retinoic acid

Temozolomided

Temozolomidec

Temozolomideb vs radiotherapy alone (randomized)

Temozolomidea vs radiotherapy alone (randomized)

Paclitaxel

Paclitaxel

Topotecan

Topotecan

Chemotherapy

Applications in Malignant Brain Tumors 171

100 0 0

OP+RT (?) OP+RT+CHT (0%) OP+RT (56%) OP+RT (37%)

Carboplatin+etoposide (median four cycles) Carboplatin+etoposide (mean four cycles) Cisplatin+etoposide (median two cycles) Cisplatin+ifosfamide (median three cycles) Ifosfamide, carboplatin + etoposide (median four cycles)

CCNU+benznidazole (median three cycles) BCNU, DBD+unknown number of cycles

21

31

16

27

36

23

19

26c 11d

Ameri et al. (1997)

Van den Bent et al. (1999)

Van den Bent et al. (1998)

Sanson et al. (1996)

Bleehen et al. (1989)a

a

Stein et al. (1999)

Hildebrand et al. (1998)

Bleehen et al. (1989)

0

Carboplatin + RMP-7 (median OP+RT (?) three cycles)

42

Gregor et al. (1999)a

CCNU (median three cycles)

OP+RT (?)

OP+RT (0%)

OP+RT (0%)

OP+RT+CHT (0%)

0 0

0

0

100

100

55 56

45

45

53

42

40

50

46

46

42

45

Gregor et al. (1999)a 0

49

100

OP+RT+CHT (0%)

Carboplatin (mean four cycles)

20

Poisson et al. (1991) OP+RT (?)

25 8

80

42 53

82 51

Individual (?)

Temozolomide (median two cycles)

213

Chang et al. (2004b)

Carboplatin+RMP-7 (median four cycles)

15

80

42

60

Individual (18%)

Temozolomide (median ﬁve cycles)

162

10

?

12

9

9

?

?

?

70 70

?

WHO II ?

WHO II ?

70

ECOG I

WHO I

70

?

70

80

60

?

Yung et al. (1999)

WHO I

44

30

Individual?

Temozolomide (median four cycles)

103

Interval (months)f

Bower et al. (1997)

KPS (%)

CHT (%)

Pre-tr.

Number Treatment

Reference

Age (years)e

0 100

37

35

28

56

44

45

52

38

38

22 44

25

30

29

25

?

45

?

?

?

26

49 32

33 45

61

25

88

20

Non-GBM MOS (weeks) (%)

24

20g

?

?

?

13

12 55

?

?

28

19

13

15g 14

13

16

?

32

30g

25

10

16g 16h 21 10 ?

35

?

CR+PR (%)

24

17

TTP (weeks)

Table 12.3. Results of chemotherapy for recurrent malignant gliomas. The studies included some patients with oligodendroglioma, transformed low-grade glioma, and more than one recurrence. Diagnosis of recurrence was based on imaging criteria

172 C. Nieder and M. R. Gilbert

Irinotecan+BCNU (mean two cycles) Irinotecan+BCNU (mean three OP+RT+TMZ cycles)

42

Brandes et al. (2004)

80

90

WHO I

?

90

ECOG I

80

ECOG I

80

?

?

11

?

5

?

29

26

?

?

15

?

?

0

28

0

20

100

33

45

> 40

39

0

0

49

31

30

43

81

48

35

19 50

40

28

26

17

11

14

12

33

8

18

11 18

19

?

?

21

13

4

15

13

8

30

4c 11h

6

21

13

b

No oligodendroglioma and transformed low-grade glioma included All patients had histological conﬁrmation of recurrence, separate MOS, and TTP for GBMc and non-GBMh d Anaplastic astrocytoma e Median in years (some papers reported mean rather than median value) f Median interval from primary treatment to recurrence in months (some papers reported mean values) g Only median duration of response available; no data for non-responders h Only anaplastic astrocytoma; 79% had other chemotherapeutic regimens after further progression

a

Pre-tr. individual pre-treatment combination of surgical resection (OP), radiotherapy (RT) and chemotherapy (CHT), also shown is the percentage of patients with resection for recurrence before initiation of chemotherapy. CHT percentage of patients with one or more previous chemotherapy regimen(s), non-GBM original histology at initial diagnosis other than glioblastoma multiforme, MOS median overall survival from treatment of recurrence in weeks, TTP median time to further progression in weeks, CR+PR complete or partial remission based on imaging and criteria of McDonald et al. (1990), TMZ temozolomide, KPS median Karnofsky performance status or other classiﬁcation (some papers reported mean values)

53

45

Individual (8%) 82 100

52

0

OP+RT

39

46

Individual (3%) 68

47

51

49

32

20

100

49

100

Individual (?)

Reardon et al. (2004)

Taxol (median 3.5 cycles)

Chamberlain and Kormanik 24 (1999) h

Individual (?)

Irinotecan (mean four cycles)

Anthracycline MX-2 HCl (median three cycles)

55

Clarke et al. (1999)

OP+RT (25%)

27

Procarbazine+tamoxifen unknown number of cyles

53

Brandes et al. (1999)

Individual (?)

Raymond et al. (2003)

MOP unknown number of cycles

63

Galanis et al. (1998)b

42

37

Individual (61%)

Irinotecan unknown number of cycles

Six drug combinations (median three cycles)

51

Rostomily et al. (1994)

61

68

Individual (?)

60

“8-in-one” (median four cycles)

19

Boiardi et al. (1992)

56

50

Individual (?)

Friedman et al. (1999)

PCV (median four cycles)

16

Boiardi et al. (1992)

Applications in Malignant Brain Tumors 173

C. Nieder and M. R. Gilbert

174 Table 12.4. Toxicity and adverse events Regimen

Typical side effects

Brain tumor treatment in general

Thromboembolic complications, increased edema/intracranial pressure, hair loss, skin toxicity, endocrine dysregulation/hormone deﬁciency/infertility

Nitrosourea-based chemotherapy

Hematological toxicity, gastrointestinal toxicity, lung ﬁbrosis

Vincristine-containing chemotherapy

Peripheral and cranial nerve neuropathies

Temozolomide

Hematological toxicity, gastrointestinal toxicity, immunosuppression

et al. 1997). In tumors expressing PGP, chemoresistance could putatively be overcome by adding PGP antagonists. Another mechanism is intracellular drug inactivation or transformation as a result of increased concentrations of detoxifying enzymes such as gluthatione S-transferases (GST), 06 -methylguanine methyl-transferase (MGMT), or poly (ADPribose) polymerase (PARP). The GST catalyzes the conjugation of glutathione with a large number of compounds with an electrophilic center, including chemotherapeutic agents. Nitrosoureas may be deactivated by denitrosylation via GST or methylation by MGMT. The GST immunoreactivity has been found in tumor blood vessels as well as neoplastic cells, without evidence of a correlation between the frequency of reactive cells and grade of malignancy. Belanich et al. (1996) showed that BCNU-treated patients with high levels of MGMT had a significantly shorter time to progression and OS than those with lower levels. Friedman et al. (1998) reported that MGMT level might be a valuable predicitive factor for response to temozolomide. It has recently been investigated whether MGMT promoter methylation in GBM tissue from 206, i.e., 36% of all, patients in a randomized trial is associated with a benefit from temozolomide (Hegi et al. 2005). Of these samples, 45% had detectable methylation. The OS was shorter in patients with unmethylated promoter in both groups (radiotherapy and radiotherapy plus temozolomide). Patients with methylated promoter treated with radiotherapy had a median OS of 15 months, those treated with radiation plus temozolomide of 22 months (p=0.007). In the unmethylated group, the difference in median OS was only 1 month (p=0.06). Especially for these patients, alternative treatments need to be studied. Pretreatment with O6 -methylguanine, which inactivates the enzyme, may overcome resistance. Dexamethasone has been found to antagonize cisplatin toxicity in C6 rat glioma cells in vitro, most likely mediated via glucocorticoid receptors by increased GST concentration (Wolff et al. 1996). Further mechanisms of interaction between dexamethasone and chemotherapy might include the regulation of

p21WAF1/CIP1 expression and the permeability of the BBB (Naumann et al. 1998); thus, dexamethasone may reduce the efficacy of cytotoxic drugs, although this has not been demonstrated in a clinical trial.

12.2.5 Potential New Strategies Over the past decade, several genetic alterations have been linked to glial tumor development and progression. Moreover, the identification of different genetic changes in primary (de novo) and secondary (which develop from lower-grade astrocytomas) GBM has led to a subclassification based on the biological properties of the tumor cells. Mutations of the TP53 tumor suppressor gene are the hallmark of low-grade astrocytoma leading to secondary GBM. Most primary GBM, however, show an amplification of the EGFR gene without mutations of TP53. Notably, tumors with p53 mutations occur primarily in younger patients and those with EGFR gene amplification arise primarily in older patients. Sixty to 95% of patients with GBM have allelic loss on chromosome 10q, the location of tumor suppressor genes such as MMAC/PTEN and DMBT1. The DMBT1 gene may be involved early in the oncogenesis of glioma, whereas alterations in the MMAC/ PTEN gene may be related to progression of glioma, through unopposed phosphatidylinositol-3’-kinase (PI3K) activity, which signals through mtor, a major transcriptional activator, especially of anti-apoptotic mechanisms. This pathway has recently been studied in greater detail (Choe et al. 2003), potentially offering promising targets for therapeutic intervention (Table 12.5; Eshleman et al. 2002). In primary GBM, amplification of the EGFR gene can be observed in approximately 40% of patients (reviewed by Nieder et al. 2003). This rate appears to be lower in AA. The ligands EGF or transforming growth factor D (TGF-D) activate different EGFRdependent intracellular pathways including the ras and mitogen activated protein (MAP) kinase cascade

Applications in Malignant Brain Tumors Table 12.5. Overview of potential treatment strategies Experimental and clinical approaches New radiosensitizers such as motexaﬁngadolinium, RSR13, etc. Brachytherapy/stereotactic radiosurgery with or without hyperthermia New cytotoxic chemotherapeutic drugs such as temozolomide, etc. Modulation of drug resistance (PGP, AGAT, WAF1/Cip1 antisense) New pharmacological approaches such as EGFR and farnesyltransferase inhibitors, etc. Antiangiogenesis treatment with thalidomide and imatinib Antisense- or mAb-mediated VEGF inactivation (antiangiogenesis) Antisense or mAb-mediated inhibition of oncogene products such as EGFR Restoration of suppressor gene function such as wild-type p53 transfer Suicide gene therapy with or without radiotherapy Toxin conjugates Vaccination PGP P-glycoprotein, AGAT O6-alkyl-guanine-DNA-transferase (also known as MGMT), mAb monoclonal antibody, EGFR epidermal growth factor receptor, VEGF vascular endothelial growth factor.

as well as the PI3K pathway. The EGFR overexpression in GBM may be associated with more aggressive clinical behavior and treatment resistance (Smith et al. 2001; Simmons et al. 2001; Barker et al. 2001; Chakravarti et al. 2001; Muracciole et al. 2002). Numerous strategies are currently being investigated to specifically inhibit the EGFR pathway using RTK inhibitors, antibodies, immunoconjugates, or antisense technology. Such strategies can also be used for the purpose of radiosensitization of gliomas (Lammering et al. 2003). The ability of certain tumor cells to maintain signaling through AKT and ERK under EGFR inhibition may represent a potential mechanism of resistance. Recent clinical correlative data support this concept. Studies demonstrate that in the presence of Akt pathway overexpression, EGFR inhibitors (i.e., erlotinib) are inactive. Clinical responses were only noted when the PTEN gene was intact and expressed (Haas-Kogan et al. 2005; Mellinghoff et al. 2005). Potential ways to maintain PI3K signaling despite the presence of a EGF-RTK inhibitor (AG1478) include up-regulation of insulinlike growth factor (IGF) receptor I (Chakravarti et al. 2002a). Co-targeting both receptors greatly enhanced radiation-induced apoptosis in GBM

175

cells. Further intriguing data suggest that a combination of RTK inhibitor (AG1478) and monoclonal antibody (mAb 806) displayed additive, and in some cases synergistic, antitumor activity against glioma xenografts overexpressing the EGFR. AG1478 inhibited the growth of glioma in mice bearing human xenografts expressing the wild-type EGFR or a naturally occurring ligand-independent truncation of the EGFR (Johns et al. 2003). Strikingly, even subtherapeutic doses of AG1478 significantly enhanced the efficacy of cytotoxic drugs, with the combination of AG1478 and temozolomide displaying synergistic antitumor activity against human glioma xenografts. AG 1478 also abrogated the cross-resistance between sequential administration of radiation and BCNU in GBM cell lines (Chakravarti et al. 2002b). The study reported that BCNU inhibited radiation-induced apoptosis through EGFR-mediated signal transduction via RAS and that radiation inhibited BCNU-induced apoptosis, also via EGFR and RAS; thus, inactivation of this signalling might improve combined modality treatment. Further targets include transforming growth factor E (TGF-E) and platelet-derived growth factor (PDGF). Overexpression of PDGF receptor D appears to be an early event in glioma pathogenesis and is present in most grades of tumors (as reviewed by Nieder et al. 2003). Upregulation of PDGF has also been described, especially in endothelial cells localized specifically within the tumor; thus, inhibition of signal transduction could influence tumor progression via an angiogenic mechanism and is currently under clinical investigation. Upregulation of vascular endothelial growth factor (VEGF) transcription is frequently found in human brain tumors and probably regulated by both tissue hypoxia and acidic pH (Fukumura et al. 2001). At least 6080% of astrocytic glioma overexpress PDGF or VEGF (Nieder et al. 2003). The VEGF has also been associated with brain edema, because it can increase vascular permeability. The VEGF mAb inhibited growth of GBM in several mouse models. The density of vessels was decreased in antibodytreated tumors and the magnitude of response was greater in more rapidly proliferating, more angiogenesis-dependent tumors. In addition, GBM contains both tumor cells and blood vessels which are relatively resistant to radiotherapy. Blocking the binding of VEGF to its receptor (VEGFR) on the tumor endothelium might revert GBM tumor models to a radiation-sensitive phenotype (Geng et al. 2001). Some inhibitory agents have now entered clinical trials, including inhibitors of VEGFR as

C. Nieder and M. R. Gilbert

176

well as treatment to block VEGF binding to the receptor, mainly for recurrent glioma. The possible strategies of gene therapy include, among others, cell transduction or transfection with antisense DNA corresponding to genes coding for growth factors and their receptors, or with the socalled suicide genes. The latter approach includes transferring a prodrug-activating gene into the malignant cell, converting an inactive agent into a cytotoxic one. The intratumoral conversion of prodrugs would then allow for cytotoxicity within the tumor and decreased side effects into normal tissue. Such combination is exemplified by the herpes simplex/thymidine kinase gene, which converts gancyclovir and acyclovir into toxic analogs. Radiosensitization could be achieved by cytosine deaminase gene therapy, leading to conversion of 5-fluorocytidine to 5-fluorouracil. Double suicide gene therapy in rat 9L gliosarcoma transfected with vectors containing an E. coli cytosine deaminase and herpes simplex virus type-1 thymidine kinase fusion gene and implanted in the brain of rats has also been reported (Kim et al. 1998). When the prodrugs 5-fluorocytosine and ganciclovir were combined with radiotherapy and double suicide gene therapy, more than 70% of the animals with so-called advanced tumors (14 days old) were alive by day 120 (maximum observation time). Double-suicide gene therapy alone, radiotherapy alone, and combined radiotherapy and single prodrug therapy showed animal survival rates of 0– 40%. This study demonstrates the potential benefit of adding gene therapy strategies to current treatment; however, attempts to incorporate this strategy into clinical use demonstrated poor efficacy, probably related to issues of vector delivery. The identification of tumor-associated antigens that are present in tumor tissue but not normal CNS tissue, the production of homogenous, high-affinity mAb to such antigens, along with the use of compartmental administration, e.g., intralesional, has made passive immunotherapy a possible therapeutic option. Most commonly, antibody therapy has relied upon immunological effector mechanisms to target antibody-bound tumor cells. Another alternative is to develop antibody conjugates that will selectively target covalently bound drugs, toxins, or radionuclides to neoplastic cells. Thirdly, mAb may be used as antagonists to the biological functions of the tumor cell. Problems with mAb therapy currently include low uptake into tumors or heterogeneity of antigen expression. Increased uptake might be achieved by administration of antibody fragments or selective pharmacological opening of

the BBB using bradykinin or the bradykinin analogue RMP-7, which increases uptake of both cytotoxic chemotherapeutic agents and various-sized tracers (up to 70 kD) into brain tumors. Reports of up to 180 patients with malignant glioma treated with intravenous 125I-labeled anti-EGFR mAb or 131I-labeled antitenascin mAb after surgical resection and standard radiation therapy with or without chemotherapy were published (Emrich et al. 2002; Reardon et al. 2002). From the authors’ point of view, survival was encouraging (GBM 13.4 and 18 months, AA 50.9 months); however, additional results from randomized trials are needed because of concerns related to patient selection bias.

12.2.6 Recurrent Tumors Depending on previous treatment, interval to recurrence and prognostic factors, the options include surgical resection, re-irradiation, systemic and local chemotherapy, and experimental agents in the setting of a clinical trial. Usually, the decision process is highly individualized. Few randomized trials exist for treatment of recurrent disease; however, a randomized trial demonstrated that surgical resection plus BCNU wafers is better than resection plus placebo wafers (median OS 31 vs 23 weeks; Brem et al. 1995) and that systemic nitrosoureas might be a treatment option (Bleehen et al. 1989). Recent data suggest that chemotherapy is more efficacious when minimal residual disease is present (Keles et al. 2004). Table 12.3 summarizes the results of chemotherapy trials. Median OS was 1928 weeks in GBM and 4481 weeks in AA. Data from 375 patients from consecutive phase-II studies at the M.D. Anderson Cancer Center that were thought to be inactive regimens showed a median OS of 30 weeks and a median PFS of 10 weeks and a 6-month PFS rate of 15% (Wong et al. 1999). This provides an important benchmark for subsequent comparisons. As illustrated by the Paris group’s experience, multivs single-agent chemotherapy based on carboplatin increases toxicity without improving the outcome (Poisson et al. 1991; Sanson et al. 1996; Ameri et al. 1997). Temozolomide has been shown in GBM at first relapse to prolong PFS and to maintain neurological functioning and performance status for a longer time than procarbazine (Yung et al. 1999; Osoba et al. 2000; McDonald et al. 2005). There has been increasing interest in the use of signal transduction modulators, including the EGFR

Applications in Malignant Brain Tumors

inhibitor erlotinib for recurrent malignant gliomas. Response to erlotinib was more common in patients whose tumors had epidermal growth factor receptor (EGFR) gene amplification, EGFR protein overexpression and low levels of phosphorylated PKB/Akt (Haas-Kogan et al. 2005; Mellinghoff et al. 2005). In the most favorable molecular subgroup, median time to progression was 20 weeks. Individual tailoring of such strategies based on molecular profiling is hoped to improve the outcome in the future. Early trials of various forms of immunotherapy and toxin delivery demonstrate the feasibility of these approaches and encouraging median survival times of 27–39 weeks. Patients having progressed despite of commonly prescribed systemic agents, but still amenable to surgical intervention, are candidates for clinical trials of experimental, locally delivered agents. If surgery can not be performed, appropriate trials of systemic agents interfering with the newly identified molecular targets either as sole modality or combined with established agents should be considered. A previous overview showed that re-irradiation is an option for selected patients (Nieder et al. 2000b). Small studies of SFRT plus cisplatin or paclitaxel as radiosensitizers do not suggest improved results compared with radiotherapy alone (Lederman et al. 2000; Glass et al. 1997); however, a recent trial employed two strategies: (a) better target volume definition in SFRT through amino-acids positron emission tomography (PET) or single-photon emission computed tomography (SPECT) imaging; and (b) combining radiotherapy and temozolomide (Grosu et al. 2005). The trial included 44 patients with recurrent high-grade glioma after previous surgery and postoperative radiotherapy with or without chemotherapy. For SFRT planning, the gross tumor volume was defined by 11C-methionine PET or 123ID-methyl-tyrosine-SPECT/CT/MRI image fusion in 82% of the patients. In 66% chemotherapy with temozolomide was given one to two cycles before and four to five cycles after SFRT. Treatment planning based on PET(SPECT)/CT/MRI imaging was associated with improved survival in comparison with CT/MRI alone: median survival time 9 months vs 5 months (p=0.03). Median survival times were 9 and 6 months, respectively, for patients who received SFRT plus temozolomide vs SFRT alone (p=0.04). Multivariate analysis confirmed a significant survival benefit from addition of temozolomide. The question of whether SPECT/PET planning independently influences survival has to be determined in a larger series of patients.

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12.2.7 Perspectives Multimodal treatment approaches for high-grade glioma include the components of surgical resection, postoperative radiotherapy, and additive chemotherapy. In certain prognostic subgroups of patients, the role of chemotherapy is not yet fully established. In patients with favorable prognostic factors, a shift from nitrosourea-based regimens to newer drugs has started after the EORTC/NCIC trial in GBM (Stupp et al. 2005). Local delivery and CED of cytotoxic drugs and toxin-conjugates have shown encouraging potential to warrant further research; however, issues of selection bias continue to be a concern. Molecular studies have identified promising new targets for therapeutic intervention, e.g., with RTK inhibitors and mAb, whose efficacy and safety are now being studied. The current experience in cancer treatment shows that several targets should be approached to provide maximal chances of cure and that it is unlikely for a single therapeutic measure to be applicable to all patients. This includes targeting the same signal transduction pathway at different levels with different compounds; therefore, rational combinations between established treatments and new approaches, aimed for example, at inhibition of angiogenesis, induction of apoptosis, or inhibition of several signal transduction pathways, might offer the best opportunity to improve the prognosis. After initial trials in recurrent glioma, such strategies will rapidly enter testing in conjunction with established treatment modalities. Laboratory correlative studies will help to define both efficacy and optimal biological dose. Nevertheless, the treatment of high-grade glioma remains challenging. Any new treatment modality must face the difficulty of balancing the desirable effects on relatively resistant tumor cells and the potential negative impact on quality of life in patients with limited life expectancy. In addition, accessing the volume and response of diffusely infiltrating tumor cells within the normal brain is not a trivial task. A crucial point will be to learn how to integrate new approaches into existing treatment algorithms and to optimize such strategies, e.g., with regard to dose-effect relationship. The PFS at 6 months is now being used as end point in many clinical studies, especially in recurrent/progressive disease, because it has been shown to be a useful surrogate marker for OS. This change of end point facilitates rapid evaluation of new strategies. Better measures of tumor response may need to be developed in addition to standard response criteria, such as radiographic response and time to progression, which

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do not imply improved quality of life. Such data will also be needed to provide arguments in the discussion about toxicity and economic aspects of more aggressive multimodal treatment.

12.3 Oligodendroglioma Oligodendroglial tumors, approximately 25% of all glioma, tend to present with epileptic seizures and can be divided into low-grade and anaplastic subsets. The presence of mixed astrocytic and oligodendroglial differentiation might be diagnostically challenging, with considerable interobserver variability. Besides low tumor grade, young age and surgical resection are associated with a better prognosis. In low-grade tumors, 10-year survival rates might reach 85%, whereas in grade-III tumors 5-year survival is below 50% (Van den Bent et al. 2003; Lebrun et al. 2004). Oligodendroglioma (OD) frequently have deletions of chromosomal loci on 1p and 19q. In addition, loss of heterozygosity (LOH) of chromosome 10 may potentially be a negative prognostic factor (Thiessen et al. 2003; Hashimoto et al. 2003). Recent results of gene expression profiling suggest that this method may both reliably identify tumors with oligodendroglial vs astrocytic differentiation and predict survival (Huang et al. 2004). After surgical resection, further treatment is based mainly on grading and extent of resection, comparable to astrocytoma. In low-grade OD, individual decisions about the timing of radiotherapy have to be made, based on extent of resection, symptoms, quality of life, and age. In patients with no indication for immediate radiotherapy the question arose as to whether postoperative chemotherapy is better than deferred radiotherapy at the time the tumor progresses or symptoms develop. Furthermore, the optimum chemotherapy regimen has yet to be determined. High response rates to the PCV regimen were observed in the 1980s. Several authors reported that the median time to progression in patients with newly diagnosed low-grade OD treated with PCV was more than 2 years (Van den Bent et al. 2003; Stege et al. 2005). The PCV can also be used as second-line chemotherapy, e.g., after radiotherapy or to salvage patients after temozolomide failure (Triebels et al. 2004). In a recent study with central histology review, 60 patients with measurable, progressive grade-II oligodendroglial tumors received a median of 11 cycles of temozolomide 200 mg/m2 every 28 days as

initial treatment (Hoang-Xuan et al. 2004). A partial remission was seen in 17%, and after 12 months, 73% were free from progression. In OD, the presence of 1p LOH was significantly associated with response to chemotherapy as well as radiotherapy in several trials, including studies of temozolomide. For example, median PFS was 31 months for 1p intact patients and 118 months for the 1p LOH group (Thiessen et al. 2003; Hashimoto et al. 2003). Median PFS for 10q LOH patients was 31 vs 118 months for patients with intact chromosome 10. In AOD, PCV may be effective as first- or secondline therapy, as comprehensively reviewed by (Van den Bent et al. 2003). The RTOG Intergroup protocol 94-02 compared four cycles of pre-radiation intensive PCV vs radiotherapy alone to a dose of 59.4 Gy for AOD and MOA (central histology review; Shaw et al. 2004). Overall, 291 patients were randomized. In case of progression after radiotherapy alone, 80% of patients received PCV. In the pre-radiation chemotherapy arm, PFS was significantly better; however, median OS was not significantly different (4.8 vs 4.5 years), probably because of the high crossover rate. The LOH 1p/19q predicted a significantly better OS regardless of treatment. Only 25% of patients failed outside the irradiated volume. Importantly, post-chemotherapy tumor volumes would not be appropriate for target volume delineation. The toxicities of standard and intensive PCV prompted a search for alternatives. Temozolomide is also being studied after having demonstrated responses and PFS of 6 months in recurrent AOD (Yung et al. 1999). In anaplastic tumors (n=16), first-line treatment with surgical resection and temozolomide plus radiotherapy resulted in 4-year PFS of 48% and OS of 78% (Kocher et al. 2005). This limited experience suggests that temozolomide might not be inferior to PCV (3-year survival range in the literature 70–85%), and that further clinical trials are warranted to establish the optimal sequence of therapies and to examine whether drug combinations should be preferred over single agents. Furthermore, the usefulness of putative molecular predictive factors, in addition to the established 1p 19q LOH, needs to be confirmed.

12.4 Ependymoma Treatment recommendations for these rare, mostly pediatric tumors are based on grading, age, and extent of surgery. In cases of anaplastic tumors or

Applications in Malignant Brain Tumors

residual low-grade tumors, local radiotherapy is effective, although PFS rates continue to decline beyond 5 years (Merchant et al. 2004; Reni et al. 2004). The percentage of patients with eventual relapse is too high to base all future strategies on standard radiotherapy alone. Dose escalation with SRS and SFRT is under investigation. No randomized comparisons between local radiotherapy and radiochemotherapy have been published. For sequential treatment, an Italian group reported on 17 patients (6 anaplastic ependymoma) with residual tumor who received four cycles of vincristine, etoposide, and cyclophosphamide (Massimino et al. 2004). Most patients completed this phase of the protocol. The objective response rate was 54% and only one patient progressed. Sixteen patients proceeded to planned local radiotherapy which was mostly hyperfractionated (70.4 Gy). Five-year survival was 61% (PFS 35%, most failures local). The authors concluded that this drug regimen, like others, is not curative. Cranio-spinal irradiation with or without adjuvant chemotherapy also failed to improve the results drastically (Evans et al. 1996). In young children, pre-radiation chemotherapy has been studied; the latter was comprised of combined vincristine, cisplatin, cyclophosphamide, and etoposide (Garvin et al. 2004). Objective responses occurred in more than 50% of the children; however, the French experience with 16 months of comparable drugs showed that only 22% of children under 5 years of age remained progression-free after 4 years (Grill et al. 2001). Sparing radiotherapy was possible for 40% 2 years from the initiation of chemotherapy and 23% at 4 years. Importantly, deferred radiotherapy at the time of relapse did not compromise OS. Nevertheless, chemotherapy is still considered experimental in most situations and should be evaluated in clinical trials. In recurrent tumors, palliation can be achieved with chemotherapy.

12.5 Medulloblastoma Medulloblastoma, including both desmoplastic and classic variants, is the most common malignant brain tumor in childhood. Multimodal treatment recommendations are based on resectability, age and stage, or risk group. In average-risk tumors (M0, age >3 years, residual disease <1.5 cm2), 5-year OS reaches 70% or more (Tabori et al. 2005; Rood et al. 2004; Taylor et al. 2004). Maximal surgery

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and postoperative radiotherapy to the cranio-spinal axis with posterior fossa boost have long been the mainstay of treatment (Carrie et al. 2005). Avoidance of boost targeting deviations is very important (Taylor et al. 2004). Highly conformal boost irradiation techniques with photons and the use of proton beams might allow for both dose escalation and limited toxicity. In very young children, strategies of radiotherapy avoidance have been explored, because of the potential toxicity and the fact that responses to chemotherapy were observed in approximately 6070% of these tumors (Taylor et al. 2005; Rutkowski et al. 2005). In a recently reported trial, the prognosis of children under 2 years of age was poor despite of postoperative vincristine, etoposide, carboplatin, cyclophosphamide, and methotrexate (Rutkowski et al. 2005). In addition, their neuropsychological performance was significantly reduced, especially if radiotherapy had to be given after chemotherapy; however, children under 3 years of age without metastases or residual tumor treated with this regimen had 5-year OS of 93%. In 20 of 31 children, radiotherapy was not necessary. The value of treatment intensification by preradiation chemotherapy has also been evaluated. In a randomized trial, vincristine, etoposide, carboplatin, and cyclophosphamide were administered to M0-1 patients, i.e., no metastases or positive CSF cytology, before cranio-spinal plus boost irradiation (35 plus 20 Gy; Taylor et al. 2004). Event-free survival (EFS) was significantly improved. Besides combined treatment, completion of radiotherapy within 50 days improved EFS. Another approach is chemotherapy after radiotherapy or combined radiotherapy plus vincristine (Douglas et al. 2004). In that study with 33 patients the dose to the craniospinal axis was reduced to 23.4 Gy, as also reported by (Packer et al. 1999), without compromising the results. Overall, the optimal sequencing of radioand chemotherapy remains an unanswered question. Surgery and chemotherapy with vincristine, etoposide, carboplatin, and cyclophosphamide, with or without radiotherapy in tumors with macroscopic metastases (M2M3), resulted in 5-year OS of 44% (Taylor et al. 2005). Despite considerable toxicity and mortality, high-dose chemotherapy with autologous stem-cell rescue might improve the survival of patients with high-risk or recurrent tumors (Chi et al. 2004; Perez-Martinez et al. 2005). Treatment protocols often include supratentorial primitive neuroectodermal tumors as well. Patients with medulloblastoma should be treated within prospective clinical trials.

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12.6 Meningioma Benign meningioma (WHO grade I) can be cured by complete surgical resection. In elderly or comorbid patients and inaccessible or recurrent tumors, radiotherapy (FSRT, SRS) results in local control rates of 90% or more (Chamberlain and Blumenthal 2004). The risk of local recurrence after FSRT was greater in WHO grade-II tumors (Harris et al. 2003; Milker-Zabel et al. 2005). Even malignant meningioma patients might have 5-year PFS in the order of 70% after SRS, although survival beyond 10 years is uncommon (Harris et al. 2003). Hydroxyurea or temozolomide can be considered for chemotherapy in situations where no more local treatment options exist. With temozolomide, median time to progression was 5 months (Chamberlain et al. 2004). It was somewhat longer in small trials of hydroxyurea where the best results were obtained in benign tumors (Mason et al. 2002; Newton et al. 2004; Loven et al. 2004); however, the overall activity of both drugs appears modest and no head-to-head comparison exists. Studies of combined radiochemotherapy have not yet been published.

12.7 Brain Metastases Local control of a limited number (mostly one to three) of brain metastases (BM) can effectively be

achieved by surgical resection or SRS with or without adjuvant WBRT (Table 12.6). The number of patients dying from uncontrolled BM despite intensive local treatment is low and ranges from 20 to 30%; thus, relatively few patients with multiple BM which are not suitable for one of these approaches might be candidates for combined chemotherapy and WBRT to increase the palliative effect of WBRT alone. In the latter group, the aim of maximizing local control within the brain is reasonable only in case of controlled extracranial disease and good performance status. The choice of chemotherapy regimen is often complicated by previous systemic treatment and takes into account the activity of the drugs in extracranial metastatic disease and the issue of drug concentration within the CNS. Sometimes, the question arises whether patients with newly detected BM and the indication for systemic treatment of extracranial disease can undergo standard systemic chemotherapy with the option of deferred, rather than immediate, radiotherapy of the brain. The literature contains numerous small reports on this issue, mainly in malignant melanoma, breast cancer, lung cancer, and ovarian cancer, but very few sufficiently powered randomized trials. To date, outside of prospective clinical trials, no firm role for chemotherapy or radiochemotherapy of BM has been established. A potential chemotherapy indication might exist as palliative option for patients who have progressive BM after radiotherapy. Agents investigated so far include cisplatin and cisplatin combinations (with fotemustin, teniposide, etoposide, vinorelbine), paclitaxel, topotecan,

Table 12.6. Results of surgery and stereotactic radiosurgery (SRS) for brain metastases Reference

Number (patients/lesions)

Prescribed dose [median; range (Gy)]a

Median OS

1-year PFS (%)

Patchell et al. (1990)

25/25

Surgery

9.5

80

Patchell et al. (1998)

49/49

Surgery

11

82

Pirzkall et al. (1998)

236/311

20; 10–30

5.5

89

Cho et al. (1998)

73/136

17.5; 6–50

7.8

80

Kocher et al. (1998)

106/157

20; 12–25

8

85

Sneed et al. (1999)

62/118b 43/117c

18; 15–22 17.5; 15–22

11.3 11.1

80 86

Varlotto et al. (2003)

137/208

16; 12–25

?

90

Andrews et al. (2004)

164/269d

?; 15–24

6.5

82

OS overall survival in months, PFS progression-free survival, ? data not reported, WBRT whole-brain radiotherapy aPrescription isodose or point varied, some series included SRS plus WBRT bSRS only cSRS plus WBRT (no signiﬁcant difference in OS and PFS between both groups) dSRS plus WBRT

Applications in Malignant Brain Tumors

temozolomide, and capecitabine, as well as RTK inhibitors such as gefitinib. With chemotherapy alone, response rates of 20–50% have been published. In responding patients, the effect was transient and mostly limited to 3–6 months. Median survival was 3–10 months. While radiotherapy is usually well tolerated (Nieder and Grosu 2004), no systematic evaluation of neurotoxicity or quality of life after chemotherapy is available yet. In this context it is noted that signs of neurotoxicity are sometimes caused by antiepileptic drugs (Nieder et al. 1999; Klein et al. 2002). The addition of cisplatin to temozolomide did not improve these results in 32 patients, mainly with lung and breast primaries and previous brain irradiation (Christodoulou et al. 2005). Median survival was 5.5 months, time to progression 2.9 months, and CR+PR rate 31%. The following clinical trials deserve further discussion. A randomized study in BM from non-small cell lung cancer (NSCLC) compared these strategies: arm A (n=86) received cisplatin 100 mg/m2 on day 1 plus vinorelbine 30 mg/m2 on days 1, 8, 15, and 22 (repeated every 4 weeks; Robinet et al. 2001). After two cycles, responders continued with up to four additional cycles. Non-responders received WBRT with ten fractions of 3 Gy. In arm B (n=85), simultaneous WBRT with 30 Gy started on day 1 of the first chemotherapy cycle. There was no significant difference between simultaneous and deferred WBRT in terms of response of BM (27 vs 33%) and median OS (24 vs 21 weeks). Another randomized study with 120 patients with BM from small-cell lung cancer (SCLC) compared teniposide 120 mg/m 2 three times per week every 3 weeks with the same chemotherapy plus WBRT with ten fractions of 3 Gy (Postmus et al. 2000). The WBRT started within 3 weeks of the first teniposide administration. In that study, the response rate (22 vs 57%) and time to progression of BM were significantly worse after chemotherapy alone; however, survival was comparable. A small randomized study with only 52 patients evaluated WBRT with 20 fractions of 2 Gy vs combined WBRT and temozolomide 75 mg/m2 day-1 (Antonadou et al. 2002). In the combined modality arm, temozolomide continued for six more cycles (200 mg/m2 day-1 for 5 days every 4 weeks). There was a significantly higher response rate in the temozolomide arm resulting from increased numbers of PR (96 vs 67%). The influence on OS was not significant (7 vs 8.6 months). A second randomized trial of temozolomide (75 mg/m2 day-1 and two additional cycles with 200 mg/m2 day-1 for 5 days every 4 weeks) plus WBRT (30 Gy) was designed as phase-II study

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with 82 patients and therefore also does not allow to draw definitive conclusions (Verger et al. 2005). The OS and response rates were similar, whereas PFS at 90 days was better for combined treatment (72 vs 54%; p=0.03). Death from BM was more common after WBRT alone (69 vs 41%; p=0.03). Chemotherapy with low-dose WBRT does not seem to be an attractive option, as illustrated in a randomized trial that was closed prematurely after 42 patients with NSCLC because of poor accrual (Guerrieri et al. 2004). In that study, daily carboplatin was added to WBRT with five fractions of 4 Gy. Median OS was 4.4 vs 3.7 months with disappointing response rates of 10 vs 29%. Topotecan daily i.v. in addition to WBRT has been evaluated in a phase-I/II trial (Kocher et al. 2005a). Median OS was 5 months, and CR+PR rate in assessable patients was 58%. This drug is currently under further investigation. When designing new trials to prove the concept of simultaneous radiochemotherapy for BM, the following key questions need to be adressed: 1. What are the most relevant study end points? 2. What is the price in terms of toxicity, quality of life, and cost? 3. What are the most relevant WBRT and drug administration regimens? From the present-day point of view, chemotherapy and radiochemotherapy for newly diagnosed BM need to undergo further critical evaluation before standard clinical implementation.

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C. Nieder and M. R. Gilbert patients with metastatic (M2-3) medulloblastoma treated with SIOP/UKCCSG PNET-3 chemotherapy. Eur J Cancer 41:727–734 Thiessen B, Maguire JA, McNeil K et al (2003) Loss of heterozygosity for loci on chromosome arms 1p and 10q in oligodendroglial tumors: relationship to outcome and chemosensitivity. J Neurooncol 64:271–278 Triebels VH, Taphoorn MJ, Brandes AA et al (2004) Salvage PCV chemotherapy for temozolomide-resistant oligodendrogliomas. Neurology 63:904–906 Van den Bent MJ, Schellens JH, Vecht CJ et al (1998) Phase II study on cisplatin and ifosfamide in recurrent high grade gliomas. Eur J Cancer 34:1570–1574 Van den Bent MJ, Pronk L, Sillevis Smitt PA, Vecht CJ, Eskens FA, Verweij J (1999) Phase II study of weekly dose-intensified cisplatin chemotherapy with oral etoposide in recurrent glioma. J Neurooncol 44:59–64 Van den Bent M, Chinot OL, Cairncross JG (2003) Recent developments in the molecular characterization and treatment of oligodendroglial tumors. Neuro-oncology 5:128–138 Van Rijn J, Heimans JJ, van den Berg J et al (2000) Survival of human glioma cells treated with various combinations of temozolomide and X-rays. Int J Radiat Oncol Biol Phys 47:779–784 VarlottoJM, Flickinger JC, Niranjan A, Bhatnagar AK, Kondziolka D, Lunsford LD (2003) Analysis of tumor control and toxicity in patients who have survived at least one year after radiosurgery for brain metastases. Int J Radiat Oncol Biol Phys 57:452–464 Verger E, Gil M, Yaya R et al (2005) Temozolomide and concomitant whole brain radiotherapy in patients with brain metastases: a phase II randomized trial. Int J Radiat Oncol Biol Phys 61:185–191 Vos MJ, Uitdehaag BM, Barkhof BM et al (2003) Interobserver variability in the radiological assessment of response to chemotherapy in glioma. Neurology 60:826–830 Walker MD, Alexander E, Hunt WE et al (1978) Evaluation of BCNU and/or radiotherapy in the treatment of anaplastic gliomas. J Neurosurg 49:333–343 Walker MD, Strike TS, Sheline GE (1979) An analysis of doseeffect relationship in the radiotherapy of malignant gliomas. Int J Radiat Oncol Biol Phys 5:1725–1731 Weller M, Streffer J, Wick W et al (2001) Preirradiation gemcitabine chemotherapy for newly diagnosed glioblastoma. Cancer 91:423–427 Weller M, Muller B, Koch R et al (2003) Neuro-Oncology Working Group 01 trial of nimustine plus teniposide versus nimustine plus cytarabine chemotherapy in addition to involved-field radiotherapy in the first-line treatment of malignant glioma. J Clin Oncol 21:3276–3284 Westphal M, Hilt DC, Bortey E et al (2003) A phase III trial of local chemotherapy with biodegradable carmustine (BCNU) wafers (Gliadel wafers) in patients with primary malignant glioma. Neuro-oncology 5:79–88 Wolff J, Denecke J, Jurgens H et al (1996) Dexamethasone induces partial resistance to cisplatinum in C6 glioma cells. Anticancer Res 16:805–810 Wong ET, Hess KR, Gleason MJ et al (1999) Outcomes and prognostic factors in recurrent glioma patients enrolled onto phase II clinical trials. J Clin Oncol 17:2572–2578 Yung WKA, Prados MD, Yaya-Tur R et al (1999) Multicenter phase II trial of temozolomide in patients with anaplastic astrocytoma or anaplastic oligoastrocytoma at first relapse. J Clin Oncol 17:2762–2771

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187

13 Applications in Head and Neck Cancer Deepak Khuntia, Anne M. Traynor, Paul M. Harari, and Jean Bourhis

CONTENTS 13.1 13.2 13.2.1 13.2.2 13.2.3 13.2.4 13.3 13.4 13.5 13.6 13.7

Introduction 187 Randomized Trials with Definitive Chemoradiation 187 Oropharynx 187 Larynx 188 Hypopharynx 189 Nasopharynx 190 Induction Chemotherapy 191 Induction Chemotherapy Followed by Concurrent Chemoradiation 192 Adjuvant Chemoradiation after Primary Surgery 193 Toxicity 193 Conclusion 194 References 195

13.1 Introduction Head and neck (H&N) cancer refers to a heterogeneous group of epithelial tumors involving the oral cavity, oropharynx, nasopharynx, hypopharynx, larynx, salivary glands, and paranasal sinuses. In this chapter we focus discussion primarily on squamous cell carcinoma of the H&N, particularly cancers involving the oral cavity, pharyngeal axis, and larynx. In 2006 there will be approximately 43,000 D. Khuntia, MD Assistant Professor, Department of Human Oncology, University of Wisconsin, 600 Highland Avenue, K4 312-3684, Madison, WI 53792, USA A. M. Traynor, MD Assistant Professor, Department of Medicine, University of Wisconsin, 600 Highland Avenue, K4 312-3684, Madison, WI 53792, USA P. M. Harari, MD Jack Fowler Professor, Department of Human Oncology, University of Wisconsin, 600 Highland Avenue, K4 312-3684, Madison, WI 53792, USA J. Bourhis, MD Professor, Head of Radiation Oncology Department, Institute Gustave-Roussy, 39, rue Camille Desmoulins, 94805 Villejuif Cedex, France

cases of H&N cancer diagnosed in the United States with over 500,000 cases worldwide (American Cancer Society 2005). Tobacco and alcohol use are major risk factors for the development of H&N cancer. For selected H&N tumors, data also implicates Epstein-Barr virus (EBV) and human papilloma viruses (HPV) in the pathogenesis (Gillison et al. 2000). Historically, patients with early-stage disease (stages I–II) are effectively treated with single modality therapy using radiation (RT) or surgery alone. Patients with more advanced-stage disease (stage III–IVb) have generally received combined modality therapy with surgery and radiation; however, advanced-stage H&N cancer patients commonly experience significant functional and cosmetic deficits that adversely impact both speech and swallowing capacity. In addition, ultimate diseasefree survival is modest for advanced stage patients, with 5-year survival rates on the order of 20–40%. Over the past decade, the integration of systemic chemotherapy (CT) has been shown to improve outcome for several cohorts of advanced stage H&N cancer patients. For the future, there is also reason for optimism that new molecular targeted therapies will further enhance the therapeutic approach in advanced H&N cancer. In this chapter we review the rationale and clinical results for chemoradiation in the management of locoregionally (LR) advanced H&N cancer patients.

13.2 Randomized Trials with Definitive Chemoradiation 13.2.1 Oropharynx Primary anatomic subsites of the oropharynx include the tonsil, base of tongue, upper posterior pharyngeal wall, and soft palate. Though surgery

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alone may be curative for some of these patients, RT is generally preferred in light of the reduced functional morbidity. For stage-III and stage-IV disease, randomized trials have recently validated a role for the addition of concurrent CT with RT. Potential disadvantages to concurrent chemoradiation regimens include increased acute and late toxicity (Holsti and Mantyla 1988; Calais et al. 1999). The acute toxicities, namely mucositis, can be quite severe such that patients may require treatment breaks that can compromise ultimate outcome. A major trial validating the use of chemoradiation for oropharyngeal tumors comes from the Groupe d’Oncologie Radiothérapie Tête Et Cou (GORTEC). In this trial, 226 patients were randomized between RT alone (70 Gy in 35 fractions) versus the same RT and three cycles of carboplatin (70 mg/m2) and 5fluoruracil (600 mg/m2; Calais et al. 1999; Denis et al. 2004). Like cisplatin, carboplatin is a radiosensitizer, but it offers fewer acute toxicities, including less nausea, ototoxicity, and diminished need for hydration. In the most recent update of this trial, 5year overall survival was improved from 16 to 22% in favor of the chemoradiation arm (Denis et al. 2004). Local control was also improved with CT (see Table 13.1). Pretreatment hemoglobin, stage, and

treatment were found to be of prognostic significance. Severe late morbidity rates were reported as similar in both arms; however, feeding tube dependence, swallowing function, and laryngeal function were not rigorously assessed. Few other randomized trials exist that focus solely on oropharyngeal cancer patients; however, multiple trials, including a variety of H&N tumor subsites, have been conducted to evaluate the role of concurrent CT with RT. Several of these trials identify a survival benefit for combined chemoradiation vs RT alone and are summarized in Table 13.1.

13.2.2 Larynx Patients with advanced-stage tumors of the larynx can be managed with partial laryngectomy, total laryngectomy, RT alone, or combined RT and CT. The choice of therapy depends on a variety of factors, including anatomic extent of disease, patient preference, and local practice patterns. In the U.S., patients receiving radiotherapy often receive induction-CT based on the landmark Veterans Affairs Laryngeal Cancer Study (Department of

Table 13.1. Summary of selected chemoradiation randomized trials Reference

Primary

Arms

LC (%) a

OS (%)

Al Sarraf (1998) et al.

NP

RT CRT

26 PFS 66 PFSa

46a 76a

VA Larynx (1991)

L

Induction CTÆ CRT Surgery/RT

80b 93b

68 (NS)b 68b

Forastiere (2003) et al.

L

Induction CTÆ CRT CRT RT

61c 78c 56c

55 (NS)c 54c 56c

Calais (1999, 2000) et al.

OP

RT CRT

42a/25c 66a/48c

31a/16c 51a/22%c

Brizel (2000) et al.

L, HP, OP, OC

Hyperfractionated RT Hyperfractionated CRT

44b 70a

34b 55b

Adelstein (2003) et al.

Unresectable: L; HP; OP; OC

RT CRT Split-course CRT

Bernier (2004) et al.

Resected: L; HP; OP; OC

Postop RT CRT

69c 82c

40c 53c

Cooper (2004) et al.

Resected: L; HP; OP; OC

Postop RT CRT

72a 82a

NS NS

23b 37b 27b

NS not statistically signiﬁcant, RT radiation, CT chemotherapy, CRT chemoradiation, NP nasopharynx, L larynx, OP oropharynx, HY hypopharynx, OC oral cavity aTwo-year data b Three-year data c Five-year data

Applications in Head and Neck Cancer

Veterans Affairs Laryngeal Cancer Study Group 1991). This trial was the first randomized H&N trial to use neoadjuvant CT with a primary end point of larynx preservation. Three hundred thirtytwo patients with stage-III or stage-IV laryngeal squamous carcinoma were randomized to induction CT (cisplatin and 5-FU) and RT vs laryngectomy followed by postoperative RT. Patients with no tumor response or with recurrence of their disease went on to salvage laryngectomy. Two-year survival was 68% in both arms. Though more local recurrences were found in the chemoradiation arm, there were fewer distant failures as first site of recurrence. With chemoradiation, the larynx preservation rate was 64% at 5 years (i.e., nearly two-thirds of the surviving patients had their larynx preserved). As a result of this trial, chemoradiation emerged as a standard of care treatment option for many patients with stage-III and stage-IV laryngeal cancer. In an effort to better examine the optimal timing and necessity for CT, a U.S. Intergroup study was conducted that randomized patients to either induction CT [cisplatin and 5-fluorouracil (5-FU)] then RT vs concurrent chemoradiation (cisplatin) vs RT alone (Forastiere et al. 2003). This study successfully accrued 547 patients with stage III–IV laryngeal cancer, although patients with advanced T4-stage tumors were specifically excluded. Although there was no difference in overall survival across the three arms, there was improvement in larynx preservation, the primary end point of the trial, with concurrent CT (88%) compared with the induction (75%) and RT (70%) alone arms, respectively. Patients receiving concurrent cisplatin also were found to have an improvement in local control. With both of the CT arms, an improvement in disease-free survival and distant metastasis rates was realized. As a result of this trial, concurrent cisplatin with RT has become an accepted standard of care in patients undergoing larynx preservation for stage-III and stage-IV disease.

13.2.3 Hypopharynx Hypopharyngeal tumors include tumors of the pyriform sinus, postcricoid region, and posterior pharyngeal wall. Patients with tumors of the hypopharynx tend to have a poor prognosis compared with other subsites within the H&N. Quite commonly, curative therapy requires aggressive surgical resection including at least partial or complete laryngopharyngectomy.

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In an effort to preserve the larynx, the European Organization for Research and Treatment of Cancer (EORTC) conducted a phase-III trial of 194 patients with stage-II to stage-IV hypopharyngeal tumors and randomized them to receive either definitive laryngopharyngectomy with neck dissection followed by RT vs induction CT followed by RT (Lefebvre et al. 1996). Final results showed an improvement in median survival (44 vs 25 months) with chemoradiation, but the 5-year overall survival for the two arms was the same. After 3 years, 28% of patients in the chemoradiation arm were alive with a functional larynx. This study demonstrates that sequential CT/ RT for hypopharyngeal cancer can allow for larynx preservation in some patients, without jeopardizing overall survival. With regard to definitive chemoradiation vs RT alone, few trials exist that include only primary hypopharyngeal cancers. Multiple trials exist, however, that include hypopharyngeal cancer along with other H&N primaries comparing RT alone vs chemoradiation (Adelstein et al. 2003; Brizel et al. 1998). Several of these trials are summarized in Table 13.1. In addition, the Radiation Therapy Oncology Group (RTOG) recently published findings from a randomized phase-II study incorporating paclitaxel into the concurrent chemoradiation treatment of patients with LR advanced oral cavity, oropharyngeal, and hypopharyngeal cancers (Garden et al. 2004). Two hundred forty-one patients were randomized to treatment with either cisplatin and 5-FU, hydroxyurea, and 5-FU, or weekly paclitaxel at 30 mg/m2 and weekly cisplatin at 20 mg/m2, along with RT at 70 Gy in 35 fractions. Although statistical comparisons between the arms were not performed, overall grade-3 and grade-4 treatment-related toxicities appeared slightly greater in the paclitaxel arm; however, the three treatment-related deaths all occurred on the cisplatin and 5-FU arm. Estimated 2-year overall survival measured 57.4, 69.4, and 66.6% for the three arms, prompting the investigators to recommend incorporating multi-agent, taxane-containing CT regimens into future comparative concurrent trials. There have been several meta-analyses of randomized trials performed suggesting a survival benefit with use of concurrent CT with external beam RT in H&N cancer (Munro 1995; El-Sayed and Nelson 1996; Pignon et al. 2000; Bourhis et al. 2004). Among these meta-analyses, one was based on the collection of updated individual patient data. This meta-analysis of Chemotherapy in Head and Neck Cancer (MACH-NC) previously confirmed a

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survival benefit for concurrent chemoradiation and was recently updated to include 24 new trials utilizing chemoradiation completed between 1994 and 2000 (Pignon et al. 2000; Bourhis et al. 2004). This update reconfirmed the benefit of concurrent RT/CT for patients with LR advanced disease, yielding an HR of 0.81 (p<0.001), with an absolute survival benefit of 8% at 5 years (Table 13.2). The investigators found no significant difference between mono- and poly-chemotherapy regimens used concurrently. The benefit was found to be more pronounced for platinum-based combinations with or without 5-FU. In addition, the benefit of adding chemotherapy was more significant in younger patients and progressively decreased to become non-detectable beyond the age of 70 years. Together, these data support the use of concurrent chemoradiation as a standard of care treatment option for stage-III and stage-IV H&N cancer patients who can tolerate systemic chemotherapy. Table 13.2. Meta-analysis summary results of chemoradiation vs radiation alone. (Adapted from Pignon et al. 2000) Trial category (chemotherapy)

Hazard ratio

Five-year absolute survival beneﬁt (%)

Adjuvant

0.98 (0.851.19)

1

Neoadjuvant

0.95 (0.881.01)

2

Concurrent

0.81 (0.760.88)

8

Overall, there was a 4% absolute beneﬁt after 5 years

13.2.4 Nasopharynx Tumors of the nasopharynx are generally considered distinct from other H&N tumors, because of their unique histological, epidemiological, and clinical features. On the order of 90% of patients with nasopharyngeal cancer present with cervical lymphatic involvement with up to 50% presenting with bilateral neck disease. For patients with advanced neck disease, there is a relatively high rate of distant metastasis. As a result, nasopharyngeal cancers were among the first tumors of the H&N to routinely incorporate radiochemotherapy strategies in their management. The first randomized trial comparing RT with or without CT involved 60–70 Gy of RT via split course over 10 weeks. Patients that achieved a complete response to RT were randomized to receive either

no further treatment or a combination of vincristine, cyclophosphamide, and adriamycin for six monthly cycles (Rossi et al. 1988). At 4 years, however, there was no difference in overall survival or disease-free survival. Distant failure was the primary mode of failure in about 50% of the patients on this trial, so additional studies with CT were encouraged. Chan and colleagues (1995) explored the use of neoadjuvant and adjuvant chemoradiotherapy vs RT alone as a means of intensifying CT. In that study, patients in the combined modality arm received two cycles of induction cisplatin followed by radical RT and then four cycles of adjuvant cisplatin. Again, there was no difference in overall survival, disease-free survival, local control, or distant metastasis. It was not until the completion of Intergroup Study 0099 that combined modality treatment became a broadly accepted standard of care for patients with advanced nasopharyngeal cancer. In this study, patients were randomized to concurrent and adjuvant chemoradiation vs RT alone. Patients on the experimental arm received cisplatin (100 mg/m 2) on days 1, 22, and 43 during RT. Adjuvantly, cisplatin (80 mg/m 2) and 5-FU (1000 mg/m2) every 4 weeks for three cycles were administered. The RT regimen delivered 70 Gy in 2-Gy-daily fractions in both arms (Al-Sarraf et al. 1998). At 3 years, survival was dramatically higher in the combined arm (76%) vs the RT alone arm (46%). Although this intergroup study enrolled small patient numbers (only 69 and 78 evaluable patients in the RT arm combined modality arm, respectively), achieved exceptionally poor results in the RT alone arm, had a notably different proportion of WHO-type histologies than the Asian trials where nasopharynx cancer is endemic, and could not isolate the actual benefit of the adjuvant chemotherapy, the results, nonetheless, were striking enough to promote combined RT/CT as a standard of care in the treatment of patients with advanced nasopharynx cancer. More recently, several additional trials have examined chemoradiation vs RT alone for nasopharyngeal cancer deriving from major center experiences in Southeast Asia. Wee et al. (2004) recently reported the results of SQNPO1, a phaseIII randomized trial of 220 patients receiving cisplatin and RT vs RT alone. In this trial, there was an 8% overall survival advantage at 2 years (85 vs 77%) in favor of the combined modality treatment arm. This result lends support to the findings of the U.S. Intergroup trial, although with much improved

Applications in Head and Neck Cancer

RT alone results and a smaller magnitude of difference between the treatment arms. In a similar trial design from Lee and colleagues (2004) in Hong Kong that enrolled 348 nasopharynx patients, no overall survival advantage was realized with the addition of CT (84% in both arms), though the local control (95 vs 84%) and progression-free survival (76% vs. 68%) favored the combined treatment arm; therefore, even in geographic regions where nasopharyngeal cancer (particularly WHO type III) is endemic, there remains some disparate clinical data regarding the absolute impact of CT, though the collective results support general favoring for concomitant chemoradiation in those patients with advanced-stage disease. The role of adjuvant CT in patients with nasopharynx cancer remains ill-defined. In general, the use of adjuvant chemotherapy has not proven to be of benefit for H&N cancer patients overall, and the delivery of adjuvant regimens has not been well tolerated; however, adjuvant chemotherapy was a component of the U.S. Intergroup nasopharynx trial, and it is not inconceivable that this contributed to the improved outcome for these patients. Kwong et al. (2003) recently reported on a four-arm randomized trial in Hong Kong comparing concurrent uraciltegafur with RT vs RT followed by cisplatin and 5-FU alternating with vincristine, bleomycin, and methotrexate for six cycles vs concurrent chemoradiation with adjuvant chemotherapy (per the first two arms) vs RT alone. The study was closed early due to poor accrual. In comparing arms using concurrent CT vs those that did not, concurrent RT was found to reduce distant metastases; however, there was only a borderline difference in 3-year overall survival (86.5 vs 76.8%; p=0.06). In reviewing the above nasopharynx trial results, a much smaller difference is observed between the chemoradiation vs RT arms compared with that seen in the U.S. Intergroup trial. In the Hong Kong and Singapore trials, RT alone patients achieved overall survival results that were very similar to the U.S. combined modality arm. There may well be biological differences in the natural history of nasopharynx cancer in the North American vs Asian populations. In the endemic regions, the majority of tumors are WHO grade-III histology as opposed to less than half in the U.S. Intergroup series. These histological variants carry important distinctions relating to association with EBV (WHO type III), smoking history, propensity for distant metastases, age at presentation, and other features. Based purely on the relative infrequency of nasopharynx cancer in

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the U.S., many centers have limited experience in the complex RT treatment design required for these patients.

13.3 Induction Chemotherapy Several rationales support the concept of induction CT in the multimodality treatment of LR advanced H&N cancer; these include optimal drug distribution in the untreated fully vascularized tumor, tumor shrinkage to enhance local control, treatment of distant metastases, organ preservation, and improved treatment tolerance prior to definitive radiation and/or surgery. Investigators at Wayne State University developed induction regimens using cisplatin and 5-FU (PF). Such regimens yielded overall tumor response rates of 70–90%, with complete response rates of 20–50% (Kish et al. 1985; Vokes et al. 1991); however, with few exceptions, a broad series of randomized clinical trials and meta-analyses over the past 2 decades strongly suggest that the induction CT approach does not ultimately enhance local control, disease-free survival, or overall survival. More recently, organ preservation, rather then overall survival, has served as the primary end point of several studies of induction CT, most notably the Veterans Affairs Laryngeal Cancer Study and the RTOG 9111, discussed previously. These trials established organ preservation as a tangible goal in the non-surgical treatment of LR advanced laryngeal carcinoma. Additionally, the RTOG 9111 trial shed further light on the use of induction CT followed by single agent definitive local treatment (radiotherapy in this case; Forastiere et al. 2003). In particular, induction PF for two to three cycles followed by RT did not improve larynx preservation rates, overall survival, rates of distant metastases, or local tumor control, and was more toxic compared with RT alone. As previously discussed, concurrent chemoradiation appears the preferred regimen to maximize the possibility of larynx preservation, with RT alone reserved for those patients unable to receive CT. In an effort to build upon the success of concurrent chemoradiation in H&N cancer, a renewed interest in the concept of induction CT has re-emerged. Several new cytotoxic agents have been studied as a component of induction CT. Multiple groups have investigated adding taxanes or replacing 5-FU with taxanes (Posner 2001; Posner et al. 2001; Shin et

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al. 2002; Fonseca et al. 2005). Shin (et al. 2002) demonstrated an 81% response rate in the induction setting with TIC (paclitaxel, ifosfamide, and carboplatin); however, the role of carboplatin is unclear as studies have suggested inferior efficacy results when compared head to head with cisplatin (Shin et al. 2002; De Andres et al. 1995). Fonseca et al. (2005) randomized 83 patients to induction CT with either PF or cisplatin and docetaxel in the phase-II setting. Antitumor response rates were comparable between the two arms, with 70% for the docetaxel group and 69% for the 5-FU patients. Toxicities were likewise fairly similar between the two treatments. The Dana Farber center has investigated the use of docetaxel added to PF, first with and then without leucovorin (Posner et al. 2001; Colevas et al. 1999). Forty-three patients with unrestricted primary disease sites received docetaxel at 75 mg/m 2, infusional 5-FU at 1000 mg/m2 daily times 4 days, or cisplatin at either 75 or 100 mg/m2 (TPF) for three cycles prior to definitive local therapy. All patients received prophylactic antibiotics. While toxicity was considerable, efficacy outcomes showed a 94% response rate and a pathologically complete response in 18 of the 25 patients sampled (Posner et al. 2001). Preliminary results from Katori et al. (2005) parallel the findings of RTOG 9111, in that induction CT with TPF followed by definitive RT yielded inferior 3-year survival (64%) compared with concurrent chemoradiation, using slightly dose-reduced TPF (83%). Finally, the EORTC has reported preliminary results from a phase-III trial randomizing 358 patients to four cycles of induction treatment with either PF vs cisplatin (75 mg/m2), 5-FU (infusional 750 mg/m2 daily times 5 days), and docetaxel (75 mg/m 2; TPF), followed by definitive radiotherapy (Vermorken et al. 2004). The investigational arm was less toxic with diminished nausea, vomiting, stomatitis, and fewer toxic deaths (2.3% for the TPF arm and 5.5% for PF). With a median follow-up of 32 months, tumor response (68% for TPF vs 54% for PF; p=0.007), progression-free survival and overall survival all favored patients receiving TPF. While these early data suggest that TPF may be superior to PF as an induction CT regimen, the ultimate clinical significance of induction CT preceding definitive local treatment has yet to demonstrate consistent clinical benefit. With the recent success of concurrent chemoradiation, induction CT followed by concurrent chemoradiation should be compared with definitive concurrent chemoradiation alone, before concluding that induction CT will benefit the overall population of patients with LR advanced H&N cancer.

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13.4 Induction Chemotherapy Followed by Concurrent Chemoradiation Induction chemotherapy followed by concurrent chemoradiation may provide advantages for both phases of treatment: systemic therapy to reduce distant metastases and bimodality for locoregional control. Several groups are studying this treatment scheme in controlled clinical trials. In one study, 42 H&N patients received two cycles of induction CT with cisplatin, 5-FU, and leucovorin, followed by chemoradiation with two cycles of cisplatin at 100 mg/m2 and 70 Gy of external beam RT (Psyrri et al. 2004). Two- and 5-year overall survival rates were 67 and 52%, respectively. Toxicities to both induction and concurrent CT were considered manageable. Regarding the incorporation of taxanes into induction or concurrent H&N cancer treatment, Hitt et al. (2003) completed a large phase-III study (n=387) that randomized patients to three cycles of induction CT with either PF or cisplatin, 5-FU, and paclitaxel, followed by concurrent chemoradiation using three cycles of full-dose cisplatin and 70 Gy of RT. The primary study end point was the complete response rate to induction CT, which may be at odds with historical experience that high rates of antitumor response with induction treatment fail to consistently improve survival. Patients with a variety of H&N disease sites were eligible; mucositis was less in the paclitaxel-containing arm. The primary end point of the study was met, in that the complete response rate to the paclitaxel-containing induction regimen was statistically superior (33%) than that seen with PF (14%); survival data are not yet available. This group has also published preliminary findings comparing two induction regimens (PF vs TPF), followed by cisplatin-based concurrent chemoradiation, vs concurrent chemoradiation alone (Hitt et al. 2005). Although early rates of complete response are encouraging (>80% following all treatment in both induction arms vs 47% in the concurrent arm), rates of treatment-related mortality appear quite high, exceeding 5% in all arms. The Eastern Cooperative Oncology Group (ECOG) evaluated two cycles of induction carboplatin and paclitaxel (Cmelak et al. 2005), followed by RT with weekly paclitaxel for patients with unresectable laryngeal or oropharyngeal cancer, while Haddad et al. (2005) incorporated TPF induction CT, followed by concurrent chemoradiation with concurrent weekly carboplatin plus either paclitaxel or docetaxel for LR advanced patients. While this

Applications in Head and Neck Cancer

latter study reported an 89% pathological complete response rate to induction treatment in early findings, data maturation is needed to better evaluate the impact of induction CT followed by concurrent chemoradiation as an effective and tolerable treatment regimen. Comparative trials using this approach vs concurrent chemoradiation alone, with comprehensive efficacy, toxicity, and quality-of-life analyses, are necessary to best gauge the potential merits of induction CT in the treatment of patients with LR advanced H&N cancer.

13.5 Adjuvant Chemoradiation after Primary Surgery In parallel to the success of concurrent chemoradiation in the definitive H&N treatment setting, efforts have also focused on optimizing adjuvant treatment following surgery in advanced H&N cancer. Two significant trials recently performed by the EORTC and RTOG showed clinical outcome improvements with postoperative concurrent chemoradiation vs RT alone. In the EORTC study, 334 patients with stage-III or stage-IV H&N squamous cell cancer were randomized to receive either 66 Gy of RT alone or 66 Gy with 100 mg/m 2 cisplatin given every 3 weeks for three cycles. With a median follow-up of 5 years, local control and overall survival were significantly improved in the chemoradiation arm (Bernier et al. 2004). In the RTOG trial, 459 patients were randomized to receive RT alone (60–66 Gy) vs same dose RT with 100 mg/m2 cisplatin delivered every 3 weeks (Cooper et al. 2004). At 2 years, local control was modestly improved from 72 to 82% with chemoradiotherapy but there was no difference in overall survival. In an effort to better characterize those patients most likely to benefit from postoperative chemoradiation vs radiation alone, a combined analysis of the pooled data from the RTOG and EORTC trials was conducted (Bernier et al. 2005). Patients with extracapsular nodal extension and positive margins on the primary resection derived the most benefit from addition of chemotherapy. There was a trend for improved outcome in patients with stage-III to stage-IV disease, perineural invasion, vascular embolisms, or clinically involved level-IV to level-V nodes. Patients with greater than one positive lymph node without ECE did not appear to derive this same benefit. Overall, the findings of these two trials are consistent

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with a previous randomized trial by Bachaud and colleagues (1996). In that trial, stage-III and stage-IV patients with extracapsular nodal spread were randomized to weekly cisplatin concurrently with RT vs RT alone. There was an improvement in survival and local control with chemoradiation. None of these trials identified a change in the incidence of distant metastases. For H&N cancer patients with high-risk pathological features following surgery, consideration of combined chemoradiation is warranted, although at the cost of increased toxicity. The potential value and role of CT in the management of advanced HNSCC has become much better understood in recent years. As discussed, the use of platinum-based CT in conjunction with RT has improved LR disease control, and in some instances, overall survival, however at the expense of increased toxicity in both the definitive and adjuvant settings. The most common cisplatin schedule validated in randomized trials is 100 mg/m2 on days 1, 22, and 43 during the course of RT. The role of induction CT remains in evolution. This approach has yet to establish clear survival improvement, and the results of RTOG 9111 call into question the precise contribution of induction CT to larynx preservation. Nevertheless, the potential role of more effective induction CT regimens preceding concurrent chemoradiation remains under active investigation. Finally, the optimal use of concurrent CT with altered radiation fractionation regimens requires further validation in controlled clinical trials.

13.6 Toxicity The intensified H&N chemoradiation treatment regimens are associated with significantly increased acute toxicity profiles. Efforts to reduce the side effects of treatment are actively under investigation. In the acute setting predominant treatment toxicities include mucositis, esophagitis, skin reactions, increased mucous production, and fatigue. Chronic toxicities include xerostomia, soft tissue fibrosis, and several less common adverse effects such as cervical plexopathy, soft tissue, or bone necrosis. Efforts to diminish the negative impact of xerostomia with pilocarpine have shown mixed success (Johnson et al. 1993; Warde et al. 2002; Gosselin et al. 2005). The use of amifostine has been actively studied in H&N cancer as a normal tissue protector. Trials have been conducted that show promising results with

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Fig. 13.1. Representative head and neck intensity-modulated radiation therapy (IMRT) plan. Representative IMRT plan for a patient with oropharyngeal cancer. The delineated isodose distribution illustrates sparing of the left parotid gland for reduction in xerostomia

this agent; however, issues regarding toxicity, cost, patient tolerance, and ultimate efficacy have hindered widespread implementation (Buntzel et al. 1998; Brizel et al. 2000; Wasserman et al. 2000; Wasserman and Brizel 2001a,b; Antonadou et al. 2002; Buntzel et al. 2002; Wasserman et al. 2005). Rapid advances in high-precision radiation delivery, such as intensity-modulated radiotherapy (IMRT) and tomotherapy, now afford additional opportunities for parotid gland sparing that notably reduce the severity of late xerostomia (see Fig. 13.1). Two trials conducted through the RTOG are investigating the use of IMRT for H&N cancer patients in an effort to reduce toxicity (RTOG 0022 and RTOG 0225 which recently completed accrual). Recombinant keratinocyte growth factor (KGF) is also under evaluation in an effort to reduce the acute mucosal toxicities of RT or RT/CT. Preclinical results suggest that when given prior and subsequent to RT exposure, oral mucositis may be reduced (Dorr et al. 2005).

13.7 Conclusion The H&N region is anatomically complex and densely populated with a variety of normal tissue structures and organs that are vital for daily function and life quality. The H&N cancer patients are frequently burdened with substantial cosmetic and functional morbidities from their tumors and from our current treatment regimens. As we gradually increase the percentage of patients who are cured, we may face increasing numbers of patients with chronic H&N dysfunction with regard to swallow

and speech capacity, cervical fibrosis, and other toxicities. Although the recent outcome improvement with concurrent chemoradiation for advanced H&N cancer patients appears quite real, the magnitude of the overall impact on the broad H&N cancer population is modest, and the approaches are certainly toxic, complex, and expensive to achieve. The H&N cancer patients commonly carry a variety of comorbidities in light of chronic alcohol and tobacco use, and they are prone to the development of synchronous or metachronous upper aerodigestive tract malignancies. Many patients do not meet basic eligibility criteria for intensive chemoradiation approaches. Nevertheless, improved precision and conformality of radiation dose delivery (e.g., 3D, IMRT, tomotherapy) offers high promise to diminish radiation toxicity in H&N normal tissue structures (salivary gland, auditory apparatus, mandible, spinal cord). New molecular agents that target growth factor receptors central to the growth of many H&N cancers (i.e., cetuximab reviewed in Chap. 8) similarly offer promise to provide less toxic and more discriminate approaches for the future. The hypoxic cell cytotoxin tirapazamine is now in final evaluation in two large phase-III H&N chemoradiation trials that will help define the potential role of this agent in improving outcome for advanced H&N cancer patients (Rischin et al. 2005). New salivary and mucosal protectants continue to emerge that may bring improved efficacy and ease of administration to diminish the adverse impact of RT and CT in H&N cancer patients. For each new treatment strategy, as with the current generation of chemoradiation studies, a rigorous, thorough, and dispassionate evaluation regarding the impact of treatment on the overall welfare of the H&N cancer patient population will be required.

Applications in Head and Neck Cancer

References Adelstein DJ, Li Y, Adams GL et al (2003) An intergroup phase III comparison of standard radiation therapy and two schedules of concurrent chemoradiotherapy in patients with unresectable squamous cell head and neck cancer. J Clin Oncol 21:92–98 Al-Sarraf M, LeBlanc M, Giri PG et al (1998) Chemoradiotherapy versus radiotherapy in patients with advanced nasopharyngeal cancer: phase III randomized Intergroup study 0099. J Clin Oncol 16:1310–1317 American Cancer Society (2005) Cancer Facts and Figures 2005, available online under www.cancer.org/docroot/STT/ stt_0.asp Andres L de, Brunet J, Lopez-Pousa A et al (1995) Randomized trial of neoadjuvant cisplatin and fluorouracil versus carboplatin and fluorouracil in patients with stage IV-M0 head and neck cancer. J Clin Oncol 13:1493–1500 Antonadou D, Pepelassi M, Synodinou M et al (2002) Prophylactic use of amifostine to prevent radiochemotherapy-induced mucositis and xerostomia in head-and-neck cancer. Int J Radiat Oncol Biol Phys 52:739–747 Bachaud JM, Cohen-Jonathan E, Alzieu C et al (1996) Combined postoperative radiotherapy and weekly cisplatin infusion for locally advanced head and neck carcinoma: final report of a randomized trial. Int J Radiat Oncol Biol Phys 36:999–1004 Bernier J, Domenge C, Ozsahin M et al (2004) Postoperative irradiation with or without concomitant chemotherapy for locally advanced head and neck cancer. N Engl J Med 350:1945–1952 Bernier J, Cooper JS, Pajak TF et al (2005) Defining risk levels in locally advanced head and neck cancers: a comparative analysis of concurrent postoperative radiation plus chemotherapy trials of the EORTC (#22931) and RTOG (#9501). Head Neck 27:843–850 Bourhis J, Amand C, Pignon JP (2004) Update of MACH-NC (meta-analysis of chemotherapy in head and neck cancer) database focused on concomitant chemoradiotherapy (Abstract). J Clin Oncol 22:489s Brizel DM, Albers ME, Fisher SR et al (1998) Hyperfractionated irradiation with or without concurrent chemotherapy for locally advanced head and neck cancer. N Engl J Med 338:1798–1804 Brizel DM, Wasserman TH, Henke M et al (2000) Phase III randomized trial of amifostine as a radioprotector in head and neck cancer. J Clin Oncol 18:3339–3345 Buntzel J, Kuttner K, Frohlich D et al (1998) Selective cytoprotection with amifostine in concurrent radiochemotherapy for head and neck cancer. Ann Oncol 9:505–509 Buntzel J, Glatzel M, Kuttner K et al (2002) Amifostine in simultaneous radiochemotherapy of advanced head and neck cancer. Semin Radiat Oncol 12:4–13 Calais G, Alfonsi M, Bardet E et al (1999) Randomized trial of radiation therapy versus concomitant chemotherapy and radiation therapy for advanced-stage oropharynx carcinoma. J Natl Cancer Inst 91:2081–2086 Calais G, Alfonsi M, Bardet E et al (2000) Stage III and IV cancers of the oropharynx: results of a randomized study of Gortec comparing radiotherapy alone with concomitant chemotherapy. Bull Cancer 87 (Spec no.):48–53 Chan AT, Teo PM, Leung TW et al (1995) A prospective randomized study of chemotherapy adjunctive to definitive

195 radiotherapy in advanced nasopharyngeal carcinoma. Int J Radiat Oncol Biol Phys 33:569–577 Cmelak AJ, Li S, Goldwasser M et al (2005) A phase II trial of chemoradiation (CR) for organ preservation in resectable stage III or IV squamous cell carcinomas of the larynx (L) or oropharynx (OP): a trial of the Eastern Cooperative Oncology Group (E2399). Abstract 5509, Proc Am Soc Clin Oncol, pp 5509 Colevas AD, Norris CM, Tishler RB et al (1999) Phase II trial of docetaxel, cisplatin, fluorouracil, and leucovorin as induction for squamous cell carcinoma of the head and neck. J Clin Oncol 17:3503–3511 Cooper JS, Pajak TF, Forastiere AA et al (2004) Postoperative concurrent radiotherapy and chemotherapy for high-risk squamous-cell carcinoma of the head and neck. N Engl J Med 350:1937–1944 De Andres L, Brunet J, Lopez-Pousa A et al. (1995) Randomized trial of neoadjuvant cisplatin and fluorouracil versus carboplatin and fluorouracil in patients with stage IV-M0 head and neck cancer. J Clin Oncol 13:1493-1500 Denis F, Garaud P, Bardet E et al (2004) Final results of the 94–01 French Head and Neck Oncology and Radiotherapy Group randomized trial comparing radiotherapy alone with concomitant radiochemotherapy in advanced-stage oropharynx carcinoma. J Clin Oncol 22:69–76 Department of Veterans Affairs Laryngeal Cancer Study Group (1991) Induction chemotherapy plus radiation compared with surgery plus radiation in patients with advanced laryngeal cancer. N Engl J Med 324:1685–1690 Dorr W, Reichel S, Spekl K (2005) Effects of keratinocyte growth factor (palifermin) administration protocols on oral mucositis (mouse) induced by fractionated irradiation. Radiother Oncol 75:99–105 El-Sayed S, Nelson N (1996) Adjuvant and adjunctive chemotherapy in the management of squamous cell carcinoma of the head and neck region. A meta-analysis of prospective and randomized trials. J Clin Oncol 14:838–847 Fonseca E, Grau JJ, Sastre J et al (2005) Induction chemotherapy with cisplatin/docetaxel versus cisplatin/5-fluorouracil for locally advanced squamous cell carcinoma of the head and neck: a randomised phase II study. Eur J Cancer 41:1254–1260 Forastiere AA, Goepfert H, Maor M et al (2003) Concurrent chemotherapy and radiotherapy for organ preservation in advanced laryngeal cancer. N Engl J Med 349:2091–2098 Garden AS, Harris J, Vokes EE et al (2004) Preliminary results of Radiation Therapy Oncology Group 97–03: a randomized phase II trial of concurrent radiation and chemotherapy for advanced squamous cell carcinomas of the head and neck. J Clin Oncol 22:2856–2864 Gillison ML, Koch WM, Capone RB et al (2000) Evidence for a causal association between human papillomavirus and a subset of head and neck cancers. J Natl Cancer Inst 92:709–720 Gosselin TK, Raj KA, Clough RW et al (2005) Amifostine for Xerostomia: Normal tissue protection at what cost? Abstract 212, Proc Am Soc Ther Rad Oncol, Elsevier, pp S128 Haddad RI, Tishler RB, Wirth L et al (2005) Rate of complete pathological responses (pCR) to docetaxel/cisplatin/5-fluorouracil (TPF) induction chemotherapy in patients with newly diagnosed, locally advanced squamous cell carcinoma of the head and neck (SCCHN). Abstract 5511, Proc Am Soc Clin Oncol Hitt R, Lopez-Pousa A, Rodriguez M et al (2003) Phase III

196 study comparing cisplatin (P) and 5-fluoruracil (F) versus P, F and paclitaxel (T) as induction therapy in locally advanced head and neck cancer (LAHNC). Abstract 1997, Proc Am Soc Clin Oncol Hitt R, Grau J, Lopez-Pousa A et al (2005) Phase II/III trial of induction chemotherapy(ICT) with cisplatin/5-fluorouracil (PF) vs docetaxel (T) plus PF (TPF) followed by chemoradiotherapy (CRT) vs CRT for unresectable locally advanced head and neck cancer (LAHNC). Abstract 5578, Proc Am Soc Clin Oncol Holsti LR, Mantyla M (1988) Split-course versus continuous radiotherapy. Analysis of a randomized trial from 1964 to 1967. Acta Oncol 27:153–161 Johnson JT, Ferretti GA, Nethery WJ et al (1993) Oral pilocarpine for post-irradiation xerostomia in patients with head and neck cancer. N Engl J Med 329:390–395 Katori H, Tsukuda M, Ishitoya J et al (2005) Comparison of induction chemotherapy with docetaxel, cisplatin, and 5fluorouracil (TPF) followed by radiation versus concurrent chemoradiotherapy with TPF in patients with locally advanced squamous cell carcinoma of the head and neck (SCCHN). Proc Am Soc Clin Oncol, pp 5580 Kish JA, Ensley J, Crissman J et al (1985) The role of induction chemotherapy in advanced head and neck cancer: the Wayne State University experience. Prog Clin Biol Res 201:177–189 Kwong DL, Sham JS, Au GK (2003) Concurrent and adjuvant chemotherapy for nasopharyngeal carcinoma: a factorial study. Proc Am Soc Clin Oncol 22:495 Lee AW, Lau WH, Tung SY et al (2004) Prospective randomized study on therapeutic gain achieved by addition of chemotherapy for T1-4N2-3M0 nasopharyngeal carcinoma (NPC). Abstract 5506. Proc Am Soc Clin Oncol 22 No 14S:489s Lefebvre JL, Chevalier D, Luboinski B et al (1996) Larynx preservation in pyriform sinus cancer: preliminary results of a European Organization for Research and Treatment of Cancer phase III trial. EORTC Head and Neck Cancer Cooperative Group. J Natl Cancer Inst 88:890–899 Munro AJ (1995) An overview of randomised controlled trials of adjuvant chemotherapy in head and neck cancer. Br J Cancer 71:83–91 Pignon JP, Bourhis J, Domenge C et al (2000) Chemotherapy added to locoregional treatment for head and neck squamous-cell carcinoma: three meta-analyses of updated individual data. MACH-NC Collaborative Group. Metaanalysis of chemotherapy on head and neck cancer. Lancet 355:949–955 Posner MR (2001) Docetaxel in squamous cell cancer of the head and neck. Anticancer Drugs 12 (Suppl 1):S21–S24 Posner MR, Glisson B, Frenette G et al (2001) Multicenter phase I–II trial of docetaxel, cisplatin, and fluorouracil induction chemotherapy for patients with locally advanced squamous cell cancer of the head and neck. J Clin Oncol 19:1096–1104 Psyrri A, Kwong M, DiStasio S et al (2004) Cisplatin, fluo-

D. Khuntia et al. rouracil, and leucovorin induction chemotherapy followed by concurrent cisplatin chemoradiotherapy for organ preservation and cure in patients with advanced head and neck cancer: long-term follow-up. J Clin Oncol 22:3061–3069 Rischin D, Peters L, Fisher R et al (2005) Tirapazamine, cisplatin and radiation versus fluorouracil, cisplatin and radiation in patients with locally advanced head and neck cancer: a randomized phase II trial of the Trans-Tasman Radiation Oncology Group (TROG 98.02). J Clin Oncol 23:79–87 Rossi A, Molinari R, Boracchi P et al (1988) Adjuvant chemotherapy with vincristine, cyclophosphamide, and doxorubicin after radiotherapy in local–regional nasopharyngeal cancer: results of a 4-year multicenter randomized study. J Clin Oncol 6:1401–1410 Shin DM, Glisson BS, Khuri FR et al (2002) Phase II study of induction chemotherapy with paclitaxel, ifosfamide, and carboplatin (TIC) for patients with locally advanced squamous cell carcinoma of the head and neck. Cancer 95:322–330 Vermorken JB, Remenar E, van Herpen C et al (2004) Standard cisplatin/infusional 5-flourouracil (PF) vs docetaxel (T) plus PF (TPF) as neoadjuvant chemotherapy for nonresectable locally advanced squamous cell carcinioma of the head and neck (LA-SCHHN): a phase III trial of the EORTC Head and Neck Cancer Group (EORTC #24971). Abstract 5508, Proc Am Soc Clin Oncol Vokes EE, Mick R, Lester EP et al (1991) Cisplatin and fluorouracil chemotherapy does not yield long-term benefit in locally advanced head and neck cancer: results from a single institution. J Clin Oncol 9:1376–1384 Warde P, O’Sullivan B, Aslanidis J et al (2002) A phase III placebo-controlled trial of oral pilocarpine in patients undergoing radiotherapy for head-and-neck cancer. Int J Radiat Oncol Biol Phys 54:9–13 Wasserman TH, Brizel DM (2001a) The role of amifostine as a radioprotector. Oncology (Williston Park) 15:1349–1354; discussion 1357–1360 Wasserman TH, Brizel DM (2001b) Has the outlook improved for amifostine as a clinical radioprotector. Radiother Oncol 60:334–336 Wasserman T, Mackowiak JI, Brizel DM et al (2000) Effect of amifostine on patient assessed clinical benefit in irradiated head and neck cancer. Int J Radiat Oncol Biol Phys 48:1035–1039 Wasserman TH, Brizel DM, Henke H et al (2005) Influence of intravenous amifostine on xerostomia, tumor control, and survival after radiotherapy for head-and-neck cancer: 2year follow-up of a prospective, randomized, phase III trial. Int J Radiat Oncol Biol Phys 63:985–990 Wee J, Tan EH, Tai BC (2004) Phase III randomized trial of radiotherapy versus concurrent chemo-radiotherapy followed by adjuvant chemotherapy in patient with AJCC/ UICC (1997). Stage 3 and 4 nasopharyngeal cancer of the endemic varitey. Proc Am Soc Clin Oncol 23:487

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14 Applications in Esophageal and Gastric Cancer Frank Zimmermann and Björn L. D. M. Brücher

CONTENTS 14.1 14.1.1 14.1.2 14.1.3 14.1.4 14.1.4.1 14.1.4.2 14.1.4.3 14.1.4.4 14.2

14.2.1 14.2.2 14.2.2.1 14.2.2.2 14.2.2.3 14.2.3 14.2.4 14.2.4.1 14.2.4.2 14.2.4.3

Esophageal Cancer 197 Introduction 197 Epidemiology and Staging 197 Anatomy and Tumor Spread 198 Therapy 198 Principles and Strategies 198 Radio- and Radiochemotherapy 199 Resection and Multimodal Concepts 201 Conclusion 207 Gastric Cancer and Adenocarcinoma of the Esophagogastric Junction (AEG II and III) 207 Introduction 207 Preoperative Treatment 207 Preoperative Radiotherapy 207 Preoperative Chemotherapy 207 Preoperative Radiochemotherapy 208 Intraoperative Radiotherapy 209 Postoperative Treatment 209 Postoperative Radiotherapy 209 Postoperative Chemotherapy 209 Postoperative Radiochemotherapy 210 References 211

14.1 Esophageal Cancer 14.1.1 Introduction Esophageal cancer has been regarded traditionally as an aggressive malignancy with an increasing incidence of squamous cell cancer in developing countries due to increasing consumption of alcohol and tobacco during the last decades (odds ratio of 23.1 when both risk factors are present) (Lagergren F. Zimmermann, MD Department of Radiation Oncology, Klinikum rechts der Isar der Technischen Universität München, Ismaninger Str. 22, 81675 Munich, Germany B. L. D. M. Brücher, MD Department of Surgery, Klinikum rechts der Isar der Technischen Universität München, Ismaninger Str. 22, 81675 Munich, Germany

et al. 2000), and an even more pronounced rise of adenocarcinoma of the esophagogastric junction in the western world mainly caused by reflux disease. For both entities, there is a poor outcome in all advanced stages. While surgical resection or definitive radio- or radiochemotherapy (RCT) may be curative with better long-term outcome in early stage cancer, most patients with symptomatic esophageal cancer die within 3 years after diagnosis, in spite of complex treatment concepts. Therefore, continued clinical research is justified, including the evaluation of more aggressive neoadjuvant and adjuvant treatments as well as an improvement of combined RCT.

14.1.2 Epidemiology and Staging Squamous cell cancer is the predominant histology in esophageal malignancies, with a heterogeneous worldwide pattern: regions with a very high incidence of up to 200 new cases per 100,000 inhabitants are in Iran, southern Russian republics, South Africa and central areas of China. In Europe and America, the incidence is approximately 6.6 per 100,000 residents, with male persons being affected five times more frequently than females, and a mortality of 6.1/100,000 (ESMO Guidelines 2005). Most patients are older than 30 years, with a median age of 65 years (Bareiss et al. 2002). Unfortunately, esophageal cancer is usually detected in advanced stages, with 70 % of all new cases being stage III or IV. Therefore, the 5-year survival rate of all patients is not higher than 5% (Bareiss et al. 2002). Adenocarcinoma of the pericardial area (adenocarcinoma of the esophagogastric junction, AEG) is the second most common cancer of the esophagus, and the most common one below the tracheal carina. It is subdivided into three groups, dependent on the relation to the cardia: AEG I from 5 cm to 1 cm cranial of the cardia, with a behavior similar to squamous cell cancer of the distal esophagus – and

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therefore integrated into the sections on esophageal cancer – and AEG II and III, located in the cardia and from 2 cm to 5 cm distal of the cardia, respectively, mentioned in sections on gastric cancer.

14.1.3 Anatomy and Tumor Spread The classification of esophageal cancer into subgroups depends on the location of the cancer and the resulting therapeutic procedure: cancer of the cervical part, intrathoracic cancer with close relation to the tracheobronchial tree, or infrabifurcal cancer, with the latter usually being resectable even in locally advanced stages. The former should be offered a multidisciplinary concept, in principle, with neoadjuvant chemo- or radiochemotherapy dependent on the histology and local growth, or definitive combined RCT. The second, more historical classification into two subgroups – cervical and intrathoracic cancer – was based on the surgical approach and the distribution of the lymph node involvement, but does not reflect the problems of R0 resection in all tumors close to the tracheobronchial tree, and the resulting multidisciplinary aspect. The most important prognostic factor is the tumor stage (Daly et al. 1996), or local tumor spread – infiltration of the mediastinum, tracheobronchial tree, and pericardium – and the infiltration of locoregional lymph nodes, with the latter being present in 5% of mucosal carcinoma, in 30% of submucosal cancer, and in even more than 80% of tumors extending beyond the esophagus (Hosch et al. 2001), causing about 40% of all local tumor recurrences. Cancer of the upper third of the esophagus usually infiltrates the cervical and mediastinal lymph nodes, whilst tumors of the middle third mainly spread to the mediastinal and upper perigastric lymph nodes, and carcinoma of the lower third to the lower mediastinal and abdominal lymph nodes. The distribution of lymph node infiltration has major implications on the target volume of both definitive and preoperative radiotherapy, and should be taken into account when customizing the radiation portals. Intraesophageal spread of tumor cells in submucosal lymphatics influences the target volume, too. Its likelihood increases from 4% in pT1 tumors to 30% in pT4 tumors. It should be noted that a metachronous or even synchronous secondary cancer of the upper aerodiges-

tive tract can occur in up to 10% of patients, which will have a major impact on treatment decision. The classification of esophageal cancer follows guidelines by the UICC, recently actualised in 2002 (UICC 2002) (Table 14.1) and influences the treatment decision as well the prognosis: in an analysis of 4329 patients with esophageal cancer 5-year survival rates were 42% in stage I, 29% in stage II, 15% in stage III, and only 3% in stage IV (Daly et al. 1996). Besides tumor stage, the oral and aboral resection status (R classification) has a prognostic value, too, with a R0 resection being the primary goal of the surgeon (Hermaneck 1999). In recent years, a lot of different molecular markers have been evaluated regarding their prognostic impact, but none of them is established in clinical routine (gene aberration, transcription factors, apoptotic mechanisms, etc.). An optimal and individual treatment decision is based on precise staging of the tumor: the depth of infiltration is evaluated by endoscopic ultrasound and the infiltration of adjacent organs by computed tomography (CT) and bronchoscopy. Further staging procedures depend on clinical symptoms and are not recommended on a routine basis. Magnetic resonance imaging (MRI) of the mediastinum has failed to show a higher accuracy than CT to detect mediastinal infiltration, and is therefore not recommended (Korst and Altorki 2004).

14.1.4 Therapy 14.1.4.1 Principles and Strategies

Esophageal cancer is a curable disease and the treatment decision is based on tumor extension, comorbidities and individual decision of the informed patient. Whilst esophagectomy is usually offered in early stages (uT1–2), both radical resection and combined RCT are standard procedures in locally advanced cancer (uT3). For tumors with close contact to the tracheobronchial tree preoperative RCT is used by a number of centers. To define the best individual concept, exact knowledge about the functional operability, organ function (liver, kidney, heart, lung) and expected tolerance to radio- and/or chemotherapy is essential. Continued alcohol consumption, reduced general condition (Karnofsky performance status < 70), excessive weight loss, and altered renal, hepatic, and/or

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Table 14.1. TNM stages [classification of the UICC (2002)] TNM classification of esophageal cancer T stage T1

Lamina propria, submucosa

T2

Muscularis propria

T3

Adventitia

T4

Adjacent structures and organs

N stage (regional lymph nodes) N1

Regional

M stage (distant metastases) For tumors of the lower esophagus M1a

Coeliac lymph nodes

M1b

Other distant metastases

For tumors of the upper esophagus M1a

Cervical lymph nodes

M1b

Other distant metastases

For tumors of the middle thoracic esophagus M1a

Non-existent

M1b

Distant lymph node or organ metastases

Stages in esophageal cancer Stage 0

Tis

N0

M0

Stage I

T1

N0

M0

Stage IIA

T2, T3

N0

M0

Stage IIB

T1, T2

N1

M0

Stage III

T3

N1

M0

T4

All N

M0

Stage IV

All T

All N

M1

Stage IVA

All T

All N

M1a

lung function are contraindications for aggressive treatment, regardless of whether resection or simultaneous RCT is considered (Law et al. 2004). A risk score combining respiratory, hepatic, and cardiac function, as well as general condition of the patient, helps to create three classes of patients with regard to 30-day postoperative mortality: 3.6% in the low (11–15 points), 8.7% in the medium (16–21 points), and 28% in the high risk group (22–23 points), respectively (Bartels et al. 1998). It seems advisable not to offer multimodal concepts or even the procedure of esophagectomy to patients of the latter risk group. Optimal supportive care (percutaneous endoscopic gastrostomy, feeding tubes, etc. in patients with weight loss of more than 5% within the last 3 months) is very important and should be started immediately after diagnosis.

14.1.4.2 Radio- and Radiochemotherapy 14.1.4.2.1 Radiotherapy

In principle, tumors of the esophagus are radiosensitive, but usually high doses are necessary to produce remission rates of about 80% (54–60 Gy in conventional fractionation, or 39 Gy in hypofractionated palliative regimens with doses of 3 Gy per fraction). Despite good palliative effects, long-term survival is dismal with 2-year survival between 4%– 27 % and 5-year survival rates below 15% (Badwe et al. 1999). To obtain long-lasting local tumor control, radiation doses might be increased by endoluminal brachytherapy or by shortening the overall treat-

200

ment time, usually done with hyperfractionated accelerated schedules (i.e. 2 u 1.5 Gy per day from the 3rd week onwards to a total dose of 68.4 Gy). The latter has shown advantages in two randomised trials (Shi et al. 1999; Wang et al. 2002). These studies have found an improvement in mean survival to approximately 3 years, which is comparable to either resection or combined RCT. Such schedules should be used if resection and/or combined RCT is not feasible, but the patient is compliant and in good general condition. 14.1.4.2.2 Radiochemotherapy

For locally advanced tumors of the esophagus, combined RCT is the treatment modality chosen by approximately 30% of patients in the US (Daly et al. 1996). 5-Fluorouracil (5-FU) and cisplatin are the main compounds used with radiation therapy concurrently. There are close to 20 randomised trials on definitive RCT, comparing either primary RCT with primary radiotherapy alone (Rebecca and Richard 2003; Zhao et al. 2005), definitive RCT with preoperative RCT (Stahl et al. 2005; Bedenne et al. 2002), or definitive RCT with primary resection – the latter with very preliminary data from China (Chiu et al. 2005). There was tremendous heterogeneity across all the studies, with the sequence of chemotherapy (simultaneous better than sequential RCT) as a very important prognostic factor. Unfortunately, the results of the studies on sequential RCT were heterogeneous, so that they could not be pooled by the Cochrane Collaboration (Wong et al. 2003). So far, the outcome of all randomised trials does not support a recommendation for sequential RCT. It rather became evident that concomitant RCT provided significant improvement in overall survival (7% after 1- and 2-year follow-up), disease-specific survival, and local tumor control (12%–45%). Two sequential clinical trials attempted to define the optimal concept of RCT (Al-Sarraf et al. 1997; Minsky et al. 2002). Within the first trial, RCT was compared to radiotherapy alone. RCT consisted of conventionally fractionated radiotherapy to a total dose of 50 Gy and four cycles of cisplatin (75 mg/sqm day 1) and 5-FU (1000 mg/ sqm day 1–4), with the first two cycles given parallel to radiation therapy. Though the radiotherapy alone arm had a higher dose, the overall survival was significantly improved by simultaneous RCT (Al-Sarraf et al. 1997). In the second trial, con-

F. Zimmermann and B. L. D. M. Brücher

comitant RCT was given in both arms at two different dose levels (50 Gy versus 64 Gy total dose) whilst chemotherapy was the same as in the former study. There was no advantage of the higher dose regimen due to a higher mortality rate. It is difficult to explain the results, because the majority of the adverse events happened before reaching a dose of 50 Gy, but it confirms that a combined RCT can cause severe side effects and that an increase of the radiation dose should only be done with due caution. Using conventional fractionation schedules (five fractions of 1.8–2.0 Gy per week) and a concomitant chemotherapy, total doses between 50 and 60 Gy might be optimal for locally advanced, non-resectable esophageal carcinoma. About four cycles of cisplatin- and 5-FU-based chemotherapy are also recommended. Based on the convincing data of radiotherapy alone given in accelerated and hyperfractionated manner (Shi et al. 1999), the idea to combine an altered fractionation schedule with concomitant chemotherapy emerged and prompted an investigation by Zhao et al. (2005). A total dose of 68.4 Gy was applied in 41 fractions within 44 days – either alone or combined with cisplatin and 5-FU. There was no significant difference in survival (5-year survival 40% vs. 28% and median survival 30.8 vs. 23.9 months in favour of RCT; p=0.31), perhaps due to an increase in severe acute toxicity (Common Toxicity Score, CTC)°III/IV: 46% vs. 25%; death: 6% vs. 0%). Poor nutrition and inadequate supportive care were suggested as major reasons for this. Therefore, altered fractionation schedules in RCT can not be recommended at the moment without further prospective data. From other recent trials – but conducted to answer a different question – it can be concluded that a concomitant RCT analogous to the schedule in Table 14.2 is able to produce similar overall survival data as a radical esophagectomy with or without previous neoadjuvant RCT (Hironaka et al. 2003; Bedenne et al. 2002; Blazeby et al. 2003). Therefore, in particular if the goal of R0 resection is difficult to achieve, a definitive simultaneous RCT will be the treatment of choice. In the presence of contradictions to chemotherapy (reduced kidney and/or liver function, severe cardiac disease, etc.), radiotherapy alone should be chosen, with the option of hyperfractionated-accelerated schedules, which were superior to conventionally fractionated treatment in a randomised trial (Shi et al. 1999).

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Table 14.2. Recommended concept of combined radiochemotherapy (majority of studies being performed with conventional fractionated radiotherapy and chemotherapy with cisplatin and 5-fluorouracil) followed by two additional cycles of chemotherapy thereafter (cisplatin, 5-FU) Radiotherapy

1.8–2.0 Gy

Days 1–39

Cisplatin

70 mg/m2 short infusion alternative: 20

5-Fluorouracil

1000

mg/m2

mg/m2

Days 1, 29, 58 and 85

short infusion

continuous infusion

Alternative: 225

mg/m2

Days 1–4, 29–32, 58–61, and 85–88

continuous infusion

14.1.4.3 Resection and Multimodal Concepts

14.1.4.3.1 Surgical Resection

Radical en-bloc resection of the esophagus including systematic mediastinal lymph node dissection is the standard surgical approach and offers longlasting local control. It is essential to achieve a complete resection of the tumor (R0 resection). Otherwise, the resection has only palliative character (Stein et al. 2000) and must be weighed against the high morbidity rate and long hospitalisation. By optimal selection of patients carrying only minimal risk factors, standardized resection and operative reconstruction procedures – twostage procedure with delay of reconstruction after resection for at least 8 days in patients with previous preoperative radiochemotherapy or severely altered cardiopulmonary function – and improvements in postoperative intensive care, the rate of life-threatening morbidity and mortality could be decreased in specialized centers to no more than 5%. It has also been proven that hospital and surgeon volume are major factors that determine postoperative mortality. For tumors of the infra- or suprabifurcal esophagus, transthoracic en-bloc resection including the esophagus and locoregional mediastinal lymph nodes is recommended, which might be extended by coeliac lymph node dissection during abdominal and left-cervical reconstruction (two-field lymphadenectomy). Only for tumors of the lower mediastinum without any contact to the tracheobronchial tree, and in patients with substantially impaired lung function, a transmediastinal approach is justified, with a lymph node dissection of the lower posterior mediastinum and the upper abdomen only.

Days 1–5 and 29–33

Days 1–39

The reconstruction in locally advanced tumors and after preoperative RCT is usually placed in the anterior mediastinum behind the sternum. Either stomach, colon or small bowel can be used (von Rahden and Stein 2004). In locally advanced stages (IIB and III) the 5year survival rate is around 20 % –40 % even in experienced centers and decreases to less than 10% in more advanced tumors (u/pT4 or pM1a), resulting from a high local recurrence rate and early distant spread. A complete resection can be achieved in only 54% of pT3 and 19% of pT4 tumours (Stein et al. 2000). 14.1.4.3.2 Multimodal Concepts

In several randomised clinical trials (> 35) and more than seven meta-analyses with more than 5000 patients in total, the value of multimodal concepts has been proven. Unfortunately, in contrast to previous trials limited to squamous cell cancer, most very recent trials included patients with squamous cell and adenocarcinoma without any stratification. Furthermore, studies are heterogeneous regarding other inclusion criteria such as tumor stage, staging procedures, and comorbidities, as well as treatment concepts: selection and dose of chemotherapy, and total dose, fractionation, dose calculation, target volume as well as technique of radiotherapy. This makes metaanalyses very difficult and explains the inclusion or exclusion of the same studies into distinct metaanalyses (Malthaner et al. 2004; Patel et al. 2004; Tierney et al. 2005). However, some very relevant statements on pre- and postoperative, adjuvant as well as additive therapies in locally advanced esophageal cancer have been given by different authors and these will be presented here in summary.

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14.1.4.3.2.1 Preoperative Radio-, Chemo- and Radiochemotherapy Preoperative Radiotherapy Preoperative radiotherapy has been evaluated in eight randomised trials. Five trials compared this approach against surgery alone, one trial within a four-arm setting against surgery alone and against postoperative radiotherapy, one trial against postoperative radiotherapy, and one trial against preoperative RCT (Malthaner et al. 2004). There was no significant increase in mortality compared to the other treatment arms. However, there was also no improvement in 1-year survival rate by preoperative radiotherapy – neither in any single study nor in pooled analysis. This can be explained at least in part by the modest number of patients in three trials with less than 70 patients per arm each, and non-standard radiation schedules in most trials [low total radiation doses in three trials (below 35 Gy), aggressive hypofractionated radiation therapy in the four-arm trial (up to 53 Gy in 20 fractions)]. Recently, a different analysis by the Cochrane Collaboration found an overall reduction in the risk of death of 11% and an absolute survival benefit of 3% at 2 and of 4% at 5 years, respectively, with borderline significance (p=0.062) in pooled data of five properly designed randomised trials including 1147 patients with a median follow-up of 9 years. The studies used for the meta-analysis mostly included

patients with squamous cell cancer. It is therefore not possible to give any advise on the treatment of adenocarcinoma of the lower esophagus (AEG I) with preoperative radiotherapy. Due to the borderline significance, preoperative radiotherapy is not recommended as standard procedure even in squamous cell carcinoma of the esophagus (Tierney et al. 2005) (Table 14.3). Preoperative Chemotherapy Preoperative chemotherapy was investigated in eight, mostly very small randomised studies (seven comparisons against surgery alone and one in combination with postoperative chemotherapy again against surgery alone) (Malthaner et al. 2004; Baba et al. 2004). Only in two trials a significant improvement in overall survival could be found (Medical Research Council 2002; Kok et al. 1997), with the latter being published as an abstract only. Thus, only one full publication in favour of preoperative chemotherapy is available, which has included adenocarcinoma in two-thirds of the cases. Most other studies were poorly designed and too small to detect any significant difference in survival (Table 14.4). Of several meta-analyses only one showed an advantage in overall survival – and only at 5 years – in favour of preoperative chemotherapy. This advantage was mainly caused by the large MRC trial. Overall, there are rather weak arguments for chemotherapy in adenocarcinoma of the lower esophagus

Table 14.3. Randomised trials of preoperative radiotherapy (RT) and surgery versus surgery (S) alone. [Modified from MALTHANER et al.( 2004) and PATEL et al. (2004)] Author (year)

Number of patients

RT schedule

2-Year survival (%)

5-Year survival (%)

30-Day mortality (%)

S

RT+S

S

RT+S

S

RT+S

S

RT+S

Launois et al. (1981)

57

67

40 Gy/12 fr

35

20

12

10

23

23

Gignoux et al. (1987)

114

115

33 Gy/10 fr

30

24

9

10

17

24

Wang et al. (1989)

102

104

40 Gy/nr

nr

nr

30

35

6

5

Nygaard et al. (1992)

50

58

35 Gy/20 fr

13

25

Nr

nr

13

11

Arnott et al. (1992)

86

90

20 Gy/10 fr

28

22

17

9

12

14

Fok et al. (1994) 39

40

24-53 Gy/10-20 fr

36

34

16

10

8

30

fr, Fractions, nr, not reported.

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Table 14.4. Randomised trials of preoperative chemotherapy (CT) and surgery versus surgery (S) alone. [Modified from Malthaner et al. (2004) and Patel et al. (2004)] Author (year)

Number of patients

CT substances

2-Year survival (%)

5-Year survival (%)

30-Day mortality (%)

S

CT+S

S

CT+S

S

CT+S

S

CT+S

50

56

Cisplatin, bleomycin

13

6

nr

nr

10

11

Schlag et al. (1992) 24

22

Cisplatin, 5-FU

32 (1 year)

20 (1 year)

nr

nr

nr

nr

Maipang et al. (1994)

22

24

Cisplatin, vinblastine, 40 bleomycin

31

nr

nr

0

7

Law et al. (1997)

73

74

Cisplatin, 5-FU

31

44

0

28

9

8

74

74

Cisplatin, etoposide

11 months

18.5 months

nr

nr

0

1

Baba et al. (2000)

21

21

Cisplatin, 5-FU; leucovorin

41 months

34 months

44

38

0

2

Ancona et al. (2001)

47

47

Cisplatin, 5-FU

55

55

22

34

nr

nr

MRC OE02 (2002)a

402

400

Cisplatin, 5-FU

34

43

15

26

10

10

Nygaard et al. (1992)

Kok et al.

(1997)a,b

a Significant b Only

advantage for preoperative CT. median survival data reported.

(AEG I) and none for the treatment of squamous cell carcinoma. Therefore, preoperative chemotherapy is not recommended in locally advanced esophageal cancer (Patel et al. 2004; Malthaner et al. 2004). Preoperative Radiochemotherapy Preoperative RCT has been investigated in 12 trials published so far: eight studies compared preoperative RCT with resection alone, one trial compared preoperative RCT with preoperative RT, one trial compared preoperative RCT alone with preoperative RCT and hyperthermia, and two trials compared preoperative RCT with definitive RCT for all responders to initial RCT (Malthaner et al. 2004; Stahl et al. 2005; Bedenne et al. 2002). In most trials, cisplatin alone or in combination with 5-FU has been used, either in a simultaneous manner or as sequential RCT. A broad variation of radiation schedules has been applied, with different total doses (20 Gy–45.6 Gy), fractionations (1.8–2.0 Gy single dose to 1.2 Gy bid), and overall treatment time, resulting in a large difference in radiobiological effectiveness. Just in one out of eight trials comparing surgery alone with preoperative RCT and esophagectomy, neoadjuvant RCT was able to improve overall sur-

vival, and in one further trial to increase disease-free survival (Table 14.5). However, the former of these trials has included adenocarcinoma only, and was criticised for premature closure with accrual of only 113 patients, unusually poor survival in the surgeryalone arm and the lack of staging CT before surgery (Walsh et al. 1996). One study described superior outcome for patients with tumor response to preoperative treatment, with significantly improved overall survival in this subgroup (Apinop et al. 1994). The overall modest results can be explained at least in part by the small number of patients in six trials with less than 58 patients per arm each, and uncommon treatment concepts in two trials using sequential RCT or very low doses of radiation (Nygaard et al. 1992; Le Prise et al. 1994). In several meta-analyses, it became obvious that preoperative RCT improves overall survival after more than 3 years of follow-up for all histologies, though the number of patients with adenocarcinoma was very small [inclusion only in two trials (Urba et al. 2001; Walsh et al. 1996)]. At 3 years, the improvement was 11%, with a relative risk for multimodal treatment of 0.53 (p=0.03), even more pronounced for concurrent RCT (relative risk 0.45; p=0.005) (Malthaner et al. 2004; Fiorica et al. 2004). There have been no significant advantages

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Table 14.5. Randomised trials of preoperative radiochemotherapy (RCT) and surgery versus surgery (S) alone. [Modified from Malthaner et al. (2004) and Patel et al. (2004)] Author (year)

Number of patients

RCT concept

2-Year survival (%)

5-Year survival (%)

30-Day mortality (%)

S

RCT+S

S

RCT+S

S

RCT+S

S

RCT+S

Nygaard et al. (1992)

50

53

Cisplatin, bleomycin sequential RT 35 Gy

13

23

nr

nr

10

10

Le Prise et al. (1994)

45

41

Cisplatin, 5-FU concurrent RT 20 Gy

33

27

nr

nr

7

9

Apinop et al. (1994)

35

34

Cisplatin, 5-FU concurrent RT 40 Gy

23

30

10

24

0

6

Bosset et al. (1997)

139

143

Cisplatin, concurrent RT 37 Gy

43

48

32

33

4

13

Walsh et al. (1996)a

55

58

Cisplatin, 5-FU concurrent RT 40 Gy

26

37

nr

nr

3

8

Urba et al. (2001)

50

50

Cisplatin, 5-FU, vinblastine concurrent RT 45 Gy

38

42

10

20

4

2

Burmeister et al. (2005)

128

128

Cisplatin, 5-FU concurrent RT 35 Gy

nr

nr

24

26

6

4

Lee et al. (2004)

50

51

Cisplatin, 5-FU concurrent RT 45.6 Gy

57

55

nr

nr

2

2

nr, not reported;

a

significant advantage for preoperative RCT

either in overall or disease-free survival at 1- or 2years of follow-up. However, the most recent randomised trial has not been included in any of these meta-analyses, and this trial was negative for neoadjuvant treatment, due to a high local recurrence rate, probably based on the extraordinarily high surgery drop-out rate in the combined treatment arm, mainly caused by patient refusal (Lee et al. 2004). This study demonstrates the potential difficulties of neoadjuvant protocols. Toxicity can be severe, with up to more than 50% CTC II–IV haematological and gastrointestinal sequelae, each. Therefore, and based on studies comparing combined neoadjuvant RCT with definitive RCT (Stahl et al. 2005; Bedenne et al. 2002), neoadjuvant RCT can not be recommended as standard care outside of clinical trials. When offered, an optimal supportive care is essential, including a dedicated intensive care unit for perioperative monitoring of the patient (Stein et al. 2000). Radiochemotherapy vs. Esophagectomy So far, no study has been able to demonstrate any significant improvement in overall survival com-

paring preoperative RCT and resection with high dose RCT alone, or resection alone with RCT. Stahl et al. (2005) and Bedenne et al. (2002) both started with cisplatin- and 5-FU-based RCT and randomised patients to esophagectomy or continued RCT if the tumor was not progressing (Table 14.6). Bedenne et al.(2002) started with 455 patients, with 259 of them responding to RCT (30–46 Gy). They were randomised to resection or further RCT (up to 45–64 Gy total dose). Although they had a break for response evaluation, median survival (19.3 months vs. 17.7 months) and 2-year survival (40% vs. 34%) were not significantly different, and quality of life was similar in both arms. Dysphagia was worse in the RCT-alone arm, and social life, nausea, and vomiting were significantly worse after resection (Blazeby et al. 2003; Bonnetain et al. 2003). Stahl et al. (2005) conducted a randomised trial with a sequential chemo- and radiochemotherapy, and could not detect a significant difference in overall survival. However, they described a significant advantage in local tumor control for the resection arm, resulting in a significant improvement in recurrence-free survival at 2 years. This has been confirmed by Liao et al. (2004) in a retrospective

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Table 14.6. Randomised trials comparing resection +/– neoadjuvant radiochemotherapy (RCT) with definitive RCT Number of patients 259 Bedenne et al. (2002) (of 455)

Stahl et al. 177 (2005)

Chiu et al. (2005)

CT

RT

Resection

Median survival (months)

Mortality

Other

Cisplatin, 5-FU

30–46 Gy

Esophagectomy

17.7

9%

2-Year survival 34%

Cisplatin, 5-FU

45–64 Gy

19.3 (ns)

1 % (s.)

2-Year survival 40% (ns)

Cisplatin, 5-FU, leucovorin, etoposide

40 Gy

16

12.8 %

19% Local recurrence

Cisplatin, 5-FU, leucovorin, etoposide

> 60 Gy

15 (ns)

3.5 % (s.)

36% Local recurrence (ns)

nr

6.8 %

2-Year survival 54.5%

nr

0%

2-Year survival 58.3% (ns)

76

Esophagectomy

Esophagectomy Cisplatin, 5-FU

50–60 Gy

nr, not reported; ns, not significant.

study with stage II and III esophageal cancer, where local tumor control was significantly improved by esophagectomy after previous RCT, but radiation dose was low in this trial. As known from both experimental and clinical studies, sequential RCT as used by Stahl et al. (2005) is not the optimal concept of RCT, because initial chemotherapy might alter the patients tolerance for consecutive RCT, produce radioresistant tumor cells, or induce repopulation of cancer cells. Furthermore, the chemotherapy protocol with etoposide and leucovorin was far from optimal, because of the toxicity of these drugs and the fact that they have no proven value in esophageal cancer. Very preliminary data were published from a Chinese group (Chiu et al. 2005), where standard esophagectomy was randomised against RCT in esophageal squamous cell cancer. This very small trial did not report a significant difference in overall or recurrence-free survival. Therefore, it confirms previous studies that could not find a significant difference in survival even after neoadjuvant treatment in the resection arm. In summary, preoperative radio- and chemotherapy are not standard procedures in locally advanced esophageal cancer, independent of histological subgroup. For locally advanced tumors and those with close contact to the tracheobronchial tree, definitive RCT or preoperative RCT should

be considered. Optimal supportive care and close follow-up of the patients is an essential prerequisite in any case. 14.1.4.3.2.2 Postoperative Radio-, Chemo- and Radiochemotherapy

Postoperative Radiotherapy Nine randomised trials have been conducted with esophagectomy and postoperative radiotherapy as one treatment arm: five trials versus resection alone, and one trial versus pre- and postoperative radiotherapy (the latter with a significantly higher mortality rate in 207 eligible patients), one trial versus preoperative radiotherapy (82 patients included during 13 years, no difference in survival), one trial versus postoperative chemotherapy (253 patients, cisplatin and vindesine, no significant difference in survival), and one four-arm trial with immunotherapy versus postoperative RCT (174 patients, no significant advantage for any treatment arm) (Malthaner et al. 2004). The five trials comparing postoperative radiotherapy and resection with resection alone failed to show any improvement in overall survival (Table 14.7), confirmed by a negative meta-analysis (Malthaner et al. 2004), with one single trial

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Table 14.7. Randomised trials of postoperative radiotherapy (RT) and surgery versus surgery (S) alone. [Modified from Malthaner et al. (2004) and Patel et al. (2004)] Author (year)

Number of patients

RT concept

2-Year survival (%)

5-Year survival (%)

S

RT+S

S

RT+S

S

RT+S

119

102

45–55.8 Gy/25–31 fr

51

50

19

21

65

65

49–52.5 Gy/14–15 fr

25

18

nr

nr

Fok (1994)

39

42

45–53 Gy

36

17

16

10

Zieren et al. (1995)

35

33

45–55 Gy/25 fr

31

29

nr

nr

Xiao et al. (2003)

275

220

50–60 Gy/25–30 fr

nr

nr

32

41

Teniere et al. (1991) Fok et al.

(1993)a

fr, Fractions; nr, not reported. Significant disadvantage for postoperative RT.

a

even demonstrating an adverse effect of additional radiotherapy (Fok et al. 1993). However, three trials were able to demonstrate a significant decrease in local recurrence rate, but in two trials morbidity was increased. One trial included patients with close margins or even incomplete tumor resection (R1 resection), and even this study with an extraordinary risk of postoperative local tumor progression was not positive for additive radiotherapy (Fok et al. 1993). Therefore, there is neither a standard indication for postoperative radiation after complete nor after incomplete resection. Such treatment might be offered if the risk of distant metastases is low and the patient has recovered rapidly and completely from resection. The individual recommendation should be based on multidisciplinary discussion as well as the decision with an informed patient. Postoperative Chemotherapy Postoperative chemotherapy with cisplatin-based regimens has been compared with postoperative radiotherapy in one (mentioned above) and with surgery alone in three randomised trials. The latter failed to demonstrate any improvement in overall survival, both in early stage carcinoma (Ando et al. 1997) and in locally advanced tumors (Pouliquen et al. 1996), as did a pooled analysis by the Gastrointestinal Cancer DSG (Malthanher et al. 2004). A subgroup analysis in nodal-positive squamous cell carcinoma from a randomised Japanese trial described a significant advantage in 5-year survival in favour of postoperative chemotherapy (52% vs. 38% with resection alone, p=0.041) (Ando et al. 2003). However, stratification was based only on resection margin and not on nodal status. There-

fore this single study does not sufficiently justify postoperative chemotherapy in clinical routine. Postoperative Radiochemotherapy In the postoperative situation, the value of combined RCT has only been evaluated in one, very small randomised trial so far (Tachibana et al. 2003). A total of 45 patients have been included, and chemotherapy was based on cisplatin and 5-FU plus 50 Gy in the RCT arm. There was no significant difference in overall survival at 1, 3, and 5 years of follow-up. Therefore, there is no evidence or indication for adjuvant RCT in esophageal cancer even in locally advanced carcinoma (Malthaner et al. 2004). It might be reasonable to offer additive RCT in case of incomplete tumor resection (R1–2 resection) because of a high risk of local tumor progression as the first localisation of clinically apparent relapse. However, there is no data supporting this hypothesis and therefore, in individual cases the decision should be made together with the informed patient. Summarizing the conflicting data, there is no evidence supporting the idea of postoperative radio-, chemo- or radiochemotherapy – independent of the result of esophagectomy: R0 or R1–2 resection. However, in individual cases and with informed consent of the patient, it might be justified to offer an additional treatment to patients after incomplete tumor resection to avoid an early local tumor progression. The high toxicity after previous esophagectomy (hematotoxicity CTC III–IV > 20%, gastrointestinal toxicity CTC°III–IV > 30%) should be taken into account, and the patient should be offered a comprehensive supportive care program.

Applications in Esophageal and Gastric Cancer

14.1.4.4 Conclusion

Treatment decision and administration is a multidisciplinary task – radiologist, endoscopist, surgeon, medical and radiation oncologist should be involved, as well as the informed patient. There is evidence supporting concomitant RCT or resection for locally advanced disease with no superiority of one of these strategies, and less evidence for combinations of both – preoperative RCT and resection – for unresectable carcinoma in patients with good clinical condition. Even patients with locally advanced carcinoma (stage III) can be cured, with 5-year recurrence-free survival of about 20% (Wong et al. 2003; Kosho et al. 2004; Malthaner et al. 2004; Patel et al. 2004). However, combined treatment can cause severe side effects and, therefore, demands an extraordinary experience of the physician and a comprehensive supportive care program, starting immediately after diagnosis.

14.2 Gastric Cancer and Adenocarcinoma of the Esophagogastric Junction (AEG II and III) 14.2.1 Introduction Survival of gastrointestinal junction (AEG II and III) and gastric cancer patients is poor given that they frequently present with locally advanced or even regional or distant metastatic disease. The mainstay of care still is surgical resection. No additive treatment can compensate for a poor resection. It was recently confirmed that extended lymphadenectomy – gastrectomy with resection of the complete locoregional lymph nodes, so-called D2-resection – is the standard procedure, being superior to limited (D1) lymphadenectomy, presumed that splenectomy and distal pancreatectomy are avoided in order to limit the risk of toxicity. In adenocarcinoma of the esophagogastric junction (AEG II and III) total gastrectomy with transhiatal resection of the lower esophagus and a D2-lymphadenectomy are usually recommended. Nevertheless, the prognosis of patients with locally advanced tumors remains unsatisfactory in spite of radical resection. Locoregional tumor recurrence is common, with 30%–80% in stage II–IIIB, and distant metastases are also frequent, up to at least 40% (Gunderson 2002, Hundahl 2002). About 80% of

207

these recurrences emerge in the original tumor bed, at the anastomotic sites, or in non-resected regional lymph nodes. Approximately 25% are pure local recurrences, making it obvious that additional local treatment is essential (Smalley 2002). Noteworthy is that a more aggressive resection could not demonstrate improved results in two randomised trials. Therefore, it was reasonable to integrate pre- and postoperative chemo- and radiochemotherapy.

14.2.2 Preoperative Treatment 14.2.2.1 Preoperative Radiotherapy

Preoperative radiotherapy might sterilize tumor cells and induce a tumor remission, to increase the chance of R0 resection and to avoid tumor cell spread during resection. In one randomised trial from China 360 patients with tumors of the cardia received preoperative radiotherapy with 40 Gy, which significantly reduced the local recurrence rate from 52% after resection alone to 39% (p<0.025). The recurrence rate in the regional lymph nodes declined from 54% to 39% (p<0.005). Therefore, though the number of distant metastases was not influenced, the overall and recurrence free-survival was significantly improved (5-year overall survival: 30% vs. 20%, p=0.009). There was no increase in severe perioperative side effects, encouraging further studies of preoperative radiotherapy (Zhang et al. 1998). As long as such data are not available preoperative radiotherapy is not yet a standard procedure. 14.2.2.2 Preoperative Chemotherapy

Phase II trials have shown that preoperative chemotherapy is feasible, with acceptable toxicity and perioperative morbidity (Lordick and Siewert 2005). It has been shown that patients who responded to neoadjuvant treatment had improved survival compared with non-responders (Ott et al. 2003). A small randomised trial of preoperative chemotherapy compared with surgery alone in 56 patients could not demonstrate a benefit of chemotherapy, but was statistically underpowered (Songun et al. 1999). Recently, the first results of the only large randomised trial of perioperative chemotherapy (three

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cycles of epirubicine, cisplatin, 5-FU pre- and postoperatively each) were presented (Allum et al. 2003). A total of 503 patients with resectable stage II and III gastric cancer (89%) or lower esophageal cancer (11%) were enrolled in this multi-institutional study (Table 14.8). There was a significant downstaging in the chemotherapy arm (T3=49% vs. 64% in the surgery-only arm), but it failed to increase the R0 resection rate. Preoperative chemotherapy resulted in a statistically significant improvement in recurrencefree survival at 2 years (45% vs. 30%, p=0.002), but in just a borderline improvement of 2-year overall survival (48% vs. 40%, p=0.063). Long-term survival data is still lacking. There was no excess in surgical complication rates for neoadjuvant cases, and toxicities were acceptable with 91% of all preoperative chemotherapy applied as planned. However, there are some objections: only 53% of the patients started the planned postoperative chemotherapy due to toxicity. The surgical quality control was not optimal, with the type of resection being left to the discretion of the local surgeon. And the staging procedures did not in general include endoscopic ultrasound or diagnostic laparoscopy (Lordick and Siewert 2005; Macdonald 2005). In summary, there is a proven value of preoperative chemotherapy, but it is not yet the standard procedure for all locally advanced gastric cancers, because long-term follow-up and confirmatory data from other randomised trials are missing. It might be offered to patients with good performance status, optimal supportive care, high risk of incomplete resection (R1), locally advanced cancer (T3–4) and

proven positive regional lymph nodes. If preoperative chemotherapy is offered, it should be done in a dedicated and experienced center, and it should be discussed interdisciplinary whether postoperative chemo- or radiochemotherapy should be offered on the basis of the relative risk for locoregional versus distant tumor recurrence. 14.2.2.3 Preoperative Radiochemotherapy

A simultaneous RCT should theoretically increase the remission rate and, therefore, allow for higher rates of R0 resection. It combines the improved local efficacy of radiation therapy with simultaneous reduction of the high risk of distant micrometastases. Several phase-I/II studies of combined simultaneous RCT (40–50 Gy total dose, 5-FU, cisplatinum, leucovorin or paclitaxel) reported tumor remission in about 40%–70%, with complete remission in roughly 10%, but up to 30% in some very recent trials (Ajani et al. 2004). Recurrence-free survival (50% after 3 years) and overall survival (4-year survival of 60% in resected patients) were promising (Allal et al. 2005; Ajani et al. 2004). The perioperative morbidity and mortality seem not to be significantly increased, making preoperative RCT an interesting treatment modality for further studies in gastric cancer. In summary, data of preoperative treatment is scarce and, therefore, neither preoperative radionor radiochemotherapy can be recommended as a routine strategy, although the integration of new

Table 14.8. Preoperative chemotherapy in gastric cancer: results of selected phase II and III trials. [Modified from Lordick and Siewert (2005) and Allum et al. (2003)] Author (year)

Regimen

Number of patients

Median survival

2-Year survival

Wilke et al.(1989)

EAP

34

18 months

26%

Ajani et al. (1991)

EFP

25

15 months

44%

Kelsen et al. (1996)

Preop FAMTX Postop. ip. CDDP/FU,iv.FU

56

15 months

40%

Siewert et al. (1997)

CDDP,FU,FA

41

ns

56%

Ott et al. (2003)

PLF

42

25 months

ns

Hartgrink et al. (2004)

FAMTX

27

18 months

44%

Allum et al. (2003)

ECF

281

ns

48%

EAP, etoposide-adriamycin-cisplatin; EFP, etoposide-fluorouracil-cisplatin; FAMTX, fluorouracil-doxorubicin-methotrexate; FU, fluorouracil; FA, folinic acid; ip, intraperitoneal; iv, intravenous; PLF, cisplatin-leucovorin-fluorouracil; ECF, etoposide-cisplatin-fluorouracil; ns, not specified.

Applications in Esophageal and Gastric Cancer

substances (gemcitabine, irinotecan) showed promising results, which warrant larger clinical trials. Preoperative chemotherapy is proven effective in one large randomised trial, but the results were worse than in the Intergroup trial on postoperative RCT. Therefore, the search for the optimal perioperative treatment continues.

14.2.3 Intraoperative Radiotherapy The value of intraoperative radiotherapy (IORT) has been tested in three randomised trials with small patient numbers (<100 in each study) and in one large Japanese trial (211 patients), either alone or in combination with external beam radiotherapy. All studies confirmed an improved local tumor control. In those trials with high total doses and a complete coverage of the gastric area including locoregional lymph nodes, overall survival was also significantly improved: 5year survival rate of 83.5% vs. 61.8% in stage II, of 62.3% vs. 36.8 % in stage III, and 14.7% vs. 0% in stage IV, respectively, and 8-year survival rates of 55% vs. 35% in stage III with pure IORT. The median survival was increased from 9.1 to 21.4 months in another trial (Kramling et al. 1997; Ogata et al. 1995; Skoropad et al. 2000). The study by Skoropad et al. (2000) included only patients with no less than a D1 resection, sometimes extended to a D2 resection if suspicious lymph nodes were present, making this study comparable to trials with European surgical standard. In all trials radiosensitive structures and organs (small and large bowel, liver, kidneys) were spared and, therefore, all studies found no increase of perioperative morbidity. Therefore, IORT seems feasible and warrants further investigation in clinical trials, with D2 resection being performed in all patients. It is not yet proven whether the positive influence of IORT on local and regional tumor control will persist under these conditions.

209

14.2.4 Postoperative Treatment 14.2.4.1 Postoperative Radiotherapy

In most clinical trials, postoperative radiotherapy was applied after incomplete tumor resection or in tumors with an extraordinary high risk of local tumor recurrence such as T3 and N+. There is only one randomised study comparing postoperative radiotherapy with gastrectomy alone, with postoperative chemotherapy (mitomycin C, 5-FU, doxorubicin) being tested in a third arm. 436 patients have been included. Local tumor control was improved significantly by postoperative radiotherapy (90% vs. 81 % with resection vs. 73% with postoperative chemotherapy). This did not result in an improved 5-year survival (12% vs. 20% with resection vs. 19 % with postoperative chemotherapy) (Hallissey et al. 1994). However, one third of the patients did not receive the prescribed adjuvant treatment, with 24 % of the patients in the radiotherapy arm not being irradiated at all, and only 68 % being treated with at least 40.5 Gy. It can be concluded that there is no proven value of postoperative radiotherapy alone. 14.2.4.2 Postoperative Chemotherapy

Adjuvant systemic therapy has been widely tested in clinical trials, either alone or as part of combined RCT with curative intent. Only very few single trials have shown an advantage in disease-specific or overall survival, and only two trials outside of Asia with a small number of included patients have revealed a significant improvement in survival by adjuvant chemotherapy. Several meta-analyses could demonstrate only minimal effects of borderline significance in favour of adjuvant chemotherapy (Lordick and Siewert 2005). This can be explained in part by the high number of poorly designed trials and the limitations of literature-based meta-analy-

Table 14.9. Meta-analyses based on publications of randomised trials on postoperative chemotherapy in gastric cancer Author (year)

Number of studies

Number of patients

Odds ratio (confidence interval)

Hermans et al. (1993)

11

2096

0.88 (0.78–1.08)

Earle and Maroun (1999)

13

1990

0.80 (0.66–0.97)

Mari et al. (2000)

21

3658

0.82 (0.75–0.89)

Janunger et al. (2002)

21

3962

0.84 (0.74–0.96)

F. Zimmermann and B. L. D. M. Brücher

210

sis without original patient data. All authors concluded that there is no sufficient evidence to recommend adjuvant chemotherapy as a routine treatment (Table 14.9). Nevertheless, it might be important that subgroups apparently showed some benefit, such as the patients from the Asian studies and the patients with node-positive disease (Janunger et al. 2002). This can guide the design of new trials. 14.2.4.3 Postoperative Radiochemotherapy

Several phase I/II and two randomised phase III trials have shown a significant improvement in locoregional tumor control and overall survival in favour of postoperative RCT. They usually used 5FU (425 mg/sqm) and leucovorin (20 mg/sqm), and a conventionally fractionated radiotherapy (five fractions of 1.8 Gy per week, up to 45 Gy). In the largest trial, SWOG9008/INT0116, 603 patients were enrolled, with 556 of them being eligible. In both arms 85% of the patients had node-positive cancer (stage IIIA–IV). Gastrectomy without relevant lymph node dissection (
mortality but 73% grade III and IV toxicity, with 54% being hematological and 33% intestinal toxicity. This resulted in a limited tolerability, with only 181 out of 281 patients (64%) completing treatment as planned. It became obvious that radiation treatment planning had to be reviewed carefully to deliver this combined modality therapy safely and effectively. In all, 34% of radiation treatment plans had to be modified after review, and two-thirds of these deviations would have resulted in under-treatment whilst one-third might have caused severe or even life-threatening toxicity. There is some important criticism on this study, mainly related to the surgical procedure: the large number of inadequate lymph node resections makes it difficult to compare the results to European standards. There was no stratification for type of resection, and due to the small number of patients with D2 resection it remains unclear whether the improvement of survival would be maintained under adequate surgical conditions. More recently published data indicates that even after a more radical resection, postoperative RCT is feasible and results in extraordinary high local control rates (>90%) with 5-year survival of more than 40% (Kollmannsberger et al. 2003). In summary, there is a proven value of postoperative RCT in locally advanced gastric cancer, especially after limited resection with less than D1 lymph node dissection. It should be offered to patients with good performance status after resection and optimal supportive care when there was an incomplete resection (R1–2), T2–3 tumor without any locoregional lymph node dissection or T3 tumor with incomplete lymph node dissection (D1 dissection). It might be reasonable to offer adjuvant RCT to patients with positive lymph nodes after D2 dissection, but this has not

Table 14.10. Randomised trials on postoperative radiochemotherapy in gastric cancer Gunderson (2002)

5-Year survival

Median survival (months)

Locoregional recurrence rate

Op

23 patients

4%

15

54%

Op + postop RCT (5-FU)

39 patients

23%

24

39%

3-Year survival

Median survival (months)

Local recurrence rate

Macdonald et al. (2001, 2005) Op

275 patients

41%

26

29%

Op + postop CTx/RCT (5-FU, leucovorin)

281 patients

50%

35

19%

Applications in Esophageal and Gastric Cancer

been proven by prospective trials. If RCT is offered, it should be done in a dedicated and experienced center and according to the consensus report of the Intergroup to avoid undertreatment as well as severe and life-threatening toxicity (Macdonald 2005). It might be reasonable to avoid leucovorin concurrent with radiotherapy, based on data in rectal cancer where it increased toxicity without any improvement in tumor control.

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F. Zimmermann and B. L. D. M. Brücher for resectable esophageal squamous cell carcinoma. Ann Oncol 15:947–954 Le Prise E, Etienne PL, Meunier B, et al. (1994) A randomized study of chemotherapy, radiation therapy, and surgery versus surgery for localized squamous cell carcinoma of the esophagus. Cancer 73:1779–1784 Liao Z, Zhang Z, Jin J, et al. (2004) Esophagectomy after concurrent chemoradiotherapy improves locoregional control in clinical stage II or III esophageal cancer patients. Int J Radiat Oncol Biol Phys 60:1484–1493 Lordick F, Siewert JR (2005) Recent advances in multimodal treatment for gastric cancer: a review. Gastric Cancer 8:78–85 Macdonald JS, Smalley SR, Benedetti J, et al. (2001) Chemoradiotherapy after surgery compared with surgery alone for adenocarcinoma of the stomach or gastroesophageal junction. N Engl J Med 345:725–730 Macdonald JS (2005) Role of post-operative chemoradiation in resected gastric cancer. J Surg Oncol 90:166–170 Maipang T, Vasinanukorn P, Petpichetchian C, et al. (1994) Induction chemotherapy in the treatment of patients with carcinoma of the esophagus. J Surg Oncol 56:191–197 Malthaner RA, Wong RKS, Rumble B, Zuraw L, Gastrointestinal Cancer Disease Site Group of Cancer Care Ontario´s Program in Evidence-based Care (2004) Neoadjuvant or adjuvant therapy for resectable esophageal cancer: a systematic review and meta-analysis. BMC Medicine 2:35–52 Mari E, Floriani I, Tinazzi A, et al. (2000) Efficacy of adjuvant chemotherapy after curative resection for gastric cancer: a meta-analysis of published randomised trials. Ann Oncol 11:837–843 Medical Research Council Oesophageal Cancer Working Party (2002) Surgical resection with or without preoperative chemotherapy in oesophageal cancer: a randomized controlled trial. Lancet 359:1727–1733 Minsky BD, Pajak TF, Ginsberg RJ, et al. (2002) INT 0123 (Radiation Therapy Oncology Group 94-05) phase III trial combined-modality therapy for esophageal cancer: highdose versus standard-dose radiation therapy. J Clin Oncol 20:1167–1174 Nygaard K, Hagen S, Hansen HS, et al. (1992) Pre-operative radiotherapy prolongs survival in operable esophageal carcinoma: a randomized, multicenter study of pre-operative radiotherapy and chemotherapy. The second Scandinavian trial in esophageal cancer. World J Surg 16:1104-1109 Ogata T, Araki K, Matsuura K, et al (1995) A 10-year experience of intraoperative radiotherapy for gastric carcinoma and a new surgical method of creating a wider irradiation field for cases of total gastrectomy patients. Int J Radiat Oncol Biol Phys 32:341–347 Ott K, Sendler A, Becker K, et al. (2003) Neoadjuvant chemotherapy with cisplatin, 5-FU, and leucovorin (PLF) in locally advanced gastric cancer: a prospective phase II study. Gastric Cancer 6:159–167 Patel M, Ferry K, Franceschi D, et al. (2004) Esophageal carcinoma: current controversial topics. Cancer Invest 22:897–912 Pouliquen X, Levard H, Hay JM, et al. (1996) 5-Fluorouracil and cisplatin therapy after palliative surgical resection of squamous cell carcinoma of the esophagus. A multicenter randomized trial. French Association for Surgical Research. Ann Surg 223:127–133 Rebecca WO, Richard MA (2003) Combined chemotherapy and radiotherapy (without surgery) compared with radi-

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213 UICC (2002) TNM classification of malignant tumours, 6th edn. (Sobin LH, Wittekind Ch, eds). Wiley & Sons, New York Urba SG, Orringer MB, Turrisi A, et al. (2001) Randomized trial of preoperative chemoradiation versus surgery alone in patients with locoregional esophageal carcinoma. J Clin Oncol 19:305–313 von Rahden BH, Stein HJ (2004) Therapy of advanced esophageal malignancy. Curr Opin Gastroentrol 20:391–396 Walsh TN, Noonan N, Hollywood D, et al. (1996) A comparison of multimodal therapy and surgery for esophageal adenocarcinoma. N Engl J Med 335:462–467 Wang M, Gu XZ, Yin W, et al. (1989) Randomized clinical trial on the combination of preoperative irradiation and surgery in the treatment of esophageal carcinoma: report on 206 patients. Int J Radiat Oncol Biol Phys 16:325–327 Wang Y, Shi XH, He SQ, et al. (2002) Comparison between continuous accelerated hyperfractionated and latecourse accelerated hyperfractionated radiotherapy for esophageal carcinoma. In J Radiat Oncol Biol Phys 54:131–136 Wong RKS, Malthaner RA, Zuraw L, Rumble RB, The Cancer Care Ontario Practice Guidelines Initiative Gastrointestinal Cancer Disease Site Group (2003) Combined modality radiotherapy and chemotherapy in nonsurgical management of localized carcinoma of the esophagus. Int J Radiat Oncol Biol Phys 55:930–942 Wilke H, Preusser P, Fink U, et al. (1989) Preoperative chemotherapy in locally advanced and nonresectable gastric cancer: a phase II study with etoposide, doxorubicin, and cisplatin. J Clin Oncol 7:1318–1326 Xiao ZF, Yang ZY, Liang J, et al. (2003) Value of radiotherapy after radical surgery for esophageal carcinoma: a report of 495 patients. Ann Thorac Surg 75:331–336 Zhang ZX, Gu XZ, Yin WB, et al. (1998) Randomized clinical trial on the combination of preoperative irradiation and surgery in the treatment of adenocarcinoma of gastric cardia (AGC) – report on 370 patients. Int J Radiat Oncol Biol Phys 42:929–934 Zhao KL, Shi XH, Jiang GL, et al. (2005) Late course accelerated hyperfractionated radiotherapy plus concurrent chemotherapy for squamous cell carcinoma of the esophagus: a phase III randomized study. Int J Radiat Oncol Biol Phys 62:1014–1020 Zieren HU, Muller JM, Jacobi CA, et al. (1995) Adjuvant postoperative radiation therapy after curative resection of squamous cell carcinoma of the thoracic esophagus: a prospective randomised study. World J Surg 19:444–449

Novel Chemoradiation in Localized Pancreatic Cancer: Clinical Studies

215

15 Novel Chemoradiation in Localized Pancreatic Cancer: Clinical Studies Christopher H. Crane, Gauri Varadhachary, Peter W. T. Pisters, Douglas B. Evans, and Robert A. Wolff

CONTENTS 15.1 15.2 15.3

15.4 15.5 15.6 15.6.1 15.6.2 15.6.3 15.6.4 15.6.5 15.7 15.8 15.8.1 15.8.2 15.8.3

15.9

Introduction 215 Diagnosis, Staging, and Initial Management of Pancreatic Cancer 216 Chemoradiation as a Component of Multidisciplinary Management of Resectable Tumors 216 Principles of Chemoradiation in Locally Advanced Disease 217 5-Fluorouracil Based Chemoradiation Trials 217 Novel Chemoradiation Combinations 218 Gemcitabine-Based Chemoradiation Trials for Locally Advanced Disease 218 Paclitaxel-Based Chemoradiation 219 Capecitabine-Based Chemoradiation 220 Novel Molecular Targeted Approaches to Chemoradiation 220 Neoadjuvant Chemoradiation for Pancreatic Cancer: Clinical Studies 222 Down-Staging Patients With Locally Advanced Disease 224 Radiotherapy Technique and Dose 224 Adjuvant and Neoadjuvant Settings 224 Locally Advanced Disease 226 Intensity Modulated Radiotherapy (IMRT) or Stereotactic Radiation Therapy for Pancreatic Cancer? 226 Conclusion 227 References 227

C. H. Crane MD Department of Radiation Oncology, Box 97, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030, USA G. Varadhachary, MD R. A. Wolff, MD Department of Gastrointestinal Medical Oncology, Box 426, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030, USA P. W. T. Pisters, MD Douglas B. Evans, MD Department of Surgical Oncology, The University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030, USA

15.1 Introduction When the use of chemoradiation for localized pancreatic cancer is considered, it is important to appreciate several disease characteristics that differ greatly from those of most other malignancies. In patients who cannot undergo curative resection the median survival is usually less than 1 year, with eventual radiographic progression of local and distant disease occurring commonly after chemoradiation or chemotherapy treatment, and very modest improvement in median survival to be expected. Even if the primary tumor is completely resected, disease-specific mortality is typically at least 80% due to the problems of local disease recurrence and distant metastases. Most pancreatic cancer patients have some combination of host-related factors, such as advanced age, poor performance status, and medical comorbidity, or tumor related factors, such as anorexia and exocrine insufficiency, that often make them relatively poor candidates for aggressive therapy. Since outcome is so poor with standard therapies in localized pancreatic cancer, these patients are appropriate for clinical trials incorporating novel chemotherapeutic agents integrated with radiotherapy as a front line treatment option. While improved local tumor control with more effective radiosensitization could have a modest impact on median survival in patients with locally advanced and resectable pancreatic cancer, significant improvement in median survival duration will require the development of more effective novel chemotherapeutic regimens that address the dominant distant failure pattern. In contrast to diseases where local disease control is the dominant problem, optimal regimens for pancreatic cancer should include a robust systemic treatment in addition to effective local treatment. The use of novel chemotherapeutic agents and molecularly targeted therapies that selectively enhance the effects of radiotherapy and chemotherapy currently seems to be the most promising avenue of clinical pancreatic cancer research. Fortunately, investigators have placed more

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emphasis on pancreatic cancer in recent years than in the past, and clinical trials of novel treatments are ongoing. It is hoped that these efforts will lead to gradual improvements in outcome for patients with pancreatic cancer. In this chapter, the clinical principles of localized pancreatic cancer management are discussed with an emphasis on the role of novel radiosensitizers.

15.2 Diagnosis, Staging, and Initial Management of Pancreatic Cancer The initial goals in the evaluation and treatment of symptomatic patients are to determine resectability, establish a histologic diagnosis, and reestablish biliary tract outflow. Pancreatic cancer is diagnosed, clinically evaluated, and managed differently from center to center in the United States, and the definition of resectability after clinical evaluation varies from surgeon to surgeon. Accurate clinical staging is critical in the clinical management of pancreatic cancer. Abdominal computed tomography (CT) is the most common diagnostic imaging technique used to reliably confirm and determine the stage of suspected pancreatic malignancies. In many centers, endoscopic ultrasonographically guided fine-needle biopsy of the pancreas is the procedure of choice for the diagnosis of pancreatic malignancies. Biliary outflow can be easily reestablished with the endoscopic placement of an endobiliary stent. Accurate determination of resectability is the most important aspect of clinical staging. Surgical resectability is based on involvement of the superior mesenteric vessels and the celiac artery and its branches. Changes in the most recent American Joint Committee on Cancer (AJCC) staging system for exocrine pancreatic cancer reflect a clinical definition of resectability based on CT assessment. The T-stage designation classifies T1 through T3 tumors as potentially resectable and T4 tumors as locally advanced (unresectable). Tumors with any involvement of the superior mesenteric artery or celiac artery are classified as T4; however, tumors that involve the superior mesenteric, splenic, or portal veins are classified as T3 because these veins can be resected and reconstructed, provided that they are patent (American Joint Committee on Cancer 2002). Therefore, three criteria are necessary for resectability: (1) localized disease, (2) lack

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of involvement of the celiac axis or superior mesenteric artery, and (3) patency of the superior mesenteric/portal venous confluence. Inaccurate clinical determination of surgical resectability leads to incomplete resections which are not curative and do not prolong median survival (Neoptolemos et al. 2001). Inadequate clinical staging is a major problem in clinical practice and is reflected in the results of clinical trials of resected pancreatic cancer that have reported local tumor recurrence rates.

15.3 Chemoradiation as a Component of Multidisciplinary Management of Resectable Tumors Chemoradiation has been shown to reduce the probability of local tumor recurrence in patients with gastrointestinal malignancies who have undergone potentially curative surgery (Anonymous 1987; Krook et al. 1991; Kapiteijn et al. 2001; Macdonald et al. 2001). Locoregional control rates of 90% or greater are achieved in virtually every tumor site where combined modality approaches are the standard (head and neck cancer, breast cancer, sarcoma, rectal cancer). Improved local tumor control with the use of postoperative chemoradiation has also been shown to improve overall survival in many gastrointestinal tumor sites, including pancreatic cancer. Chemoradiation accomplishes this by eradicating microscopic residual disease remaining in the tumor bed after complete tumor resection or through the reduction in regional lymph node recurrence. In the case of pancreatic cancer, the retroperitoneal margin is nearly always close and often positive, and isolated lymph nodal recurrences are rare. Therefore, locoregional therapy in pancreatic cancer can be optimized with complete gross tumor resection and treatment of microscopic disease at the retroperitoneal margin with chemoradiation. With appropriate patient selection, multidisciplinary teamwork, and combined modality therapy, local disease control rates of 90% or greater are achievable in pancreatic cancer (Breslin et al. 2001). Unfortunately, however, nearly all multiinstitutional trials have reported strikingly high rates of local tumor recurrence. Local tumor recurrence (or more likely) persistence was identified as a component of the first site of failure in 39% of patients enrolled on the Gastrointestinal Tumor Study Group (GITSG)

Novel Chemoradiation in Localized Pancreatic Cancer: Clinical Studies

trial (Anonymous 1987), 53% of patients enrolled on the European Organisation for Research and Treatment of Cancer (EORTC) trial (Klinkenbijl et al. 1999), and 62% of patients enrolled on the ESPAC-1 trial (Neoptolemos et al. 2004). Given the universally recognized propensity for early and frequent distant disease recurrence in pancreatic cancer patients, first-site local recurrence rates this high can only mean that significant numbers of patients had incomplete gross resections. Attention to locoregional disease with appropriate clinical staging and surgical quality control is a critical starting point for future improvement in outcome in patients with resectable pancreatic cancer. Because resectable pancreatic cancer is an uncommon disease, we can realistically only expect gradual improvement in the proportion of patients undergoing gross total resections and locoregional control will remain a significant component of the pattern of disease recurrence in multiinstitutional studies. The investigation of novel radiosensitizers is therefore of interest in patients who have undergone pancreaticoduodenectomy.

15.4 Principles of Chemoradiation in Locally Advanced Disease Locally advanced pancreatic cancer is generally incurable and all therapies have significant limitations. Early clinical trials established that the concurrent use of 5-fluorouracil (5-FU) with radiotherapy afforded superior median survival compared to radiation alone (Anonymous 1979; Moertel et al. 1981) and to chemotherapy alone (Anonymous 1988), but these studies included small numbers of patients and are possibly not relevant in the context of newer chemotherapeutic agents and modern radiotherapy. In reality, patients probably benefit modestly from both systemic therapy and chemoradiation; these approaches are complementary and should both be considered in patients with locally advanced disease. Although there have been no new phase III chemoradiation trials in the last 20 years, the development of novel cytotoxic and targeted therapeutic agents over the past 8 years has stimulated the investigation of novel chemoradiation combinations in phase I and phase II trials. Since the impact of standard therapies is so limited, all patients with locally advanced pancreatic cancer should be considered for protocol-based

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therapy. Patients with locally advanced disease are usually eligible for clinical trials evaluating systemic therapy alone as well as trials evaluating novel chemoradiation regimens. If they refuse or are not eligible, patients should receive a relatively well-tolerated chemoradiation regimen, either preceded or followed by systemic gemcitabine-based chemotherapy. Unlike disease sites such as anal cancer, head and neck cancer, and cervical cancer where the primary purpose of concurrent chemotherapy is the enhancement of local disease control through radiosensitization, the ideal concurrent chemotherapeutic agent in the treatment of pancreatic cancer should have systemic activity as well as radiosensitizing properties. Additionally, because the median survival in patients with locally advanced disease is generally less than 1 year and the benefit of treatment is limited, the concurrent agent should be well tolerated with radiotherapy. Acute toxicity can be dramatically reduced if the radiation fields are confined to the gross primary tumor and clinically enlarged lymph nodes, regardless of the radiosensitizing chemotherapy that is used. Treating uninvolved regional lymph nodes requires larger amounts of gastric and duodenal mucosa to be treated which can lead to higher rates of gastrointestinal toxicity and is not likely to improve median survival.

15.5 5-Fluorouracil Based Chemoradiation Trials Chemoradiation therapy has been part of the foundation of therapy for locally advanced disease and has been shown to prolong survival compared to radiation alone and chemotherapy alone. In GITSG studies of 5-FU–based chemoradiation therapy in patients with locally advanced pancreatic adenocarcinoma (Anonymous 1979; Moertel et al. 1981) patients were randomly assigned to receive 40 Gy of radiation plus 5-FU, 60 Gy plus 5-FU, or 60 Gy without chemotherapy. Radiation therapy was delivered as a split course, with 20 Gy given over 2 weeks followed by a 2-week rest. 5-FU was delivered IV at a bolus dose of 500 mg/m2/day for the first 3 days of each 20-Gy cycle and given weekly (500 mg/m2) following the completion of chemoradiation therapy. The median survival was 10 months in each of the chemoradiation therapy groups and 6 months for the group that received 60 Gy without 5-FU.

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In subsequent GITSG studies, neither doxorubicin (Anonymous 1985) used as a radiation potentiator nor multidrug chemotherapy [streptozocin, mitomycin, and 5-FU (SMF)] alone or continued after chemoradiation therapy (Anonymous 1988) was found to be superior to 5-FU–based chemoradiation therapy. Additional chemotherapy after 5-FU–based chemoradiation therapy increased the toxicity without an apparent therapeutic benefit. In contrast to the results from the GITSG study demonstrating better survival with 5-FU–based chemoradiation therapy than with SMF chemotherapy alone, an Eastern Cooperative Oncology Group (ECOG) study suggested no benefit to chemoradiation therapy over 5-FU alone (Klaassen et al. 1985). The ECOG study randomly assigned patients with locally advanced or incompletely resected pancreatic adenocarcinoma to receive chemoradiation therapy (40 Gy and 600 mg/m 2/day 5-FU for 3 days) or 5-FU alone (600 mg/m 2/week). The chemoradiation therapy group received weekly bolus administration of 5-FU following chemoradiation therapy until there was evidence of disease progression. Similar to the GITSG studies, all patients were surgically staged and entered in the study within 6 weeks of surgery. Patients with incomplete resections and patients with limited peritoneal involvement were allowed to participate. The median survival was 8.3 months in the group that received chemoradiation therapy and 8.2 months in the group that received 5-FU alone. It was evident both in the GITSG studies and in the ECOG trial that patients with locally advanced, unresectable pancreatic cancer who are symptomatic to the point of not being fully ambulatory do not benefit from anticancer therapy. More recent trials of chemoradiation for locally advanced pancreatic cancer have investigated continuous-infusion 5-FU. The ECOG performed a phase I study to determine the maximal tolerated dose (MTD) of prolonged infusional 5-FU when combined with 59.4 Gy in patients with pancreatic or extrahepatic biliary tumors. The MTD of 5-FU was 250 mg/m 2/day, with gastrointestinal toxicity as the dose-limiting factor (Whittington et al. 1995). A subsequent study conducted in Japan demonstrated the feasibility of utilizing low-dose, continuous-infusion 5-FU (200 mg/m 2/day) given over 5.5 weeks combined with a single course of radiotherapy to 50.4 Gy for patients with locally advanced pancreatic cancer (Ishii et al. 1997). This was followed by weekly 5-FU treatments until disease progression was documented. In all, 85% of

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patients completed the chemoradiation therapy. The median survival of patients treated was 10 months, similar to the survival of patients treated with bolus 5-FU in the GITSG trials. Thus, while infusional 5FU may provide greater radiosensitivity compared with bolus 5-FU, no clear survival advantage has been established for this approach.

15.6 Novel Chemoradiation Combinations 15.6.1 Gemcitabine-Based Chemoradiation Trials for Locally Advanced Disease The introduction of gemcitabine was a modest step forward in the treatment of pancreatic cancer. Its value as a systemic agent in pancreatic cancer and the recognition of its radiosensitizing properties stimulated the study of combinations of gemcitabine with external beam irradiation (EBRT) for patients with localized pancreatic cancer (Blackstock et al. 1999; McGinn et al. 2001; Pipas et al. 2001; Wolff et al. 2001). Several strategies have been investigated including seven-weekly injections of gemcitabine with short course EBRT (30 Gy), twice-weekly gemcitabine with 50.4 Gy of EBRT, weekly gemcitabine with 50.4 Gy of EBRT, and full dose weekly gemcitabine with escalating doses of radiation. Most of these studies suggested gastrointestinal toxicity as a dose-limiting factor, but hematologic toxicity has also been observed. At the present time, there is no standard approach for combining gemcitabine and radiation, but several variables appear to be important in predicting the MTD. These include variations in the size of the radiation portal, the total radiation dose, possibly the dose of radiation per fraction, and whether gemcitabine is administered once or twice weekly (Crane et al. 2001a). Three multiinstitutional studies have been completed evaluating gemcitabine-based chemoradiation. In a small study performed in Taiwan, 34 patients with locally advanced pancreatic cancer were randomized to receive 5-FU based chemoradiation (500 mg/m 2 daily for 3 days, every 14 days with radiation to a total dose of 50.4–61.2 Gy) or gemcitabine and radiation (600 mg/m2 weekly with equivalent doses of radiation) (Li et al. 2003). The objective response rate to gemcitabine and radiation was 50% and only 13% for 5-FU chemoradiation. In addition, median survival was substan-

Novel Chemoradiation in Localized Pancreatic Cancer: Clinical Studies

tially better using gemcitabine compared with 5-FU (14.5 months versus 6.7 months, p=0.027). These efficacy results must be interpreted with caution because of the limited accrual (34 patients) and the poor results in the control group. Although the authors concluded that there was no increase in toxicity in the gemcitabine arm, therapy was actually poorly tolerated in both arms. Only 75% of patients were able to complete the full dose of radiotherapy and roughly one third of the patients in both arms were hospitalized for 2–6 weeks due to the acute toxicity of treatment. A phase II study conducted in patients with locally advanced pancreatic cancer by the Cancer and Leukemia Group B (CALGB) evaluated gemcitabine given at 40 mg/ m 2 twice weekly. In that study, there were 35% and 50% grade 3 or 4 gastrointestinal and hematologic toxicities, respectively, and the median survival was only 8.5 months (Blackstock et al. 2001). Not surprisingly, the CALGB abandoned this approach in locally advanced pancreatic cancer. Both of these studies used regional nodal fields that likely contributed to the significant gastrointestinal toxicity. In contrast, the approach that was developed at the University of Michigan delivers the manufacturer’s recommended dose of gemcitabine (1 g/m 2) and a slightly lower radiotherapy dose (36 Gy in 15 fractions over 3 weeks), with conformal radiation fields encompassing the gross tumor volume alone. At that institution, the irradiation of a smaller volume of normal tissue was reported to be well tolerated (McGinn et al. 2001). Investigators have since embarked on a multi-institutional phase II study evaluating the same regimen. Preliminary results indicate that approximately 25% of patients experience grade 3 or 4 gastrointestinal toxicity (McGinn et al. 2004). Several points about gemcitabine-based chemoradiation are worth emphasizing. Similar to its value as a systemic agent (Burris et al. 1997), gemcitabine is probably only modestly better than 5FU when it is used with radiotherapy, but it is not tolerated as well (Crane et al. 2002). The gastrointestinal toxicity reported in the three multi-institutional studies using gemcitabine demonstrate that the therapeutic ratio is narrow with the combination of gemcitabine and radiation. Typically, either the radiation dose or the gemcitabine dose must be attenuated if the combination is to be given safely. Finally, compared with radiotherapy fields that target the gross tumor only, elective regional nodal irradiation results in increased gastrointestinal toxicity. Certainly, if gemcitabine is used in

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combination with irradiation on esophageal, gastric, or duodenal mucosa, the volume of mucosa being treated should be minimized or there will be a significant risk of severe acute toxicity. While it is reasonable for investigators and clinicians with experience using any of these regimens to use them, a dose and schedule that is well tolerated in their experience should be used, particularly if the goal is to build on these studies through the incorporation of novel chemotherapeutic agents such as those that target tumor specific molecular pathways.

15.6.2 Paclitaxel-Based Chemoradiation Paclitaxel is a chemotherapeutic agent that has radiosensitizing properties as well as systemic activity in pancreatic cancer. It has been combined with radiotherapy in a phase I study that included patients with locally advanced pancreatic cancer (Safran et al. 1999). The dose-limiting toxicities were related to gastrointestinal effects in the radiation field: nausea, anorexia, and abdominal pain. At the dose recommended for further study, therapy was reported to be well tolerated. Subsequently, a phase II study was conducted by the RTOG. At a cost of significant but acceptable acute toxicity, patients achieved a median survival of 11.3 months, which compares favorably with that of historical control subjects (Rich et al. 2004). In an effort to build on this regimen, gemcitabine was combined with paclitaxel in RTOG PA-0020, which has recently reached full accrual (Willett et al. 2003). In a phase II study at M.D. Anderson Cancer Center of neoadjuvant chemoradiation in patients with potentially resectable tumors, the use of paclitaxel resulted in increased acute toxicity, but the histologic responses were similar to those in historical controls (Pisters et al. 2002). Because of this, paclitaxel was abandoned in favor of investigation of concurrent gemcitabine-based chemoradiation. Concurrent paclitaxel and radiotherapy can cause significant acute treatment-related morbidity. These studies all used radiation fields that targeted the regional lymph nodes. Treatment would likely be better tolerated if the gross tumor alone were treated.

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15.6.3 Capecitabine-Based Chemoradiation Capecitabine appears to have similar efficacy to intravenously administered 5-FU (Cassidy et al. 2004), and is an appropriate substitute for infusional or bolus 5-FU when used with radiotherapy. It is an orally administered agent that has a clinical benefit response similar to that of gemcitabine in patients with locally advanced or metastatic pancreatic cancer (Cartwright et al. 2002) and unlike gemcitabine can be given at systemic doses with regional nodal irradiation with a favorable toxicity profile in patients with locally advanced pancreatic cancer. In a recently published phase I trial, 800 mg/m 2 was the recommended dose when capecitabine was given on days of radiation only (Saif et al. 2005a). As demonstrated in a recently completed phase I trial conducted at our institution bevacizumab, capecitabine, and radiotherapy is also a well tolerated combination (discussed below), indicating that capecitabine may make an attractive chemoradiation platform upon which to integrate biologic agents. Only 2/47 (4%) of patients developed grade 3 gastrointestinal toxicity and there was no significant hematologic toxicity (Crane et al. 2006).

15.6.4 Novel Molecular Targeted Approaches to Chemoradiation Oncology has entered an era of molecular therapy, and details regarding the incorporation of molecular agents into anticancer therapy are discussed throughout this volume. In GI tumors, most notably colon cancer, agents such as bevacizumab and cetuximab have begun to change the standard of care for patients with advanced disease, and very recently erlotinib has shown some benefit in pancreatic cancer. Most investigations of these and other drugs have focused on their benefits as components of systemic therapy in patients with advanced disease, although investigation of their benefits in the adjuvant setting are now underway in colon cancer. However, these molecular therapies may play important roles as radiosensitizers. In pancreatic cancer, the anti-vascular endothelial growth factor (VEGF) agent bevacizumab has been combined with gemcitabine as a treatment for patients with advanced disease, and the drug’s radiosensitizing properties are now being appreciated clinically. The possible mechanisms of radiosensitization are not clear, but

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could include enhanced lethality of the endothelial cell (Gorski et al. 1999), the tumor cell (Wey et al. 2005), or the improvement in vascular physiology leading to a reduction in tumor hypoxia (Jain 2005). The first report of bevacizumab as a radiosensitizer was reported by Willett et al. (2004, 2005). In the 11 patients treated on this study, bevacizumab was administered prior to the initiation of radiation in a group of patients with rectal cancer. Rapid changes in tumor perfusion, interstitial intratumor pressure, and circulating endothelial cells were all observed. In a recently completed phase I dose escalation study conducted at our institution, capecitabine and bevacizumab were administered in combination with radiation (50.4 Gy) to 47 patients with locally advanced pancreatic cancer. The study demonstrated that bevacizumab is generally safe when combined with chemoradiation in patients with locally advanced pancreatic cancer. The acute toxicity was minimal and easily managed with dose adjustments of capecitabine, without interruption or attenuation of either the bevacizumab or radiation dose. Even though there was a 43% incidence of grade 2 gastrointestinal toxicity and a 21% incidence of grade 2 hand-foot syndrome, adjusting the dose of oral capecitabine in 43% of patients for grade 2 toxicity was sufficient to avoid grade 3 toxicity in the majority of patients. In addition, limiting radiotherapy fields to the gross tumor volume alone was probably a factor that contributed to minimizing the incidence of grade 3 acute toxicity to 4.3%. Bevacizumab did not appear to enhance acute toxicity; however, tumors with invasion of the duodenum appeared to be at higher risk for bleeding or perforation. Importantly, there were no bleeding events in the final 18 patients that were accrued after a protocol modification excluded patients with duodenal invasion. Overall, the tumors in nine (20%) of 46 evaluable patients had an objective partial response to initial therapy. This included 6 of 12 tumors treated at a dose of 5 mg/kg of bevacizumab (Crane et al. 2006). Despite the overall tolerability of this regimen, the four subacute mucosal adverse events (ulceration, bleeding, perforation) in the radiation field are concerning. These events occurred between 3 and 20 weeks after the completion of chemoradiation and were observed at each of the dose levels of bevacizumab. Since tumor-associated duodenal bleeding can occur in patients with locally advanced disease treated with chemoradiation alone (Saif et al. 2005b), it is not certain that these events are directly related to the addition of bevacizumab to chemoradiation. This potential risk should be

Novel Chemoradiation in Localized Pancreatic Cancer: Clinical Studies

assessed within the context of the possible improvement in local tumor control. In this study, there was a high percentage of confirmed radiographic tumor response (6 out of 12 patients at the 5mg/kg level) and durable stabilization of local disease in 28 of remaining 35 patients. Additionally, 4–20 weeks after the last dose of bevacizumab, four patients in our study underwent pancreaticoduodenectomy, a very complex operation, without perioperative complication. The RTOG has completed accrual on a phase II trial evaluating capecitabine-based chemoradiation with bevacizumab (RTOG PA04-11, Table 15.1) followed by systemic therapy with concurrent gemcitabine and bevacizumab. Patients with tumor invasion of the duodenum are specifically excluded due to the risk of duodenal hemorrhage, and preliminary toxicity analysis revealed similar low rates of gastrointestinal toxicity with only one grade 3 or greater bleeding event among 82 patients accrued. The American College of Surgical Oncology Group (ACOSOG) has proposed a phase II neoadjuvant study (Z5041) in patients who have radiographically resectable tumors. That study will incorporate concurrent bevacizumab and gemcitabine before pancreaticoduodenectomy and capecitabine, radiotherapy, and bevacizumab after pancreaticoduodenectomy. The recommended dose of bevacizumab

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for further study is 5 mg/kg every 2 weeks with radiotherapy (50.4 Gy in 28 fractions) and concurrent capecitabine (825 mg/m2 twice daily Monday through Friday). A phase III trial (CALGB 80303) is evaluating the 10 mg/kg dose with gemcitabine compared to gemcitabine alone in patients with metastatic disease. EGFR inhibitors also hold promise as radiosensitizers, although none of the currently available inhibitors (gefitinib, erlotinib, or cetuximab) have been evaluated in multiinstitutional trials in combination with radiation in locally advanced pancreatic cancer. A phase I dose escalation study has recently been published from Brown University combining gemcitabine, 75 mg/m2, and paclitaxel, 40 mg/m2, weekly and daily erlotinib with 50.4 Gy to the primary tumor and regional lymphatics. The maximum tolerated dose of erlotinib was 50 mg/m2. The median survival was 14 months and 6/13 (46%) of locally advanced patients had a partial response, indicating that erlotinib-based chemoradiation regimens are possibly worthy of further study (Iannitti et al. 2005). However, the inability to give full dose erlotinib could have been due to the concurrent gemcitabine and paclitaxel as well as the use of regional nodal irradiation. Another phase I study is ongoing at Memorial Sloan Kettering evaluating gemcitabinebased chemotherapy in combination with erlotinib.

Table 15.1. Selected trials for patients with locally advanced pancreatic cancer Study

Design

ECOG 1200

Randomized phase IIa

Arms

Endpoints 2

Gem 500 mg/m +Cisplatin + 5-FU, followed by PVI 5-FU + XRT 50.4 Gy + 5.5 weeks

Primary: resectability

Gem 500 mg/m2 weekly × 5 + XRT 50.4 Gy over 5.5 weeks ECOG/RTOG 4201

Randomized phase III

Gem 1 gm/m2 weekly × 3 (maximum 7 cycles) XRT 50.4 Gy over 5.5 weeks + Gem 600 mg/m2 followed by Gem 1 g/m2 weekly × 3 (maximum 5 cycles)

RTOG PA 0411

Phase II

XRT 50.4 Gy over 5.5 weeks + Cape 825 mg/m2 (PO BID Mon–Fri) + Bev 5 mg/kg every 2 weeks followed by Gem 1 g/m2 weekly × 3 (maximum 3 cycles) + Bev 5 mg/kg every 2 weeks

Primary: median OS Secondary: RR, RFS, toxicity, QOL

Primary: 1-year OS Secondary: RR, toxicity, QOL

PVI, protracted venous infusion; 5-FU, 5-fluorouracil; Gem, gemcitabine; Cape, capecitabine; Bev, bevacizumab; XRT, radiotherapy; OS, overall survival; RR, response rate; RFS, relapse-free survival; QOL, quality of life; BID, twice daily; PO, orally; RTOG, Radiation Therapy Oncology Group; ECOG, Eastern Cooperative Oncology Group. aIntended

for “marginally resectable” patients without vessel encasement.

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Cetuximab has been shown to improve local tumor control and overall survival in combination with EBRT alone in locally advanced head and neck cancer (Bonner et al. 2004). This study is the first phase III evidence that EGF inhibition with radiotherapy can improve outcome. Cooperative group trials are planning to evaluate both cetuximab and bevacizumab for their radiosensitizing properties in both the adjuvant (Table 15.1) and locally advanced settings (Table 15.2). A phase II study at our institution is evaluating gemcitabine, oxaliplatin and cetuximab, followed by capecitabine, radiation therapy (50.4 Gy) and cetuximab, followed by gemcitabine and cetuximab until progression. Trials that combine cetuximab or erlotinib with bevacizumab and EBRT for the treatment of pancreatic cancer are anticipated in the near future, as are studies that combine bevacizumab with gemcitabine and EBRT.

15.6.5 Neoadjuvant Chemoradiation for Pancreatic Cancer: Clinical Studies Neoadjuvant chemoradiation has been used as a strategy to improve tumor control rates in patients who have resectable disease at the time of clinical evaluation. The rationale for the use of neoadjuvant therapy, as opposed to postoperative adjuvant therapy, has been discussed in detail elsewhere (Pisters et al. 2005). Starting in 1988, investigators at the University of Texas M.D. Anderson Cancer Center have conducted a series of clinical trials evaluating neoadjuvant chemoradiation (Evans et al. 1992; Pisters et al. 1998, 2002; Wolff et al. 2001, 2002). These trials have had identical eligibility criteria using a CT-based definition of resectable disease, a requirement of biopsy proven adenocar-

Table 15.2. Selected multiinstitutional trials for patients with resectable adenocarcinoma of the pancreas Study

Design

Arms

ACOSOG Z5031

Phase II

XRT (50.4 Gy/5.5 weeks) + PVI 5-FU + IFN + CDDP weekly

EORTC 40013

Phase II/III (ydjuvant/post-op)

Surgery Gem Surgery Gem, then Gem + XRT

ESPAC-3

Phase III

5-FU + LV (No XRT) Gem (no XRT)

ECOG/GI Intergroupa

Randomized phase II (adjuvant/post-op)

Surgery Gem + C-225 Cape + C-225 + XRT (50.4 Gy/5.5 weeks) Gem + C-225 Surgery Gem + Bev Cape + Bev + XRT (50.4 Gy/5.5 weeks) Gem + Bev

ACOSOG Z5041a

Phase II (neoadjuvant/pre-op)

Gem + Bev Surgery Cape + XRT (45 Gy/5 weeks) + Bev

SWOG S0527a

Phase II (neoadjuvant/pre-op)

Gem + Ox C-225 + XRT (50.4 Gy/5.5 weeks) Surgery Gem + Ox

ECOG, Eastern Cooperative Oncology Group; GI, gastrointestinal; PVI, protracted venous infusion; 5-FU, 5-fluorouracil; CDDP, cisplatin; Gem, gemcitabine; Cape, capecitabine; C-225, cetuximab; Bev, bevacizumab; XRT, radiotherapy; RTOG, Radiation Therapy Oncology Group; ACOSOG, American College of Surgical Oncology Group; IFN, Interferon; SWOG, Southwest Oncology Group; Ox, oxaliplatin; EORTC, European Organization for Research and Treatment of Cancer ; ESPAC, European Study Group for Pancreatic Cancer. a

In development.

Novel Chemoradiation in Localized Pancreatic Cancer: Clinical Studies

cinoma of the pancreatic head, a uniform pancreaticoduodenectomy technique, and a standardized system for pathologic evaluation of surgical specimens including resection margins [as described by Pisters et al. (2005)]. The high frequency of positive-margin resections in clinical studies supports the concern that the retroperitoneal margin of excision, even when negative, may include a few millimeters of normal tissue, making surgery alone inadequate local therapy for most patients. Neoadjuvant treatment of the retroperitoneal margin prior to surgery appears to improve both the margin negative resection rate, and the prognosis of patients with microscopic positive resections. A total of 14% of patients treated with neoadjuvant chemoradiation at M.D. Anderson Cancer Center have had a microscopic positive margin (R1), none have had gross positive margins (R2), and patients with R1 resection have had a similar outcome to those patients with negative margin (R0). Radiographic evidence of local recurrence has occurred in only 10% of patients (Breslin et al. 2001). In contrast, patients treated with initial surgery with R1 or R2 resections without the use of neoadjuvant chemoradiation have consistently been reported to have inferior local tumor control and survival (Sohn et al. 2000; Breslin et al. 2001). Thus, high quality CT imaging, appropriate patient selection and neoadjuvant chemoradiation, followed by pancreaticoduodenectomy optimizes the treatment of the retroperitoneal margin and minimizes local tumor recurrence. The initial preoperative regimen at M. D. Anderson reported in 1992 was 50.4 Gy over 5.5 weeks (standard fractionation to the tumor and regional lymph nodes) with concurrent protracted infusional 5-FU (300 mg/m 2/day, Monday through Friday). In addition, intraoperative radiotherapy (IORT) was used in selected cases. Because of the significant acute gastrointestinal toxic effects (nausea, vomiting, and dehydration) hospital admission was required in approximately onethird of patients. Therefore, that radiation dose was modified in favor of a short course of “rapid fractionation” radiotherapy (30 Gy in 10 fractions over 2 weeks to the tumor and regional lymph nodes) using the same chemotherapy with a supplemental 10 Gy dose of IORT delivered at the time of surgical resection in all patients. The effective dose delivered to the tumor bed with the latter approach is comparable with that delivered with standard fractionation, based on linear quadratic modeling (Rich et al. 1997). Efficacy measures

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in these studies have included eventual resection, the degree of pathologic cell kill based on a standardized evaluation (Evans et al. 1992), and median survival. Although the pancreatic tumors remained technically resectable after chemoradiation, approximately 40% were not resected due to the recognition of metastatic disease at the time of radiographic restaging 4–5 weeks later (Pisters et al. 1998). A pathologic partial response to therapy (>50% of the tumor cells non-viable) was seen in approximately 40% of the specimens. Local tumor control and median survival were similar with the standard-fractionation (50.4 Gy in 5.5 weeks) and rapid-fractionation chemoradiation regimens and comparable to results of reported with postoperative chemoradiation (median survivals 18 and 25 months, respectively). Prior to the advent of gemcitabine, paclitaxel was investigated as a preoperative radiosensitizer in a group of patients with resectable pancreatic cancer. Paclitaxel did not provide an advantage over 5-FU-based chemoradiation in terms of toxicity, resection rate, local treatment effect, or overall survival (Pisters et al. 2002). Most recently, gemcitabine was incorporated with the same rapid-fractionation radiotherapy schedule and technique (Wolff et al. 2002). The dose of 400 mg/m 2 given weekly for 7 weeks was chosen based on a phase I trial in patients with locally advanced disease (Wolff et al. 2001). The use of IORT was omitted in that study due to the possibility of toxic effects of the combination of IORT and gemcitabine. A total of 86 patients were enrolled in this clinical trial. Toxicities were similar to those observed in the initial phase I trial. Despite a longer elapsed time from enrollment to surgery (pancreaticoduodenectomy) compared to previous trials with 5-FU and EBRT (11–12 weeks rather than 7–9 weeks), 74% of patients underwent successful pancreaticoduodenectomy (compared to 57%–60% with 5-FU-based chemoradiation). A pathologic partial response was seen in over half of the surgical specimens and there were two pathologic complete responses – something not observed in the 5-FU studies. Currently, patients with potentially resectable pancreatic cancer seen at our institution are receiving systemic therapy using a combination of gemcitabine and cisplatin, followed by gemcitabine-based chemoradiation prior to planned pancreaticoduodenectomy on protocol.

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15.7 Down-Staging Patients With Locally Advanced Disease There is a widespread perception that unresectable pancreatic tumors can be converted to resectable ones with the use of chemoradiation. The interpretation of whether this actually occurs is limited by inconsistent and subjective definitions of resectability and by inadequate preoperative radiologic assessments of resectability. Probably the most variable factor in determining resectability and thus interpreting whether a tumor has been converted to resectable from unresectable is the meaning of vascular involvement. Although most surgeons would agree that tumor encasement of either the celiac artery or the superior mesenteric artery constitutes unresectable disease, opinions vary with regard to more limited arterial involvement. It is probably in this group of patients that, theoretically, active cytotoxic therapy could lead to down-staging. At M.D. Anderson Cancer Center, patients with locally advanced tumors who have undergone margin-negative resections have typically had very limited arterial involvement (< one third the circumference and < 1 cm along the length of the artery) and tumors that have responded to chemoradiation (Crane et al. 2001). These cases are sometimes referred to as “marginally resectable.” Another factor affecting the determination of resectability and of whether resectability can be increased is the meaning of tumor involvement of the superior mesenteric/portal venous confluence. Tumor extension to a venous structure without occlusion is not an absolute contraindication to resection. Veins can be successfully resected and reconstructed at the time of pancreaticoduodenectomy. However, many surgeons would consider this type of tumor extension, seen either during surgery or on preoperative imaging, as evidence of unresectability. Thus, the attribution of increased resectability to chemoradiation in some studies could simply be due to a difference in surgical opinion and practice. Thus, the existence of broader definitions of locally advanced pancreatic cancer gives the impression that resectability is increased more commonly than it actually is. Another potential confounding variable in the interpretation of resectability is the lack of reproducible imaging before and after chemoradiation. Imaging that is not designed to address the issue of vascular involvement may not have resolution that is adequate for making an assessment. Thus, CT scans taken of the same patient at different

C. H. Crane et al.

times may result in different interpretations, even without therapy being administered. An objective clinical definition of resectability is critical in the assessment of patients with localized pancreatic cancer. In order to evaluate whether a particular therapy has converted an unresectable tumor to a resectable one, reproducible imaging with adequate resolution during phase contrast administration before and after chemoradiation must be used (Tamm et al. 2003). Although many studies have reported that increased resectability following chemoradiation has occurred, fulfillment of these criteria is the exception rather than the rule. Even with loose criteria and inconsistent imaging technique, down-staging after 5-FU–based chemoradiation is uncommon. Review of the available literature (Table 15.3) suggests that a small number (8%–16%) of clinically unresectable cases treated with chemoradiation eventually have undergone margin-negative resection regardless of the concurrent chemotherapeutic agent that has been used. The use of newer radiosensitizers, such as gemcitabine and capecitabine with biologic agents with radiotherapy could result in increased local tumor response and possibly increased resectability in patients with locally advanced disease, but this has not been clearly demonstrated yet. Ideally, all studies using novel chemoradiation regimens should adhere to a strict CT-based definition of locally advanced pancreatic cancer that includes arterial involvement (low-density tumor inseparable from the superior mesenteric artery or celiac axis on contrast-enhanced CT) or occlusion of the superior mesenteric/portal venous confluence when the issue of converting an unresectable tumor to a resectable one is addressed.

15.8 Radiotherapy Technique and Dose 15.8.1 Adjuvant and Neoadjuvant Settings The standard dose of radiotherapy in the postoperative setting is typically 50.4 Gy in 28 fractions. Field reductions are often made after 45 Gy. Standard fractionation EBRT to 50.4 Gy has also been used in the neoadjuvant setting. As discussed above, 30 Gy in 10 fractions has provided equivalent local tumor control especially when combined with gemcitabine as a radiosensitizer. It is likely that the

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Table 15.3. Experience with chemoradiation to allow eventual surgical resection in patients with locally advanced pancreatic cancer First author (year)

Number EBRT dose of patients (Gy)

Chemotherapy

Margin-nega- Median tive resections survival (%) (months)

Kornek et al. (2000)

38

55

5-FU+ LV+cisplatin

8

14

Bajetta et al. (1999)

32

50

5-DFUR

16

9

White et al. (1999)

25

45

5-FU + Mito (12) or cisplatin (10)

8

NA

Todd et al. (1998)

38

0

5-FU + LV + Mito + dipyridamole

11

15.5

Kamthan et al. (1997)

35

54

5-FU + STZ + cisplatin

14

15

Jessup et al. (1993)

16

45

5-FU

13

9.6‡

Jeekel and Treurniet-Donker (1991)

20

50 (split course) 5-FU

10

10

DiPetrillo et al. (2000)

40

50.4

Paclitaxel

8

8.5

Safran et al. (1999)

24

50.4

Paclitaxel

8

NA

McGinn et al. (2000)

22

24-50.4

Gem

23

NA

Brunner et al. (2000)

24

55.8

Gem + cisplatin

54

NA

Epelbaum et al. (2000)

20

50.4

Gem

10

12

Wilkowski et al. (2000)

10

45

Gem + 5-FU

40

NA

Crane et al. (2001)

51

30-33

Gem

12

11

48

50.4

Bevacizumab + capecitabine

8

14

5-FU-based chemoradiation

Taxol-based chemoradiation

Gemcitabine-based chemoradiation

Targeted Therapy Crane et al. (2006)

EBRT, external-beam radiation therapy; 5-FU, 5-fluorouracil; 5-DFUR, doxifluridine; Mito, mitomycin C; Gem, gemcitabine; LV, leucovorin; STZ, streptozocin.

majority of the benefit from chemoradiation results from the treatment of the retroperitoneal margin. While there may not be universal agreement about the size and shape of standard radiation fields, the superior mesenteric artery origin and the celiac axis must be covered with adequate margins. A three- or four-field technique using anterior, posterior, and opposed lateral fields allows critical tissues, such as the liver, kidneys, stomach, spinal cord, and small bowel, to be spared. For tumors located in the pancreatic head, the anterior and posterior fields typically cover the T11–L3 vertebral bodies, although the visceral anatomy is quite variable in relation

to the bony anatomy. The porta hepatis should be identified on CT and included in all fields. Inferiorly, the goal is to cover the tumor and duodenal bed with a 2-cm margin. The right border of the anterior and posterior fields and the anterior extent of the lateral fields are defined by the preoperative location of the duodenum. The left border of the anterior and posterior fields is placed 2 cm to the left of the vertebral body edge, as long as there is adequate coverage of the preoperative tumor volume. This usually means that the upper right border of the anterior and posterior fields is located 4–5 cm to the right of the vertebral body edge, and the anterior aspect of

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the lateral field is 5–6 cm from the anterior vertebral body edge. Blocking is placed over the inferior pole of the right kidney in the anterior and posterior fields, bisecting the vertebral bodies in the lateral fields. Corner blocks are typically placed in the anterior aspect of the lateral fields as well. Care should be taken not to block the preoperative tumor volume or the porta hepatis in the lateral fields. For lesions of the pancreatic body and tail, similar principles are applied to field location and the splenic hilum is covered while the porta hepatis and duodenal bed are not; the right field border is typically located 2 cm from the right vertebral body edge. Similar treatment fields are recommended for patients with an intact pancreas if the goal is neoadjuvant therapy with planned surgical resection. However, if the concurrent chemotherapeutic agent is gemcitabine, we recommend conformal radiation fields confined to the gross tumor, grossly enlarged adenopathy, superior mesenteric artery, and celiac axis.

15.8.2 Locally Advanced Disease Because patients with locally advanced tumors probably do not benefit from regional lymph node irradiation, radiotherapy fields should be confined to the gross tumor. This strategy reduces the gastrointestinal toxicity of chemoradiation. It is important therefore to identify the pancreatic tumor correctly. On contrast-enhanced CT, pancreatic tumors are typically hypodense compared with the surrounding pancreatic parenchyma. When there is doubt about the location of the primary tumor, the CT images should be reviewed with a diagnostic radiologist. Administration of an oral contrast agent at the time of simulation illuminates the duodenal “c-loop.” Endobiliary stents can also be visualized, which facilitates identifying the common bile duct. The pancreas and duodenum move a median of 1 cm with respiratory excursion (Bussels et al. 2003). If the gross tumor alone is to be treated, respiratory motion must be either controlled or accounted for in radiotherapy planning. The most common way that this is accomplished is by simply adding an additional margin to the planned radiation fields in the cranial and caudal directions. However, because axial tumor motion is negligible, an additional margin for motion in the axial directions is not necessary. Radiation treatment that is gated to the respiratory cycle (respiratory gating) (Balter et al. 1998) is a necessary component of radiation dose

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escalation studies that seek to deliver >60 Gy to the primary tumor while sparing the duodenum. Thus, radiation fields designed to spare the duodenum that are tightly confined to the primary tumor without correction for organ motion could lead to underdosing of the tumor target, or “marginal miss.”

15.8.3 Intensity Modulated Radiotherapy (IMRT) or Stereotactic Radiation Therapy for Pancreatic Cancer? IMRT and stereotactic radiation therapy are relatively recent technical innovations in radiotherapy. Both techniques are capable of very precise delivery of radiation to a target that is not moving. If that target is not near a radiosensitive structure, it is possible that the dose could safely be escalated, which may or may not improve outcome. Pancreatic tumors move considerably with respiration and are virtually always surrounded by the duodenum, which is a radiosensitive structure. Finally, dose escalation of radiotherapy beyond 50.4 Gy has never been demonstrated to improve outcome. We abandoned the investigation of IMRT after our phase I trial failed to reduce the toxicity of gemcitabine-based chemoradiation in spite of improved dose precision at the target (Crane et al. 2001). Stereotactic radiation therapy using a radiation delivery system known as the CyberKnife (Accuracy Inc., Sunnyvale, Ca.) with very careful control of organ motion using implanted metallic markers at the time of laparoscopy, laparotomy, or percutaneously under CT guidance, has been evaluated in a phase I dose escalation trial using a single fraction of radiation at Stanford University (Koong et al. 2004). The final dose of 25 Gy was well tolerated and has been recommended for further study. The median time to progression was 2 months and there have been no objective responses among an updated experience of 80 patients (Koong, personal communication, 7/05). This study was conducted at a center with very specialized capabilities that are not yet ready for use outside the setting of a clinical trial. Even so, the authors acknowledge that it was “impossible to avoid treating” the duodenum to a high dose in the majority of cases. Given the lack of any convincing prospective data, the constraints of organ motion, and the lack of any evidence that dose escalation in pancreatic cancer improves outcome in any meaningful way, there is no role for either IMRT or stereotactic radiation to be used outside the set-

Novel Chemoradiation in Localized Pancreatic Cancer: Clinical Studies

ting of a clinical trial in pancreatic cancer patients. As discussed in the previous section, treatment of locally advanced pancreatic cancer is very well tolerated and a modest median survival benefit is seen when the treatment volumes are confined to the gross tumor and clinically enlarged lymph nodes. This can be accomplished with a standard four-field conformal plan. The dose to the spinal cord, kidneys, and liver can very easily be kept within tolerance using this straightforward approach.

15.9 Conclusion Improving the treatment of pancreatic cancer is a challenge. Whenever possible, patients should be enrolled in investigational studies that evaluate novel therapies. Outside of a clinical trial, postoperative chemoradiation is the current standard adjuvant treatment after pancreaticoduodenectomy in the United States, but results from all randomized trials indicate significant rates of local tumor recurrence. For locally advanced disease, improving local tumor control rates is an important goal as well. In both cases, patients probably benefit from gemcitabine-based chemotherapy as well as chemoradiation. A strategy that incorporates both probably takes advantage of the best-available established therapies. The incorporation of molecularly targeted therapy with well-tolerated chemoradiation and chemotherapy regimens is a promising approach that addresses the limitations of conventional therapy without introducing unacceptable toxicity. Fortunately, investigators have placed more emphasis on pancreatic cancer in recent years than in the past, and many more clinical trials evaluating novel radiosensitizers are available to patients. Enrollment of patients in these studies is critical to the improvement of outcome in this disease.

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16 Applications in Lung Cancer Jochen Fleckenstein and Christian Rübe

CONTENTS 16.1 16.1.1 16.1.2 16.1.3 16.1.4 16.1.4.1 16.1.4.2 16.1.4.3 16.1.4.4 16.1.4.5 16.1.5 16.1.5.1 16.1.5.2 16.1.5.3 16.1.6 16.1.6.1 16.1.6.2 16.1.6.3 16.1.6.4 16.2 16.2.1 16.2.2 16.2.3 16.2.4

Non-Small Cell Lung Cancer 231 Introduction 231 Radiotherapy Regimens 231 Chemotherapeutic Agents 232 Rationale for a Multimodality Approach in (Potentially) Resectable Stage-III Disease 233 Prognostic Subgroups 233 Neoadjuvant Chemotherapy 233 Neoadjuvant Radiochemotherapy 234 Adjuvant Chemotherapy 236 Surgery vs Radiochemotherapy 236 Inoperable Stage-III Disease 238 Sequential vs Simultaneous Chemoradiotherapy 238 Sequential Plus Simultaneous Chemoradiotherapy 240 Radiochemotherapy and Consolidation Chemotherapy 241 Targeted Therapy/Novel Agents 241 Introduction 241 Inhibition of the Epidermal Growth Factor Receptor 242 COX-2 Inhibitors 243 Inhibition of Tumour Angiogenesis 243 Small-Cell Lung Cancer 243 Introduction 243 Radiotherapy Regimens 244 Chemotherapeutic Agents/Novel Agents 245 Sequencing of Radiochemotherapy 245 References 247

J. Fleckenstein, MD Department of Radiotherapy and Radiation Oncology, Saarland University Medical School, 66421, Homburg, Germany C. Rübe, MD, PhD Head of Department of Radiotherapy and Radiation Oncology, Saarland University Medical School, 66421, Homburg, Germany

16.1 Non-Small Cell Lung Cancer 16.1.1 Introduction For about two decades the development of multimodal treatment strategies in non-small-cell lung cancer (NSCLC) has led to some major, but often underestimated, progress in cure rates. This is especially the case for the locally advanced stages IIIA and IIIB, whereas in the early stages surgery continues to play the most dominant role and just recently the addition of chemotherapy became a therapeutic standard. The presumed superiority of multimodal therapy in the advanced stages can now generally be disregarded. At the same time the sheer number of possible treatment options with respect to, for example, the choice of chemotherapeutic agents, the sequence of available therapeutic elements, radiotherapeutic fractionation schedules and emergence of “targeted therapy options” create a complex problem to find “the right” multimodal approach for the individual patient. The simple division of patients into stages IIIA (which is particularly heterogeneous) and stage IIIB alone does not satisfy the needs for deciding upon the appropriate differential therapy. Some crucial other factors, such as, for example, age, (potential) resectability, general health status and cardiopulmonary function, and availability and quality of staging methods have to be weighted against each other and evaluated as prognostic factors in the context of a multimodality approach; thus, the necessity for optimal selection criteria as well as a renewal of the staging system can be derived from such considerations.

16.1.2 Radiotherapy Regimens In radiotherapy of NSCLC with curative intent tumour doses of 66 Gy in 2-Gy fractions can be considered as

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232

standard of care. The Radiation Therapy Oncology Group (RTOG) 73-01 dose-escalation trial (Perez et al. 1980) could initially show higher response rates and a lower incidence of local failure in patients treated with 60 Gy compared with patients treated with 40 or 50 Gy. Still, in only 15% of patients undergoing radiotherapy alone local tumour control could be achieved with doses of 65 Gy (Le Chevalier et al. 1991). To improve local control both higher radiation doses and the combination with chemotherapy are mandatory (Emami 1996). The RTOG trial 9311 (Bradley et al. 2005) examined the possibility of further dose escalation using a state-of-the-art threedimensional conformal radiotherapy. Depending on the percentage of the total lung volume that received >20 Gy [V(20)] patients were stratified at escalating radiation dose levels. For patients with V(20) values of <25% the radiation dose could safely be escalated to 83.8 Gy, and those with values of 25–36% could safely be escalated to 77.4 Gy, in conventional fractionation. Thereby locoregional control was achieved in 50–78% of patients. Excess mortality was oberserved at the 90.3-Gy dose level. The patients did not receive concomitant chemotherapy. If chemotherapy is being administered simultaneously, current indications suggest that the maximum tolerated dose is in the range of 70–74 Gy (Bradley 2005). Another potential means to enable individual dose escalation is the implementation of positron emission tomography (PET) in radiotherapy planning, which has been increasingly used during the past few years. The more safely the planning target volume can be confined to morphologically and functionally visible tumour manifestations, the easier it might be to allow for an increase in dose. In a Dutch planning study (De Ruysscher et al. 2005a,b) the use of PET-CT led to a significant increase in tolerable total dose from 55.2 Gy (only CT-based planning) to 68.9 Gy. The maximum tolerable dose was determined by equivalent estimated toxicity levels of the lungs, oesophagus and spinal cord. In a prospective clinical study by the same group (De Ruysscher et al. 2005a) 44 patients with NSCLC stages I–IIIB received an accelerated radiotherapy (without chemotherapy) exclusively of the primary tumour and the fluorodeoxyglucose (FDG)-PET positive mediastinal areas. The patterns of recurrence were thoroughly examined consecutively. The authors found a local recurrence in 11 patients (25%) after a median follow-up of 16 months, but only 1 patient developed an isolated nodal failure. Similar future trials with addition of chemotherapy will be needed to support the role of FDG-PET.

From a theoretical radiobiological viewpoint alternative fractionation regimens, i.e. especially a hyperfractionated accelerated radiotherapy, can be advantageous. By means of the reduction of the dose per fraction to less than 1.6 Gy, the late toxicity might be reduced while tumour response using twice-daily irradiation with at least 6 h interval should not be hampered. The shortening of total treatment time is supposed to antagonize the phenomenon of “accelerated repopulation” of clonogenic tumour cells during the course of radiotherapy. In this context the CHART study (continuous hyperfractionated accelerated radiotherapy) made an important contribution (Saunders et al. 1997). A total of 563 patients were accrued and received either CHART (three daily fractions of 1.5 Gy with 6-h interval on 12 consecutive days, i.e. weekends included) up to a total dose of 54 Gy, or a conventionally fractionated radiotherapy with 60 Gy in the control arm. The 2-year survival rate in the CHART arm was significantly increased to 30% compared with 21% in the control arm. This was due to an increased tumour control. In squamous cell carcinoma even a reduction in distant metastases could be observed. As expected, the incidence of acute toxicity, especially oesophagitis, was significantly higher in patients treated with CHART, whereas no significant differences considering late toxicity were oberserved. Mature results of the German multicentre-study CHARTWEL-Bronchus that examined the effectiveness of CHART without treatment on weekends, in comparison with a conventional regime with an increase in dose to 66 Gy, are awaited (Baumann et al. 1997). A preliminary presentation suggests that CHARTWEL to 60 Gy in 2.5 weeks was not superior (Baumann et al. 2005). Acute toxicity of CHART protocols certainly limits the applicability of simultaneous chemotherapy. A combination of hyperfractionated-accelerated radiotherapy and full-dose chemotherapy is feasible only if the total radiation dose is reduced to a maximum of 45–50 Gy (Jeremic et al. 1996). This limitation makes such protocols suitable for a neoadjuvant treatment setting (see 16.1.4.2) but, for toxicity reasons, inappropriate for definitive radiochemotherapy regimens.

16.1.3 Chemotherapeutic Agents The addition of chemotherapy in the treatment of non-metastasized NSCLC has to fulfil two major

Applications in Lung Cancer

premises: firstly, the substances used have to have a clear effect against the tumour itself; and secondly, the toxicity to the (radiation-) dose-limiting normal tissues should be minimal. The intrinsic tumour toxicity of chemotherapeutic agents can be best observed in the treatment of stage-IV disease. Derived from the experience in treating metastatic NSCLC, platinum-based chemotherapy regimens define the standard of care. Meanwhile a solid database exists demonstrating prolonged survival in stage-IV NSCLC when using platinum-based chemotherapy (Rapp et al. 1988). Le Chevalier et al. (1994) reported that administering cisplatin in a doublet with a second-generation agent can further increase median survival time (cisplatin + vinorelbine was superior to cisplatin alone). Meanwhile a variety of new chemotherapeutic agents with proven “single-agent activity” is available also for the use in combined radiochemotherapy regimens; these include, besides vinorelbine, paclitaxel, docetaxel, gemcitabine, irinotecan and topotecan. The Cancer and Leukemia Group B (CALGB) study 9431 (Vokes et al. 2002) evaluated three different platinum-based doublets in unresectable stage-III NSCLC. All patients were given two cycles of induction therapy followed by two additional cycles of the same drugs with concomitant radiotherapy (total dose 66 Gy, 2 Gy/day). Cisplatin was combined either with gemcitabine (arm 1), paclitaxel (arm 2) or vinorelbine (arm 3). Whereas generally no dose reduction of cisplatin is needed during radiotherapy (patients received 80 mg/m2 per cycle) the three new agents were given in a reduced dose during simultaneous chemoradiotherapy. The analysis included 175 patients. Incidence of grade-III and grade-IV oesophagitis during concomitant therapy was 49% (arm 1), 31% (arm 2) and 25% (arm 3). Tumour reduction (complete or partial remission) was observed in 58, 50 and 55%, and the median survival time was 18.3, 14.8 and 17.7 months, respectively. Even though the design of this phase-II trial does not allow for statistical comparison of the three arms, the combination of cisplatin and vinorelbine was quite clearly the most tolerable one. The observed survival rates exceeded those in former CALGB trials. In a meta-analysis questions concerning the temporal administration of chemotherapy during radiotherapy were addressed (Rakovitch et al. 2004). Ten studies involving 1802 patients were included. Comparing the daily administration of lower chemotherapy doses (mostly cisplatin) with higher doses administered weekly with respect to mortality and toxicity, no statistically significant difference between either of the schedules could be found.

233

16.1.4 Rationale for a Multimodality Approach in (Potentially) Resectable Stage-III Disease 16.1.4.1 Prognostic Subgroups

Especially in operable stage-III disease resection alone leads to poor long-term results, even though a wide range in 5-year survival rates from 6 to 35% is reported in different series (Vansteenkiste et al. 1998). This is basically due to the heterogeneity of stage IIIA and the prognostic relevance of the extent of N2 disease. In a large retrospective study 702 patients with resected N2 NSCLC were analyzed and subdivided according to their detailed N2-status: patients with clinical N2 (cN2) and those with minimal N2 (mN2) disease as well as involvement of one or multiple lymph node levels (N2L1 vs N2L2+; Andre et al. 2000). A multivariate analysis identified cN2 status, N2L2+, pT3 to T4 stage and no preoperative chemotherapy as negative prognostic factors. Five-year survival rates were 18 and 5% for cN2 patients treated with and without preoperative chemotherapy, respectively. Categorization of further subsets of stage IIIA(N2) has also been proposed (Ruckdeschel 1997) to establish more detailed and reliable criteria, e.g. to decide upon the indication for “upfront surgery”, which should be avoided in “bulky” (>2 cm in short-axis diameter) or “multistation” N2-disease (“IIIA4” according to Ruckdeschel’s subdivision; Robinson et al. 2003). As the term “resectability” is always somewhat subjective and dependent on the experience and judgement of the thoracic surgeon, a more objective basis is needed to select patients for tumour resection. Besides age, cardiopulmonary/functional status and other comorbidity, there is emerging evidence that poor response to induction therapy has a high negative predictive value, especially if FDG-PET is performed as a restaging procedure after induction therapy (Hellwig et al. 2004). Other important factors include the probability of pneumonectomy and R1-resection status. This topic is discussed in the following paragraphs. 16.1.4.2 Neoadjuvant Chemotherapy

As in stage IIIA, no satisfactory results concerning overall survival, local tumour control and incidence of distant metastases can be achieved with surgery as a single modality, adding neoadjuvant therapy

J. Fleckenstein and C. Rübe

234

may be an option to improve the treatment results. The strongest theoretical arguments, in general oncological terms, include preoperative sterilization of tumour cells to avoid intraoperative tumour cell spread, downsizing (or even downstaging) of the tumour to improve resectability, eradication of possibly present subclinical distant metastases and higher patient acceptance of induction compared with adjuvant therapy. On the other hand, one has to be aware of the delay in removal of the primary tumour as well as of the increase in perioperative morbidity or mortality. In Table 16.1 the most relevant studies addressing the topic induction chemotherapy are summarized. It is obvious that the total number of patients treated in these trials is small, and some did examine not only stage IIIA but also stages I and II. This is the case for the randomized trial conducted in France from 1991 until 1997 (Depierre et al. 2002). Three hundred seventy-three patients were enrolled with a subset of 167 stage-IIIA patients. Stages were determined clinically based on chest CT and all lymph nodes >1 cm in short axis were defined as positive. Invasive mediastinal staging did not take place, which makes the study prone to imbalances between treatment arms. No advantages of preoperative chemotherapy in survival were observed in the N2 subgroup. A positive effect of preoperative chemotherapy on survival were only observed in stages I and II. A significant survival benefit for all treated patients receiving chemotherapy could not be demonstrated

(median survival 37 vs 26 months; p=0.15). Results may have also been critically influenced by a surprisingly high rate of pneumonectomies (82%). More promising data were provided by the Spanish group (Rosell et al. 1994, 1999) and the M.D. Anderson Cancer Center (Roth et al. 1994, 1998). Rosell and coworkers (1994, 1999) compared three cycles of induction chemotherapy consisting of mitomycin, ifosfamide and cisplatin followed by surgery with surgery alone in stage IIIA (73% of patients underwent initial mediastinoscopy). Patients receiving induction chemotherapy had a significant survival advantage (median survival 22 vs 10 months, p<0.005; 2-year survival 29 vs 5%). Roth et al. (1998) carried through a similar study with 60 patients randomized between an induction chemotherapy arm (three cycles cyclophosphamide, etoposide, and cisplatin) followed by surgery and a surgery-alone arm. Of the patients, 83% were invasively staged prior to treatment. The median survival was 21 months for the chemotherapysurgery arm vs 14 months for the surgery-only arm (p<0.048). 16.1.4.3 Neoadjuvant Radiochemotherapy

Preoperative treatment can be intensified by adding simultaneous radiotherapy to induction chemotherapy in order to improve local control or even to eventually reach resectability in primarily unresectable disease. Several phase-II trials exist, which

Table 16.1. Induction chemotherapy vs surgery alone in stage-IIIA non-small-cell lung cancer (NSCLC): phase-III trials Reference

Induction arms

No. of patients

Median survival Survival (%) (months)

Pass et al. (1992)

Cisplatin, etoposide

27

29

42 (3 years)

16

12 (3 years)

None

(p=0.095) Roth et al. (1994, 1998)

Cisplatin, etoposide, cyclophosphamide

60

None

21

33

14

79 (R0 and pCR)

(p=0.048) Rosell et al. (1994, 1999)

Ifosfamide, mitomycin, cisplatin

60

None

22

46 (3 years), 36 (5 years)

10

19 (3 years), 15 (5 years)

(p<0.005) Depierre et al.

(2002)a

Mitomycin, cisplatin, ifosfamide

167

Not reported

None a

Trial enrolled 355 patients (stage IB–IIIA) with a proportion of 47% stage-IIIA disease

28 (5 years) 21 (5 years)

Applications in Lung Cancer

235

Table 16.2. Preoperative radiochemotherapy in stage-III NSCLC: phase-II trials Preoperative treatment

Patients stage IIIA/IIIB

R0 resectiona Total R0

pCR

Albain et al. (1995)

RT/CT

75/51

87 (69%)

Choi et al. (1997)

hfRT/CT

42/-

Eberhardt et al. (1998)

CT – hfRT/CT

52/42

Reference

Survival (%) 3 yearsb

TL (%)

39 (31%)

41 (R0+pCR)

10

34 (81%)

14 (33%)

79 (R0+pCR)

7

50 (53%)

24 (26%)

54 (R0)

6

56 (R0, TR>90%)

9

60 (R0+pCR)

7

(43%)c

Thomas et al. (1999)

CT – hfRT/CT

25/29

34 (63%)

23

Grunenwald et al. (2001)

hfRT/CT

-/40

23 (58%)

15 (38%)

CT chemotherapy, RT radiotherapy, hfRT hyperfractionated radiotherapy, hfRT/CT chemotherapy concurrent to hyperfractionated radiotherapy; TL therapy-associated lethality rate. a R0 resection: complete resection; pCR: pathologic complete response (in removed mediastinal lymph nodes) b Three-year survival rates in designated patient groups: R0, patients with complete resection; R0+pCR, patients with complete resection and pathologic complete response in removed mediastinal lymph nodes; R0 and TR>90%, patients with complete resection and tumour regression >90% in the primary lesion and removed mediastinal lymph nodes c Tumour regression >90%: <10% residual tumour cells detectable in the primary lesion and/or only focal microscopic tumour cells in removed mediastinal nodes

proved the feasibility of this concept (Table 16.2). The Southwest Oncology Group (SWOG) trial (Albain et al. 1995) is the largest of these trials and used concurrent conventionally fractionated radiochemotherapy. Like the other trials it aimed at achieving high rates of complete resection and complete pathological responses, which were mostly determined in removed mediastinal lymph nodes. Because both stages IIIA and IIIB were included in the listed phase-II trials and the total number of treated patients is low, firm conclusions cannot be drawn. It is also unclear whether the comparatively high therapy-associated lethality is due mainly to the high frequency of pneumonectomies or can at least be attributed partly to the intensified preoperative treatment. Meanwhile results have been provided of a phase-III trial conducted by the German Lung Cancer Cooperative Group (Thomas et al. 2004) evaluating the additional impact of simultaneous hyperfractionated radiochemotherapy (hfRT) on resectability and survival in patients with stage-III NSCLC. A total of 558 patients (of which 481 had available outcome data at time of publication with median follow-up of 46 months) were randomized after mandatory invasive mediastinal staging to (arm A) three cycles of cisplatin/etoposide (PE) followed by hfRT (45 Gy; 2u1.5 Gy/day) with concurrent carboplatin/vindesine, then surgery and, if no or R1/R2resection, additional hfRT vs (arm B) three cycles of PE followed by surgery and then RT (54 Gy, 1.8 Gy/

day) or, if no or R1/R2-resection 68.4 Gy. Patient characteristics were well balanced between treatment arms with a predominance of stage IIIB vs IIIA (69/66% vs 31/34%). Considering effectiveness no significant differences with respect to response rate after induction (52/47%; p=0.35), the proportion of patients with complete tumour resection (45/50%; p=0.30) and the progression-free survival (3-year rate 17/18%; p=0.37) were found, whereas the addition of radiochemotherapy caused a significantly higher rate of grade-3/4 oesophagitis (15 vs 4%; p<0.001). Interestingly, the occurrence of grade-3/4 pneumonitis was significantly more pronounced with postoperative radiotherapy. The authors concluded that these results do not necessitate the addition of radiochemotherapy to chemotherapy prior to planned surgery in stage-III disease. The chairs of the North American Intergroup Trial 0139 consider in the next trial generation to randomize stage IIIA patients between chemoradiotherapy followed by surgery and then further chemotherapy vs chemotherapy only followed by surgery and then further chemotherapy. So far, there is not enough evidence to administer preoperative radiochemotherapy outside clinical trials. The role of preoperative radiochemotherapy is further addressed in paragraph 16.1.4.5 (compared with definitive radiochemotherapy).

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16.1.4.4 Adjuvant Chemotherapy

As in stage IIIA no satisfactory results concerning overall survival, local tumour control and avoidance of distant metastases can be achieved by (upfront) surgery alone, in the 1980s additional adjuvant chemotherapy began to be investigated. Still, in most of these studies predominantly early stages were examined and stage IIIA rarely exceeded 20%. The NSCLC Collaborative Group performed a metaanalysis containing 52 randomized trials revealing a (non-significant) 5% reduction in the absolute risk of death in patients treated with adjuvant cisplatin-based chemotherapy vs surgery alone (p=0.08) in stages I–III (Stewart et al. 1995). Nevertheless, this meta-analysis has to be interpreted with caution, as in a substantial number of examined trials cisplatin was combined with substances now known to have only a small effect in NSCLC (e.g. doxorubicin, cyclophosphamide, 5-fluorouracil). Cisplatin was mostly given at comparatively low doses (40–60 mg/m2 instead of 80–120 mg/m2 per cycle) and the majority of patients did not receive the full prescribed chemotherapy dose according to the protocol. In a high priority North American Intergroup trial (Keller et al. 2000) also postoperative combined modality therapy in stages II and IIIA had no significant benefit over postoperative radiotherapy (PORT) alone. The median survival in patients receiving four 28-day cycles of cisplatin/etoposide concurrently with radiotherapy (50.4, 1.8 Gy/day) was 39 months compared with 38 months in the control arm (p=0.56). Rates of local recurrence were also similar (12 vs 13%; p=0.84). The Adjuvant Lung Project Italy (ALPI; Scagliotti et al. 2003) examined 937 eligible patients after surgery (310 with stage-IIIA disease), half of which received adjuvant chemotherapy with three cycles of cisplatin (100 mg/ m2), mitomycin and vindesine. But only 69% of these patients received all three planned cycles of chemotherapy. The option for additional radiotherapy was individually decided by each centre. After a median follow-up time of 64.5 months there was no statistically significant difference between the two patient groups in overall survival or progression-free survival. In contrast, the “International Adjuvant Lung Trial (IALT)” generated more promising data concerning the benefit of adjuvant chemotherapy (Arriagada et al. 2004). A total of 1867 patients (more than those included in the meta-analysis

J. Fleckenstein and C. Rübe

mentioned above) were randomly assigned to three or four cycles of cisplatin-based chemotherapy or to observation. Of the patients, 36.5% had pathological stage-I disease, 24.2% stage II and 39.3% stage III. In 56% of cases in the chemotherapy-arm cisplatin was combined with etoposide, vinorelbine in 26.8%, vinblastine in 11% and vindesine in 5.8%. Of the patients, 73.8% received at least 240 mg/m2 cisplatin. The median follow-up was 56 months. Patients with chemotherapy had both a significantly higher survival rate (44.5 vs 40.4% at 5 years; p<0.03) and disease-free survival rate (39.4 vs 34.3% at 5 years) than those without. The lethal toxicity in the chemotherapy-arm was 0.8%. No subgroup of patients could be identified that was more likely to benefit from chemotherapy. In an additional analysis, the IALT study demonstrated an advantage in diseasefree survival in patients with stage-IIIA receiving PORT (Rosell et al. 2005). The results of the IALT trial have recently been confirmed by the ANITA trial (Douillard et al. 2005), which included a total of 840 patients with NSCLC, postoperative stages I (T2N0), stage II or stage IIIA. Pneumonectomy was performed in 37% of patients, lobectomy in 58%. Radiotherapy policy was predetermined by each centre. After a median follow-up of >70 months at present median survival in patients having received adjuvant cisplatin/vinorelbine was 65.8 vs 43.7 months in the observation-arm (p=0.013). No benefit was observed in stage I. Five patients (1%) in the chemotherapy arm died of drug-related toxicity. Based on the results of the latter two trials adjuvant chemotherapy in stages IBIIIA is now being considered as the "new" standard of care. In this context the role of PORT certainly also has to be reevaluated as it remains unclear whether it should be conducted as a concurrent or sequential radiochemotherapy (and in which order) and even whether its intrinsic benefit on local control melts down if patients receive full-dose platin-based chemotherapy; thus, further randomized trials are needed to answer these questions. 16.1.4.5 Surgery vs Radiochemotherapy

Considering surgery and primary, definitive radiochemotherapy as two competing treatment options with curative potential in stage-III disease in a remarkable proportion of such patients it is not clearly evident which option should be preferred. In any case, it should first of all be differentiated between initially resectable and unresectable dis-

Applications in Lung Cancer

ease. For a number of reasons, not every patient with resectable disease might automatically be a first choice candidate for resection, whereas patients with unresectable might benefit from neoadjuvant (radio-) chemotherapy to render their disease resectable. This choice cannot be made by simple division into stages IIIA and IIIB. Apart from the phase-II trials discussed in paragraph 16.1.4.3, data from two phase-III trials have now been provided, which compare a trimodality approach (surgery after neoadjuvant radiochemotherapy) with definitive radiochemotherapy. The Intergroup trial 0139 (Albain et al. 2005) put its focus on primarily resectable stage IIIA(pN2) disease. All patients received cisplatin 50 mg/m 2 on days 1, 8, 29, 36, and etoposide 50 mg/m 2 days 15 and days 2933 (PE) and radiotherapy (RT) to 45 Gy (1.8 Gy/day) beginning on day 1. Arm 1 then had resection [if no progression (PD)], then two further cycles of chemotherapy (PEu2). Arm 2 completed RT to 61 Gy with subsequent PEu2. A total of 396 eligible patients were enrolled (arm 1, 202; arm 2, 194; wellbalanced for all factors). Progression-free survival was superior in arm 1 (median 12.8 vs 10.5 months; p=0.017), yet improvement in 5-year survival was not significant (22.4 vs 11%). Currently, more patients in arm 1 are alive without PD (p=0.008), but more died without PD (p=0.021). Overall survival (OS) curves overlap for 2 years, then separate and show a trend towards better survival in arm 1 (median OS 23.6 vs 22.2 months (p=0.24); 5-year OS 27.2 vs 20.3% [p=0.10, odds ratio 0.63 (0.36–1.10)]. The 5-year OS in arm 1 in the subgroup pN0 at surgery was 41%, pN1N3, 24% and no surgery (due to progressive disease) 8% (p<0.0001). Besides the survival data that were slightly beneficial for trimodality therapy, special attention has to be paid to the treatment-related side effects. The rate of treatmentrelated deaths in arm 1 was 7.9% (5% within 30 days postop) vs 2.1% in arm 2. It could clearly be shown that the risk of death was dependent on the type of surgery performed. Whereas only 1% of patients who underwent lobectomy died, the rate increased tremendously with simple pneumonectomy (22%) and complex pneumonectomy (29%). The authors concluded that (a) progression-free survival but not overall survival is significantly improved when surgery is performed in patients with stage IIIA (pN2) NSCLC, (b) there is a trend for better 5-year overall survival with trimodality therapy, (c) pN0 at surgery predicts long-term survival, (d) surgery after CT/RT can be considered in physically fit patients and (e)

237

the trimodality approach seems to be inappropriate if pneumonectomy is needed. The European Organisation for Research and Treatment of Cancer (EORTC) trial 08941, on the contrary, included patients with stage IIIAN2 NSCLC, whose tumours were initially considered as unresectable (Van Meerbeeck et al. 2005) and no neoadjuvant radiochemotherapy but induction chemotherapy only was administered. Selected patients first were given three cycles of platinum-based induction chemotherapy. Cisplatin or carboplatin were combined with either gemcitabine, paclitaxel or docetaxel (three phase-II trials to investigate the efficacy of these different induction-chemotherapy regimens were nested within this phase-III EORTC trial). Only responding patients (whose tumours were rendered resectable) were randomized between (a) radical resection with lymph node dissection and optional PORT, which was recommended only in case of incomplete resection, and (b) sequential thoracic radiotherapy (without concurrent chemotherapy) in shrinking-field technique to a total dose of 60 Gy (2 Gy/days). By means of induction chemotherapy an average response rate of 61.5% could be achieved; thus, finally 333 patients were randomized (167 to surgery and 166 to radiotherapy). In the 154 surgically treated patients the following rates were observed: exploratory thoracotomy 14%; radical resection 51%; pathological downstaging 42%; operative mortality 4%; and PORT in 39%. With a median follow-up of 72 months, median, 2- and 5-year overall survival for patients randomized to surgery or radiotherapy were 16.4 vs 17.5 months, 35 vs 41% and 16 vs 13%. Median and 2-year progression-free survival were 9.0 vs 11.4 months and 27 vs 24% respectively. It was concluded that surgery improved neither overall- nor progression-free survival as compared with thoracic radiotherapy. This weighs even more since it could be argued that radiotherapy was underdosed with 60 Gy and was not supplemented by simultaneous chemotherapy. In summary, in stage IIIA (N2) surgery seems to be a therapeutic tool of enormous value as long as no pneumonectomy is needed, as long as complete resection is achieved, the tumour is already initially resectable and patients are in good physical condition prior to surgery. These seem to be the most important selection criteria in this context.

J. Fleckenstein and C. Rübe

238

16.1.5 Inoperable Stage-III Disease 16.1.5.1 Sequential vs Simultaneous Chemoradiotherapy

There is general agreement that in “bulky N2-” and N3-situation, extensive mediastinal tumour invasion constitutes unresectable stage III disease, if it is not for impaired cardiopulmonary function that no surgery can be done. In three meta-analyses in the 1990s the superiority of combined radiochemotherapy over radiotherapy alone was confirmed (Stewart et al. 1995; Pritchard et al. 1996; Marino et al. 1997). Overall, there was 13–30% reduction in the risk of death with platinum-based chemotherapy regimens. The absolute benefit was 4% at 2 years and 2% at 5 years (p=0.05). Median survival times were increased from 9–11 months with radiotherapy alone to 12–14 months with combined radiochemotherapy. As mentioned previously, from the present point of view in most of the early studies both cisplatin and radiotherapy doses were comparatively low and especially with the emergence of 3D conformal radiotherapy more precise irradiation and doseescalated regimes became possible; thus, these older data can hardly be translated in the presence. Nevertheless, they already guided the way to multimodality treatment. Induction chemotherapy followed by radiotherapy alone has the theoretical advantage that higher doses of chemotherapeutic agents can be given to achieve a higher probability of initial eradication of

subclinical distant metastases. In Table 16.3 three prospective randomized clinical trials are presented, all designed to test the effectiveness of sequential chemoradiotherapy compared with radiotherapy alone. In the large British trial (Cullen et al. 1999) 15% of patients in the chemotherapy arm had a poor performance status of 2 (vs 11% in the control arm), which might – as well as the comparatively low radiation doses – have influenced the results. In the French trial by Le Chevalier and associates (1991) the distant failure rate for chemotherapy plus radiotherapy was lower than in the control arm (22 vs 46% at 1 year, respectively). On the other hand, locoregional failures were disappointingly high in both groups with 85 vs 83% at 1 year. In contrast to the sequential chemoradiotherapy approach, concomitant radiochemotherapy regimes perform better with respect to the crucial aim of locoregional control. The two most relevant studies to demonstrate improvement in survival by means of concomitant radiochemotherapy as compared with radiotherapy alone were published by SchaakeKoning et al. (1992) and Jeremic et al. (1996). The study by Schaake-Koning and associates (1992) from The Netherlands Cancer Institute, Amsterdam, randomly assigned 331 patients with nonmetastatic inoperable NSCLC to one of three treatment arms: (a) split-course radiotherapy alone (30 Gy, 3 Gy/ day, then a 3-week break followed by 25 Gy, 2.5 Gy/ day); (b) radiotherapy on the same schedule, combined with 30 mg/m2 cisplatin given on first day of each treatment week; (c) radiotherapy on the same schedule combined with 6 mg/m2 cisplatin, given daily before radiotherapy. Survival was significantly

Table 16.3. Sequential chemoradiotherapy in inoperable stage-III NSCLC: phase-III trials References

Design

No. of patients

Median survival (months)

Survival (%) 1 year

3 years

Dillmann et al. (1996)

2uPVbla-60 Gy vs 60 Gy

156

13.8 9.7

55 40

23 (p=0.007) 11

Le Chevalier et al. (1991)

3uPVbl-65 Gy vs 65 Gy

353

12 10

50 41

12 (p=0.002) 4

Sause et al. (2000)

2uPVbl-69.6 Gy (2u1.2 Gy) vs 2uPVbl-60 Gy vs 60 Gy

452

12.2

51

–

13.8 11.4

60 46

– –

MIPb-40–60 Gyc vs 4064 Gyc

446

11.7 9.7

16d

20d (p=0.14)

Cullen et al. (1999) a

PVbl: cisplatin/vinblastin mitomycin/ifosfamide/cisplatin cMedian: 50 Gy dTwo-year survival bMIP:

Applications in Lung Cancer

improved in the radiotherapy-daily-cisplatin group as compared with the radiotherapy group (54% 1 year, 26% 2 years, 16% 3 years vs 46, 13 and 2%, respectively; p=0.009). This survival advantage was attributed to improved local control (59% 1 year, 31% 2 years vs 41 and 19%, respectively). The weekly cisplatin-group results were intermediate and not significantly different from each other group. Considering the low doses of cisplatin administered in this study, the results strongly support the hypothesis for the existence of an intrinsic radiosensitizing effect of cisplatin. While split-course radiotherapy as used in the Netherlands trial has to be considered as unfavourable and obsolete, Jeremic et al. (1997) applied hyperfractionated-accelerated radiotherapy (hfRT) in their trial. A total of 131 patients received either (a) hfRT alone with 1.2 Gy twice daily to total dose of 69.6 Gy (n=66), or (b) same hfRT with concurrent chemotherapy (50 mg of carboplatin and 50 mg of etoposide given on each RT-day; n=65). The latter group had a significantly longer survival time: median survival time 22 vs 14 months and 4-year survival rates of 23 vs 9% (p=0.015). The median time to local recurrence and 4-year recurrencefree survival rate were also significantly higher in patients receiving chemotherapy (25 vs 20 months and 42 vs 19%, respectively). Distant-metastasis-free survival did not differ between groups. Incidence of acute and late high-grade toxicity was also similar. Based on these favourable data for additional chemotherapy, sequential or concomitant, several groups investigated sequential and concomitant radiochemotherapy in direct comparison. An important contribution to this topic was made by a Japanese study (Furuse et al. 1999). Patients in unresectable stage-III NSCLC received in the concurrent arm (n=156) cisplatin (80 mg/m2on days 1 and 29), vindesine (3 mg/m2 on days 1, 8, 29, 36) and mitomycin (8 mg/m2 on days 1, 29) and split-course radiotherapy to 56 Gy (2 Gy/fraction) with a 10-day break after 28 Gy. In the sequential arm (n=158), the same chemotherapy was given, followed by RT with 56 Gy, but without a break in the middle. Treatment arms were well balanced. The response rate in the concurrent arm was significantly higher (84%) than in the sequential arm (66%; p=0.0002). Median survival was higher in the concurrent arm (16.5 vs 13.3 months; p=0.039) as well as 2-, 3-, 4- and 5-year survival rates. While incidence of oesophagitis was identical in both treatment arms, in the concurrent arm the rate of myelosuppression was significantly higher.

239

These data in favour of concomitant radiochemotherapy were confirmed by a Czech study (Zatloukal et al. 2000; Zemanova et al. 2002) and the RTOG 9410 trial (Curran et al. 2000, 2003), which have only been published as abstracts thus far. The RTOG 9410 trial was designed as a three-arm randomized phase-III study comparing one sequential with two different concomitant radiochemotherapy concepts. In the sequential setting (arm 1) patients received cisplatin (100 mg/m2; days 1, 29) and vinblastine (5 mg/m2; five consecutive days; weekly) followed by conventionally fractioned RT to 60 Gy. In arm 2 the same chemotherapy was given concurrently to the same RT. Arm-3 patients received cisplatin (50 mg/m2, days 1, 8, 29, 36) and oral etoposide (50 mg, twice daily over 5 days in weeks 1, 2, 5 and 6) during hyperfractionated-accelerated RT (2u 1.2 Gy) to 69.6 Gy. Rates of acute grade-3 to grade-4 nonhaematological toxicity were higher with concurrent than sequential therapy but late toxicity rates were similar (595 analyzable patients). Concerning survival, patients in arm 2 had a significantly better 4-year survival than patients in the sequential arm 1 (21 vs 12%; p=0.046). In a recently published French phase-III trial (Fournel et al. 2005) a total of 205 patients in unresectable stage III were either assigned to sequential chemoradiotherapy (cisplatin, 120 mg/m2 on days 1, 29, 57 and vinorelbine, 30 mg/m2 week) from days 1– 78; afterwards thoracic radiotherapy with 66 Gy, 2 Gy/day) or concurrent chemoradiotherapy followed by consolidation chemotherapy (same radiotherapy, concurrently two cycles of cisplatin 20 mg/m2 day-1 and etoposide 50 mg/m2 day–1 (days 1–5 and 29–33, respectively), then consolidation therapy with cisplatin 80 mg/m2 on days 78 and 106, and vinorelbine 30 mg/m2 per week from days 7 to 127). Median survival was 14.5 months in the sequential arm and 16.3 months in the concurrent arm (p=0.24). Two-, 3-, and 4-year survival rates were also better in the concurrent arm (39, 25 and 21%, respectively) than in the sequential arm (26, 19 and 14%, respectively). Oesophageal toxicity was, as expected, significantly more frequent in the concurrent arm. The authors interpreted these survival differences, although significance levels were not reached, as clinically important, suggesting that concurrent chemoradiotherapy has to be considered as the optimal therapy at present. Flaws in this study certainly are the uncertainty remaining with respect to the role of consolidation chemotherapy as well as the use of different agents in induction and concurrently. Table 16.4 gives an additional overview of these four trials.

J. Fleckenstein and C. Rübe

240

Table 16.4. Sequential vs concurrent chemoradiotherapy in inoperable stage-III NSCLC: randomized trials Reference

Furuse et al. (1999)

Design

MVP a / 56 Gy conc.b MVP a

Curran et al. (1991)

Fournel et al. (2005)

Survival

156

16.5

p-value

Median % (months) (years) 19 (5)

0.04

Side effects (grades 3−4; %) Hematological

Oesophageal

98 h

3

76 h

2

–

–

158

13.3

9 (5)

595 g

14.6

12 (4)

VP d / 60 Gy conc.

17.0

21 (4)

–

–

PE e / 69.6 Gy conc.

15.2

17 (4)

–

–

14.5

14 (4)

88 i

3

16.3

21 (4)

75 i

32

13.0

12 (2)

39.6 i

4.2

20.4

42 (2)

64.7 i

17.6

VP c

/ 56 Gy seq.

No. of patients

/ 60 Gy seq.

VrP f / 66 Gy seq.

205 g

PE e / 66 Gy conc. / VrP Zemanova et al. (2002)

VrP f / 60 Gy seq.

Zatloukal et al. (2000)

VrP f / 60 Gy conc.

102 g

0.046

0.24

0.02

a

MVP = mitomycin + vindesine + cisplatin Split-course radiotherapy with 10-day break after 56 Gy c VP = vinblastine + cisplatin d VP = vinblastine + cisplatin e PE cisplatin + etoposide f VrP = vinorelbine + cisplatin g Total number of eligible patients h Leucopaenia i Neutropaenia b

16.1.5.2 Sequential Plus Simultaneous Chemoradiotherapy

To determine if intensification of therapy, i.e. combining the sequential and simultaneous approach leads to further improvement in outcome in irresectable stage-III NSCLC several phase-II and phase-III studies have been conducted. The German BROCAT group (Huber et al. 2003) assigned 219 patients, whose tumours did not progress under two cycles of induction chemotherapy with paclitaxel and carboplatin, to receive subsequently either radiotherapy alone (to a minimum of 60 Gy) or the same RT with simultaneous weekly paclitaxel (60 mg/m 2). Only preliminary data are available to date, leading the authors to conclude that the sequential plus concurrent approach with paclitaxel was feasible (discontinuation of paclitaxel due to allergy in 1.3% of patients), the toxicity was modestly increased and that more responses (complete and partial remission after 3 months of therapy 15.8 and 39.5%, respectively, vs 6.5 and 39.1% in the control arm) and less progression were observed. In the CALGB and ECOG phase-III trial conducted by Clamon and associates (1999) all

patients underwent induction chemotherapy and thereafter received either radiotherapy alone (to a total dose of 60 Gy) or the same radiotherapy with additional carboplatin (100 mg/m 2 per week) concurrently. In the latter arm (with 146 patients) the rate of complete responses was better (18 vs 10%; p=0.10) but with respect to failure-free survival (10% with carboplatin and 9% with RT alone) and overall survival at 4 years (13 vs 10%) no statistically significant difference could be detected. The authors concluded that concurrent carboplatin at the (low) dose given has, if at all, only minor impact on outcome. Vokes and coworkers (2004) presented a larger phase-III trial (CALGB 39801) as abstract, comparing induction therapy prior to simultaneous chemoradiotherapy with immediate chemoradiotherapy. As in induction, two cycles of carboplatin (AUC 6) and paclitaxel (200 mg/m 2) were administered, the simultaneous chemoradiotherapy consisted in each arm of carboplatin AUC 2 and paclitaxel 50 mg/m 2 given weekly during radiotherapy to 66 Gy. The combination of paclitaxel/ carboplatin was the most commonly used combination for locally advanced NSCLC at that time. A total of 366 patients were randomized. In the

Applications in Lung Cancer

sequential plus concurrent arm median survival was 14 months compared with 11.4 months in the concurrent arm (p=0.154). The sequential plus concurrent arm was significantly more toxic with an incidence in overall grade-4 toxicity of 41% of patients compared with 24% in the concurrent arm (p=0.001). The median survival in both arms is low for uncertain reasons. No indication for sequential plus concurrent chemoradiotherapy can be derived from this study. With a similar chemotherapy regimen as in the latter trial Choy et al. (2002) published preliminary data of a phase-II study including three different treatment concepts consisting of (a) sequential chemoradiotherapy [two cycles of paclitaxel/carboplatin followed by daily RT (63 Gy)], (b) sequential plus concurrent chemoradiotherapy (two cycles of the same chemotherapy followed by same RT and concurrent paclitaxel/carboplatin) and (c) concurrent plus consolidation chemoradiotherapy (same concurrent regime plus adjuvant paclitaxel/carboplatin). There was a trend towards better median survival times in the concurrent plus consolidation arm, which was also the most toxic one. In this arm 67% of patients completed the concurrent treatment and 75% completed consolidation chemotherapy. Lee et al. (2005) chose three cycles of gemcitabine and vinorelbine as induction agents in their recently published phase-II study with 42 patients with irresectable stage-III disease. Then patients underwent thoracic radiotherapy to 63 Gy (1.8 Gy/fraction) with concurrent cisplatin/etoposide. The median survival time was relatively high with 23.2 months. Whereas induction treatment was tolerated well, in the concurrent part, grade-3/4 haematological toxicity was observed in 76% of patients and grade-3 oesophagitis in 24% of patients, respectively. There were two treatment-related deaths. As the higher toxicity rates, which are consistently reported from concurrent radiochemotherapy demand a thorough patient selection and intensive surveillance of therapy and have to be watched even more carefully when adding induction chemotherapy, the trial performed by Lee et al. (2005) demonstrates that by using newer agents survival might be positively influenced. Overall, the sequential plus simultaneous approach can only be recommended if embedded in controlled clinical trials.

241

16.1.5.3 Radiochemotherapy and Consolidation Chemotherapy

In section 16.1.5.2 we already discussed the trial performed by Choy et al. (2002), which showed favourable results for concurrent radiochemotherapy plus maintenance chemotherapy. A further important contribution was made by Gandara et al. (2003), i.e. the phase-II SWOG trial S9504. The primary objective of this trial was to estimate, within the limitations of a historical comparison, whether substitution of docetaxel for continued cisplatin/etoposide, as used in the predecessor-trial S9019 (Albain et al. 2002), would improve survival at acceptable toxicity rates. In detail, 83 eligible patients with stage-III NSCLC underwent concurrent radiochemotherapy (RT to 61 Gy plus cisplatin 50 mg/m 2 days 1, 8, 29 and 36, and etoposide 50 mg/m 2 on days 15 and days 2933). Then, in the absence of progressive disease (78% of patients), consolidation therapy with docetaxel was initiated at 75 mg/m2 in cycle 1 and repeated every 3 weeks, with escalation to 100 mg/ m2 during cycles 2 and 3. Two patients died after concurrent therapy due to probably radiation-associated pneumonitis. Neutropaenia during consolidation docetaxel was common (57% with grade 4) and most frequent during escalation. Median progression-free survival was 16 months, median survival was 26 months, and 1-, 2-, and 3-year survival rates were 76, 54 and 37%, respectively. Brain metastases was the most common site of failure. In SWOG trial 9019 median survival was only 15 months, and 1-, 2-, and 3-year survival rates were 58, 34 and 17%, respectively. Based on these promising results an additional phase-III trial by the SWOG will follow to further examine the concept with docetaxel as consolidation treatment. In 2005 a German trial started (GILT-1), evaluating oral vinorelbine as consolidation therapy vs best supportive care after concurrent radiochemotherapy (RT to 66 Gy, 2 Gy/day plus two cycles cisplatin/oral vinorelbine).

16.1.6 Targeted Therapy/Novel Agents 16.1.6.1 Introduction

As Gridelli et al. (2003) expressed it, “Molecular targeted therapy describes treatment strategies that focus on cell signalling and other biological path-

J. Fleckenstein and C. Rübe

242

ways involved in tumorigenesis”. The “target” in the tumour cell can be any molecular structure which is involved in the steering of tumour cell growth. Based on current knowledge this can either be a growth-factor receptor on the cell surface, a protein or enzyme, which is essential in an important signal transduction pathway or another cellular molecular structure crucial for cell growth or division, apoptosis, cell migration or tumour angiogenesis. Function of these molecular targets can be critically impaired by means of interaction with “targeted” therapeutic agents such as (a) monoclonal antibodies aiming at (usually) proteins active in these processes, (b) small molecules interfering with or blocking enzymatic activity, (c) antisense constructs leading to downregulation of decisive protein transcription and (d) molecules exhibiting pharmacological interactions with subcellular structures of determined specificity. Emergence of numerous “novel agents” during the past couple of years opened a new dimension of effective cancer treatment to supplement conventional antitumoral strategies. An overview of different substance classes is given in Table 16.5. While a large amount of experimental data already exists, only few substances have reached clinical maturity; thus, knowledge of implementation of these novel agents in the treatment of lung cancer, especially in direct combination with radiotherapy, is still limited, and preliminary results are, in part, disillusioning, and in part, very promising. Subsequently, the currently most relevant agents are discussed in more detail.

16.1.6.2 Inhibition of the Epidermal Growth Factor Receptor

The EGF-receptor family has been paid most attention of the molecular targets, and efforts to create targeted small molecules resulted so far in the development of gefitinib and erlotinib as substances blocking the tyrosine kinase on the inner side of the cell membrane and, among others, cetuximab as a monoclonal antibody against the extracellular domain of EGFR. The EGFR plays a major role in (tumour-) cell proliferation and its overexpression has been associated with a more aggressive course of disease in a variety of malignancies including lung cancer (Salomon et al. 1995). The potential of gefitinib (Iressa) has been examined in several clinical trials. IDEAL-1 and IDEAL-2 were two randomized phase-II trials showing remission rates between 10 and 19% in patients with advanced (stages III and IV) NSCLC, who had already been previously treated with chemotherapy and had progressive disease (Kris et al. 2003; Fukuoka et al. 2003). In IDEAL-2 patients experienced improvement of symptoms in up to 85%, and median overall survival time was 8 months. Drug-related toxicity, consisting mainly of skin reactions and diarrhoea, was moderate. These promising results could not be confirmed in the INTACT-1 and INTACT-2 trials (Giaccone et al. 2004; Herbst et al. 2004); both were phase-III randomized trials examining the efficacy of gefitinib in combination with concurrent chemo-

Table 16.5. Examples of molecular targeted therapies Target structure

Mode of operation

Substances

Clinical studies with RT/RCT

Cell surface receptors with tyrosine kinase activity

Inhibition of epidermal growth factor receptor (e.g., by means of antibody or inhibition of tyrosine kinase)

Iressa, Tarceva, Erbitux, ABX-EGF

CALBG 30106; SWOG 5411, SWOG 0023

Angiogenesis (VEGF, matrix metalloproteinases, etc.)

Antibody to vascular endothelial growth factor (VEGF) receptor

Avastin, Neovastat, Vitaxin, Endostatin, Angiostatin, SU 11248

Phase-III study of CT + RCT in NSCLC stage III (Lu et al. 2003)

Ras mutation

For example, inhibition of farnesyltransferase

ISIS 2503,ISIS 5132, BAY 43-9006, CI-1040, Zarnestra, Sarasar

Phase-I study (Hahn et al. 2002)

COX-2

Inhibition of cyclooxygenase 2

Celebrex, Vioxx

Trials with NSCLC have been initiated (Vokes and Choy 2003)

Proteasome inhibitors

Inhibition of the NF-NB signaling pathway: induction of apoptosis; antiangiogenic effect

PS 341, Velcade

Planning of phase-I studies

Applications in Lung Cancer

therapy in altogether over 2000 patients with inoperable stage-III or stage-IV NSCLC. Neither in combination with gemcitabine and cisplatin (INTACT-1) nor with paclitaxel and carboplatin (INTACT-2) did additional gefitinib increase survival times. In INTACT-2 only a subgroup of patients with adenocarcinoma who received more than 90 days of chemotherapy demonstrated a statistically significantly prolonged survival, suggesting a gefitinib maintenance effect. In a similar population with stage-III or stage-IV NSCLC a phase-III study was conducted (“ISEL-trial”; Thatcher et al. 2005) to evaluate the impact of gefitinib as second- or third-line treatment vs best supportive care alone. A total of 1129 patients were assigned to gefitinib, 563 to placebo. As in previous studies, gefitinib given in a dose of 250 mg/m2 was well tolerated. At a median follow-up of 7.2 months, median survival did not differ significantly between the groups in the overall population (5.6 months for gefitinib and 5.1 months for placebo) or among the 812 patients with adenocarcinoma. Subgroup analyses showed significantly longer survival in the gefitinib group for never-smokers and patients of Asian origin (8.9 vs 6.1 months and 9.5 vs 5.5 months, respectively). More encouraging data have recently been published for the other far-developed tyrosine kinase inhibitor erlotinib (Tarceva). In a placebo-controlled double-blind trial the effect of erlotinib as second- or third-line agent in advanced NSCLC was determined (Sheperd et al. 2005). In the 731 patients who were assigned to the erlotinib arm an improvement of the response rate (8.9 vs <1% in the placebo group; p<0.001)), the median duration of response (7.9 vs 3.7 months), progression-free survival (2.2 vs 1.8 months; p<0.001) and also overall survival (6.7 vs 4.7 months; p<0.001) could be demonstrated. The response rates were significantly higher for patients with adenocarcinoma and patients of Asian origin, but not for patients with positive EGFR expression. Studies to evaluate erlotinib in combination with radiotherapy are being planned. Cetuximab (C225), which is a chimerized monoclonal antibody, also targets EGFR. Phase-II studies testing cetuximab exist for recurrent NSCLC (Lilenbaum et al. 2005), in which low overall toxicity rates were shown. There is also an ongoing trial in combination with chemoradiation (Werner-Wasik et al. 2005), whose first results concerning efficacy have to be awaited.

243

16.1.6.3 COX-2 Inhibitors

Overexpression of cyclooxygenase-2 (COX-2) is common in lung cancer and other malignancies, whereas it is rare in healthy tissue. Both in vitro and in vivo studies have shown enhancement of radiation response of tumour cells seemingly dependent on tumoral COX expression (Pyo et al. 2001). It has been suggested that the effect might be due to radiationinduced apoptosis (Milas et al. 1999) or a radiosensitizing effect (Petersen et al. 2000). Clinical trials to test the efficacy of COX-2 inhibitors with concurrent radiotherapy in patients with advanced NSCLC have been initiated, among them two RTOG trials. 16.1.6.4 Inhibition of Tumour Angiogenesis

As angiogenesis is a requirement for tumour growth, its inhibition could play a key role in treating cancer. A variety of drugs have been developed, inhibiting for instance matrix metalloproteinases (MMP) or the vascular endothelial growth factor (VEGF), like neovastat. In numerous experimental studies antiangiogenic substances were given concurrently with irradiation and an additional tumour growth delay could be demonstrated (Zips et al. 2003). Yet, so far no data are available from randomized clinical trials, so the use of such agents is still in the investigational phase.

16.2 Small-Cell Lung Cancer 16.2.1 Introduction Due to the strong propensity of small-cell lung cancer (SCLC) to cause metastases in the early course of disease, chemotherapy plays the central role in treatment. Whereas radiotherapy is beneficial in most patients with limited disease with respect to local control and survival, the role of surgery is confined to the earliest stage of SCLC (T1 N0 M0). Two metaanalyses confirmed the superiority of combination chemoradiotherapy over chemotherapy alone in limited disease (Pignon et al. 1992; Warde and Payne 1992). In patients receiving a combined treatment, the relative risk of death as compared with the chemotherapy group was 0.86 (95% confidence

244

interval 0.78–0.94; p=0.001), the 2-year local failure rate was 23 vs 48% and the 3-year survival rate 14.3 vs 8.9%. The survival benefit was shown to persist beyond 5 years. The two meta-analyses examined 13 studies, which included a total of 2140 patients and were initiated before or at the beginning of the 1980s. In none of theses studies was a concurrent radiochemotherapy regimen administered, and because of the technical and diagnostic restrictions at those times, radiotherapy was less conformal and more toxic than at present. The progress that has been made since then can be ascribed to alterations in fractionation of radiotherapy and sequencing and timing of radiochemotherapy. Yet, the best way of integrating chemotherapy and radiotherapy is still unclear. Different aspects in treatment optimization is outlined in the following paragraphs.

16.2.2 Radiotherapy Regimens As far as radiotherapy target volume is concerned, it is considered as common standard to treat the morphologically visible tumour and (potentially) involved hilar and (at least) ipsilateral mediastinal lymph node regions with an appropriate safety margin of 1.5 cm. Nevertheless, only one randomized trial was performed to examine this issue (Kies et al. 1987). No relevant differences in recurrence rates were found in this study between patients in whom either the pre- or post-chemotherapy tumour volumes were treated. This is in accordance with general treatment guidelines, in which, favourable also for toxicity reasons, confinement to the post-chemotherapy extension (as to the primary tumour) is recommended (Stuschke and Pöttgen 2004). More effort has been undertaken to evaluate the impact of different fractionation schedules on treatment outcome. Accelerated radiotherapy regimens seem attractive since (accelerated) repopulation obviously is an important mechanism of treatment failure. Tumour doubling times in SCLC are more rapid compared with other malignancies and especially NSCLC (Simon et al. 2001). Beyond that, SCLC tumour cells consistently show rather weak repair of radiation-induced sublethal damage as compared with other lung cancer cell lines (Duchesne et al. 1986; Carmichael et al. 1989; Brodin et al. 1991). In an Intergroup trial this knowledge was translated into a clinical setting: 417 patients with limited SCLC received four cycles of chemotherapy (cispla-

J. Fleckenstein and C. Rübe

tin/etoposide) upfront and were then randomized to undergo concurrent radiochemotherapy with either 45 Gy in two daily fractions of 1.5 Gy or with 45 Gy but once-daily 1.8 Gy (Turrisi et al. 1999). After a median follow-up of almost 8 years, the median survival for patients receiving twice-daily radiotherapy was 23 months, whereas it was 19 months for those receiving once-daily radiotherapy (p=0.04). Twoyear and 5-year survival rates for the twice-daily group were 47 and 26% vs 41 and 16% in the oncedaily group. As would be expected, the incidence of grade-3 oesophagitis was significantly higher in the twice-daily group (27 vs 11% in the once-daily group; p=0.001). This impressive improvement in survival by means of hyperfractionated-accelerated radiotherapy seems to vanish, if twice-daily irradiation is used in a split-course regimen; the latter was examined by Bonner et al. (1999) in 262 patients with limited-stage SCLC. In this randomized phase-III trial, patients having received induction chemotherapy were then assigned to receive either twicedaily radiotherapy concurrently with chemotherapy (2 cycles cisplatin/etoposide) with 48 Gy in 32 fractions, with a 2.5-week break after the initial 24 or 50.4 Gy in 28 fractions without a break and the same concurrent chemotherapy. No differences between the two treatment arms could be demonstrated with respect to progression rates or overall survival; therefore, these results support the hypothesis that in radiotherapy of SCLC a short overall treatment time is of major importance. Another important issue is the definition of the appropriate total dose. Unlike in NSCLC, in SCLC high rates of partial and complete remissions are observed at doses of 4550 Gy in conventional fractionation. This dose range became a treatment standard in limited stage SCLC since toxicity is acceptable at this level, the tumour is radiosensitive and patients have to receive an intensive chemotherapy in addition. Lower doses than used in the treatment of NSCLC were also considered to be sufficient as control of micrometastatic disease was regarded as crucial with respect to prognosis rather than sustained local control. In fact, beneficial effects of further dose escalation could not consistently be shown. Arriagada et al. (1992) reviewed data of phase-II trials of the French Cancer Centers’ Lung Group. In these trials, a proportion of patients received higher doses of up to 65 Gy, but no improvement in local control was observed. The results have to be inter-

Applications in Lung Cancer

preted cautiously, as the radiotherapy applied in these trials consisted of split-course regimens. In the recently published RTOG 97-12 phase-I trial a dose escalation was performed to 64.8 Gy (Komaki et al. 2005). Sixty-four patients received four cycles of cisplatin (60 mg/m2) and etoposide (120 mg/m 2; days 1–3) with concurrent radiotherapy, starting as once-daily RT with 1.8 to 36 Gy, and subsequently in the different arms given twice daily as concomitant boost and increased from 50.4 to 64.8 Gy. The authors found that 61.2 Gy was the maximum tolerated dose in this setting with grade-3 acute oesophagitis in 2 of 11 patients. The authors also suggested an improvement in the estimated short-term survival (18 months) by dose escalation from 50.4 to 61.2 Gy (25 vs 82%, respectively). On this basis a phase-III trial will be initiated by the RTOG to show if current dose recommendations might be too low.

16.2.3 Chemotherapeutic Agents/Novel Agents Whereas cyclophosphamide formerly was the key agent in the treatment of SCLC, presently, at least in limited disease, platinum-based chemotherapy regimens have become the standard. In three meta-analyses the superiority of platinum-containing chemotherapy [mostly combined with etoposide (EP)] was demonstrated (Chute et al. 1997; Mascaux et al. 2000; Pujol et al. 2000). Especially in combination with radiotherapy, rates of myelosuppression, oesophagitis and pneumonitis were lower with EP than with cyclophamide, vincristine and an additional anthracycline (Sundstrom et al. 2002). Carboplatin can apparently be given instead of cisplatin without measurable loss of activity but with improved tolerance. The Hellenic Cooperative Oncology Group examined 147 patients who received etoposide (100 mg/m2; days 1–3) and cisplatin (100 mg/m2) or carboplatin (300 mg/m 2) concurrently with radiotherapy (Skarlos et al. 1994). Response and survival were similar in both arms with significantly lower toxicity in patients receiving carboplatin, particularly nausea, vomiting, nephroand neurotoxicity and (not significantly) lower rates of myelosuppression. As to newer substances, especially paclitaxel, ifosfamide, topotecan, and irinotecan, some phase-II studies demonstrated feasibility in a combined radiochemotherapy regimen, although superiority to the combination of cisplatin and etoposide has

245

not yet been demonstrated. Particularly the role of irinotecan is actively being investigated, since in extensive SCLC the combination of irinotecan and cisplatin has been proven to be superior to etoposide and cisplatin with respect to median survival and 2-year survival (Noda et al. 2002). As far as the issue “targeted therapy” in context with SCLC is concerned, much less data and experience exists than in the treatment of NSCLC. Some phase-I and phase-II studies are ongoing, testing some of the novel agents discussed in section 16.1.6, but no conclusive data are available yet. Special focus is put on a subset of receptor tyrosine kinase, so-called c-KIT RTK, which is commonly overexpressed in SCLC cells and might be an excellent target in SCLC (Wang et al. 2000). A substance blocking c-KIT activity is imatinib mesylate, which is being evaluated in clinical studies (Johnson et al. 2002). Fossella et al. (2002) are performing a phase-I study with BB-10901, which is an immunoconjugate tumour-activated prodrug under development for the treatment of SCLC and other neuroendocrine malignancies. The conjugate is bound specifically by the tumour cell, internalized and then an antimitotic cytotoxine is released.

16.2.4 Sequencing of Radiochemotherapy A continuing debate addresses two major issues in the integration of chemotherapy and radiotherapy. Should radiotherapy be implemented early or late in the treatment concept, and is it advantageous to administer chemotherapy simultaneously or rather sequentially? As Erridge and Murray (2003) outlined in their review paper, reasonable arguments both for early and late radiotherapy exist. From a theoretical point of view the following considerations support early radiotherapy, conducted preferably as an early simultaneous radiochemotherapy: initially (immediately after diagnosis and staging) the probability of microscopic distant metastastic disease is lowest; therefore, for the sake of prevention of metastases an initial maximum therapy effort could be justified, enabling the farthest possible extent in reduction of tumour cells and preventing tumour cells from rapidly repopulating. This requires a high logistic capability of the treating institutions and an efficacious interdisciplinary management, particularly a rapid, yet thorough, radiation therapy planning. The radiation oncologist has to make sure

J. Fleckenstein and C. Rübe

246 Table 16.6. Randomized trials of early vs late radiotherapy in limited-stage SCLC. Trial

Chemoradiotherapy

Patients early/late

Start time

Survival

Signiﬁcance

Median (months)

5 years (%)

Early

Late

Late

Early

Early

Late

(p)

Week1

Week 9

13.0

14.5

6.6

12.8

n.s.

CALGBa

CEVA/ 40 Gy cfg

Aarhusb

CAV/ 99/100 EP/40 Gy cfg,h

Weeks 1, 3

Weeks 18, 23

10.7

12.9

10.0

10.0

n.s.

NCICc

CAV/ EP/40 Gy cfg

155/153

Week3

Week 15

21.2

16.0

22.0

13.0

0.013

Yugoslaviand Carbo/EPh/ 36 Gy hf-aci

52/51

Week 1

Week 6

34

26

30

15

0.027

HeCOGe

Carbo/E/ 30 Gy hf-aci

42/39

Week 1

Week 9

17.5

17

22.0

13.0

n.s.

JCOGf

EPg/45 Gy hf-aci

114/114

Week 1

Week 15

27.2

19.7

23.7

18.3

0.097

125/145

C cyclophosphamide, E etoposide, V vincristine, A doxorubicin, Carbo carboplatin, P Cisplatin, n.s. not signiﬁcant et al. (1987, 1998) b Work et al. (1997) c Murray et al. (1993) d Jeremic et al. (1997) e Skarlos et al. (2001) f Takada et al. (2002) gConventional fractionation hPerformed as split-course radiotherapy iHyperfractionated-accelerated regimen aPerry

that the risk of treatment toxicity remains within tolerable limits, especially because the full initial tumour extension has to be treated. This fact is a contraindication for this approach in a relevant proportion of patients and is at the same time a strong argument for the sequential approach with upfront chemotherapy alone, besides that it is logistically easy to perform. Several phase-III trials investigated the “earlyvs late” issue as shown in Table 16.6. The results of these trials are discordant. Two of them, the National Cancer Institute of Canada (NCIC) trial (Murray et al. 1993) and the Yugoslavian trial (Jeremic et al. 1997), show a significant survival benefit for patients receiving “early” radiotherapy. In the NCIC trial both progression free- and overall survival were significantly improved, and patients in the late thoracic irradiation arm had a higher risk of brain metastases. This finding supports the hypothesis that early therapy, as aggressive as tolerable, might prevent further manifestation of distant metastases. The Hellenic (Skarlos et al. 2001), the Yugoslavian

and the JCOG trial (Takada et al. 2002) can be considered as underpowered to detect smaller than 30% survival differences between treatment arms. The Aarhus trial (Work et al. 1997) contained an unfavourable split-course radiotherapy regimen as well as relatively low doses of accompanying chemotherapy. The JCOG trial addressed another important issue. It was not particularly designed to compare early to late radiotherapy but rather (early) concurrent with (late) sequential radiochemotherapy. Concurrent radiotherapy yielded better survival than sequential radiotherapy (p=0.097) with a median survival time in the concurrent arm of 27.2 vs 19.7 months in the sequential arm using a hyperfractionatedaccelerated radiotherapy regimen. Even though, in the overall scope, early and concurrent radiotherapy seems to generate better results, it is for toxicity reasons not wise to use it in locally extended limited-stage SCLC. More phase-III trials are needed with clear-cut inclusion criteria and excellent staging procedures to demonstrate how to ideally select patients for the early or late approach.

Applications in Lung Cancer

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Integration of Radiation Therapy and Systemic Therapy for Breast Cancer

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17 Integration of Radiation Therapy and Systemic Therapy for Breast Cancer Seungtaek Choi, Howard D. Thames, and Thomas A. Buchholz

CONTENTS 17.1 17.1.1

17.1.2 17.2 17.2.1 17.2.2 17.2.3 17.2.4 17.2.5 17.3 17.3.1 17.3.2 17.3.3 17.4

Introduction 251 Integration of Chemotherapy/Hormonal Therapy/ Biological Therapy with Surgery and Radiation in the Management of Breast Cancer 252 Non-invasive Breast Cancer: Ductal Carcinoma in Situ 252 Early-Stage Breast Cancer 253 Sequencing of Radiation Therapy and Chemotherapy after Breast-Conservation Therapy 255 Sequencing of Radiation Therapy and Chemotherapy in Patients Treated with Mastectomy 258 Sequencing of Radiation and Hormonal Therapy 258 Sequencing of Chemotherapy and Hormonal Therapy 259 New Directions: Radiation Therapy and Biological Therapy 259 Locally Advanced Breast Cancer 260 Neoadjuvant Chemotherapy 260 Patients with High-Risk Disease Who May Benefit from Concurrent Treatment 262 Radiation Therapy and Biological Therapy 262 Conclusion 262 References 263

17.1 Introduction The past decade has arguably been the most exciting time in breast cancer history, as progressive advances in treatment have reshaped the progno-

S. Choi, MD Department of Radiation Oncology, The University of Texas M.D. Anderson Cancer Center, 1515 Holcolmbe Blvd., Houston, TX 77030, USA H. D. Thames, PhD Department of Biomathematics/Biostatistics, The University of Texas M.D. Anderson Cancer Center, 1515 Holcolmbe Blvd., Unit 1202, Houston, TX 77030, USA T. A. Buchholz, MD Department of Radiation Oncology, The University of Texas M.D. Anderson Cancer Center, 1515 Holcolmbe Blvd., Houston, TX 77030, USA

sis of patients with this disease. These advances have occurred in all of the disciplines involved in breast cancer treatment, including surgery, radiation therapy, chemotherapy, hormonal therapy, and most recently in biological therapy. The relevance of these advances are very significant on a national scale, as invasive breast cancer remains the most commonly diagnosed cancer in women in the United States, with an estimated incidence of 211,240 cases in 2005 (American Cancer Society 2005). Furthermore, the incidence of breast cancer in the United States is predicted to significantly increase due to the aging population and the increasing percentage of women with delayed childbirth and other risk factors. The good news concerning breast cancer is that treatment advances are improving outcome. According to the American Cancer Society, the mortality rate for breast cancer patients decreased steadily by 2.3% per year from 1990 to 2001 (American Cancer Society 2005). For patients younger than 50 years of age, the improvement in survival was even more marked, with the mortality rate decreasing by 3.3% per year during the same time period. While some of this improvement has occurred because of increased screening and early detection, improvements in chemotherapy, hormonal therapy, and radiation have also significantly contributed. It is interesting to note that the advances in breast cancer treatment have consisted of a series of incremental improvements. For example, initial studies of systemic treatments indicated that chemotherapy and/or hormonal therapy improved outcome compared with no systemic treatments (Early Breast Cancer Trialists’ Collaborative Group 2005). It was then discovered that anthracycline containing regimens offered an advantage over non-anthracycline containing regimens (Early Breast Cancer Trialists’ Collaborative Group 2005). Subsequently, more recent studies have shown that the addition of taxanes and the dose scheduling of chemotherapy can also improve out-

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come (Henderson et al. 2003; Mamounas et al. 2005; Martin et al. 2003; Citron et al. 2003). With respect to hormonal therapy, aromatase inhibitors have been found to further improve the benefits of tamoxifen (Early Breast Cancer Trialists’ Collaborative Group 2005; Atac Trialists’ Group 2005; Thurlimann et al. 2005; Jakesz et al. 2005; Coombes et al. 2004). Finally, modern techniques of delivering radiation have been found to offer an additional improvement in survival of selected patients beyond those achievable with systemic treatment alone (Early Breast Cancer Trialists’ Collaborative Group 2000; Van de Steene 2004).

17.1.1 Integration of Chemotherapy/Hormonal Therapy/Biological Therapy with Surgery and Radiation in the Management of Breast Cancer The majority of breast cancer patients are currently treated with a combination of surgery, radiation, and systemic therapy. This is because all these approaches have proven to be valuable for patients with non-invasive disease, patients with early stage disease, and patients with locally-advanced breast cancer. How to best integrate surgery, radiation, and systemic treatments has become a highly relevant clinical question, and one that affects hundred of thousands of patients each year; therefore, it has become very important for breast cancer patients to be managed by a multidisciplinary team, with participation of the surgeons, radiation oncologists, medical oncologists, pathologists, and diagnostic radiologists. Multidisciplinary management allows for better coordination of each treatment modality, which may increase the efficacy of the combined treatment, while minimizing its toxicity. This chapter focuses on discussing the role of radiation therapy and systemic therapy in the management of breast cancer, with special emphasis on what is currently known about the optimal integration and sequencing of these treatment modalities.

17.1.2 Non-invasive Breast Cancer: Ductal Carcinoma in Situ Most patients diagnosed with DCIS are candidates for breast conservation therapy (BCT) and will

S. Choi et al.

undergo a lumpectomy as their initial therapy. Data from three randomized trials have indicated that the addition of radiation treatment to the breast after lumpectomy reduces the probability of recurrence. The National Surgical Adjuvant Breast and Bowel Project (NSABP) B-17 trial, which randomized 818 patients with DCIS to either radiation therapy or observation after lumpectomy, found that radiation therapy decreased the risk of local recurrence at 12 years from 31.7 to 15.7% (p<0.000005; Fisher et al. 2001). The European Organization for Research and Treatment of Cancer (EORTC) 10853 trial randomized 1010 patients with DCIS treated with lumpectomy to either radiation therapy or no radiation therapy (Julien et al. 2000). The results of this study also showed that radiation therapy decreased local recurrence (4-year rates 16 vs 9%; p=0.005). Finally, a phase-III trial conducted by the United Kingdom Coordinating Committee on Cancer Research (UKCCCR) DCIS Working Party found a similar proportional reduction in breast recurrences with the addition of radiation [UK Coordinating Committee on Cancer Research (UKCCCR) DCIS Working Party 2003]. In addition to radiation therapy, adjuvant tamoxifen has been found to reduce breast recurrence risk. The NSABP B-24 trial randomized 1804 patients with DCIS to either tamoxifen (20 mg daily for 5 years) or no tamoxifen after lumpectomy and radiation therapy (Fisher et al. 2001). The use of tamoxifen led to a significant reduction in the 7-year rates of all breast cancer events, including ipsilateral and contralateral breast recurrences. The NSABP B-35 trial is currently comparing anastrozole, an aromatase inhibitor, against tamoxifen as adjuvant treatment after lumpectomy and radiation therapy for patients with DCIS. The sequencing of hormonal therapy and radiation for patients with DCIS has never been formally studied. In the NSABP B-24 trial, tamoxifen and radiation therapy were given concurrently without any apparent increase in skin or pulmonary toxicity (Fisher et al. 1999); however, this study did not directly compare concurrent versus sequential use of radiation and tamoxifen for patients with DCIS. This question of sequencing of hormonal therapy and radiation is also relevant to patients with invasive disease and is discussed in greater depth later in this chapter.

Integration of Radiation Therapy and Systemic Therapy for Breast Cancer

17.2 Early-Stage Breast Cancer Most of the patients diagnosed with breast cancer either present with stage-I or stage-II disease and are usually treated with a combination of surgery, radiation, and systemic therapy. Typically, patients who present with relatively small primary tumors (i.e., <3 cm) undergo surgery as their initial treatment. For such patients, surgery can consist of either BCT or a modified radical mastectomy (MRM). Several large randomized trials have conclusively demonstrated that the outcome associated with both of these treatment modalities is equivalent. One example of these trials is the NSABP B-06 trial, which was reported in 2002 with 20 years of follow-up (Fisher et al. 2002). The results of this trial showed that patients treated with BCT achieved equivalent disease-free survival, distant disease-free survival, and overall survival rates as patients treated with MRM. This trial also examined the value of radiation therapy after lumpectomy for patients treated with BCT. In this study, the patients treated with radiation after lumpectomy had a significantly lower ipsilateral breast recurrence rate compared with those treated with lumpectomy alone (14.3 vs 39.2%; p<0.001). This reduction in local recurrence was independent of lymph node status. Postoperative radiation therapy also plays an important role in selected patients treated with mastectomy. The Danish Breast Cancer Cooperative Group (DBCCG) 82b trial randomized 1708 premenopausal women with either stage-II or stage-III breast cancer treated with mastectomy and chemotherapy with cyclophosphamide, methotrexate, and 5-fluorouracil (CMF) to postoperative radiation vs no further therapy (Overgaard et al. 1997). This study found that the patients randomized to the postmastectomy radiation therapy arm had significantly improved 10-year locoegional control rate (91 vs 68%; p<0.001) and overall survival rate (54 vs 45%; p<0.001). A similar trial reported by Ragaz et al. (2005) also found that the use of postmastectomy radiation was associated with a statistically significant benefit in 20-year locoregional control, distant disease-free survival, and overall survival. Based on these data, postmastectomy radiation therapy is recommended to patients at high risk of local regional recurrence; these include patients with T3 or T4 disease, and/or four or more positive axillary lymph nodes. Whether patients with one to three positive lymph nodes benefit from postmastectomy radiation therapy is controversial, as most retrospective

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studies of patients with one to three positive lymph nodes treated with MRM and chemotherapy have shown low locoregional recurrence rates. In a review of the M.D. Anderson Cancer Center (MDACC) experience, Woodward et al. (2003) reported a 10year locoregional recurrence of 13% for patients with T1 or T2 tumors and one to three lymph nodes positive who underwent mastectomy and adjuvant chemotherapy. When postmastectomy radiation was added, the risk of local-regional recurrence was reduced to 3% (p=0.003). Unfortunately, a randomized trial designed to determine the benefit of postmastectomy radiation in this patient group was prematurely closed due to poor national accrual. Systemic therapy is also recommended for most patients with stage-I or stage-II invasive breast cancers. The meta-analysis by the Early Breast Cancer Trialists’ Collaborative Group (EBCTCG) showed that women with both lymph node-negative disease and lymph-node-positive disease have a significantly improved overall survival when treated with adjuvant polychemotherapy (Early Breast Cancer Trialists’ Collaborative Group 2005). Patients also had benefit with chemotherapy regardless of their age and the estrogen receptor status of their tumor. Furthermore, their data indicated that anthracycline (doxorubicin, epirubicin) containing regimens offered a survival advantage over nonanthracycline containing treatments. In addition to the benefits offered by anthracyclines, there has been an increase in the use of taxanes (paclitaxel, docetaxel) in the adjuvant treatment of breast cancer. Three large randomized trials have shown a significantly improved outcome when taxanes are added to anthracycline-based chemotherapy regimens. The Cancer and Leukemia Group B (CALGB) 9344 trial randomized 3121 patients with positive lymph nodes to either four cycles of doxorubicin and cyclophosphamide (AC) followed by four cycles of paclitaxel (T) or four cycles of AC alone (Henderson et al. 2003). Results after 5 years of follow-up showed that the addition of paclitaxel improved both disease-free survival (70 vs 65%; p=0.0023) and overall survival (80 vs 77%; p=0.0064). The NSABP B-28 trial was very similar in design to the CALBG 9344 trial and also showed a significant reduction in the disease-free survival (DFS) in the AC+T arm compared with the AC arm (p=0.006; Mamounas et al. 2005). Finally, the Breast Cancer International Research Group (BCIRG) conducted a trial (BCIRG 001) randomizing 1491 patients with lymph-node-positive breast cancer to either FAC (5-FU, doxorubicin, cyclophos-

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phamide given every 3 weeks for six cycles) or TAC (docetaxel, doxorubicin, cyclophosphamide given every 3 weeks for six cycles) chemotherapy (Martin et al. 2003). After 55 months of follow-up, patients in the TAC arm were found to have significantly improved disease-free survival (75% in the TAC arm vs 68% in the FAC arm; p=0.001) and overall survival (87 vs 81%; p=0.008). More recent trials have attempted to increase the efficacy of chemotherapy by increasing the dose density (by giving the same dose in a shorter amount of time). The CALGB 9741 study randomized patients to conventional AC and T scheduling (given every 3 weeks) or dose-dense chemotherapy (given every 2 weeks with G-CSF support; Citron et al. 2003). This study found a significant improvement in both disease-free survival (82 vs 75%; p=0.01) and overall survival (92 vs 90%; p=0.013) with the dose-dense regimen. Based on these data, the optimal adjuvant chemotherapy for most patients, particularly those with positive lymph nodes, should contain an anthracycline and a taxane given in a dose-dense schedule. Hormonal therapy is another critical component of treatment and is indicated for almost all patients with estrogen or progesterone receptor-positive disease. The EBCTCG analysis showed that treatment with 5 years of tamoxifen decreases the likelihood of cancer recurrence and improves overall survival (Early Breast Cancer Trialists’ Collaborative Group 2005). Furthermore, several recent trials have shown improved outcome with the use of aromatase inhibitors when compared to tamoxifen. The anastrozole vs tamoxifen alone or in Combination (ATAC) trial randomized 9366 postmenopausal women with stage-I or stage-II breast cancers to either anastrozole alone (1 mg daily), tamoxifen alone (20 mg daily), or both anastrozole and tamoxifen (ATAC Trialists’ Group 2005). After 68 months of follow-up, patients on anastrozole were found to have an improved disease-free survival (with reduction in time to recurrence, contralateral breast cancers, and distant metastases) compared with the other two arms. The BIG 1-98 trial randomized patients to four arms: tamoxifen alone (20 mg daily); letrozole alone (2.5 mg daily); and tamoxifen for 2 years followed by 3 years of letrozole (Thurlimann et al. 2005). An interim analysis, with a median follow-up of 25.8 months, was performed comparing only the tamoxifen and the letrozole arms. The results from this analysis showed a significant improvement in the disease-free survival for patients taking letrozole compared to tamoxifen (HR

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0.81; p=0.003), with a reduction in both local recurrence (0.5 vs 0.9%; p=0.047) and distant disease (4.4 vs 5.8%; p=0.006). The patients in the two crossover arms were not analyzed; however, there have been several studies that have investigated the question of changing the hormonal therapy from tamoxifen to an aromatase inhibitor. The Austrian Breast Cancer Study Group (ABCSG 8) and the German Adjuvant Breast Cancer Group (ARNO 95) randomized 3234 patients after 2 years of tamoxifen to either anastrozole (to complete 5 years of hormonal treatment) or additional tamoxifen (also to complete 5 years; Jakesz et al. 2005). The results of the study showed improved 3-year event-free survival (95.8 vs 92.7%; p<0.001) and distant disease-free survival (97 vs 95%; p=0.0067) for patients who crossed over to anastrozole after 2 years of tamoxifen. There was no statistical difference in overall survival between the two groups (97 vs 96%; p=0.16). The International Exemestane Study (IES) was of similar design and randomized 4742 patients (Coombes et al. 2004). After a median follow-up of 37.4 months, the patients on the exemestane arm had a significantly improved event-free survival (89 vs 85%; p<0.001). Finally, aromatase inhibitors have been studied as additional therapy after 5 years of tamoxifen. The NCIC MA.17 trial randomized patients after 5 years of tamoxifen to either 5 years of letrozole or placebo (Goss et al. 2005). The results of the study after 30 months of median follow-up showed that patients who received letrozole after tamoxifen had a 4.6% absolute reduction in the breast cancer events over patients who received placebo after tamoxifen (94.4 vs 89.8%; p<0.001). Although there was no difference in overall survival for the entire study population, the use of letrozole improved overall survival in patients with lymph-node-positive disease. The results of these trials show that there are several options for the hormonal treatment of postmenopausal patients, including anastrozole for 5 years (based on the ATAC study), letrozole for 5 years (based on BIG 1-98), tamoxifen for 2–3 years followed by either anastrozole (based on ABCSG 8/ARNO 95) or exemestane (based on IES) for a total of 5 years of hormonal therapy, or tamoxifen for 5 years followed by 5 years of letrozole (based on NCIC MA.17). Premenopausal patients should not be treated with aromatase inhibitors, as they do not inhibit the formation of estrogen by the ovaries; therefore, premenopausal patients should receive tamoxifen for hormonal therapy.

Integration of Radiation Therapy and Systemic Therapy for Breast Cancer

17.2.1 Sequencing of Radiation Therapy and Chemotherapy after Breast-Conservation Therapy With the increased use of adjuvant chemotherapy in early-stage disease, there has been significant interest in the sequencing of radiation therapy and chemotherapy after breast-conserving surgery. During the 1990s there was significant debate over this issue. One of the first retrospective studies to report on sequencing of radiation and chemotherapy showed that a delay in radiation treatments in order to give chemotherapy may increase the risk of breast recurrence. In this retrospective review of 295 patients treated at the Joint Center for Radiation Therapy (JCRT) by Recht et al. (1991), the 5-year breast recurrence was 4% in patients receiving radiation therapy first, 8% in patients receiving radiation therapy given between chemotherapy courses, 6% in patients receiving concurrent radiation therapy and chemotherapy, and 41% in patients receiving all of their chemotherapy first. Although the results of this study suggested that radiation therapy should be given first, many worried that a delay in chemotherapy delivery may adversely affect the positive benefits that systemic treatments offer in preventing distant metastases. To further investigate this issue, a number of centers and cooperative groups conducted retrospectively studies, some of which are summarized in Table 17.1. As shown, the results from these studies were inconsistent and did not definitely answer the question of optimal sequencing of radiation and chemotherapy for patients with early-stage breast cancer. This, in part, was due to the limitations of retrospective research. Specifi-

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cally, patients in these studies were not randomized; therefore, the sequencing decisions were often based on disease characteristics, which likely affected outcome more than the sequencing. In addition, treatment sequencing may have had different impacts on different populations. For example, radiation delay may have had a greater significance for patients with close or positive surgical margins, whereas chemotherapy delay may have had more of an effect in patients with multiple positive lymph nodes, who have higher risk of micrometastases. To more definitively address the question of how adjuvant chemotherapy and radiation should be sequenced after breast-conserving surgery, investigators at the JCRT conducted a phase-III clinical trial that randomized 244 patients with early-stage breast cancer treated with BCT to either 12 weeks of chemotherapy with cyclophosphamide, doxorubicin, methotrexate, 5-fluorouracil, and prednisone (CAMFP) followed by radiation therapy (CT first) or radiation therapy followed by the same chemotherapy (RT first). In the initial report of the study (with a median follow-up of 58 months), the authors reported that the 5-year actuarial rate of distant metastases was higher in the RT-first arm compared with the CT-first arm (36 vs 25%; p=0.05; Recht et al. 1996). In contrast, the crude 5-year local recurrence rate was lower in the RT-first arm (5% in RTfirst arm vs 14% in the CT-first arm). In an update of this study (with a median follow-up of 135 months), there were no statistically significant differences between the RT-first arm and CT-first arm in the 10-year event-free survival rate (49 vs 54%), distant metastasis-free survival rate (64 vs 65%), or overall survival rate (67 vs 72%; Bellon et al. 2005); however, the sequencing of radiation therapy and

Table 17.1. Retrospective studies comparing sequencing of chemotherapy and radiation therapy for breast cancer Reference

No. of patients

Type of surgery

Five-year local recurrence (%)

Five-year distant recurrence (%)

Five-year mortality (%)

RT ﬁrst

CT ﬁrst

RT ﬁrst

CT ﬁrst

RT ﬁrst

CT ﬁrst

Recht et al. (1991)

295

BCS (100%)a

4

41 (0.03)

24

50 (NS)

Buzdar et al. (1993)

552

BCS (15%)a

4.6

3.1 (NS)

19.1

28.4 (NS)

Mastectomy (85%)

3.5

4.2 (NS)

36.0

35.5 (NS)

9.4

10.5 (NS)

38

22 (NS)

28.4

22.6 (NS)

6

0 (NS)

23

8 (NS)

11

11 (NS)

Nguyen et al. (1993)

312

BCS

(47%)a

Mastectomy (53%) Buchholz et al. (1999)

124

The p-values are in parentheses BCS breast-conservation surgery

BCS (100%)a

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chemotherapy did affect locoregional control when patients were analyzed by margin status. In patients with negative surgical margins (n=123), the crude local recurrence rates were 13% for the RT-first arm and 6% for the CT-first arm. In comparison, among women with close margins (n=47), the crude local recurrence rate was significant lower in the RT-first arm compared with the CT-first arm (4 vs 32%). In patients with positive margins (n=51), the local recurrence rates were 20% in the RT-first patients and 23% in the CT-first patients. The authors concluded that the sequence of radiation therapy and chemotherapy does not affect clinical outcome in patients receiving 12 weeks of chemotherapy as long as negative margins are achieved. For patients with close or positive margins, the authors recommended re-excision. Based on the results from this study, most oncologists recommend that adjuvant therapy consist of chemotherapy followed by radiation therapy. It is important to note that the JCRT trial predominantly enrolled patients with lymph-node-positive breast cancer and evaluated a systemic regimen that treated patients with only four cycles of chemotherapy prior to the start of radiation; therefore, these data may have limited applicability to some patients, especially those with lymph-node-negative breast cancer who have a lower risk of metastatic disease. In these patients, the risk of locoregional recurrence most likely outweighs the risk of distant disease. To determine the importance of sequencing of chemotherapy and radiation therapy in this patient population, Buchholz et al. (1999) performed a retrospective review of 124 patients with lymph-nodenegative disease treated with breast-conserving surgery at MDACC who then underwent either chemotherapy followed by radiation therapy or radiation therapy followed by chemotherapy. The results of this study showed no statistically significant differences in local control (100 vs 94%, respectively), recurrence-free survival (92 vs 77%), or overall survival (89 vs 89%) between the patients who received chemotherapy first or those who received radiation therapy first. There are limited data investigating the effect of more extended delays in radiation start date in order to accommodate more prolonged chemotherapy schedules. In the CALGB 9344 trial, patients treated with AC+T had a longer interval between their surgery and the start of their radiation treatment in order to complete their full course of adjuvant chemotherapy. Despite this, the data from this study showed that the patients who underwent breast-con-

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serving surgery who were then treated with AC+T had a lower locoregional recurrence rate than those treated with surgery followed by AC alone (3.7 vs 9.7%; p=0.04; Sartor et al. 2005). In the NSABP B-28 trial, patients receiving a longer duration of chemotherapy with AC+T before radiation therapy also had a slightly decreased locoregional recurrence rate than patients receiving a shorter course with AC only (6.5 vs 7.6%; Mamounas et al. 2005). In summary, the available data suggests that for breast cancer patients who have negative surgical margins after breast-conserving surgery, radiation therapy can be given after adjuvant chemotherapy without compromising the efficacy of the treatment. If possible, patients with close or positive margins should undergo re-excision in an effort to minimize the risk of local recurrence. Sequencing chemotherapy and radiation therapy concurrently has the theoretical advantage of treating both the locoregional and micrometastatic diseases at the same time, as well as possibly having radiosensitization from the chemotherapy. There have been several reports in the literature studying the feasibility of treating breast cancer patients with concurrent chemotherapy and radiation therapy. A single-arm prospective study conducted at the JCRT treated 112 patients with early-stage breast cancer with concurrent chemotherapy (with 6 months of CMF) and radiation therapy (Dubey et al. 1999). In this study, the radiation dose was decreased (to 39.6 Gy to the breast, followed by a 16-Gy boost to the operative bed) to minimize the risk of normal tissue injury. After 2 years of follow-up, the local recurrence rate was 3.6% and the distant metastasis rate was 17.9%. The risk of adverse side effects was low, with only 4.5% of the patients needing treatment breaks due to moist desquamation and only 1 patient developing grade-2 radiation pneumonitis. Faul et al. (2003) reported the results of treating 73 patients with early-stage breast cancer prospectively with concurrent chemotherapy (with CMF) and radiation therapy after lumpectomy. These patients were compared with a matched group of 40 patients treated with sequential treatment. After 2.6 years of follow-up, the local and distant control rates were high in both groups. There were no local failures and one distant failure in the concurrent group, compared with one local failure and four distant failures in the sequential group. Concurrent treatment did not affect the ability to deliver optimum dose of radiation therapy or chemotherapy. There was no significant difference in skin reactions or complications between the two groups. There was

Integration of Radiation Therapy and Systemic Therapy for Breast Cancer

no difference in cosmetic scores between the two groups; however, there was a small, but significant, delay of 1.32 days in the delivery of radiation therapy in the concurrent group (p=0.03). Haffty et al. (2005) reported on a retrospective trial which examined at 455 patients who either received concurrent chemotherapy (with cyclophosphamide, mitoxantrone, and 5-FU) and radiation therapy or sequential treatment. Because the study was retrospective, patients in the concurrent treatment arm tended to be younger, with a higher incidence of lymph-nodepositive disease or positive margins. Despite the presence of these adverse risk factors, the patients in the concurrent treatment arm had an improved 10year local control rate compared with the sequential treatment arm (92 vs 83%; p<0.001). Patients treated with the concurrent treatment arm had acceptable cosmesis (good to excellent in 77% of patients) and acute toxicity (20% moist desquamation). Arcangeli et al. (2005) recently reported on an Italian trial which randomized 206 patients with early-stage breast cancer who underwent quadrantectomy and axillary node dissection to either concurrent chemotherapy (with CMF) and radiation therapy or sequential treatment (with chemotherapy given before radiation therapy). The results showed no difference in the 5-year breast recurrence-free, metastasis-free, disease-free, and overall survival rates between the two treatment groups. In addition, there was no evidence of increased risk of toxicity in the concurrent treatment arm. Calais et al. (2005) also reported on a phase-III trial of 716 patients randomized to either concurrent chemotherapy (with cyclophosphamide, mitoxantrone, and 5-FU) or sequential chemotherapy and radiation therapy. The results of this study showed no significant differences in locoregional control, disease-free survival, or overall survival rates after 6.7 years of follow-up between the two treatment groups; however, in patients with lymph-node-positive disease, patients who received concurrent treatment had a significantly higher locoregional control rate than the patients who received sequential treatment. In contrast to the findings of Arcangeli et al. (2005), the incidences of both acute grade t2 esophagitis (23 vs 7%) and hematological toxicity were increased in the concurrent arm. There was no difference in late toxicities. The increased incidence of acute toxicities with concurrent treatment was also noted in a study by Fiets et al. (2003), which prospectively compared 266 patients undergoing concurrent chemotherapy (either CMF or AC) and radiation therapy or radiation therapy alone. The results of that study showed

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that patients receiving concurrent treatment had higher incidence of high-grade skin toxicity, esophagitis, dyspnea, malaise, anorexia, nausea, and hospital admission compared with those treated with radiation alone. The relevance of studies investigating concurrent CMF chemotherapy and radiation after breast-conserving surgery is becoming less with the adoption of anthracycline and taxane containing chemotherapy regimens as the standard of care for early-stage disease. As doxorubicin has potent radiosensitizing normal tissue effects, there has been a general reluctance to investigate giving this agent concurrently with radiation; however, the use of concurrent paclitaxel and radiation therapy has been investigated by a number of groups. Hanna et al. (2002) reported increased skin and pulmonary toxicity with concurrent paclitaxel and radiation therapy, with 65% of patients developing grade-2 or higher skin reaction, and 20% of patients developing radiation pneumonitis. Burstein et al. (2005) reported on a phase-I/ II trial treating 40 patients with stage-II and stageIII breast cancer with concurrent radiation therapy and chemotherapy with paclitaxel after surgery and chemotherapy with AC. The first 16 patients were treated with weekly paclitaxel, with 4 patients developing dose-limiting toxicity (including one patient with grade-2 pneumonitis and two patients with grade-3 pneumonitis). The chemotherapy regimen was therefore changed; paclitaxel was given every 3 weeks for the remaining 24 patients. This regimen was better tolerated, with no patients developing dose-limiting toxicity; however, two patients (8%) developed grade-2 pneumonitis (which did not require steroid therapy). The authors concluded that weekly paclitaxel should not be given concurrently with radiation therapy. In contrast, Taghian et al. (2001) did not notice any difference in the incidence of pneumonitis in patients who received concurrent paclitaxel and radiation therapy (compared with patients who received sequential treatment; however, the authors did note that patients who received paclitaxel appeared to have a higher incidence of pneumonitis when compared with historical controls (who did not receive paclitaxel). Finally, Ellerbroek et al. (2003) treated 24 patients with early-stage breast cancer with breast-conserving surgery followed by adjuvant chemotherapy with four cycles of AC followed by concurrent chemotherapy with paclitaxel (four cycles given every 3 weeks) and radiation therapy. The patients tolerated the concurrent treatment well, with 7 patients experiencing grade-1 skin toxicity and 17 patients

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experiencing grade-2 skin toxicity. Eight patients required a short break in treatment due to a skin reaction. None of the patients required a reduction in the chemotherapy dose, although one patient had to stop the paclitaxel after three cycles due to bilateral upper extremity neuropathy. With 11.5 months of follow-up, there was no incidence of interstitial pneumonitis or brachial plexopathy. In summary, while randomized trials have shown that concurrent treatment with radiation and some chemotherapy regimens can be given safely, most of these regimens are no longer considered to be the most effective systemic treatments. As shown above, the data regarding the use of concurrent radiation therapy and modern chemotherapy regimens (including an anthracycline and a taxane) are very sparse and suggest that concurrent treatment may lead to increased toxicity (especially pneumonitis). Furthermore, when given after surgery in a sequential fashion with radiation therapy, modern chemotherapy regimens lead to very low locoregional recurrence rates for early-stage breast cancer; therefore, although there is limited randomized data showing the advantage of concurrent chemotherapy and radiation therapy in a subset of patients (i.e., lymph-node-positive disease), a rational approach that is widely adopted is to complete the adjuvant course of chemotherapy and then follow with radiation.

17.2.2 Sequencing of Radiation Therapy and Chemotherapy in Patients Treated with Mastectomy There are very few data available concerning the sequencing of chemotherapy and radiation for women treated with mastectomy. In the Danish 82b trial, radiation therapy was sequenced very early in the adjuvant treatment course (Overgaard et al. 1997). Since then, there have been several other trials which have shown that the radiation may be delayed safely while the patients are receiving chemotherapy. In the CALGB 9344 trial, there was no decrease in the locoregional recurrence rate in patients treated with mastectomy followed by AC+T in comparison with patients treated with mastectomy followed by AC alone (3.5 vs 4.3%; Sartor et al. 2005). Cakir et al. (2003) reported a retrospective review of 176 patients with stage-II and stageIII disease who underwent mastectomy treated by radiation therapy followed by chemotherapy with

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six cycles of either CMF or CAF (n=40), six cycles of chemotherapy followed by radiation therapy (n=54), or three cycles of chemotherapy given before and then after radiation therapy (“sandwich therapy”; n=82). In that study, there was no difference in the 5year locoregional disease-free survival between the three groups (95 vs 96 vs 90%, respectively, p=0.2); however, there were significant differences in the 5-year systemic disease-free survival (75 vs 86 vs 62%, respectively; p=0.003), the 5-year disease-free survival (74 vs 85 vs 60%, respectively; p=0.001), and the 5-year cancer specific survival (84 vs 86 vs 66%; p=0.01), with the patients receiving sandwich treatment having a worse outcome than the patients in other two treatment groups. Based on these results, as well as the favorable outcome seen in patients receiving chemotherapy first in the breast-conservation setting, most oncologists have adopted a similar treatment approach for patients with early-stage breast cancer treated with mastectomy (i.e., chemotherapy followed by radiation therapy).

17.2.3 Sequencing of Radiation and Hormonal Therapy Another area of clinical controversy surrounding treatment sequencing is whether to administer hormonal therapy concurrently or sequentially with radiation. Historically, sequential treatment was recommended based on preclinical data suggesting that tamoxifen may arrest breast cancer cells in radioresistant cell-cycle phases, which theoretically would decrease the efficacy of radiation treatment (Sutherland et al. 1983). In addition, tamoxifen has been associated with increased levels of circulating TGF-E, which is an important mediator of radiation normal tissue injury (Colletta et al. 1990; Knabbe et al. 1991). Several recent retrospective studies have shown that the sequence of tamoxifen in relation to radiation therapy likely does not affect clinical outcome. Ahn et al. (2005) reported on 495 patients either treated with concurrent radiation therapy and tamoxifen or sequential treatment with tamoxifen started after the end of the radiation therapy. There was no difference in the ipsilateral or contralateral breast recurrence-free survival, distant metastasisfree survival, or overall survival. Harris et al. (2005) reported similar results in 278 patients treated with either concurrent or sequential radiation therapy and radiation therapy. Furthermore, there were no

Integration of Radiation Therapy and Systemic Therapy for Breast Cancer

differences seen between the two groups in the incidence of breast edema, arm edema, symptomatic pneumonitis, or rib fracture. Finally, Pierce et al. (2005) reported on 309 patients treated with either concurrent or sequential radiation therapy and tamoxifen. As with the two other studies, there were no differences seen in clinical outcome. Based on these results, we recommend that patients be treated with sequential radiation therapy and tamoxifen, as there is no difference in the recurrence-free or overall survival rates with sequential treatment (as compared with concurrent treatment). Furthermore, there is some data suggesting that concurrent treatment may lead to increased pulmonary and subcutaneous tissue fibrosis (Bentzen et al. 1996; Azria et al. 2004). It is noteworthy that the importance of the interaction between of radiation and tamoxifen may become less clinically relevant as more patients receive aromatase inhibitors as adjuvant hormonal therapy. To date, there have been no data published regarding the optimal sequencing of radiation therapy and aromatase inhibitors.

17.2.4 Sequencing of Chemotherapy and Hormonal Therapy Many patients with estrogen receptor-positive breast cancer are treated with both adjuvant chemotherapy and hormonal therapy. The optimal sequencing of chemotherapy and hormonal therapy was recently investigated in a phase-III trial run by the Southwest Oncology Group (SWOG 8814), which randomized patients with pathological stage-I to stage-IIIA breast cancer to concurrent chemotherapy with CAF (cyclophosphamide, doxorubicin, 5-flurouracil) chemotherapy with tamoxifen or chemotherapy followed by tamoxifen or tamoxifen alone (Albain et al. 2004). After 10 years of follow-up, there was an improvement in disease-free survival (60 vs 53 vs 48%, respectively; p=0.002) and overall survival (68 vs 62 vs 60%, respectively; p=0.04) with the sequential treatment compared with the concurrent treatment and tamoxifen only arms. Based on the findings of this trial, most oncologists recommend that hormonal therapy be started after the end of chemotherapy rather than given concurrently.

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17.2.5 New Directions: Radiation Therapy and Biological Therapy A recent exciting advance in the treatment of breast cancer has been the finding that trastuzumab, a humanized monoclonal antibody to the extracellular domain of the HER2 protein, when combined with chemotherapy, improves the overall survival of patients with HER2 positive disease. Two large randomized trials regarding the use of trastuzumab as adjuvant treatment in operable breast cancer were recently published. The Intergroup Study (comprising of the NSABP B-31 and the North Central Cancer Treatment Group (NCCTG) study N9831) treated patients with HER2 positive (defined as 3+ on immunohistochemistry or amplified by FISH) breast cancer with either adjuvant chemotherapy with trastuzumab or adjuvant chemotherapy alone (Romond et al. 2005). In the B-31 trial, patients were initially treated with four cycles of AC followed by either 12 weeks of paclitaxel (given either every 3 weeks or weekly) with or without concurrent trastuzumab. The trastuzumab was given weekly for 1 year. In the N9831 trial, the patients were randomized to three groups: (a) four cycles of AC, followed by 12 weeks of weekly paclitaxel; (b) the same regimen as (a), but with weekly trastuzumab for 1 year starting at the end of the paclitaxel; and (c) same regimen as (a), but with weekly trastuzumab for 1 year given concurrently with the paclitaxel. The combined analysis of these two trials showed that the addition of trastuzumab increased both 3-year recurrence free survival (87.1 vs 75.4%; p<0.0001) and 3-year overall survival (94.3 vs 91.7%; p=0.015) at the cost of increased risk of congestive heart failure (CHF) or death from cardiac cause (4.1% in NSABP B-31, 2.9% in N9831). The Herceptin Adjuvant (HERA) trial conducted by the Breast International Group randomized 5081 women with HER2 positive (defined as 3+ on immunohistochemistry or amplified by FISH) breast cancer after surgery, chemotherapy, and radiation therapy to observation or treatment with trastuzumab for either 1 or 2 years. Piccart-Gebhart et al. (2005) recently reported the data of the patients on the observation and 1-year treatment arms. The patients in the trastuzumab arm were found to have an absolute increase in the 2-year disease-free survival of 8.4% (which translated into an unadjusted hazard ratio of 0.54; p<0.0001). Most of this improvement was seen in the reduction of distant metastases. There was no difference in overall sur-

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vival. The patients on the trastuzumab arm had a higher incidence of cardiac toxicity, with a 0.54% absolute increase in the incidence of severe CHF, 1.67% absolute increase in symptomatic CHF, and a 4.87% absolute increase in the incidence of left ventricular ejection fraction (LVEF) reduction. The optimal sequencing of radiation therapy and biological therapy is unknown at this time. It is interesting to note that radiation therapy was given before trastuzumab in the HERA trial, whereas it was given concurrently in the Intergroup trial. A recent article by Tan-Chiu et al. (2005) analyzed patients in the NSABP B-31 trial for cardiac dysfunction. The results showed that the patients who received trastuzumab were at higher risk of developing a cardiac event (defined as New York Heart Association classIII or class-IV congestive heart failure or cardiac death) when compared with patients who did not receive the treatment (4.1 vs 0.8%; p<0.0001); however, the addition of radiation therapy (for patients with left-sided tumors who received trastuzumab) did not seem to increase the risk of developing cardiac events. The risk of developing class-III or class-IV CHF was 3.2% in the patients who received left-sided radiation compared with 4.0% in patients who did not (p=0.59). Although this result is very encouraging, it must be interpreted with caution, as the median follow-up of this report was only 27 months. Much longer follow-up will be needed before one can fully evaluate the potential toxicity of concurrent radiation therapy and trastuzumab therapy. We believe that this question of optimal sequencing of radiation therapy and biological therapy will continue to be an important one, as newer agents (such as bevacizumab) are constantly being discovered and tested in patients with breast cancer.

17.3 Locally Advanced Breast Cancer Locally advanced breast cancer (stage-III disease) requires multimodality treatment. Many of the same principles regarding the integration of systemic treatment and radiation for patients with advanced disease are similar to those discussed for patients with early stage breast cancer; however, patients who present with locally advanced breast cancers are at higher risk for both locoregional and distant disease recurrence and require multidisciplinary care for optimal disease management.

17.3.1 Neoadjuvant Chemotherapy Some patients presenting with advanced primary and nodal disease have unresectable disease. In the 1980s investigators began exploring a sequencing approach that used chemotherapy prior to surgery for such patients. These early studies demonstrated that anthracycline containing chemotherapy regimens could achieve a partial or complete clinical response in over 80% of treated patients. This permitted many patients with initially unresectable disease to become operative candidates. With this success, the use of neoadjuvant chemotherapy was then investigated for patients with advanced but operable disease in an effort to increase rates of breast conservation. The NSABP conducted the B-18 trial, which compared neoadjuvant chemotherapy to adjuvant chemotherapy in patients with stage-II or stage-III breast cancer (Wolmark et al. 2001). At 9 years there was no difference in local recurrence, disease-free survival, or overall survival seen between the two arms; however, neoadjuvant chemotherapy increased the likelihood that patients could undergo breast-conservation therapy (68% in the neoadjuvant chemotherapy arm vs 60% in the adjuvant chemotherapy arm, p=0.002). This increase was directly due to a greater percentage of patients with T3 disease being offered breast conservation after first responding to chemotherapy (22% breast conservation rate vs 8%, respectively). Neoadjuvant chemotherapy has some additional advantages beyond increasing the probability of breast conservation. Using chemotherapy prior to surgery has allowed for comparisons of different systemic regimens based on how often they can achieve pathological complete response, which is a good surrogate for subsequent survival. This provides investigators with outcome data many years earlier than studies that compare chemotherapy treatments in the adjuvant setting. Another research benefit associated with neoadjuvant chemotherapy is that it allows for measurement of biological changes during the course of treatment, which may help to identify genetic and protein determinants of chemotherapy response. The increasing use of neoadjuvant chemotherapy had raised new questions concerning the indications for adjuvant radiation therapy, particularly for patients who subsequently undergo mastectomy. This is because the historical indications used to determine which patients should be treated with postmastectomy radiation were based on the patho-

Integration of Radiation Therapy and Systemic Therapy for Breast Cancer

logical extent of disease. As previously highlighted, neoadjuvant chemotherapy changes the extent of disease in over 80% of the cases. It remains unclear how these changes should affect the indications for radiation. In one of the only studies available that has addressed this issue, Huang et al. (2004) compared the outcomes of 542 patients who received neoadjuvant chemotherapy, mastectomy, and radiation therapy with those of 134 patients who were treated with neoadjuvant chemotherapy and mastectomy alone. While all of these patients were treated on prospective clinical trials, radiation therapy was not a randomized variable in these studies. In general, the patients treated with radiation therapy had more advanced T-stage, N-stage, combined clinical stage, higher number of positive lymph nodes, poorer response to neoadjuvant chemotherapy, and higher percentage of close or positive margins. Despite these higher-risk features, the 10-year locoregional recurrence rate was significantly lower in the patients treated with postmastectomy radiation therapy than in those who did not receive radiation therapy (11 vs 22%; p=0.0001). Radiation therapy reduced locoregional recurrence for patients with clinical T3 or T4 tumors, stage-IIB disease or greater (by 1988 AJCC staging criteria), pathological tumor size >2 cm, or four or more positive lymph nodes by 30–40% and in these cohorts was associated with an improved survival. In general, most patients treated with neoadjuvant chemotherapy are either operative candidates at diagnosis or become operative candidates after responding to neoadjuvant chemotherapy; however, to try to improve the response rates in patients with locally advanced breast cancer, several investigators have explored using concurrent chemotherapy and radiation as neoadjuvant treatment. Kao et al. (2005) reported on a phase-I/II trial treating 15 patients with concurrent radiation therapy and pacl-

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itaxel (with or without vinorelbine) for unresectable locally advanced breast cancer. Of the 15 patients, 14 patients had a clinical response and 7 patients had a pathological CR. Eight patients had grade-3 or grade4 acute skin toxicity, and 2 patients had grade-3 late skin toxicity. One patient had grade-3 lymphedema. Formenti et al. (2003) treated 44 patients with stage-IIB or stage-III breast cancer with concurrent radiation therapy and chemotherapy (with twiceweekly paclitaxel) as neoadjuvant treatment before mastectomy. These patients were then treated with either doxorubicin and paclitaxel or doxorubicin and cyclophosphamide. The median follow-up was 32 months. Almost all of the patients responded to the neoadjuvant treatment, with an overall clinical response rate of 91%. The pathological response rate was 34%, with 16% of the patients achieving a complete pathological response. The preoperative radiation therapy and chemotherapy was relatively well tolerated, with 7% of the patients developing grade3 skin desquamation, 2% hypersensitivity (to paclitaxel), and 3% stomatitis. Interestingly, the complete pathological response achieved in this study was lower than those achieved in two recently reported studies using neoadjuvant chemotherapy only (if both an anthracycline and a taxane are given). In the Aberdeen trial, the complete pathological response rate was 34% (Smith et al. 2002), and in the NSABP B-27 trial, the rate was 26.1% (Bear et al. 2003). The optimal sequencing of radiation and chemotherapy for most patients with locally advanced disease is similar to that in patients with early-stage disease. As discussed above, concurrent chemotherapy and radiation therapy seem to be associated with increased risk of toxicity, without significant increase in clinical benefit; therefore, we recommend that patients be treated in a sequential fashion, with radiation therapy given after the completion of their systemic and surgical therapies.

Table 17.2. Risk factors for locoregional recurrence after mastectomy and chemotherapy and postmastectomy radiation Patients treated with mastectomy, adjuvant chemotherapy, and postmastectomy radiation

Patients treated with neoadjuvant chemotherapy, mastectomy, and postmastectomy radiation

Pathological tumor size of 4 cm or greater

Pathological tumor size >2 cm and four or more positive lymph nodes

Estrogen-negative disease with four or more positive lymph nodes

Estrogen -negative disease and four or more positive lymph nodes

Supraclavicular disease involvement at presentation

- Pathological demonstration of skin or nipple involvement - Positive surgical margins on the mastectomy specimen

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17.3.2 Patients with High-Risk Disease Who May Benefit from Concurrent Treatment Despite the advances in chemotherapy and radiation, there remain small cohorts of patients who do poorly with conventional treatments. Specifically, results from MDACC show that patients with significant disease burden after neoadjuvant chemotherapy and patients with advanced estrogen-negative disease have suboptimal local control after mastectomy and postmastectomy radiation (Woodward et al. 2003; Huang et al. 2005). Table 17.2 lists disease features found in studies that are associated with locoregional recurrence rates in excess of 20% after treatment with anthracycline-based chemotherapy, mastectomy, and postmastectomy radiation. For such patients, MDACC is currently investigating whether concurrent capecitabine given during the course of postmastectomy radiation will help improve these outcomes. Capecitabine is an oral prodrug of 5-fluorouracil that undergoes sequential conversion to its active metabolite via an enzymatic pathway that is preferentially expressed in tumor cells (compared with normal tissues). In addition, treatment of tumor cells with radiation selectively upregulates the expression of one critical enzyme in this pathway, providing a mechanism for synergistic cell killing. Preclinical studies have confirmed this upregulation, and have also indicated that administration of capecitabine concurrently with radiation leads to synergistic cell kill in a number of tumor types, including breast cancer (Sawada et al. 1999). This strategy is also being used for patients with unresectable disease who fail to respond to a course of neoadjuvant treatment that includes an anthracycline and a taxane.

17.3.3 Radiation Therapy and Biological Therapy As stated previously, there have been two recently published studies [the Intergroup (NSABP B-31/ NCCTG 9831) and HERA trials] which showed improved recurrence-free survival and overall survival (Romond et al. 2005; Piccart-Gebhart et al. 2005). These studies allowed the inclusion of patients with locally advanced breast cancers; however, the percentage of the enrolled patients who had large primary tumors was low. In the NSABP B-31 trial, 16.7% of patients had tumors greater than 4.0 cm, and 42.6% of patients had four or more positive

lymph nodes (Romond et al. 2005). In the NCCTG 9831 study, 14.2% of patients had tumors greater than 4.0 cm, and 39.1% of patients had four or more positive lymph nodes. In the HERA study, only 4.4% of patients on the 1-year trastuzumab arm had T3 disease (Piccart-Gebhart et al. 2005). Of interest, 28.3% of patients had four or more lymph nodes positive. Because of the low number of patients with T3 cancers, it is difficult to extrapolate if there was benefit for this cohort of patients with trastuzumab; however, these studies suggest that patients with N2 disease, which are positive for HER2, should be treated with adjuvant trastuzumab. Herceptin has also been used as part of neoadjuvant treatment. Buzdar et al. (2005) reported the results of a trial from MDACC, which randomized 42 patients with HER2 positive breast cancer (T1T4, N0-N2, M0) treated with four cycles paclitaxel followed by four cycles of FEC (5-fluorouracil, epirubicin, cyclophosphamide) to either concurrent trastuzumab (given weekly) or additional therapy as neoadjuvant treatment. Patients either underwent BCT or mastectomy after their chemotherapy. The trial was originally designed to accrue 162 patients, but was stopped early due to significant improvement in the pathological complete response in the concurrent trastuzumab arm. The pathological CR for patients in the concurrent trastuzumab arm was 65.2%, compared with 26.0% in the chemotherapy alone arm (p=0.016).

17.4 Conclusion The last 20 years have yielded significant advances in the treatment of breast cancer. Adjuvant radiation therapy, chemotherapy, and hormonal therapy have all been shown to improve event-free and overall survival and are now part of the standard treatment in the management of breast cancer. Although there has been significant progress in determining the optimal combination and sequencing of these treatments, additional studies are still required to better integrate these therapies with each other. Furthermore, newer treatments, such as aromatase inhibitors and trastuzumab, also need to be integrated with conventional therapies to maximize their effectiveness and minimize their toxicity; therefore, the importance of the multidisciplinary management of breast cancer, with participation of the surgeons, radiation oncologists, medical oncologists, patholo-

Integration of Radiation Therapy and Systemic Therapy for Breast Cancer

gists, and diagnostic radiologists, must once again be emphasized. This is truly an exciting time in the management of breast cancer. Newer treatment techniques and modalities are constantly being developed. Coupled with the increasing knowledge about the biology of breast cancer, these treatments are allowing us to treat patients on a more individualized basis, with the aim of continually improving the rates of cure, as well as decreasing the risk of acute and late side effects.

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264 therapy and radiation therapy in early breast cancer has no effect on treatment delivery. Eur J Cancer 39:763–768 Fiets WE, van Helvoirt RP, Nortier JWR, van der Tweel I, Struikmans H (2003) Acute toxicity of concurrent adjuvant radiotherapy and chemotherapy (CMF or AC) in breast cancer patients: a prospective, comparative, nonrandomised study. Eur J Cancer 39:1081–1088 Fisher B, Smith R, Dignam J, Begovic M, Wolmark N, Wickerham DL et al (1999) Tamoxifen in treatment of intraductal breast cancer: National surgical adjuvant breast and bowel project B-24 randomised controlled trial. Lancet 353:1993– 2000 Fisher B, Land SR, Mamounas E, Dignam J, Fisher ER, Wolmark N (2001) Prevention of invasive breast cancer in women with ductal carcinoma in situ: an update of the national surgical adjuvant breast and bowel project experience. Semin Oncol 28:400–418 Fisher B, Anderson S, Bryant J, Margolese RG, Deutsch M, Fisher ER et al (2002) Twenty-year follow-up of a randomized trial comparing total mastectomy, lumpectomy, and lumpectomy plus irradiation for the treatment of invasive breast cancer. N Engl J Med 347:1233–1241 Formenti SC, Volm M, Skinner KA, Spicer D, Cohen D, Perez E et al (2003) Preoperative twice-weekly paclitaxel with concurrent radiation therapy followed by surgery and postoperative doxorubicin-based chemotherapy in locally advanced breast cancer: a phase I/II trial. J Clin Oncol 21:864–870 Goss PE, Ingle JN, Martino S, Robert NJ, Muss HB, Piccart MJ et al (2005) Randomized trial of letrozole following tamoxifen as extended adjuvant therapy in receptor-positive breast cancer: updated findings from NCIC CTG MA.17. J Natl Cancer Inst 97:1262–1271 Haffty BG, Kim JH, Higgins SA (2005) Concurrent chemoradiotherapy in conservatively managed early stage breast cancer (Abstract). Int J Radiat Oncol Biol Phys 63 (Suppl 1): S53 Hanna YM, Baglan KL, Stromberg JS, Vicini FA, Decker D (2002) Acute and subacute toxicity associated with concurrent adjuvant radiation therapy and paclitaxel in primary breast cancer therapy. Breast J 8:149–153 Harris EER, Christensen VJ, Hwang WT, Fox K, Solin LJ (2005) Impact of concurrent versus sequential tamoxifen with radiation therapy in early-stage breast cancer patients undergoing breast conservation treatment. J Clin Oncol 23:11–16 Henderson IC, Berry DA, Demetri GD, Cirrincione CT, Goldstein LJ, Martino S et al (2003) Improved outcomes from adding sequential paclitaxel but not from escalating doxorubicin dose in an adjuvant chemotherapy regimen for patients with node-positive primary breast cancer. J Clin Oncol 21:976–983 Huang EH, Tucker SL, Strom EA, McNeese MD, Kuerer HM, Buzdar AU et al (2004) Postmastectomy radiation improves local-regional control and survival for selected patients with locally advanced breast cancer treated with neoadjuvant chemotherapy and mastectomy. J Clin Oncol 22:4691–4699 Huang EH, Tucker SL, Strom EA, McNeese MD, Kuerer HM, Hortobagyi GN et al (2005) Predictors of locoregional recurrence in patients with locally advanced breast cancer treated with neoadjuvant chemotherapy, mastectomy, and radiotherapy. Int J Radiat Oncol Biol Phys 62:351–357

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Integration of Radiation Therapy and Systemic Therapy for Breast Cancer therapy for operable HER2-positive breast cancer. N Engl J Med 353:1673–1684 Sartor CI, Peterson BL, Woolf S, FitzGerald TJ, Laurie F, Turrisi AJ et al (2005) Effect of addition of adjuvant paclitaxel on radiotherapy delivery and locoregional control of nodepositive breast cancer: Cancer and Leukemia Group B 9344. J Clin Oncol 23:30–40 Sawada N, Ishikawa T, Sekiguchi F, Tanaka Y, Ishitsuka H et al (1999) X-ray irradiation induces thymidine phosphorylase and enhances the efficacy of capecitabine (Xeloda) in human cancer xenografts. Clin Cancer Res 5:2948–2953 Smith IC, Heys SD, Hutcheon AW, Miller ID, Payne S, Gilbert FJ et al (2002) Neoadjuvant chemotherapy in breast cancer: significantly enhanced response with docetaxel. J Clin Oncol 20:1456–1466 Sutherland RL, Hall RE, Taylor IW (1983) Cell proliferation kinetics of MCF-7 human mammary carcinoma cells in culture and effects of tamoxifen on exponentially growing and plateau-phase cells. Cancer Res 43:3998–4006 Taghian AG, Assaad SI, Niemierko A, Kuter I, Younger J, Schoenthaler R et al (2001) Risk of pneumonitis in breast cancer patients treated with radiation therapy and combination chemotherapy with paclitaxel. J Natl Cancer Inst 93:1806–1811 Tan-Chiu E, Yothers G, Romond E, Geyer CE, Ewer M, Keefe D et al (2005) Assessment of cardiac dysfunction in a randomized trial comparing doxorubicin and cyclophosphamide followed by paclitaxel, with or without trastuzumab as adjuvant therapy in node-posi-

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18 Applications in Rectal and Anal Cancer Claus Rödel and Rolf Sauer

CONTENTS 18.1 18.1.1 18.1.2 18.1.2.1 18.1.2.2 18.1.2.3 18.1.2.4 18.1.2.5 18.1.3 18.1.3.1 18.1.3.2 18.1.3.3 18.1.3.4 18.1.4 18.2 18.2.1 18.2.2 18.2.3 18.2.4

Rectal Cancer 267 Introduction 267 5-Fluorouracil-Based Radiochemotherapy 267 Randomized Trials of Postoperative Concurrent RCT 268 Randomized Trials to Optimize 5-FU-Based Postoperative RCT 269 Randomized Trials to Optimize the Sequence: Preoperative RCT 270 Concomitant Chemotherapy with Preoperative Radiation Therapy? 271 Conclusions from Trials with 5-FU-Based RCT 272 Integrating Novel Chemotherapeutic Agents into Preoperative Combined Modality Treatment 273 Oral Fluoropyrimidines 274 Oxaliplatin 276 Irinotecan 277 Targeted Therapy 277 Future Challenges for Combined-Modality Rectal Cancer Treatment 278 Anal Cancer 279 Introduction 279 Randomized Trials of RCT in Anal Cancer 279 Current Randomized Trails to Optimize Concurrent RCT 280 Future Directions in Anal Cancer Treatment with New Agents 281 References 281

18.1 Rectal Cancer 18.1.1 Introduction The rational for using combinations of radiation and systemic chemotherapy as a component of adjuvant treatment in stage T3/4 and/or node-positive rectal cancer (UICC stages II and III) is based on the risk of relapse after surgery alone and the evidence of radio- and drug-responsiveness derived from both laboratory studies and clinical trials. The past four decades have witnessed the development of a variety of preoperative and postoperative radio- and radiochemotherapy schedules designed to optimize the sequence of treatment modalities and the most appropriate scheduling of irradiation and 5-fluorouracil-based chemotherapy. Given that with optimized local treatment, including preoperative radiotherapy and total mesorectal excision (TME) surgery distant metastasis is by far the predominate pattern of tumor failure in rectal cancer presently, the future challenge is to integrate more effective systemic therapy into the multimodal concepts for this disease.

18.1.2 5-Fluorouracil-Based Radiochemotherapy

C. Rödel, MD Klinik and Poliklinik für Strahlentherapie, Universitätsklinikum Erlangen, Postfach 2306, Universitätsstrasse 27, 91054 Erlangen, Germany R. Sauer, MD Professor, Direktor der Strahlenklinik, Universitätsklinikum Erlangen, Postfach 2306, Universitätsstrasse 27, 91054 Erlangen, Germany

5-fluorouracil (5-FU), an analog of the pyrimidine uracil with a fluorine atom substituted in place of hydrogen at the carbon 5 (C-5) position, has been the most commonly used single chemotherapeutic agent for colorectal cancer during the past four decades, and will certainly also continue to be the backbone of modern drug combinations in the near future. Since its synthesis in 1957 by Heidelberger et al. (1957), the metabolism and mechanism of action of 5-FU have been studied in detail. 5-FU enters a complex anabolic process that accounts for cytotoxicity at the cellular level by interfering with normal DNA and RNA function. Heidelberger et al. (1958) also initially discov-

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Group 1985). Although rates of distant metastases were slightly lower in the two arms that contained chemotherapy, no single arm had a significant impact on distant failure; thus, the survival advantage achieved with combined RCT appeared to relate primarily to the marked reduction in local relapse rates. These result were later confirmed by a trial conducted by the Norwegian Adjuvant Rectal Cancer Project Group (Tveit et al. 1997). Again, the local relapse rate was significantly decreased from 30 to 12% by combined postoperative RCT compared with surgery alone, an effect which also translated into an improvement in 5-year survival, though no significant impact on distant metastases was achieved. The more recent NSABP R-02 also showed that combined RCT resulted in a significantly reduced local failure rate compared with chemotherapy alone (8 vs 13%); however, this small absolute reduction did no longer translate into a difference in overall survival (Wolmark et al. 2000). Evidently, in all these trials, the effect of concomitant 5-FU chemotherapy was primarily mediated through its radiosensitization properties rather than through its own systemic efficacy. This conclusion is further strengthened by a recent Italian study that showed no significant effect on local control and survival when postoperative radiotherapy (RT) and chemotherapy was applied sequentially rather than concomitantly (Cafiero et al. 2003). The NCCTG 794751 trial was the first to integrate a course of full-dose chemotherapy before as well as

ered that the addition of 5-FU to radiation in rodent tumors markedly enhanced the effects of radiation therapy. Based on these early preclinical data, Moertel et al. (1969) administered 5-FU with radiation to patients with gastrointestinal cancers and noted significant activity. The pioneering contribution to the use of combined radiotherapy and FU was made by Byfield et al. (1982), who demonstrated that 5FU radiosensitization resulted from specific time and concentration factors: The sensitizing effects of 5-FU in vitro are maximal when its exposure occurs for at least 24 h and up to 48 h after the radiation exposure, thus supporting a prolonged 5-FU exposure approach when given with fractionated irradiation. 18.1.2.1 Randomized Trials of Postoperative Concurrent RCT

Historically, the combination of postoperative radiotherapy and 5-FU-based chemotherapy has been shown in several randomized trials to reduce local recurrence rates and to improve overall survival compared with (conventional) surgery alone or surgery plus postoperative radiotherapy (Table 18.1). In the early GITSG 7175 trial, the best local control was achieved with combined RCT (local relapse rate of 11 vs 20% with RT alone), whereas no impact on local control was noted with chemotherapy as single adjuvant treatment (local relapse rate of 27 vs 24% with surgery alone; Gastrointestinal Tumor Study

Table 18.1. Randomized trials of postoperative radiation (RT), chemotherapy (CT), or combined radiochemotherapy (RCT) for locally advanced rectal cancer (UICC II and III) Reference

Treatment

Local failure (%) Distant failure (%) Five-year survival (%)

GITSG 7175 Surgery (Gastointestinal Tumor Surgery + RT Study Group 1985) Surgery + 5-FU/MeCCNU

24

34

45

20 (p=0.08)

30

52 (p<0.05)

27

27

56

Surgery + RT+5-FU/ MeCCNU 11

26

59

NCCTG/Mayo 794751 (Krook et al. 1991)

Surgery + RT

25 (p=0.04)

46 (p=0.01)

48 (p=0.025)

Surgery + RT+5-FU/MeCCNU

13.5

29

58

Norway trial (Tveit et al. 1997)

Surgery

30 (p=0.01)

39

50 (p=0.05)

Surgery + RT+5-FU

12

33

64

13 (p=0.02)

29

64

NSABP R-02 (Wolmark et al. 2000) Italy trial (Caﬁero et al. 2003)

aMale

Surgery + CT

a

Surgery + RCT

8

31

64

Surgery + RT

20

38

59

Surgery + 5-FU/LEV + RT + 5-FU/LEV (RT and CT applied sequentially)

22

27

43

patients received MOF (MeCCNU, Vincristin, 5-FU) or 5-FU/leucovorin; female patients only 5-FU/leucovorin

Applications in Rectal and Anal Cancer

after combined RCT in an attempt to exploit both the radiosensitization properties of 5-FU and its potential to reduce the incidence of distant metastases (Krook et al. 1991). Indeed, this was also the first trial in which both local relapse and distant metastasis rates were significantly reduced in the experimental arm. The National Cancer Institute Consensus Conference concluded in 1990 that combined RCT was the standard adjuvant treatment for patients with TNM stage-II and stage-III rectal cancer (NIH Consensus Conference 1990). 18.1.2.2 Randomized Trials to Optimize 5-FU-Based Postoperative RCT

Further trials by the GITSG (7180) and NCCTG (864751) investigated the need for methyl-CCNU in the chemotherapy regimen and found that it added no benefit to the 5-FU regimen (Table 18.2; Gastrointestinal Tumor Study Group 1992; O’Connell et al. 1994); thus, this compound is no longer used for

269

adjuvant RCT in rectal cancer. The NCCTG (864751) also tested the best method of administering 5-FU during radiotherapy: Bolus 5-FU (500 mg/m 2 for 3 days during weeks 1 and 5 of radiation therapy) was compared with continuous infusion (225 mg/m2 during the whole course of radiotherapy): a 10% disease-free and overall survival advantage was achieved with continuous infusion 5-FU during radiotherapy (Table 18.2). The INT 0144 trial tested the question whether additional continuous infusion 5-FU instead of bolus 5-FU before and after RCT (or modulation of 5-FU through addition of leucovorin and levamisol) may further increase tumor control. Data were reported at the 2003 annual meeting of the American Society of Clinical Oncology (ASCO) and showed no difference in 3-year survival (Table 18.2; Smalley et al. 2003). Results of a four-arm intergroup trial, INT 0114, also showed no significant differences in local control and survival among patients receiving either bolus 5-FU, bolus 5-FU + folinic acid, bolus 5-FU + levamisol, or bolus 5-FU + folinic acid + levami-

Table 18.2. Randomized trials of postoperative combined radiochemotherapy (RCT) in locally advanced rectal cancer Reference

Treatment

DFS (%)

OS (%)

GITSG 7180 (GITSG 1992)

RCT bolus 5-FU + bolus 5-FU (six cycles, escalating 5-FU)

68 (3 years)

75 (3 year)

RCT bolus 5-FU + bolus 5-FU/MeCCNU (12 months treatment)

54 (3 years; p=0.20)

66 (3 years; p=0.58)

Two cycles of bolus 5-FU (± MeCCNU) + RCT bolus 5-FU + two cycles of bolus 5-FU (± MeCCNU)

53 (4 years)

60 (4 years)

Two cycles of bolus 5-FU (± MeCCNU) + RCT PVI 5-FU + two cycles of bolus 5-FU (± MeCCNU)

63 (4 years; p=0.01)

70 (4 years; p=0.005)

Two cycles bolus 5-FU + RCT bolus 5-FU + two cycles bolus 5-FU

54% (all)

64% (all)

Two cycles bolus 5-FU/LV + RCT bolus 5-FU/LV + two cycles bolus 5-FU/LV

No significant difference

No significant difference

Two cycles bolus 5-FU + RCT PVI 5-FU + two cycles bolus 5-FU

68–69 (3 years)

81–83 (3 years)

PVI 5-FU + RCT PVI 5-FU + PVI 5-FU

No significant difference

No significant difference

RCT bolus FU/LV + six cycles bolus 5-FU/LV

81 (4 years)

84 (4 years)

Two cycles bolus 5-FU/LV + RCT bolus FU/LV + 4 cycles bolus 5-FU/LV

70 (4 years; p=0.04)

82 (4 years; p=0.39)

NCCTG 864751 (O’Connell et al. 1994)

INT 0114 (Tepper et al. 2002)

Two cycles bolus 5-FU/LEV + RCT bolus 5-FU + 2 cycles bolus 5-FU/LEV Two cycles bolus 5-FU/LV/LEV + RCT bolus 5-FU/LV + two cycles bolus 5-FU/LV/LEV INT 0144 (Smalley et al. 2003)

Two cycles bolus 5-FU/LV/LEV + RCT bolus 5-FU/LV + two cycles bolus 5-FU/LV/LEV Korean trial (Lee et al. 2002)

DFS disease-free survival, OS overall survival, LV leucovorin, LEV levamisole, PVI protracted venous infusion

270

sol (Tepper et al. 2002); however, gastrointestinal toxicity was higher in folinic acid containing regimens. The largest German adjuvant rectal cancer trial (FOGT 2) compared 5-FU + levamisol to 5-FU + levamisol + folinic acid and 5-FU + levamisol + interferone alpha as systemic treatment added to 45–50.4 Gy of radiotherapy. Toxicity was highest in the interferone containing arm, which was closed prematurely. Long-term results did not show any difference in failure rates and survival between the other groups (Staib et al. 2004). Given all these results, the standard design of postoperative RCT is to deliver six cycles of 5-FU chemotherapy with concurrent radiation therapy during cycles 3 and 4. During radiotherapy continuous infusion 5-FU regimens (e.g., 225 mg/m2 day –1 during the whole course of radiation, or 1000 mg/ m2 day –1 as 120-h continuous infusion during weeks 1 and 5 of radiation, like in the German CAO/ ARO/AIO-95-study; see below), are recommended. A recent randomized Korean trial (see Table 18.2) suggests that radiation should start with cycle 1 rather than cycle 3, which supports the radiobiological paradigm that subclinical disease in the pelvis is best controlled if RT is applied as soon as possible after surgical resection to account for any regrowth of residual tumor cells (Lee et al. 2002). 18.1.2.3 Randomized Trials to Optimize the Sequence: Preoperative RCT

The interest in preoperative radiochemotherapy for resectable tumors of the rectum is based not only on the success of the combined modality approach in the postoperative setting, but also on many radioand tumorbiological advantages of the preoperative approach. Among those are downsizing effects that possibly enhance curative surgery in locally advanced disease, and sphincter preservation in low-lying tumors. The small bowel in an unviolated abdomen will be mobile and less likely to be within a pelvic radiation portal, the irradiated volume does not require coverage of the perineum, as in the cases after abdominoperineal resection (APR), and there is no irradiation of the anastomotic region; thus, preoperative irradiation should cause less acute and late toxicity and more patients are likely to receive full-dose therapy. In addition, a certain dose of irradiation seems to be more effective if given preoperatively compared with postoperatively, most probably due to the fact that oxygen tension within the tumor may be higher prior to surgical compromise

C. Rödel and R. Sauer

of the regional blood flow. This may improve the radiosensitivity of the tumor by decreasing the more radioresistant hypoxic fraction. Until recently, the only randomized trial that directly compared preoperative to postoperative radiation therapy (both without chemotherapy) in rectal cancer has been the Uppsala trial, which was carried out between 1980 and 1985 in Sweden (Frykholm et al. 1993). In the preoperative arm, patients received intensive short-course radiation (five fractions of 5.1 Gy to a total dose of 25.5 Gy in 1 week), postoperatively conventional radiation therapy (2 Gy to a total of 60 Gy with a 2-week split after 40 Gy) was applied. Preoperative radiation significantly decreased local failure rate (13 vs 22%; p=0.02), however, there was no significant difference in 5-year survival rates (42 vs 38%). Prospective randomized trials comparing the efficacy of preoperative with standard postoperative RCT in UICC stage-II and stage-III rectal cancer were initiated both in the United States through the Radiation Therapy Oncology Group (RTOG 94-01) and the NSABP (R-03) as well as in Germany (Protocol CAO/ARO/AIO-94). Unfortunately, both U.S. trials suffered from lack of accrual and were closed prematurely. A preliminary report of the NSABP R03 trial (with a median follow-up of only 1 year) revealed that the percentage of patients who underwent sphincter sparing surgery and were without evidence of disease was higher in the preoperative vs the postoperative arm (44 vs 34%; Roh et al. 2001). The German study (CAO/ARO/AIO-94) has recently been completed with more than 820 patients included. The design of this trial and the treatment schedule is depicted in Fig. 18.1. Results were recently reported (Table 18.3): Compared with postoperative RCT, the preoperative combined modality approach was superior in terms of local control, downstaging, acute and chronic toxicity, and sphincter preservation in those patients judged by the surgeon to require an APR (Sauer et al. 2004). Given these advantages preoperative RCT is now the preferred adjuvant treatment for patients with locally advanced rectal cancer in Germany as well as in most parts of Europe; however, it needs to be emphasized that, with a median follow-up of 46 months, there was no difference in 5-year disease-free and overall survival rates between both treatment arms.

Applications in Rectal and Anal Cancer

271

Arm I: 5-FU 5-FU 5 x 1000 mg/m2 5 x 1000 mg/m2 120h-infusion 120h-infusion

4 cycles of adjuvant chemotherapy with 5-FU 500 mg/m2/d i.v. bolus for 5 days 3 weeks break

OP RT: 50.4 Gy + 5.4 Gy Boost

Arm II: 4 cycles of adjuvant chemotherapy with 5-FU 500 mg/m2/d i.v. bolus for 5 days 3 weeks break

5-FU 5-FU 5 x 1000 mg/m2 5 x 1000 mg/m2 120h-infusion 120h-infusion

OP RT: 50.4 Gy

Fig. 18.1. Design of the German CAO/ARO/AIO-94 study comparing postoperative (arm I) with preoperative radiochemotherapy (arm II) in locally advanced rectal cancer

Table 18.3. German Rectal Cancer Study Group randomized trial of preoperative compared with postoperative radiochemotherapy for rectal cancer. (From Sauer et al. 2004) Five-year outcome

Preoperative RCT (%)

Postoperative RCT (%)

p-value

Locoregional recurrence rate

6

13

0.006

Distant recurrence rate

36

38

0.84

Disease-free survival

68

65

0.32

Overall survival

74

76

0.80

Any grade-3/4 acute toxicity

27

40

0.001

Any grade-3/4 late toxicity

14

24

0.01

39

19

0.004

Sphincter preservation rate

a

RCT radiochemotherapy a In patients deemed to require abdominoperineal resection by the surgeon before randomization

18.1.2.4 Concomitant Chemotherapy with Preoperative Radiation Therapy?

The concurrent use of chemotherapy as part of the preoperative regimen is another important point, as it is not clear by now whether data from postoperative radiochemotherapy in resectable rectal cancer can be translated to the preoperative setting. For the treatment of primarily “unresectable,” fixed T4-rectal cancer, several institutions have applied preoperative RT and RCT. The goal is to convert (“downsize”) a tumor, which is clinically not amenable to curative resection at presentation,

to a resectable status. Minsky et al. (1992) compared preoperative radiotherapy (50.4 Gy) with or without 5-FU/folinic acid and showed that 90% of the patients with initially “unresectable” tumors were converted to resectable lesions by preoperative combined therapy as compared with only 64% of those who received radiation therapy alone. Moreover, a complete pathological response was found in 20% of patients receiving combined modality therapy as compared with 6% receiving radiotherapy alone, indicating an enhancement of radiation-induced “downstaging” by concomitant 5-FU-based RCT. In a recent randomized phase-III study comparing radiotherapy alone with combined radiochemo-

C. Rödel and R. Sauer

272

therapy for primarily unresectable T4-rectal cancer, Frykholm et al. (2001) could demonstrate that the addition of chemotherapy to radiotherapy significantly improved local control rates, albeit again no significant difference in survival was found between the groups. A Polish randomized trial compared preoperative short-course irradiation (5×5 Gy) and immediate surgery with conventionally fractionated RCT (1.8– 50.4 Gy) and delayed surgery in 316 patients with locally advanced (T3/T4) low rectal cancer (Bujko et al. 2004). The primary end point of the trial was the rate of sphincter preserving surgery. Despite a significant increase in tumor response in the RCT group (pathological complete remission, 16 vs 1%; mean largest tumor diameter on the operative specimen, 29 vs 48 mm), the rate of sphincter preservation was 61% in the immediate surgery group and 58% in the delayed group, indicating a strong commitment of the surgeons in this trial not to change their choice whatever the tumor response was after neoadjuvant RCT. In primarily resectable tumors (cT3/4 and/or cN+), the European Organization for Research and Treatment of Cancer (EORTC) has conducted a fourarm trial that treated all patients with preoperative radiation in conventional fractionation (45 Gy in Table 18.4. Preoperative conventionally fractionated radiotherapy with or without 5-FU/LV-based chemotherapy. Results of EORTC 22921 and FFCD 9203 randomised trials. (From Bosset et al. 2005; Gerard et al. 2005) Five-year outcome

Preoperative Preoperative p-value RT RCT

EORTC 22921 (n=1011) pCR rate

5.3%

13.7%

<0.001

ypN0

60.5%

71.9%

<0.001

Tumor size (median) 30 mm

25 mm

<0.0001

Sphincter preserved

52.4%

55.6%

0.05

Local failure

17%

8%

0.002

Overall survival

64.8%

65.6%

0.79

pCR rate

3.7%

11.7%

<0.0001

Sphincter preserved

52.6%

51.7%

n.s.

Grade-3+4 toxicity

2.7%

14.6%

<0.0001

Local failure

8%

16.5%

n.g.

Overall survival

66%

67%

n.g.

FFCD 9203 (n=762)

RT radiotherapy, RCT radiochemotherapy, pCR pathologic complete remission, n.s. not signiﬁcant, n.g. not given

25 fractions) and tested whether preoperative concurrent RCT with 5-FU/folinic acid, postoperative 5-FU/folinic acid, or both are superior to preoperative radiation alone (Table 18.4; Bosset et al. 2005a; Bosset et al. 2005b). The FFCD 9203 was a 2-arm trial also randomizing patients to preoperative 45 Gy with or without bolus 5-FU/folinic acid (Gerard et al. 2005). All patients received postoperative chemotherapy in this trial. First results of both trials were reported at the ASCO meeting 2005 and indicated that the addition of 5-FU/folinic acid to preoperative conventionally fractionated radiation therapy significantly increased the pathological complete response rates, reduced tumor size and lymph nodal invasion, increased sphincter preservation (in EORTC 22921 only), and long-term local control rates, yet, these advantages once again did not translate into a survival benefit for patients treated by combined radiation and chemotherapy (Table 18.4). 18.1.2.5 Conclusions from Trials with 5-FU-Based RCT

In summary, if the available data on post- and preoperative RCT with 5-FU-based chemotherapy for rectal cancer are considered, the following conclusions can be drawn: 1. There is evidently a higher local effectiveness of concurrent radiation and 5-FU as compared with surgery alone or adjuvant radiotherapy or chemotherapy alone. In the postoperative setting, this is manifested by a higher probability of the combined approach to eradicate subclinical disease left behind after potentially curative surgery and, consequentially, by improved long-term local control rates (GITSG 7175, NCCTG 794751, Norway trial, NSABP R-02). In the preoperative setting, increased tumor downsizing and downstaging, increased pathological complete regression, and improved local control rates are seen with concurrent radiation and 5-FU (EORTC 22921; FFCD 9203; Frykholm et al. 2001; Bujko et al. 2004). 2. It is likely that these phenomena are due not only to pure additive effects of both cytotoxic modalities but also to some forms of interaction between radiotherapy and 5-FU (as suggested by the negative results of the sequential Italy trial as compared with the positive results of concurrent RCT trials; Table 18.1). These interactions may range from classical “radiosensitization,” as shown in in vitro and animal studies, to more complex processes, such as 5-FU-induced inhibition

Applications in Rectal and Anal Cancer

of (accelerated) repopulation during fractionated radiotherapy. As predicted by early laboratory studies, prolonged administration of 5-FU during radiotherapy seems to be more effective in this respect compared with 5-FU bolus programs (NCCTG 864751), although this has not consistently been shown (INT 0144). Conversely, biochemical modulation 5-FU (by folinic acid, levamisol, or both) has not been proven to be superior to 5-FU alone (INT 0114, INT 0144). 3. If in clinical trials the absolute differences in local control rates between the combined modality approaches and unimodal adjuvant treatment or surgery alone are in the range of 10% and above, these differences potentially translate into survival beneﬁts (GITSG 7175, NCCTG 794751, Norway trial). With the advent of modern surgical techniques, including total mesorectal excision, the absolute number of local events has been markedly reduced and, thus, the absolute differences in local control rates, although still signiﬁcant, are smaller and do not readily translate into any survival beneﬁt (as shown in NSABP R-02, CAO/ARO/AIO-94, EORTC 22921, FFCD 9203). 4. The impact of 5-FU-chemotherapy and the various ways of its administration and modulation on the control of distant disease is less clear. The NCCTG 794751 demonstrated both reduced local and distant relapse rates with 5-FU-based chemotherapy during as well as before and after RCT. Although the necessity of maintenance chemotherapy has been questioned both in the adjuvant (Hellenic trial; Table 18.2) and neoadjuvant setting (EORTC 22921), most oncologists now use continuous infusion 5-FU concurrently with

273

preoperative radiation therapy and four courses of 5-FU with or without folinic acid as additional systemic treatment following surgery. As shown in the recent German CAO/ARO/AIO-94 trial, this approach, together with TME surgery, has led to a local failure rate of only 6%; however, it became also evident that the pattern of failure is now dominated by distant metastases (36% at 5 years in CAO/ARO/AIO-94). Improvement of results in the treatment of rectal cancer will obviously require a more effective systemic approach.

18.1.3 Integrating Novel Chemotherapeutic Agents into Preoperative Combined Modality Treatment Novel chemotherapeutic agents, such as capecitabine, oral uracil and tegaful (UFT), tomudex, oxaliplatin, and irinotecan, as well as targeted therapies, such as bevacizumab and cetuximab, which have improved results of patients treated in the adjuvant and metastatic setting for colorectal cancer, are currently incorporated into phase-I/II combined modality programs for rectal cancer as well. All suggest higher pathological complete response (pCR) rates compared with 5-FU-radiochemotherapy alone (Tables 18.5–18.10); however, for some agents, with this increased pCR rate is an associated increase in acute toxicity. Clearly, phase-III trials are needed to determine if these regimens offer an advantage compared with 5-FU-based combined modality regimen.

Table 18.5. Phase-I studies of radiochemotherapy for locally advanced rectal cancer using orally administered ﬂuoropyrimidines Reference

Number

Concurrent radiochemotherapy

Dose-limiting toxicity

Recommended dose

Dunst et al. (2002)

36

Preop., postop., or palliative RT: 1.8–50.4 Gy Capecitabine 250–1250 mg/m2 bid for duration of RT

Grade-3 hand-foot syndrome at a dose level of capecitabine 1000 mg/m2 day–1 bid

Capecitabine 825 mg/m2 bid for duration of RT

Postop. RT: 1.8–50.4 Gy Capecitabine 500–850 mg/m2 bid for duration of RT

Grade-3 diarrhea at a dose level of capecitabine 850 mg/ m2 day–1

Capecitabine 800 mg/m2 bid for duration of RT

Preop. RT: 1.8–50.4 Gy Capecitabine 425–1000 mg/m2 bid Monday to Friday for duration of RT

Grade-3 diarrhea at a dose level of capecitabine 1000 mg/ m2 day–1 bid Monday to Friday for duration of RT

Capecitabine 900 mg/m2 bid Monday to Friday for duration of RT

Souglakos et al. 31 (2003)

Ngan et al. (2004)

RT radiotherapy

28

C. Rödel and R. Sauer

274

Table 18.6. Phase-II studies of preoperative radiochemotherapy for locally advanced rectal cancer with orally administered ﬂuoropyrimidines Reference

Number Concurrent radiochemotherapy

Kim et al. (2002)

45

Fernandez-Martos 94 et al. (2004) 95

Kim et al. (2005)

Toxicity

pCR (%)

Grade-3 hand–foot synPreop. RT: 1.8–50.4 Gy Days 1–14 and 22–35: Capecitabine 825 mg/m2 bid drome 7%, diarrhea 4%, fatigue 4%

31

Preop. RT: 1.8–45 Gy UFT 400 mg/m2 day–1, 5 days a week for 5 weeks

Grade-3 diarrhea 14%, leukopenia 14%

9

Preop. RT: 2.0–50 Gy Capecitabine 825 mg/m2 bid during RT

Grade-3 diarrhea 3%, neutropenia 1%

12

RT radiotherapy, UFT oral uracil and tegaful, pCR pathological complete response

Table 18.7. Phase-I studies of preoperative radiochemotherapy for locally advanced rectal cancer using oxaliplatin-based combined modality treatment Reference

Number Concurrent radiochemotherapy

Dose-limiting toxicity

Recommended dose of oxaliplatin

Freyer et al. (2001)

17

Preop. RT: 1.8–45 Gy Days 1–5 and 29–33: 5-FU 350 mg/m2 day-1, LV 100 mg/m2 day-1; days 1 and 29: oxaliplatin 80, 100, 130 mg/m2 day-1

MTD not reached

Days 1, 29: oxaliplatin 130 mg/m2 day-1

Rödel et al. (2003)

6

Preop. RT: 1.8–50.4 Gy Days 1–14 and 22–35: capecitabine 825 mg/m2 bid; days 1, 8 and 22, 29: oxaliplatin 50–60 mg/m2 day-1

Grade-3 diarrhea at a Days 1, 8, 22, 29: oxaliplatin dose level of oxaliplatin 50 mg/m2 day-1 60 mg/m2 day-1

Gambacorta et al. (2004)

18

MTD not reached Preop. RT: 1.8–50.4 Gy Days 1, 19, 38: Raltitrexed 3 mg/m2 day-1, oxaliplatin 65, 85, 110, 130 mg/m2 day-1

Days 1, 19, 38: oxaliplatin 130 mg/m2 day-1

Aschele et al. (2005)

25

Preop. RT: 1.8–50.4 Gy Duration of RT: 5-FU 200, 225 mg/m2 day-1, oxaliplatin 25, 35, 45, 60 mg/m2 day-1 once weekly for a total of six courses

MTD not reached

Weekly oxaliplatin 60 mg/ m2 day-1; 5-FU 225 mg/m2 day-1 during RT

Loi et al. (2005)

16

RT: 1.8–50.4 Gy 5-FU 200 mg/m2 day-1 5 days, 7 days per week during RT; Days 1, 15, 29: oxaliplatin 70, 85 mg/m2 day-1

Grade-3 diarrhea at a dose level of 5-FU 200 mg/m2 day-1, 7 days per week, and oxaliplatin 85 mg/m2 day-1

5-FU 200 mg/m2 day-1, 5 days per week during RT; days 1, 15, 29: oxaliplatin 85 mg/m2 day-1

RT radiotherapy, LV leucovorin, MTD maximum tolerated dose

18.1.3.1 Oral Fluoropyrimidines

Capecitabine is an oral fluoropyrimidine that mimics the pharmacokinetics of continuous 5-FU infusion and is preferentially converted to the active 5-FU metabolite within tumor cells by exploiting the higher activity of the enzyme thymidine phos-

phorylase in tumor tissue compared with normal tissue (Schuller et al. 2000). This tumor-selective activation of capecitabine might be improved further when combined with RT, which upregulates thymidine phosphorylase in tumor cells but not in healthy tissue (Sawada et al. 1999). Preclinical studies have shown that the combination of capecitabine and radiotherapy has highly enhanced antitumor

Applications in Rectal and Anal Cancer

275

Table 18.8. Phase-II studies of preoperative radiochemotherapy for locally advanced rectal cancer using oxaliplatin-based combined-modality treatment Reference

Number Concurrent radiochemotherapy

Toxicity

pCR (%)

Carraro et al. (2002)

22

Preop. RT: 1.8–50.4 Gy Days 1–4 and 29–32: 5-FU 375 mg/m2 day-1, LV 20 mg/m2 day-1, oxaliplatin 25 mg/m2 day-1; day 15: oxaliplatin 50 mg/m2; four weeks after RT, one additional cycle of oxaliplatin, 5-FU/LV (same dose as during RT)

Grade-4: leukopenia 4.5% Grade-3: diarrhea 27%; leukopenia 4.5%

25

Gérard et al. (2003)

40

Preop. RT: 1.8–45 Gy (concomitant boost to 50 Gy) Days 1–5 and 29–33: 5-FU 350 mg/m2 day-1, LV 100 mg/m2 day-1; days 1 and 29: oxaliplatin 130 mg/ m2 day-1

Grade-4: diarrhea 2.5%; mucositis 2.5% Grade-3: fatigue 7.5%; diarrhea 5%; proctitis 5%; neutropenia 2.5%

15

Rödel et al. (2003)

26

Preop. RT: 1.8 Gy to 50.4 Gy Days 1–14 and 22–35: capecitabine 825 mg/m2 bid; days 1, 8, 22, 29: oxaliplatin 50 mg/m2 day-1

Grade-3: diarrhea 8%; skin (local) 8%

19

Preop. RT: 1.8–50.4 Gy Days 1, 19, 38: raltitrexed 3 mg/m2 day-1; oxaliplatin 130 mg/m2 day-1

Grade-3: leukopenia 10%; vomiting 3%; proctitis 3%

30

Gambacorta et al. 30 (2004) 25

Aschele et al. (2005)

Preop. RT: 1.8–50.4 Gy Grade-3: diarrhea 16%; skin 28 Duration of RT: 5-FU 225 mg/m2 day-1, oxaliplatin (local) 12%; anemia 4% 60 mg/m2 day-1 once weekly for a total of six courses

pCR pathological complete response, RT radiotherapy, LV leucovorin

Table 18.9. Phase-I studies of preoperative radiochemotherapy for locally advanced rectal cancer using irinotecan-based combined-modality treatment Reference

Number Concurrent radiochemotherapy

Dose limiting toxicity Recommended dose of CPT-11 Grade 3 diarrhea at dose level CPT-11 105 mg/m²/d

28 Voelter et al. (2003)

Preop. RT: 1.6 Gy bid to 41.6 Gy (started on day 8) Days 1, 8, 15: CPT-11 30–105 mg/m2 day-1

Hofheinz 19 et al. (2005)

Grade 3 diarrhea at Preop. RT: 1.8–50.4 Gy Days 1–38: capecitabine 500, 625 mg/m2 day-1 dose level CapecitabDays 1, 8, 15, 22, 29: CPT-11 50 mg/m2 day-1 ine 625 mg/m²/d

Days 1, 8, 15: CPT-11 90 mg/m²/d Days 1–38: Capecitabine 500 mg/m²/d; days 1, 8, 15, 22, 29: CPT-11 50 mg/m²/d

Table 18.10. Phase-II studies of preoperative radiochemotherapy for locally advanced rectal cancer using irinotecan-based combined-modality treatment Reference

Number

Concurrent radiochemotherapy

Toxicity

pCR (%)

Mehta et al. (2003)

32

Preop. RT: 1.8–50.4 Gy Days 1–33: 5-FU 200 mg/m2 day-1; days 1, 8, 15, 22: CPT-11 50 mg/m2 day-1

Grade 3: diarrhea 28%; mucositis 21%; proctitis 21%; abdominal cramping 9%

37

Klautke et al. (2005)

37

Preop. RT: 1.8–50.4 Gy Duration of RT: 5-FU 250 mg/m2 day-1; CPT-11 40 mg/m2 day-1 once weekly for a total of six courses

Grade 4: diarrhea 5%; leukopenia 2%; grade 3: diarrhea 27%; leukopenia 8%

22

pCR pathological complete response, RT radiotherapy

276

activity compared with radiation or capecitabine alone (Sawada et al. 1999). Three phase-I studies have been conducted to determine the maximum tolerated dose (MTD) of capecitabine in combination with standard RT in patients with rectal cancer (Table 18.5). Capecitabine plus RT demonstrated promising activity in the study by Dunst et al. (2002), including one pathological complete remission (pCR) and nine partial responses (PR) in the 10 patients treated in the neo-adjuvant setting. Furthermore, no grade-3 or grade-4 toxicities occurred in patients treated at the recommended dose (continuous capecitabine 825 mg/m2 twice daily in combination with standard RT). In the two other phase-I studies, the MTD of capecitabine was reached at a dose level of 1000 mg/ m2 twice daily on Monday to Friday throughout the course of preoperative pelvic RT, and at a dose of 800 mg/m2 twice daily during postoperative radiotherapy, respectively (Ngan et al. 2004; Souglakos et al. 2003). Phase-II studies of preoperative radiotherapy with capecitabine and UFT indicate pCR rates in the range of 9 and 31%, with diarrhea and hand– foot syndrome as the main grade-3 acute toxicity (Table 18.6; Fernandez-Martos et al. 2004; Kim et al. 2005; Kim et al. 2002). An ongoing German phase-III trial currently compared capecitabine with standard infusional 5-FU in patients undergoing pre- or postoperative radiotherapy for locally advanced rectal cancer. The NSABP R-04 trial is a prospective randomized trial of neoadjuvant radiotherapy with capecitabine vs infusional 5-FU (r oxaliplatin in both arms). The use of postoperative adjuvant chemotherapy is left open to investigators or they may enter intergroup study E5202 (postoperative FOLFOX r avastin vs 5-FU/LV r avastin). Based on the available data in adjuvant and metastatic colon cancer trials, that compared capecitabine to intravenous 5-FU plus folinic acid (Twelves et al. 2005; Van Cutsem et al. 2004), it is likely that oral fluoropyrimidines will finally replace infusional 5FU with radiotherapy in rectal cancer as well. 18.1.3.2 Oxaliplatin

Oxaliplatin is a very reasonable candidate for inclusion into neoadjuvant downsizing regimens because of its rapid cytoreductive capacity and its relative lack of acute dose-limiting side effects when added to 5-FU or capecitabine. As a preoperative regimen for initially unresectable liver metastases, the com-

C. Rödel and R. Sauer

bination of oxaliplatin and 5-FU/folinc acid resulted in tumor downsizing in 59% of patients and in a complete resection rate of 38% (Giacchetti et al. 1999). Randomized phase-III trials have demonstrated the superiority of combined oxaliplatin and 5-FU/folinic acid compared with 5-FU/folinic acid in metastatic colorectal disease in terms of response and progression-free survival and, more recently, also in the adjuvant treatment of colon cancer in terms of improved disease-free survival (Andre et al. 2004; Giacchetti et al. 2000). In vitro and in vivo preclinical studies have demonstrated oxaliplatin to be a potent radiosensitizing agent (Cividalli et al. 2002; Magne et al. 2003). In the in vivo xenograft model of HT-29 colon carcinoma, oxaliplatin showed increased cytotoxicity when combined with irradiation (Blackstock et al. 1999). Although it remains controversial whether oxaliplatin should be delivered before or after radiation to maximize its radiosensitizing activity, more recent investigations suggest that oxaliplatin should likely be given a number of hours before RT to maximize benefit (A.W. Blackstock et al., unpublished data). Freyer et al. (2001) have recently published results from a phase-I study of RT (45 Gy over 5 weeks) plus oxaliplatin and 5-FU/folinic acid demonstrating the feasibility of such an intensified chemotherapy regimen when given concomitantly with preoperative RT (Table 18.7). For historical reasons, chemotherapy was administered only in the first and fifth week of RT in this study: using escalating doses of oxaliplatin (80, 100, or 130 mg/m2 on days 1 and 29), 5-FU (350 mg/m2 on days 1–5 and 29–33) and leucovorin (100 mg/m2 on days 1–5 and 29–33) the MTD was not reached. In a subsequent phase-II trial, Gerard et al. (2003) demonstrated that such a preoperative combined RCT regimen (with 130 mg/m 2 oxaliplatin on days 1 and 29) was well tolerated with no increase in surgical toxicity and a promising complete patholological response rate of 15%. If the goal of preoperative chemoradiation is to maximize tumor shrinkage prior to surgery as well as to improve systemic control, concomitant chemotherapy should be as dense as possible (i.e., applied as often as possible during RT) to maximize local effectiveness by radiation sensitization, and as intense as possible to effectively eradicate microscopic distant disease. In addition, acute toxicity may be substantially reduced through chemotherapy dose fractionation, that may also allow a higher cumulative dose to be administered during radiotherapy; thus, subsequent trials developed and tested novel combined modal-

Applications in Rectal and Anal Cancer

ity regimen that incorporated oxaliplatin at a weekly rather than a monthly basis. Aschele et al. (2005) reported the feasibility and promising activity (pCR rate 28%) of an intensified preoperative RCT regimen where oxaliplatin was administered weekly at a dose of 60 mg/m2 for six cycles together with 5-FU 225 mg/m2 day-1 as continuous infusion during the whole course of RT (50.4 Gy/28 fractions). Rödel et al. (2003) used a combination of capecitabine and oxaliplatin given weekly with preoperative RT, apart from a 7-day break during the third week of RT. This group also found this preoperative regimen to be well tolerated and effective (pCR rate 19%). It is noteworthy that, for all the studies summarized in Table 18.7 and 18.8, either no postoperative chemotherapy at all was applied or adjuvant chemotherapy was left to the discretion of the treating physician. Given the fact that (a) in previous 5-FU-based phase-III trials concomitant as well as sequential (adjuvant) cycles of chemotherapy were applied, and (b) the overall cumulative doses of the new drugs reached during radiotherapy is substantially lower than in adjuvant colon cancer trials, two multicenter phase-II trials (the French CORE study, and a multicenter phase-II study from the German Rectal Cancer Study Group) currently are investigating the role of preoperative concomitant RCT with capecitabine and oxaliplatin plus four to six cycles of adjuvant XELOX chemotherapy. The double-arm randomized CHRONICLE trial in the United Kingdom tests the question of whether six cycles of adjuvant XELOX after 5-FU based preoperative RCT and curative resection improves disease-free survival compared with no adjuvant chemotherapy at all. 18.1.3.3 Irinotecan

Irinotecan, a semisynthetic derivate of camptothecin, is a potent inhibitor of topoisomerase I, a nuclear enzyme that plays a critical role in DNA replication and transcription. This drug has now become standard therapy in first- and second-line treatment of metastatic colorectal cancer in combination with bolus or infusional 5-FU. With a mechanism of action interfering with DNA replication, irinotecan also showed radiosensitizing properties in preclinical studies, which showed maximum synergistic effects when irinotecan was administered 1 h before irradiation (Rich et al. 2001). A valid concern in using topoisomerase inhibitors with 5-FU and pelvic irradiation, however, is overlapping toxicity, particularly the development of severe diarrhea.

277

Reminiscent of the combined modality approaches with oxaliplatin and for the same reasons, weekly schedules of irinotecan administration (in the dose range of 40–50 mg/m2 day-1 given once weekly) have been developed in combination with continuous infusion 5-FU or capecitabine (Tables 18.9, 18.10). The published phase-I/II trials with this novel combination suggest that gastrointestinal acute toxicity is manageable and pCR rates are highly promising (Hofheinz et al. 2005; Klautke et al. 2005; Mehta et al. 2003; Voelter et al. 2003). 18.1.3.4 Targeted Therapy

The epidermal growth factor receptor (EGFR) is expressed in 50–70% of colorectal cancer. Enhanced EGFR signaling may affect cell cycle control, apoptosis, and angiogenesis, leading to tumor growth and progression. In a cohort of patients with rectal cancer treated by surgery alone, increased EGFR levels were significantly associated with unfavorable histopathological factors, such as lymph node involvement, more advanced UICC-TNM stages, and predicted for a reduced overall survival (Kopp et al. 2003). In a group of rectal cancer patients treated with preoperative radiotherapy and surgery, Giralt et al. (2005) identified EGFR expression as an indicator for poor pathological response to radiotherapy, and reduced disease-free survival following curative surgery. Several preclinical studies have shown that blocking EGFR ligand binding via monoclonal antibody (e.g., cetuximab) can enhance tumor radiosensitivity (Baumann and Krause 2004). Clinical studies of preoperative RCT have now been initiated to evaluate EGFR inhibitors as radiosensitizers in rectal cancer as well. Figure 18.2 depicts the design of our own study incorporating capecitabine, oxaliplatin, and cetuximab plus preoperative radiotherapy in locally advanced rectal cancer. First experiences with this schedule do not indicate increased toxicity apart from acne-like rash commonly associated with the EGFR antibody. The ongoing EXPERT-C trial is a multicenter randomized phase-II trial comparing oxaliplatin, capecitabine, and preoperative radiotherapy with or without cetuximab for magnetic resonance imaging (MRI)-defined poor risk rectal cancer. Whether or not these combinations will further improve the pathological complete response rates, and whether or not this possible improvement will finally translate into an improved disease-free survival, needs to be awaited.

C. Rödel and R. Sauer

278

Radiotherapy: 28 x 1.8 Gy

50. 4 G y

Chemotherapy

d 1 - 14

d 22 - 35

Capecitabine (1650 mg/m2/d) d8

d1

Oxaliplatin (35–50 mg/m2/d)

d 22

Cetuximab

d 29

6 x 2 5 0 mg/m /d d -7

d1

1 x 400 mg/m2 Week

Fig. 18.2. Design of a German multicenter phase-II trial of preoperative radiation therapy plus capecitabine, oxaliplatin, and cetuximab in rectal cancer

-1

d 15

d8

1

2

d 22

3

d 35

d 29

4

Inhibition of vascular endothelial growth factor (VEGF) via an anti-VEGF antibody (e.g., bevacizumab) has been shown to block the growth of a number of human cancer cell lines, including colorectal, in nude mice (Ferrara and Davis-Smyth 1997). Recent experimental studies in human tumor xenograft models indicate that VEGF blockade serves as a potent enhancer of radiation therapy. Willett et al. (2004a) have reported on a phase-I study of preoperative bevacizumab (5–10 mg/kg days 1, 15, 29, 43), 5-FU (225 mg/m2 day-1 days 15– 52), and radiation therapy (50.4 Gy days 15–52) for clinical T3 or T4 rectal cancer. Preliminary data indicate both the safety of this regimen and significant activity (6 of 7 evaluable patients demonstrated only microscopic disease in the surgical specimen 7 weeks after completion of neoadjuvant treatment). In a meticulous analysis of the first 6 patients performed 12 days after the first bevacizumab infusion, this group revealed a significant decrease in tumor blood perfusion and blood volume, and a significant decrease in tumor microvessel density (Willett et al. 2004b). This was accompanied by a decrease of the interstitial fluid pressure, indicating that a «normalization» of the tumor vasculature by anti-VEGF treatment may contribute to the high efficacy of bevacizumab in this and other recent clinical trials.

18.1.4 Future Challenges for Combined-Modality Rectal Cancer Treatment New data have been collected and progress has been made both in surgery and perioperative radio(chemo)therapy. Better knowledge of microscopic lymphatic spread within the mesorectum has led to

5

6

the use of total mesorectal excision for mid and low rectal cancer. With this “optimized” surgery, local control rates have been markedly increased and local failure rates above 15–20% are now no longer acceptable. Technical advances in radiotherapy, including tumor- and radiobiologically optimized fractionation, 3D treatment planning and intensity-modulated radiation therapy, will further allow realization of more sophisticated treatment volumes to reduce irradiation of normal tissue and increase the therapeutic index. Moreover, novel chemotherapeutic and biological agents, e.g., capecitabine, oxaliplatin, irinotecan, cetuximab, and bevacizumab, are currently incorporated in multimodality regimens. Evidently, the current monolithic approaches, established by studies more than a decade ago, to either apply the same schedule of preoperative or postoperative 5-FU-based radiochemotherapy to all patients with TNM stage-II/III rectal cancer or to give preoperative intensive short-course radiation according to the Swedish and Dutch concept for all patients with resectable rectal cancer irrespective of tumor stage and treatment goal (e.g., sphincter preservation), need to be questioned. The inclusion of different multimodal treatments into the surgical oncological concept, adapted to the tumor location and stage and to individual patient’s risk factors is mandatory. Clearly, future developments will aim at identifying and selecting patients for the ideal treatment alternatives; thus, clinicopathological and molecular features as well as accurate preoperative imaging and staging methods with endorectal ultrasound and MRI will take an important and integrative part in multimodality treatment of rectal cancer.

Applications in Rectal and Anal Cancer

279

18.2 Anal Cancer 18.2.1 Introduction Anal cancer serves as a paradigm for the successful application of RCT and the concept of radiosensitization. For this solid tumor, combined-modality therapy is now the mainstay of a curative approach with surgery reserved as a salvage for non-responders or recurrent disease. Before the 1980s, radical surgery with APR was the most frequently recommended treatment, as early results obtained with radiotherapy alone varied considerably with respect to oncological results, and radiation-related complications were considered unacceptable. The earliest report on concomitant RCT for anal cancer with modest doses of RT (30 Gy/15 fractions) administered concomitantly with continuous infusion 5-FU (1 g/m2 days 1–4, 28–31) and mitomycin-C (MMC) bolus injection (10–15 mg/m2 days 1) was by Nigro et al. (1974). This regimen was scheduled as a planned preoperative therapy; however, it soon became doubtful whether radical surgery was necessary, because the majority of resected specimen were completely free of tumor on pathological examination; thus, routine APR was abandoned and definitive RCT became standard of care. Since then, several retrospective and prospective non-randomized phase-II trials have reported on results with combined RCT without primary surgery in the treatment of anal cancer patients (Table 18.11);

all revealed complete tumor regression in the range of 67–95%, with salvage surgery being necessary for local failure in 6–29%, and an overall survival of 65–90% (Allal et al. 1993; Bosset et al. 2003; Doci et al. 1996; Ferrigno et al. 2005; Grabenbauer et al. 2005; Martenson et al. 1995; Rich et al. 1993; Sischy et al. 1989; Tanum et al. 1991).

18.2.2 Randomized Trials of RCT in Anal Cancer Although these phase-II trials of combined modality anal cancer treatment demonstrated the feasibility and efficacy of this approach, the value of sensitizing chemotherapy remained unproven. Two European phase-III trials compared combined RCT with radiotherapy alone (Table 18.12). The EORTC trial required a locally advanced tumor (T3-4 or T1/2 N+), whereas the UKCCCR trial allowed patients with any stage of disease (Bartelink et al. 1997; UKCCCR Anal Cancer Trial Working Party 1996). Although no overall survival benefit was observed, both studies revealed increased tumor regression and a significantly improved local control rate with the combined-modality treatment using continuous infusion 5-FU and bolus MMC; thus, these two randomized trials gave clear evidence of the benefit of concomitant chemotherapy in primary anal cancer treatment. The intergroup study (ECOG/RTOG) examined the importance of MMC in the standard regimen (Flam et al. 1996). The RT consisted of 45 Gy given

Table 18.11. Selected phase-II trials and retrospective studies of concurrent radio- and chemotherapy for anal cancer Reference

Number Median F/U Treatment (months)

CR Local failures Overall survival (%) (%) (%)

Sischy et al. (1989)

79

79

RT: 40.8 Gy + 5-FU, MMC

90

29/3 years

73/3 years

Tanum et al. (1991)

86

>36

RT: 50 Gy + 5-FU, MMC

84

n.g.

72/5 years

Allal et al. (1993)

68

48

RT: 50–57 Gy + 5-FU, MMC

67.5 32

65/5 years

Martenson et al. (1995)

50

n.g.

RT: 50–53 Gy + 5-FU, MMC

74

20/7 years

58/7 years

Rich et al. (1993)

18

20

RT: 54 Gy + 5-FU, cisplatin

95

15/2 years

94/2 years

Doci et al. (1996)

35

37

RT: 54–58 Gy + 5-FU, cisplatin

94

6

94/5 years

Bosset et al. (2003)

43

30

RT: 59.4 Gy, gap 2 weeks after 36 Gy + 5-FU, MMC

91

12/3 years

81/3 years

Ferrigno et al. (2005) 43

42

RT: 55 Gy + 5-FU, MMC

93

21

68/5 years

90

RT: 50.4 Gy r boost + 5-FU, MMC

84

14/5 years

72/5 years

Grabenbauer et al. (2005)

101

F/U follow-up, RT radiotherapy, MMC mitomycin C, CR complete remission, n.g. not given

C. Rödel and R. Sauer

280

Table 18.12. Results of randomized clinical trials of concurrent radio- and chemotherapy in anal cancer Reference

Treatment

No. of Three-year Three-year CR patients (%)a local controlb overall survival

UKCCCR 1996 T1-T4, N0-N+

279 RT alone: 45 Gy/20–25 fx + 6-week gap: 15- to 25-Gy boost, if CR/PR RT + 5-FU (1 g/m2 days 1–4, 29–32) + 283 MMC (12 mg/m2 day 1)

Flam et al. (1996) RT 45–50.4 Gy/25–28 fx + 5-FU (1 g/m2 day 1–4, 29–32) + 9-Gy boost (+5-FU/Cis)c RT + 5-FU + MMC (ECOG/RTOG) (10 mg/m2 days 1, 29) + 9-Gy boost (+5-FU/Cis)c T1-T4, N0-N+ Bartelink et al. (1997; EORTC) T1-2 N+ or any T3/4

RT alone: 45 Gy/25 fx + 6-week gap: 15- to 20-Gy boost, if CR/PR RT + 5-FU (750 mg/m2 days 1–5, 29–33) + MMC (15 mg/m2 day 1)

30 39

39* 61*

145

85

146

92

66 (4 years)* 84 (4 years)*

52

54* 80*

55* 69*

51

58 65 67 (4 years) 76 (4 years) 64 69

a

Assessment of complete response (CR) was 6 weeks after 45 Gy (before boost) in UKCCCR, and 4–6 weeks after completion of 50.4 and 60–65 Gy in ECOG/RTOG and EORTC, respectively b In UKCCCR salvage surgery (for non-responders or treatment morbidity) was considered local failure, in EORTC patients who underwent surgery to achieve local control at the completion of radiotherapy (RT) were considered locally controlled c If postinduction biopsy 4–6 weeks after completion of radiochemotherapy positive: 9 Gy/ﬁve fractions boost + 5-FU (1 g/m2 days 1–4) + cisplatin (100 mg/m2 day 2) *p<0.05

in 1.8-Gy fractions with a boost for positive lymph nodes or residual local disease to 50.4 Gy. If postinduction biopsy 4–6 weeks after completion of RCT was positive, additional RCT was applied to salvage residual disease prior to surgical salvage and permanent colostomy. As shown in Table 18.12, the addition of MMC to 5-FU significantly reduced local failure rates and improved colostomy-free and disease-free survival rates compared with 5-FU alone. In a previous non-randomized series of subsequent prospectives protocols, Cummings et al. (1991) also found a significant advantage in adding MMC to 5-FU and radiotherapy in terms of local control compared with radiotherapy alone or radiotherapy with 5-FU alone; thus, reminiscent of the combined modality approaches in rectal cancer treatment, the concomitant addition of two-drug combination chemotherapy (infusional 5-FU+MMC) to radiation therapy resulted in improved tumor regression and sustained local control as compared with radiotherapy alone or radiotherapy with 5-FU alone in the treatment of anal cancer, too. Synergistic interactions between radiation and 5-FU or MMC and between 5-FU and MMC have been demonstrated in mammalian tumor cell lines in vitro (Dobrowsky et al. 1992). Conversely, and also reminiscent of rectal cancer treatment, if in clinical trials chemotherapy and radiotherapy were administered sequentially, as, for example, in a series of 42 patients who received sequential 5-FU plus MMC followed by radiation therapy for anal cancer, complete tumor regression has been observed in only 45% (Miller et al. 1991).

18.2.3 Current Randomized Trias to Optimize Concurrent RCT Although the above-mentioned series have established that combined RCT is superior to radiotherapy alone in terms of local control, the most appropriate radiotherapy dose, fractionation, techniques, duration of gap (if any), and the most effective chemotherapy regimen (agents, number of neoadjuvant, concomitant, adjuvant cycles) await further investigation. Given the fact that MMC is associated with significant acute hematological toxicity and possibly also with long-term effects to the lungs and bone marrow, and considering that cisplatin-based chemotherapy strategies are effective in the treatment of other squamous-cell cancers, the role of cisplatin in the neoadjuvant, concurrent, and adjuvant setting of anal cancer treatment is currently under assessment in a variety of trials. The EORTC 22011/40014 investigates the value of cisplatin as a substitute to 5-FU. The RTOG-9811 trial tests two cycles of cisplatin + 5-FU, followed by concomitant RCT with both drugs against the standard treatment of RCT with 5-FU + MMC. The UKCCCR ACT-II trial is a randomized trial of a 2×2 design, comparing RT + 5-FU+MMC with RT + 5-FU + cisplatin. The second part of the randomization compares two further cycles of adjuvant 5-FU and cisplatin with no further treatment after RCT. A French trial (FFCD 9804) already assumes cisplatin-based RCT to be the standard treatment and randomizes patients

Applications in Rectal and Anal Cancer

between a low-dose or high-dose RT boost, and between induction chemotherapy or no induction chemotherapy.

18.2.4 Future Directions in Anal Cancer Treatment with New Agents Given the positive results of combination chemotherapy and radiation therapy in the above-mentioned phase-III trials, a pilot study in the United Kingdom (ACT II pilot) is currently testing a triple chemotherapy and radiation approach with integration of 5-FU, MMC, and cisplatin into the combined modality treatment of anal cancer. A phase-II study at the M.D. Anderson Cancer Center (Houston, Texas) investigates the role of capecitabine and oxaliplatin with radiation therapy in patients with locally advanced anal cancer (AJCC stage II–IIIB). In this trial, patients received capecitabine (1650 mg/m2 orally Monday through Friday), weekly oxaliplatin (50 mg/m2) and radiation therapy (45 Gy for T1, 55 Gy for T2, or 59 Gy for T3–T4 lesions). Preliminary data indicate the feasibility of this approach (Eng et al. 2005). In a recent randomized phase-II trial, the addition of another radiosensitizing agent, namely intracavitary hyperthermia, to RCT with 5-FU and MMC resulted in a significantly improved local recurrence-free and colostomy-free survival time (Kouloulias et al. 2005). A further possibility to improve the local efficacy of radiotherapy may well arise from targeted therapies. Squamous cell carcinoma in other tumor sites strongly expresses epidermal growth factor receptors. In a recent study of 21 patients with anal cancer, all tumors strongly expressed EGFR, indicating that clinical studies with EGFR inhibitors are warranted in the treatment of anal cancer as well (Le et al. 2005). Given all these different possibilities and combinations, the future challenge in the treatment of anal cancer is to identify and select patients for the appropriate treatment alternatives; these may well range from radiotherapy alone in early lesions to combined modality approaches including (neo-)adjuvant and concurrent cycles of chemotherapy and targeted therapies in more advanced disease.

281

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283 tration to colorectal cancer patients. Cancer Chemother Pharmacol 45:291–297 Sischy B, Doggett RL, Krall JM et al (1989) Definitive irradiation and chemotherapy for radiosensitization in management of anal carcinoma: interim report on Radiation Therapy Oncology Group study no. 8314. J Natl Cancer Inst 81:850–856 Smalley SR, Benedetti J, Williamson S et al (2003) Intergroup 0144: phase III trial of 5-FU based chemotherapy regimens plus radiotherapy (XRT) in postoperative adjuvant rectal cancer. Bolus 5-FU vs prolonged venous infusion (PVI) before and after XRT + PVI vs bolus 5-FU + leucovorin (LV) + levamisole (LEV) before and after XRT + bolus 5FU + LV. Proc Am Soc Clin Oncol, Abstract 1006 Souglakos J, Androulakis N, Mavroudis D et al (2003) Multicenter dose-finding study of concurrent capecitabine and radiotherapy as adjuvant treatment for operable rectal cancer. Int J Radiat Oncol Biol Phys 56:1284–1287 Staib L, Kornmann M, Roettinger E et al (2004) Adjuvant radiochemotherapy in resectable stage II, III rectal cancer: results of the FOGT-2 trial. Proc Am Soc Clin Oncol, Abstract 3608 Tanum G, Tveit K, Karlsen KO et al (1991) Chemotherapy and radiation therapy for anal carcinoma. Survival and late morbidity. Cancer 67:2462–2466 Tepper JE, O’Connell M, Niedzwiecki D et al (2002) Adjuvant therapy in rectal cancer: analysis of stage, sex, and local control-final report of intergroup 0114. J Clin Oncol 20:1744–1750 Tveit KM, Guldvog I, Hagen S et al (1997) Randomized controlled trial of postoperative radiotherapy and short-term time-scheduled 5-fluorouracil against surgery alone in the treatment of Dukes B and C rectal cancer. Norwegian Adjuvant Rectal Cancer Project Group. Br J Surg 84:1130–1135 Twelves C, Wong A, Nowacki MP et al (2005) Capecitabine as adjuvant treatment for stage III colon cancer. N Engl J Med 352:2696–2704 UKCCCR Anal Cancer Trial Working Party. (1996) Epidermoid anal cancer: results from the UKCCCR randomised trial of radiotherapy alone versus radiotherapy, 5-fluorouracil, and mitomycin. Lancet 348:1049–1054 Van Cutsem E, Hoff PM, Harper P et al (2004) Oral capecitabine vs intravenous 5-fluorouracil and leucovorin: integrated efficacy data and novel analyses from two large, randomised, phase III trials. Br J Cancer 90:1190–1197 Voelter V, Stupp R, Matter M et al (2003) Preoperative hyperfractionated accelerated radiotherapy (HART) and concomitant CPT-11 in locally advanced rectal carcinoma: a phase I study. Int J Radiat Oncol Biol Phys 56:1288–1294 Willett CG, Chung D, Sahani D et al (2004a) Phase I study of neoadjuvant bevacizumab, 5-fluorouracil, and radiation therapy followed by surgery for patients with primary rectal cancer. Proc Am Soc Clin Oncol, Abstract 3589 Willett CG, Boucher Y, di Tomaso E et al (2004b) Direct evidence that the VEGF-specific antibody bevacizumab has antivascular effects in human rectal cancer. Nat Med 10:145–147 Wolmark N, Wieand HS, Hyams DM et al (2000) Randomized trial of postoperative adjuvant chemotherapy with or without radiotherapy for carcinoma of the rectum: National Surgical Adjuvant Breast and Bowel Project Protocol R-02. J Natl Cancer Inst 92:388–396

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19 Concomitant Radiation and Chemotherapy in Muscle-Invasive Bladder Cancer Jürgen Dunst, Claus Rödel, Anthony Zietman

CONTENTS

19.9

19.1 19.2

19.9.1

19.3 19.4 19.5 19.6 19.6.1 19.6.2 19.6.3 19.7 19.7.1

19.7.2 19.7.3 19.7.4 19.7.4.1 19.7.4.2 19.7.4.3 19.7.4.4 19.7.4.5 19.7.4.6 19.7.4.7 19.7.4.8 19.8 19.8.1 19.8.2 19.8.3

Introduction 285 Organ Preservation in Urinary Bladder Cancer: Theoretical Aspects 285 Limitations of Historical Series 286 Cystectomy vs Radiotherapy: Randomized Trials 287 Pre- or Postoperative Radiochemotherapy with Planned Cystectomy 287 Modern Series with a Trimodality Approach and the Goal of Organ Preservation 288 Overall Survival 288 Prognostic Factors 290 Role of Salvage Cystectomy 291 Role of Chemotherapy 292 Adjuvant and Neoadjuvant Chemotherapy in Non-Metastatic Urothelial Bladder Cancer: Meta-Analyses 292 Neoadjuvant Chemotherapy 292 Concurrent Radiochemotherapy 292 Type of Drugs in Combined Regimens 293 Cisplatin 293 Carboplatin 293 Taxanes 294 5-Fluorouracil and Capecitabine 294 Gemcitabine 294 Vinblastine 294 Multidrug Regimes 294 Novel Molecular and Targeted Therapies 295 Acute and Late Toxicity 295 Acute Toxicity of Concurrent Radiochemotherapy 295 Late Toxicity After Radiochemotherapy 295 Organ Preservation and Bladder Function 296

19.9.2 19.9.3 19.9.4 19.9.5 19.9.6 19.10

Current Strategy in an OrganPreserving Treatment Concept 296 Indication for Radiochemotherapy in a Multimodal Approach with Organ Preservation 296 Transurethral Surgery 297 Radiotherapy 297 Chemotherapy 297 Omission of Chemotherapy? 298 Response Evaluation 298 Future Research Issues 299 References 299

19.1 Introduction Organ- and function preservation has become a major goal in contemporary oncological treatment concepts. In some tumor sites, e.g., breast, larynx, anal cancer or soft tissue sarcomas, organ preservation is considered as standard approach for most patients with radical surgery restricted to salvage treatment for failures after conservative therapy. Urothelial bladder cancer is a radiosensitive disease and radiation therapy offers an effective method for organ preservation, especially if combined with simultaneous chemotherapy.

19.2 Organ Preservation in Urinary Bladder Cancer: Theoretical Aspects J. Dunst, MD Professor, Department of Radiation Oncology, University Hospital Schleswig-Holstein, Campus Lübeck, Ratzeburger Allee 160, 23538 Lübeck, Germany C. Rödel, MD Department of Radiation Oncology, Friedrich-AlexanderUniversität Erlangen, Universitätsstrasse 27, 91054 Erlangen, Germany A. Zietman, MD Department of Radiation Oncology, Massachusetts General Hospital, 101 Blossom Street, Boston, MA 02114, USA

Radical cystectomy is considered as standard of care for muscle-invasive bladder cancer by most urologists; however, the concept of organ preservation by limited surgery and radiochemotherapy which is currently used in larynx, other head and neck, or anal-canal cancers may also be effective in urothelial bladder cancer. Despite evidence from several series, this approach is so far not widely accepted (Gospodarowicz 2002). In a

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survey, Moore and coworkers (1988) asked expert physicians about their attitude on treatment of locally advanced bladder cancer. Nearly all U.S. urologists and medical oncologists favored radical cystectomy as standard approach. In contrast, one-third of the British urologists recommended radiotherapy (Table 19.1). The best explanation for these discrepancies is the fact that radiotherapy has been widely used as primary treatment for locally advanced bladder cancer in the UK. Large series from single institutions in Great Britain and the largest randomized trial, also from the UK, have over years proven the general efficacy of radiotherapy. Additional theoretical support for an organpreserving approach comes from the biology of muscle-invasive bladder cancer. In general, muscle-invasive cancers (Tt2) behave more aggressively as compared with the more frequent superficial tumors. They are characterized by a higher risk of local recurrence after transurethral surgery as well as a high frequency of occult systemic spread. Even in case of radical cystectomy, about 50% of all patients will eventually die from metastatic disease. This situation is comparable to lymph-node-positive breast cancer. Organpreserving treatment in breast cancer has been clearly demonstrated to be as effective as radical mastectomy in terms of overall survival. The same holds probably true for muscle-invasive bladder cancer. Moreover, urothelial cancers are relatively radiosensitive. The TCD50 (calculated from selected series or estimated from series with preoperative radiotherapy and planned cystectomy) is comparable or even lower than the TCD50 of squamous cell carcinomas of the head and neck (Maciejewski and Majewski 1991). The efficacy of radiotherapy or combined radiochemotherapy in head and neck cancers, however, has been proven.

19.3 Limitations of Historical Series Most historical series of radiotherapy for bladder cancer have yielded survival figures inferior to those obtained in surgical series of the same time period. These differences in outcome (absolute difference in 5-year overall survival about 20% for T2 category and 10% for T3 category) do not necessarily reflect a superiority of radical surgery but are due mainly to other reasons. In most series, radical cystectomy was used as primary treatment for muscle-invading bladder cancer with radiation restricted for patients unsuitable for major surgery; thus, radiotherapy patients reflect a negative selection with regard to age distribution and performance status despite comparable clinical stages. Age and performance status, however, are major independent prognostic factors in locally advanced bladder cancer, together with pretreatment anemia and elevated erythrocyte sedimentation rate. These patient-related prognostic factors have a stronger impact on long-term survival than T-category and can be used for the prediction of treatment outcome especially in irradiated patients. The selection bias in historical series becomes evident if one compares series from the same institution or region and if one further analyzes the results of subgroups. For example, two reports from the Norwegian Radium Hospital summarize the results of surgery and radiotherapy for bladder cancer over the same time period in a distinct region of Norway (Fossa et al. 1993; Waehre et al. 1993). Surgery was the treatment of first choice; therefore, surgical patients were significantly younger and had a better stage distribution and less comorbidity than irradiated patients. The highly significant difference in survival between surgically treated and irradiated patients (5-year survival 58 vs 24%) decreases if one compares subgroups of comparable age and T-categories (Dunst et al. 2001). Taking into account the lacking

Table 19.1. Expert physicians’ attitude toward radiotherapy in bladder cancer (probably depends more on geographical and educational factors than scientific data). (Adapted from Moore et al. 1988) Recommended therapy

U.S. urologists (%)

British urologists

Medical oncologists

Radiation oncologists

Cystectomy

60

11

29

4

Preop. XRT + cystectomy

8

15

18

39

Chemotherapy + cystectomy

20

4

25

8

Definitive radiotherapy (XRT)

0

44

0

31

Others

12

26

20

18

Concomitant Radiation and Chemotherapy in Muscle–Invasive Bladder Cancer

information on other patient-related prognostic factors, the difference between radical cystectomy and definitive radiotherapy is probably small, if there is any. Furthermore, inclusion of superficial tumors or intraoperative exclusion of non-resectable advanced cancer may improve the results of radical surgery. This becomes obvious if contemporary cystectomy series are analyzed in detail (Table 19.2). The second reason is related to tumor staging. Patients in radiation therapy series are clinically staged as compared with pathologically staged patients in series with cystectomy. Clinical staging in bladder cancer, however, results in an important understaging error in the range of 30% and above as compared with pathological staging. This partly explains the differences in outcome especially in patients with less advanced tumors (T2). Suboptimal treatment concepts also play an important role. Major surgical aspects of an organ-preserving treatment concept which presently would be considered as mandatory have not been specifically addressed in historical series. A complete transurethral resection of the tumor was not routinely performed. Restaging after radiotherapy was also not systematically done and curative salvage surgery for local failure in the bladder was not generally offered. Also additional chemotherapy was not administered. Finally, modern treatment planning based on computed tomography (CT planning) was not performed and a lot of series used ancient fractionation regimens with high doses per fraction. This may have contributed to a higher risk of late sequelae, especially bladder shrinkage or chronic radiation cystitis.

19.4 Cystectomy vs Radiotherapy: Randomized Trials So far, four relatively small randomized trials have compared preoperative radiotherapy and planned cystectomy vs definitive radiotherapy alone. The smallest study from the M.D. Anderson Hospital showed a benefit for radical cystectomy; however, the surgical patients in this study were treated not only with cystectomy alone but with an additional potentially curative preoperative radiation regimen with 50 Gy. The other studies demonstrated comparable results with preoperative radiotherapy and planned cystectomy vs radical radiotherapy with salvage cystectomy in selected cases. A meta-analysis demonstrated a small survival benefit for preopera-

287

Table 19.2. Selection bias improves the results of radical cystectomy. Analysis of one of the largest contemporary series in the literature (Stein et al. 2001). The 5-year overall survival of 60% is better than in radiotherapy (XRT) series, but includes favorable prognostic categories with pT<2. Total no. of cystectomies in the period 1971–1997

1471

Exclusion due to non-urothelial histology or salvage 305 cystectomy after XRT Cystectomies for urothelial cancers

1166

Intraoperative exclusion due to irresectability

23

Intraoperative exclusion due to detection of metastases

46

Intraoperative exclusion due to R2 resection

43

Curative cystectomies

1054

Five-year overall survival after curative cystectomy

60%

Superficial tumors (pTa, pTis, pT1)

421

Five-year overall survival of patients with superficial tumors

79%

Cystectomies for muscle-invading tumorsT2−4

633

Five-year overall survival of patients with muscleinvading tumors

47%

No. of all patients with muscle-invading tumors and 745 (attempted or performed) cystectomy Five-year overall survival of all patients with muscle-invading tumors

|

If only muscle-invading tumors are analyzed (as are included in radiotherapy series), the 5-year overall survival is only 47%. Moreover, 112 cases were treated surgically but later excluded because of metastases or irresectable tumor. If these cases would have been included (this is necessary for comparison with a radiotherapy series because the exclusion was based on intraoperative findings), the 5-year overall survival of all surgically treated patients with muscle-invading tumors would probably be <42%.

tive radiotherapy plus planned cystectomy, but it is questionable whether these data can be extrapolated to modern series with a bladder-sparing approach (Shelley et al. 2004). In summary, a significant advantage of cystectomy has not yet been proven.

19.5 Pre- or Postoperative Radiochemotherapy with Planned Cystectomy Preoperative irradiation prior to cystectomy may yield a complete histological response in about 30%

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of patients; however, this effect has not increased survival rates and has not been integrated in standard therapy guidelines. There are currently no data on concurrent radiochemotherapy in conjunction with planned cystectomy for advanced bladder cancer.

19.6 Modern Series with a Trimodality Approach and the Goal of Organ Preservation 19.6.1 Overall Survival Over the past 1015 years, the concept of organ preservation by conservative surgery and combined

radiochemotherapy has been investigated in several prospective series from single centers and multicenter cooperative groups. The data from the Boston and Radiation Therapy Oncology Group (RTOG) studies as well as from other studies are listed in Tables 19.3 and Table 19.4. All of these series used transurethral resection and subsequent radiochemotherapy. Most of the series used cisplatin-based regimens. The 5-year survival figures obtained are at least comparable to the survival from large series with radical cystectomy if only patients with muscle invasion (as included in radiotherapy series) are analyzed and if lymph-node-positive patients (which are also excluded in some surgical series or reported separately) are included (Table 19.5); however, about 75% of the patients treated with a bladder-sparing trimodality approach and radiochemotherapy maintained their own bladders.

Table 19.3. Massachusetts General Hospital (MGH) and RTOG series of combined modality treatment and selective bladder preservation Series/reference

Num- Clinical Induction treatment ber stage Neoadjuvant Concurrent treatment treatment

Complete Consolidation RCT response regimen for compCR (%) plete responders (± adjuvant chemotherapy)

5-Yr Overall Survival (%)

5-Yr OS with Bladder (%)

MGH 1986−1993 106 (Kachnic et al. 1997)

T2−4a

TURBIT two cycles MCV

39.6 Gy in 1.8 Gy plus cisplatin

66

25.2 Gy in 1.8 Gy plus cisplatin

52

43

RTOG 85–12/ 1986−1988 (Tester et al. 1993)

42

T2-4a

TURBT

40 Gy in 2 Gy plus cisplatin

66

24 Gy in 2 Gy plus cisplatin

52

42

RTOG 88–02/ 1988−1990 (Tester et al. 1996)

91

T2−4a

TURBT two cycles MCV

39.6 Gy in 1.8 Gy plus cisplatin

75

25.2 Gy in 1.8 Gy plus cisplatin

62 (4 yr)

44 (4 yr)

RTOG 89–03/ 123 1990−1993 (Shipley et al. 1998)

T2−4a

TURBT plus 39.6 Gy in two cycles 1.8 Gy plus MCV vs no cisplatin chemotherapy

61 vs 55

25.2 Gy in 1.8 Gy plus cisplatin

49 vs 48

36 vs 40

MGH 1993−1994 (Zietman et al. 1998)

18

T2−4a

TURBT

42.5 Gy in 1.25 and 1.5 Gy bid plus 5-FU and cisplatin

78

22.5 Gy in 1.25 and 83 1.5 Gy bid plus 5-FU (3 yr) and cisplatin, three cycles of adjuvant MCV

78 (3 yr)

RTOG 95–06/ 1995−1997 (Kaufman et al. 2000)

34

T2−4a

TURBT

24 Gy in 3 Gy bid plus 5-FU and cisplatin

67

20 Gy in 2.5 Gy bid plus 5-FU and cisplatin

83 (3 yr)

66 (3 yr)

RTOG 97–06/ 1997−1999 (Hagan et al. 2003)

47

T2−4a

TURBT

40.8 Gy in 1.8 and 1.6 Gy bid plus Cisplatin

74

24 Gy in 1.5 Gy bid 61 plus cisplatin, three (3 yr) cycles of adjuvant MCV

48 (3 yr)

Concomitant Radiation and Chemotherapy in Muscle–Invasive Bladder Cancer

289

Table 19.4. Additional series of combined modality treatment and selective bladder preservation. n.g. not given Clinical Induction treatment stage Neoadjuvant Concurrent treatment treatment

Complete Consolidation response RCT regimen for complete respond(%) ers (radjuvant chemotherapy)

Five-year 5-year OS overall with bladsurvival der (%) (OS; %)

Russell et al. 34 (1990)

T14

TURBT

44 Gy at 2 Gy plus 5-FU

81

16 Gy at 2 Gy plus 5-FU

64 n.g. (over(4 years) all rate of cystectomy: 10 of 34)

Rotman et al. 20 (1990)

T14

TURBT

6065 Gy at 1.8 Gy plus 5-FU

74

_

39

n.g. (19 of 20 maintained bladder)

93

T24

TURBT; two or three cycles MVAC or MCV

64.8 Gy at 1.8 Gy plus cisplatin (49 patients)

63

−

39

n.g. for patients treated with RCT

T24

TURBT

24 Gy at 3 Gy plus cisplatin/ 5-FU

77

20 Gy at 2.5 Gy plus 63 cisplatin/5-FU

−

41

Reference

Given et al. (1995)

Number

Housset et al. 120 (1993, 1997) Fellin et al. (1997)

56

T24

TURBT; plus two cycles of MCV

40 Gy at 1.8 Gy plus cisplatin

50

24 Gy at 2 Gy plus cisplatin

55

Cervak et al. (1991)

105

T2−4

TURBT; two to four cycles MCV

−

52

50 Gy at 2 Gy

58 45 (4 years) (4 years)

Zapatero et al. (2000)

40

T24

TURBT; plus three cycles MCV

−

70

60 Gy at 2 Gy

84 82.6 (4 years) (4 years)

Arias et al. (2000)

50

T24

TURBT; plus two cycles M-VAC

45 Gy at 1.8 Gy plus cisplatin

68

20 Gy at 2 Gy

48

−

Rödel et al. (2002a,b)

415

T14

TURBT

50.459 Gy at 1.8 Gy plus carboplatin/ cisplatin

72

−

50

42

Chen et al. (2003)

23

T34

TURBT

6061.2 Gy at 1.8/2 Gy plus cisplatin/5-FU/ leucovorin

89

−

69 n.g. (3 years)

Danesi et al. (2004)

77

T24

TURBT; two cycles induction

Hyperfractionated XRT plus cisplatin/5-FU

90

−

59

47%

Hussain et al. 41 (2004)

T24

TURBT

50 Gy at 2.5 Gy plus 5-FU/ MMC

69

−

36

14 of 16 survivors maintained bladder

T2

TURBT

24 Gy at 3 Gy plus cisplatin/5-FU

74

Two additional cycles of radiochemotherapy (doses not given)

60 (cancer specific)

n.g. (overall rate of cystectomy: 25.6%

Peyromaure et al. (2004)

43

J. Dunst et al.

290 Table 19.5. Results of radical cystectomy. Current series with publication date between 1980 and 2000. (Adapted from Dunst and Rödel 2003) Reference

Stage

Number

Five-year overall survival (%)

Bredael et al. (1980)

pT3b pN0

24

25

pT4 pN0

11

18

pN+

26

4

Smith and Whitmore (1981)

pN+

134

10

Skinner et al. (1982)

pN+

36

35

Giuliani et al. (1985)

pT3 pN0

61

11

pT4 pN0

18

0

Zincke et al. (1985)

pN+

57

10

Skinner and Lieskovsky (1988)

pT2 pN0

n.a.

69

pT3b pN0

29

Malkovicz et al. (1990)

pT2 pN0

Pagano et al. (1991)

pT2 pN0

22 58

Frazier et al. (1993)

76 63

pT3a pN0

n.a.

67

pT3b pN0

n.a.

22

pT4 pN0 Wishnow et al. (1991)

83

pT3a pN0

40

21

pT3b pN0

48

58

pT4 pN0

21

49

90

64

pT2 pN0 pT3−4 pN0

240

39

Vieweg et al. (1999)

pN+

193

31

Gschwend et al. (2000)

pT2 pN0

121

82

pT3a pN0

74

71

pT3b pN0

128

44

Hautmann et al. (1998) Bassi et al. (1999)

All patients in all series

pT4b pN0

29

26

pT2-3a pN0

85

89

pT3b-4 pN0

50

53

pT2 pN0-1

67

63

pT3 pN0-1

142

43

pT4 pN0-1

49

28

1824

43

19.6.2 Prognostic Factors Several well-known prognostic factors have been established over decades in large trials; these include tumor-related parameters (mainly T-category, but also multifocality and papillary vs solid-infiltrating growth pattern) as well as patient-related parameters (age, performance status, pretreatment anemia). The most important single prognostic

factor is the completeness of transurethral surgery (TUR) prior to radiotherapy. The overwhelming impact of a complete TUR on local control and survival has first been demonstrated by Shipley and coworkers (1987). In a recent analysis of a large series from the University of Erlangen, patients undergoing definitive radiotherapy were classified in three subgroups depending on the completeness of the preceding TUR (Dunst et al. 1994, Rödel et al. 2002a). The TUR was performed as “differenti-

Concomitant Radiation and Chemotherapy in Muscle–Invasive Bladder Cancer

ated” TUR with separate resection of the tumor, the deep tumor ground and the lateral areas around the tumor. The completeness of the TUR was classified according to the R-classification: R0 relates to macroscopically complete TUR with no visible tumor left, on histology no evidence of microscopic tumor in the specimens from the border and ground of resection; R1: macroscopically complete TUR with no visible tumor left, on histology evidence of microscopic tumor in at least one of the specimens from the border and/or ground of resection; R2: macroscopically incomplete TUR with visible tumor left or irresectable tumor. In the Erlangen series, the completeness of the TUR was highly dependent on the clinical T-category; however, the residual tumor after TUR was the most important and (in a multivariate analysis) the only independent prognostic factor for local control and survival (Fig. 19.1). The small group of T3- and T4-tumors with a complete TUR had a prognosis comparable to that of T2 R0-tumors, whereas the prognosis of tumors after incomplete TUR was poor irrespective of whether T2- or T3-tumors were treated. The 5-year overall survival was 81% after R0-TUR, 53% after R1-TUR, and 31% after macroscopically incomplete TUR. The fact that a complete TUR is the most important single prognostic factor is not necessarily proof that the TUR is the most important part of an organpreserving treatment approach. If the urologist attempts a complete TUR, then a R0-TUR results in part from the quality of the surgical procedure and the skills and experience of the surgeon; however, it also reflects the biology and growth pattern of the tumor. If the tumor growth pattern is relatively superficial and circumscript, then the urologist will probably be able to successfully remove the tumor 1.0 0.9

Overall Survival

0.8 0.7 0.6

R0

0.5 0.4

R1

0.3 0.2 0.1 0.0

R2

pp < 0.0001 < 0.0001 0

10

20

30

40

50

60

70

80

90 100 110 120 Month

Fig. 19.1. Impact of residual tumor after TUR (R-classiﬁcation) on overall survival. (Data from the University of Erlangen)

291

with free margins; however, if there is deep invasion or extensive submucosal spread, a complete TUR cannot be achieved. Thus, a histologically complete TUR is probably the best prognostic parameter because it reflects the extent of deep muscle invasion. Moreover, if one assumes that patients with a R0-TUR are those with tumors that infiltrate only the inner part of the muscle wall (corresponding to pT2a), this subgroup in a radiotherapy series would correspond to the pT2a group in series with radical cystectomy. The radiotherapy series in which these histological factors have been determined have reported excellent survival figures for this favorable subgroup (e.g., a 5-year overall survival of 88% for T23 R0-tumors in the Erlangen series) which are as good or better than the survival figures for early muscle-infiltrating cancers in surgical series.

19.6.3 Role of Salvage Cystectomy Salvage cystectomy plays an important role in an organ-preserving treatment concept in bladder cancer. In contrast to local recurrences after radical cystectomy, which are considered as incurable and are therefore nearly exclusively treated with palliative intent, local recurrences in the preserved bladder can be treated with curative intent. Thirty to 40% of patients who undergo an organ-preserving treatment with radio- or radiochemotherapy present with residual microscopic disease or locally recurrent tumors after completion of radiotherapy. About half of these “recurrences” are superficial tumors which play an important role in the longterm follow-up of patients. Most of these tumors represent new primaries and are not true local recurrences. Non-invasive tumors (Tis, Ta) can be successfully managed by transurethral surgery again, either as sole treatment or in combination with intravesical chemo- or immunotherapy. Deeply infiltrating muscle invasive recurrences (most of them are probably residual tumors or true recurrences) require a salvage cystectomy; however, the prognosis of patients after salvage cystectomy is relatively good with 5-year overall survival figures after salvage treatment in the range of 40% (Table 19.6). The mortality of salvage cystectomy is not significantly higher than the mortality of primary cystectomy. The relatively good prognosis of a local recurrence in the preserved organ in case of radical salvage treatment is comparable to the situation in breast cancer

J. Dunst et al.

292 Table 19.6. Prognosis after salvage cystectomy for failure after radiotherapy or radiochemotherapy Reference

No. of patients

Five-year overall survival after salvage cystectomy (%)

Wallace and Bloom (1976)

18

52 (T3)

Swanson et al. (1981)

62

43 64 (dcT2) 25 (tcT3)

Timmer et al. (1985)

16

44

Yu et al. (1985)

47

51

Dunst et al. (1994)

53

32 overall 46 (patients with recurrence after CR) 16 (non-responders)

Nieuwenhuijzen et al. 27 (2004)

33 overall

1995; Advanced Bladder Cancer Meta-Analysis Cooperation 2005a, 2005b). The results demonstrate that adjuvant chemotherapy after surgery has no impact on survival, neoadjuvant chemotherapy prior to radical surgery has a modest, but significant, impact on mortality and increases the 5-year overall survival by absolute 5%. Chemotherapy concurrent with radiotherapy has been investigated in only one small study and the results with respect to overall survival rates were not significant; however, the relative reduction of mortality (hazard ratio) was more pronounced in this study as compared with studies which used chemotherapy together with surgery. Although the database is small, the results of the meta-analyses in conjunction with the data from numerous phase-II studies suggest that radiation plus simultaneous chemotherapy is superior to radiation alone in the treatment of urothelial bladder cancer and offers the best chance for local control, bladder preservation, and overall survival.

54 after interstitial radiotherapy 14 after external radiotherapy

where in-breast recurrences after tumorectomy and radiation have also been shown to have a more favorable prognosis as compared with local recurrences after radical mastectomy; thus, close follow-up of patients after organ-preserving treatment is clearly indicated to maintain a second curative approach by salvage surgery in case of local failure.

19.7.2 Neoadjuvant Chemotherapy There are few data on neoadjuvant chemotherapy prior to radiotherapy. An RTOG phase-II study tested two courses of MVAC prior to radiotherapy plus cisplatin (Tester et al. 1996). The response rate was 62% and identical to the response of earlier trials with identical radiationcisplatin regimens without additional MVAC, suggesting that upfront MVAC does not improve response or bladder preservation. There is, therefore, currently no indication for upfront chemotherapy prior to radiotherapy.

19.7 Role of Chemotherapy

19.7.3 Concurrent Radiochemotherapy

19.7.1 Adjuvant and Neoadjuvant Chemotherapy in Non-Metastatic Urothelial Bladder Cancer: Meta-Analyses

The combination of chemotherapy and radiotherapy has yielded significantly higher local remission rates of far advanced tumors than radiation alone. The histologically proven complete remission (CR) rates of advanced, transurethrally unresectable tumors lie in the range of 4050% with radiotherapy alone if standard radiation doses in the range of about 60 Gy are administered. The addition of two to three courses of cisplatin increased the pathological CR rate to 6070%. The data suggest that the addition of (mainly cisplatin-based) chemotherapy improves local CR rates irrespective of radiation dose.

On the basis of the high frequency of micrometastatic spread at diagnosis, chemotherapy has been used as adjuvant or neoadjuvant (preoperative) treatment of muscle-invasive urothelial cancers in combination with radical surgery. The results of the prospective randomized studies have recently been investigated in three meta-analyses (Ghersi et al.

Concomitant Radiation and Chemotherapy in Muscle–Invasive Bladder Cancer

293

Table 19.7. Randomized study comparing definitive or preoperative radiotherapy vs definitive or preoperative radiochemotherapy. (From Coppin et al. 1996) Radiotherapy

Radiotherapy + cisplatin

Number

48

51

Complete remission (%)

31

47

n.s.

Pelvic control (%)

40

58

p=0.038

Distant metastases (%)

38

31

n.s.

Three-year overall survival (%)

33

47

n.s.

One randomized trial from Canada has compared radiation alone vs radiation plus cisplatin as preoperative treatment prior to cystectomy or as definitive treatment (Table 19.7). The results of this small study with 100 patients confirm that cisplatin improves local control but has no effect on distant metastases (Coppin et al. 1996). The significant improvement in local control was, in this small study, not associated with a significant improvement in overall survival, although there was trend towards higher survival figures in patients treated with combined radiation plus chemotherapy.

19.7.4 Type of Drugs in Combined Regimens 19.7.4.1 Cisplatin Most of the studies have used cisplatin as single drug so that this drug should be considered as the preferred drug for multimodal protocols. The most widely used regimens are the RTOG or Boston regimen (70 mg/m2 cisplatin every 3 weeks for a total number of three courses) or the Erlangen regimen (25 mg/m2 cisplatin on days 1–5 and 29–33 of radiotherapy). All regimens have yielded nearly identical results in terms of remission rates, survival, and bladder preservation. Because local enhancement of the radiation effect is the main objective of chemotherapy, low-dose cisplatin regimens seem to be advantageous because of their lower toxicity profile and comparable oncological results. This suggestion is supported by findings in squamous cell head and neck and cervical cancers. From these data, the goal should be to administer a total dose of about 200mg/m2 cisplatin during a 6-week course of radiotherapy.

Significance

Intraarterial cisplatin has been used in one prospective study with results comparable to those of intravenous cisplatin. Early results of this study have suggested a higher rate of sciatic nerve neuropathy (Eapen et al. 1989). In a recent update of theses data, results appear comparable to those of intravenous cisplatin with no increased toxicity (Eapen et al. 2004). With regard to the oncological results, intraarterial cisplatin remains an attractive approach but should be used only within welldefined clinical protocols.

19.7.4.2 Carboplatin Carboplatin has been used as single agent together with radiotherapy at the University of Erlangen (Table 19.8; Sauer et al. 1998) and seems to be less effective than cisplatin, probably because equieffecTable 19.8. Acute toxicity (grades 34) of radio(chemo)therapy WHO WHO grade 3 (%) grade 4 (%) Leukopenia

13

3

Thrombocytopenia

7

3

Anemia

2

0

Elevation of serum creatinine

3

0

Nausea/vomiting

3

0

Diarrhea

5

1

Cystitis

5

0

Data from the University of Erlangen; 415 patients treated in the period from 1984 through 1999.

J. Dunst et al.

294

tive doses of carboplatin as compared with cisplatin are difficult to administer during a 6-week course of pelvic radiotherapy due to the higher hematological toxicity of carboplatin.

19.7.4.3 Taxanes Taxanes, mainly paclitaxel, belong to the most effective drugs in metastatic urothelial bladder cancer and are used in polychemotherapy regimes especially in patients with renal dysfunction (Vaughn et al. 2002). In patients with metastatic cancer and contraindications to cisplatin, paclitaxel has been used as substitute for cisplatin with comparable response rates (Dreicer et al. 1996). Taxanes have radiosensitizing properties and are therefore an interesting drug for multimodal protocols with radiotherapy. In a recent phase-II study performed by Mueller et al. (pers. commun.), paclitaxel (twice weekly 30– 35 mg/m2) has been used in conjunction with simultaneous radiotherapy in patients with reduced renal function. Therapy was well tolerated without further impairment of renal function, and the response rates were comparable to what could be expected in this poor-risk population with cisplatin chemotherapy. The results of a combination of paclitaxel and carboplatin with concurrent radiation have been reported in eight patients (Nichols et al. 2000). Three patients remained disease-free after a median follow-up of 27 months and no late toxicity in survivors was reported. Biweekly docetaxel (single dose 40 mg/m2, later reduced to 20 mg/m2) has been used with concurrent radiation (total dose 68–74 Gy) and biweekly cisplatin (single dose 30 mg/m 2) in 42 patients (Vaveris et al. 1997). A clinical CR rate of 50% in T2–4 cancers was observed. This study, however, reported a relatively high frequency of hematotoxicity (22% grade-3 thrombocytopenia and 22% grade1 to grade-3 hypersensitivity reaction) as well as a high frequency of late toxicity (4 cases with contracted bladders, 1 sigmoid stricture, 1 peripheral motor dysfunction). Although the late complications are more likely caused by high radiation doses, the reported side effects suggest that this regimen should not be applied outside of clinical trials. The RTOG has recently started a trial using paclitaxel and cisplatin concomitantly with twice-daily irradiation followed by either selective bladder preservation or radical cystectomy and adjuvant chemotherapy with gemcitabine and cisplatin (RTOG 99–06).

19.7.4.4 5-Fluorouracil and Capecitabine Continuous infusional 5-FU has been used in several studies and has yielded results comparable to those of cisplatin (Table 19.4). There is so far one small study in which capecitabine has been used in patients with relatively poor performance status (Patel et al. 2005). Fourteen patients with a median age of 80 years and contraindications to cisplatin received capecitabine at a median dose of 1600 mg/m2 daily (range 12001800 mg/m2) over the whole period of radiotherapy. The drug was considered as safe, although a frequency of 29% grade-3 diarrhea and 20% unplanned hospitalization was reported. Complete response was observed in 11 of 13 evaluable patients.

19.7.4.5 Gemcitabine Gemcitabine is a promising drug with proven efficacy and good tolerance in metastatic urothelial cancers. So far, results of three phase-I trials with radiation and concurrent gemcitabine have been reported in patients with urothelial bladder cancers (Caffo et al. 2003; Kent et al. 2004; Sangar et al. 2005) which have together recruited 48 patients. In a study with hypofractionated radiotherapy (52.5-Gy total dose in 20 fractions), the recommended dose of gemcitabine was 100 mg/m2 once weekly and 7 of 8 patients had a CR in this study with no late toxicity. In two protocols with conventional fractionation, the recommended doses of gemcitabine were 400 mg/m2 once weekly (with additional cisplatin 100 mg/m2 every 3 weeks) or 27 mg/m2 twice weekly in the other study.

19.7.4.6 Vinblastine A phase-II study with vinblastine has yielded longterm local control rates of 55% but was associated with a high frequency of impaired bladder function (Kragelj et al. 2005).

19.7.4.7 Multidrug Regimes Increasing the intensity of chemotherapy is an attractive approach for improving treatment results

Concomitant Radiation and Chemotherapy in Muscle–Invasive Bladder Cancer

295

Table 19.9. Erlangen series of combined-modality treatment for bladder cancer Treatment period

Number

Clinical stage

Radiotherapy/radiochemotherapy

Complete response Five-year Five-year overall (%), overall (after overall survival with incomplete TURBT) survival (%) bladder (%)

1982−1985

126

T1 (high risk)–T4

RT alone

61 (46)

40

37

1985−1993

95

T1 (high risk)–T4

RT plus carboplatin

66 (57)

45

40

1985−1993

145

T1 (high risk)–T4

RT plus cisplatin

82 (78)

62

47

1993−2000

49

T1 (high risk)–T4

RT plus 5-FU/cisplatin 87 (82)

65

54

in bladder-sparing protocols either with the objective to improve local response and bladder preservation and also with the goal of better systemic control. The intensification of the Erlangen concurrent chemotherapy protocols over the past 18 years clearly yielded an increase in CR rates with 61% for patients treated with RT alone, 66% after RCT with carboplatin, 82% after RCT with cisplatin, and 87% after RCT with 5-FU/cisplatin (Table 19.9; Rödel et al. 2002b, Rödel et al. 2004). This remains also true if adjusted for the most important prognostic factor, the completeness of the initial TUR, with the rate of CR after incomplete TUR (R1/R2 resection) being 46% after RT alone, 57% after RCT with carboplatin, 78% after RCT with cisplatin, and 82% after RCT with 5-FU/cisplatin. In another phase-II study, cisplatin and 5-FU together with concurrent radiation have also yielded encouraging response data (Zietman et al. 1998); however, an advantage of aggressive chemotherapy in addition to radiation has to be proven, and multidrug regimens should therefore be used only in welldefined clinical protocols.

19.7.4.8 Novel Molecular and Targeted Therapies Future aspects of radiosensitization relate to the potential inhibition of oncogene products frequently overexpressed in bladder cancer and associated with worse prognosis or response to radiotherapy, such as H-ras and c-erbB-1, or Her-2 (Chakravati et al. 2005; Weiss et al. 2005). Treatment of mice expressing activated H-ras bladder cancer cell line tumors with farnesyltransferase inhibitors (which inhibit the posttranslational modifications of H-ras) before irradiation significantly decreased tumor cell clonogenicity and tumor regrowth (Cohen-Jonathan et al. 2000). Specific molecular therapies such as inhibition of epidermal growth factor receptor

activity with small molecule tyrosin kinase inhibitors or antibodies against receptors may also markedly increase tumor radiosensitization in bladder cancer (Bellmunt et al. 2003; Gupta et al. 2003; Maddineni et al. 2005).

19.8 Acute and Late Toxicity 19.8.1 Acute Toxicity of Concurrent Radiochemotherapy Most of the patients treated with a curative radiation regimen experience some mild treatment toxicity, especially bladder and bowel toxicity. Mild to moderate acute radiation cystitis with dysuria and urinary frequency (grades 1 and 2) is present in about half of the patients, but few patients require specific medication (Zietman et al. 1993). The symptoms usually resolve within 24 weeks after completion of radiotherapy. In our own experience, patients with a history of multiple TURs or multiple courses of intravesical chemo- or immunotherapy prior to radiotherapy are predisposed to develop some kind of acute radiation cystitis. Acute bowel toxicity is present in <1015% of patients. If concurrent chemotherapy is administered, mild to moderate hematological toxicity is frequent. Severe leukopenia requiring supportive use of growth factors or thrombocytopenia are rarely observed. The toxicity data of the largest single center prospective study are listed in Table 19.8.

19.8.2 Late Toxicity After Radiochemotherapy Late bladder toxicity may arise in a relevant subset of patients if radiation doses above 6065 Gy are

J. Dunst et al.

296

administered to large parts of the bladder or if high doses per fraction are used; however, the total doses in current protocols lie in the range of about 60 Gy to the whole bladder and not more than 64 Gy to parts of the bladder. These doses, if administered in conventional fractionation with single doses d2 Gy, can be considered as relatively safe with regard to late bladder toxicity (Table 19.10). Salvage cystectomy due to bladder shrinkage or chronic radiation cystitis was not necessary in most series and the risk is probably far below 1%. Table 19.10 Late sequelae (grades 24) after TUR and radio(chemo)therapy Frequency (%) Grade-2 sequelae

19.8.3 Organ Preservation and Bladder Function In most of the recent series with organ preservation, about 7080% of long-term survivors maintained a normal functioning bladder. Preservation of a functioning bladder can be achieved in three quarters of patients with muscle-invading tumors. The current data show a good to excellent bladder function in the vast majority of patients. There are few data on quality of life in long-term survivors after therapy for bladder cancer and patients seem to adapt well even in case of radical cystectomy with urinary diversion; however, the impact of cancer therapy of sexual function is poorly examined, especially in females, but is likely very high (Zietman and Skinner 2005).

Increased frequency

10

Intermittent dysuria

8

Diarrhea

5

Proctitis

2

19.9 Current Strategy in an Organ-Preserving Treatment Concept

3

19.9.1 Indication for Radiochemotherapy in a Multimodal Approach with Organ Preservation

Grade-3 sequelae Reduced bladder capacity (100−200 cm³) Grade-4 sequelae Salvage cystectomy due to bladder shrinkage

2

Surgery for bowel stenosis

1

Data from the University of Erlangen; 415 patients treated in the period from 1984 through 1999. For late bladder complications, only 186 patients with maintained bladder and follow-up of at least 6 months were evaluated.

An organ-preserving approach seems justified in all patients with muscle-invading urothelial bladder cancer. Although there are no data from recent large randomized trials, the results of phase-II studies as well as population-based studies suggest that

Resection 2–4 Weeks 4–6 Weeks

Fig. 19.2. Multimodal treatment schedule for an organ-preserving approach in bladder cancer

Concomitant Radiation and Chemotherapy in Muscle–Invasive Bladder Cancer

organ preservation with TUR and radiochemotherapy is as effective as radical surgery for muscleinfiltrating tumors. Moreover, radiotherapy offers a curative chance in patients unsuitable for major surgery. Organ-preserving protocols should presently always include a trimodality approach with transurethral surgery, radiotherapy, and chemotherapy (Fig. 19.2).

19.9.2 Transurethral Surgery Because of its overwhelming prognostic impact, a complete TUR should always be attempted. The completeness of the TUR should be histologically verified (R-classification). The urologist should give detailed information on the cystocopic findings, e.g., the location of the tumor in the bladder, visible tumor left after TUR, multifocality, and growth patterns. Marking the cystocopic findings on a scheme may be helpful in further radiation therapy planning because the cystocopic findings give additional information for target volume definiton besides diagnostic imaging procedures.

297

19.9.3 Radiotherapy Radiotherapy should normally start within 26 weeks after TUR (early start is especially indicated if TUR was not complete). Radiation is administered in conventional fractionation with five weekly fractions of 1.82.0 Gy up to a total dose of about 5055 Gy to the bladder and regional nodes followed by a small volume boost to the bladder or the tumor-bearing bladder area. Individual treatment planning using CT planning or 3D conformal therapies are considered as standard. Hyperfractionated accelerated fractionation regimens might theoretically be superior to conventional fractionation because of the proliferation rate of urothelial cancers and because of the prognostic impact of treatment time in bladder cancer. These regimens are currently investigated but should so far not be considered as standard (Zietman et al. 1998). The standard target volume includes the bladder and the regional lymph nodes up the aortic bifurcation (Fig. 19.3). The prostatic urethra should normally be included because of the risk of spread. After

Fig 19.3. Field delineation and dose distribution for standard radiotherapy

J. Dunst et al.

298

50 Gy, a boost to the whole bladder or (if possible) the tumor area within the bladder is administered. The total dose should be in the range of 54–60 Gy in case of incomplete (R1- or R2-) resection. Higher doses should be avoided due to a negative impact on bladder function and because a beneficial effect of higher doses is not proven. A critical aspect of bladder irradiation concerns the reproducibility of the bladder volume and target volume anatomy during a 6-week course of radiotherapy. Initial planning should not be based on CT scans with an empty or nearly empty bladder because patients, at least during cisplatin chemotherapy, receive large amounts of intravenous fluid. On the other hand, most patients have some kind of mild radiation cystitis at the end of radiotherapy and cannot tolerate large fluid volumes in the bladder. Critical areas for geographical miss are especially tumor locations in the bladder dome and anterior wall due to the extension of the bladder with increased filling. Target volume for a conedown boost should not be delineated too small. A beneficial effect of prophylactic treatment of clinically uninvolved lymph nodes (either surgically as lymph node dissection or by radiotherapy) has not been proven. Prophylactic node irradiation is normally recommended, but the omission of lymph node irradiation might be discussed in patients with severe risk factors in whom the extension of the target volume might significantly compromise treatment tolerance.

19.9.4 Chemotherapy Concurrent chemotherapy during the radiation course is indicated in nearly all patients who undergo radiotherapy with curative intent. Cisplatin should be used as drug of first choice. The most widely used regimens are the RTOG or Boston regimen (70 mg/m2 cisplatin every 3 weeks for a total number of three courses) or the Erlangen regimen (25 mg/m2 cisplatin on days 1–5 and 29–33 of radiotherapy; Fig. 19.4). Other drugs or combinations may be effective, but there are less data supporting their use. In case of contraindications to cisplatin, other drugs might be used as substitute, although there is currently limited experience. Carboplatin seems to be less effective than cisplatin. A probably safe and promising drug is paclitaxel. Other drugs (especially gemcitabine) are currently investigated in ongoing trials. Multidrug regimes should be restricted to clinical trials.

Fig. 19.4. Example of a cisplatin-based simultaneous radiochemotherapy protocol

19.9.5 Omission of Chemotherapy? It is currently not clear whether chemotherapy can be omitted in selected patients with good prognostic features. Retrospective data from Boston and from the University of Erlangen suggest that patients with a complete TUR prior to radiotherapy have a very good prognosis with a more than 8090% chance of definitive local control and survival. The results of TUR and radiotherapy are superior to TUR alone. A comparison of data from TUR plus radiation with the best series in the literature which has used TUR alone (Herr 1987) is listed in Table 19.11. The net effect of additional chemotherapy in this favorable subgroup of patients who undergo “adjuvant” radiotherapy is probably small; therefore, it is currently unclear whether the results of radiation alone can be further improved by the addition of chemotherapy in patients with a complete TUR. Nevertheless, we recommend the use of chemotherapy due to insufficient data.

19.9.6 Response Evaluation

Response to radiochemotherapy should be evaluated by the urologist during or early after treatment. In the Boston and RTOG protocols, response evaluation is mainly performed after 40 Gy. Complete responders are considered good candidates for bladder preservation and go on with a boost irradiation up to 64 Gy (Shipley et al. 2005). In the European protocols, definitive radiotherapy with about 60 Gy is administered to all patients and the response is evaluated 46 weeks after the end of treatment.

Concomitant Radiation and Chemotherapy in Muscle–Invasive Bladder Cancer Table 19.11. Comparison of transurethral resection (TUR) alone vs TUR plus radiotherapy or radiochemotherapy in patients with a complete TUR. The table demonstrates the world’s best series with TUR alone (Herr 1987) vs a series with a bladder-sparing approach. Patients with complete TUR have an excellent prognosis after “adjuvant” radiotherapy Herr 1987 Dunst et al. 1994 All patients with muscleinvasive tumors in series

215

201

Number of T2−3-tumors with complete R0−TUR

45 (21%)

30 (15%)

Therapy for T2−3R0

TUR

TUR + RT + cisplatin

Five-year overall survival for T2−3R0

68%

88%

Bladder preservation for T2−3R0

76%

90%

Complete responders receive no further treatment, whereas patients with residual tumor are referred for salvage cystectomy. Selected patients with superficial residual tumors may be treated with a second TUR as salvage treatment. Both strategies have theoretical advantages. The early-response evaluation tries to select nonresponders as early as possible with the aim of performing immediate salvage cystectomy. The underlying assumption is that the curative potential of cystectomy might decrease in these non-responders if cystectomy is delayed for weeks (Shipley et al. 2005). The late response evaluation may theoretically increase the chance of bladder preservation because some slow responders whose tumors have not yet completely regressed after 40 Gy may maintain their bladders with a delayed response evaluation. So far, however, both approaches seem to be equally effective in terms of bladder preservation and long-term survival. All patients should be regularly followed by an urologist over years and, if possible, life long because they remain at risk for developing recurrences (mainly new primaries) in the bladder even beyond 5–10 years. Salvage cystectomy is a curative approach for patients with invasive recurrences in the preserved bladder. The mortality is comparable to primary cystectomy.

299

19.10 Future Research Issues As more experience is acquired with organ-sparing treatment, it is clear that future directions of clinical and basic research will focus on two main topics: (a) the optimization of the treatment modalities, including incorporation of new cytotoxic agents; and (b) the proper selection of patients who will most probably benefit from the respective treatment alternatives. The optimal regimen and combination of radio- and chemotherapy remains to be established. The intensification of concurrent chemotherapy might be one strategy. Moreover, the efficacy of novel molecular therapies is currently tested in phase-I trials. Clinical criteria helpful in determining patients for bladder preservation include such variables as early tumor stage, unifocal tumor, a visibly and microscopically complete TUR, and absence of ureteral obstruction or associated carcinoma in situ. To further optimize patient selection, it should be of pivotal interest to recognize the subgroup of tumors which do not respond to RT/RCT. In the Erlangen series, patients with non-responding tumors showed a 5-year disease-specific survival rate of only 21%, even when salvage cystectomy could be performed, and more of 40% developed distant metastases within the first 2 years. Evidently, these tumors have a biologically less favorable profile, and prompt cystectomy, possibly combined with more aggressive adjuvant chemotherapy, might be more effective in these patients; however, tumor heterogeneity is so large in bladder cancer that conventional histopathological classification is inadequate for predicting the response to RCT for individual lesions. Translational research to identify molecular markers that may better identify a tumor’s true malignant potential as well as its response to specific cytotoxic therapies are desperately needed, as reviewed by Weiss et al. (2005).

References Advanced Bladder Cancer (ABC) (2005a) Meta-analysis collaboration. Adjuvant chemotherapy in invasive bladder cancer: a systematic review and meta-analysis of individual patient data. Eur Urol 48:189201 Advanced Bladder Cancer (ABC) (2005b) Meta-analysis collaboration. Neoadjuvant chemotherapy in invasive bladder cancer: update of a systematic review and meta-analysis of individual patient data. Eur Urol 48:202206

300 Arias F, Dominguez MA, Martinez E et al. (2000) Chemoradiotherapy for muscle invading bladder carcinoma. Final report of a single institutional organ-sparing program. Int J Radiat Oncol Biol Phys 47:373378 Bassi P, Ferrante GD, Piazza N et al. (1999) Prognostic factors of outcome after radical cystectomy for bladder cancer: a retrospective study of a homogeneous patient cohort. J Urol 161:14941497 Bellmunt J, Hussain M, Dinney CP (2003) Novel approaches with targeted therapies in bladder cancer. Therapy of bladder cancer by blockade of the epidermal growth factor receptor family. Crit Rev Oncol Hematol 46 (Suppl): S85S104 Bredael JJ, Croker BP, Glenn JF (1980) The curability if invasive bladder cancer treated by radical cystectomy. Eur Urol 6:206210 Caffo O, Fellin G, Graffer U et al. (2003) Phase I study of gemcitabine and radiotherapy plus cisplatin after transurethral resection as conservative treatment for infiltrating bladder cancer. Int J Radiat Oncol Biol Phys 57:13101316 Cervak J, Cufer T, Marolt F et al. (1991) Combined chemotherapy and radiotherapy in muscle-invasive bladder carcinoma. Complete remission results. ECCO Proc 6:abstract 561 Chakravati A, Winter K, Wu CL et al. (2005) Expression of the epidermal growth factor receptor and Her-2 are predictors of favourable outcome and reduced complete response rates, respectively, in patients with muscle-invading bladder cancers treated by concurrent radiation and cisplatinbased chemotherapy: a report from the Radiation Therapy Oncology Group. Int J Radiat Oncol Biol Phys 62:309317 Chen WC, Liaw CC, Chuang CK et al. (2003) Concurrent cisplatin, 5-fluorouracil, leucovorin, and radiotherapy for invasive bladder cancer. Int J Radiat Oncol Biol Phys 56:726-733 Cohen-Jonathan E, Muschel RJ, Gillies McKenna W et al. (2000) Farnesyltransferase inhibitors potentiate the antitumor effect of radiation on a human tumor xenograft expressing activated HRAS. Radiat Res 154:125132 Coppin CM, Gospodarowicz MK, James K et al. (1996) Improved local control of invasive bladder cancer by concurretn cisplatin and preoperative or definitive radiation. The National Cancer Institute of Canada Clinical Trials Group. J Clin Oncol 14:29012907 Danesi DT, Arcangeli G, Cruciani E et al. (2004) Conservative treatment of invasive bladder carcinoma by transurethral resection, protracted intravenous infusion chemotherapy, and hyperfractionated radiotherapy: long-term results. Cancer 101:25402548 Dreicer R, Gustin DM, See WA, Williams RD (1996) Paclitaxel in advanced urothelial carcinoma: its role in patients with renal insufficiency and as salvage therapy. J Urol 156:16061608 Dunst J, Sauer R, Schrott KM et al. (1994) Organ-sparing treatment of advanced bladder cancer: a 10-year experience. Int J Radiat Oncol Biol Phys 30:261266 Dunst J, Rödel C, Zietman A et al. (2001) Bladder preservation in muscle-invasive bladder cancer by conservative surgery and radiochemotherapy. Semin Surg Oncol 20:2432 Dunst J, Rödel C (2003) Harnblase. In: Radioonkologie 2: Klinik. Hrsg: Bamberg M, Molls M, Sack H. Zuckschwerdt Verlag München. 672-691 Eapen L, Stewart D, Danjoux C et al. (1989) Intraarterial cisplatin and concurrent radiation for locally advanced bladder cancer. J Clin Oncol 7:230235

J. Dunst et al. Eapen L, Stewart D, Collins J, Peterson R (2004) Effective bladder sparing therapy with intra-arterial cisplatin and radiotherapy for localized bladder cancer. J Urol 172:12761280 Fellin G, Graffer U, Bolner A et al. (1997) Combined chemotherapy and radiation with selective organ preservation for muscle-invasive bladder carcinoma. A single-institution phase II study. Br J Urol 80:4449 Fossa SD, Waehre H, Aass N et al. (1993) Bladder cancer definitive radiation therapy of muscle invasive bladder cancer. A retrospective analysis of 317 patients. Cancer 72:30363043 Frazier HA, Robertson JE, Dodge RK, Paulson DF (1993) The value of pathologic factors in predicting cancer-specific survival among patients treated with radical cystectomy for transitional cell carcinoma of the bladder and prostate. Cancer 71:39934001 Ghersi D, Stewart LA, Parmar MKB et al. (1995) Does neoadjuvant cisplatin-based chemotherapy improve the survival of patients with locally advanced bladder cancer: a metaanalysis of individual patient data from randomized clinical trials. Br J Urol:75106 Giuliani L, Giberti C, Martorana G et al. (1985) Results of radical cystectomy for primary bladder cancer. Retrospective study of more than 200 cases. Urology 26:243248 Given RW, Parsons JT, McCarley D et al. (1995) Bladder-sparing multimodality treatment of muscle-invasive bladder cancer: a five-year follow-up. Urology 46:499504 Gospodarowicz M (2002) Radiotherapy and organ preservation in bladder cancer: Are we ignoring the evidence? J Clin Oncol 20:30483050 Gschwend JE, Fair WR, Vieweg J (2000) Radical cystectomy for invasive bladder cancer: contemporary results and remaining controversies. Eur Urol 38:121130 Gupta AK, Cerniglia GJ, Ahmed MS et al. (2003) Radiation sensitisation of human cancer cells by inhibiting the acticity of PI3K using LY294002. Int J Radiat Oncol Biol Phys 56:846853 Hagan MP, Winter KA, Kaufman DS et al. (2003) RTOG 97-06: initial report of a phase III trial of selective bladder conservation using TURBT, twice-daily accelerated irradiation sensitized with cisplatin, and adjuvant MCV combination chemotherapy. Int J Radiat Oncol Biol Phys 57:665672 Hautmann RE (1998) Complications and results after cystectomy in male and female patients with locally invasive bladder cancer. Eur Urol 33 (Suppl 4):2324 Herr HW (1987) Conservative management of muscle-infiltrating bladder cancer: prospective experience. J Urol 138:11621163 Housset M, Maulard C, Chretien YC et al. (1993) Combined radiation and chemotherapy for invasive transitional-cell carcinoma of the bladder: a prospective study. J Clin Oncol 11:21502157 Housset M, Dufour E, Maulard-Durtux C et al. (1997) Concomitant 5-fluouracilcisplatin and bifractionated split course radiation therapy for invasive bladder cancer. Proc Am Soc Clin Oncol 16:319, abstract 1139 Hussain SA, Stocken DD, Peake DR et al. (2004) Long-term results of a phase II study of synchronous chemoradiotherapy in advanced muscle invasive bladder cancer. Br J Cancer 90:21062111 Kachnic LA, Kaufmann DS, Griffin PP et al. (1997) Bladder preservation by combined modality therapy for invasive bladder cancer. J Clin Oncol 15:10221029

Concomitant Radiation and Chemotherapy in Muscle–Invasive Bladder Cancer Kaufman DS, Winter KA, Shipley WU (2000) The initial results in muscle-invading bladder cancer of RTOG 9506: phase I/II trial of transurethral surgery plus radiation therapy with concurrent cisplatin and 5-fluorouracil followed by selective bladder preservation or cystectomy depending on the initial response. Oncologist 5:471476 Kent E, Sandler H, Montie J et al. (2004) Combined-modality therapy with gemcitabine and radiotherapy as a bladder preservation strategy: results of a phase I trial. J Clin Oncol 22:25402545 Kragelj B, Zaletel-Kragelj L, Sedmark B, Cufer T, Cervek J (2005) Phase II study of radiochemotherapy with vinblastine in invasive bladder cancer. Radiother Oncol 75:4447 Maciejewski B, Majewski S (1991) Dose fractionation and tumour repopulation in radiotherapy for bladder cancer. Radiother Oncol 21:163170 Maddineni SB, Sangar VK, Hendry JH et al. (2005) Differential radiosensitization by ZD1839 (Iressa), a highly selective epidermal growth factor receptor tyrosine kinase inhibitor in two related bladder cancer cell lines. Br J Cancer 92:125130 Malkowicz SB, Nichols P, Lieskovsky G et al. (1990) The role of radical cystectomy in the management of high grade superficial bladder cancer (PA, P1, PIS and P2). J Urol 144:641645 Moore MJ, O'Sullivan B, Tannock I (1988) How expert physicians would wish to be treated if they had genitourinary cancer. J Clin Oncol 6:17361745 Nichols RC, Sweetser MG, Mahmood SK et al. (2000) Radiation therapy and concomitant paclitaxel/carboplatin for muscle-invasive transitional cell carcinoma of the bladder: a well-tolerated combination. Int J Cancer 90:281286 Nieuwenhuijzen JA, Horenblas S, Meinhardt W et al. (2004) Salvage cystectomy after failure of interstitial radiotherapy and external beam radiotherapy for bladder cancer. BMJ Int 94:793797 Pagano F, Bassi P, Galetti TP et al. (1991) Results of contemporary radical cystectomy for invasive bladder cancer: a clinicopathological study with an emphasis on the inadequacy of the tumor, nodes and metastases classification. J Urol 145:4550 Patel B, Forman J, Fontana J et al. (2005) A single institution experience with concurrent capecitabine and radiation therapy in weak and/or elderly patients with urothelial cancer. Int J Radiat Oncol Biol Phys 62:13321338 Peyromaure M, Slama J, Beuzeboc P et al. (2004) Concurrent chemoradiotherapy for clinical stage T2 bladder cancer: report of a single institution. Urology 63:7377 Rödel C (2004) Current status of radiation therapy and combined-modality treatment for bladder cancer. Strahlenther Onkol 180:701709 Rödel C, Grabenbauer GG, Kuehn R et al. (2002a) Organ preservation in patients with invasive bladder cancer: initial results of an intensified protocol of transurethral surgery and radiation therapy plus concurrent cisplatin and 5-fluorouracil. Int J Radiat Oncol Biol Phys 52:13031309 Rödel C, Grabenbauer GG, Kuehn R et al. (2002b) Combined modality treatment and selective organ preservation in invasive bladder cancer: long-term results. J Clin Oncol 20:30613071 Rotman M, Aziz H, Porrazzo M et al. (1990) Treatment of

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advanced transitional cell carcinoma of the bladder with irradiation and concomitant 5-fluorouracil infusion. Int J Radiat Oncol Biol Phys 18:11311137 Russell KJ, Boileau MA, Higano C et al. (1990) Combined 5-fluorouracil and irradiation for transitional cell carcinoma of the urinary bladder. Int J Radiat Oncol Biol Phys 19:693699 Sangar VK, McBain CA, Lyons J et al. (2005) Phase I study of conformal radiotherapy with concurrent gemncitabine in locally advanced bladder cancer. Int J Radiat Oncol Biol Phys 61:420425 Sauer R, Birkenhake S, Kuehn R et al. (1998) Efficacy of radiochemotherapy with platin derivatives compared to radiotherapy alone in organ-sparing treatment of bladder cancer. Int J Radiat Oncol Biol Phys 40:121127 Shelley MD, Wilt TJ, Barber J, Mason MD (2004) A meta-analysis of randomised trials suggest a survival benefit for combined radiotherapy and radical cystectomy compared with radical radiotherapy for invasive bladder cancer: Are these data relevant to modern practice? Clin Oncol 16:166171 Shipley WU, Prot GR, Kaufman SD, Perrone TL (1987) Invasive bladder carcinoma. The importance of intial transurethral surgery and other significant prognostic factors for improved survival with full-dose irradiation. Cancer 60 (Suppl) 3:514520 Shipley WU, Winter KA, Kaufman DS (1998) Phase III trial of neoadjuvant chemotherapy in patients with invasive bladder cancer treated with selective bladder preservation by combined radiation therapy and chemotherapy: initial results of Radiation Therapy Oncology Group 89-03. J Clin Oncol 16:35763583 Shipley WU, Zietman AL, Kaufman DS et al. (2005) Selective bladder preservation by trimodality therapy for patients with muscularis propria-invasive bladder cancer and who are cystectomy candidates: the Massachusetts General Hospital and Radiation Therapy Oncology Group experiences. Semin Radiat Oncol 15:3641 Skinner DG, Lieskovsky G (1988) 16 years experience in the management of patients with deeply invasive bladder cancer. Eur Urol 14 (Suppl 1):3031 Skinner DG (1982) Management of invasive bladder cancer: a meticulous pelvic node dissection can make a difference. J Urol 128:3436 Smith JA Jr, Whitmore WF Jr (1981) Salvage cystectomy for bladder cancer after failure of definitive irradiation. J Urol 125:643645 Stein JP, Lieskovsky G, Cote R et al. (2001) Radical cystectomy in the treatment of invasive bladder cancer: long-term results in 1054 patients. J Clin Oncol 19:666675 Swanson DA, Eschenbach AC von, Bracken RB, Johnson DE (1981) Salvage cystectomy for bladder carcinoma. Cancer 47:22752279 Tester W, Porter A, Asbell S et al. (1993) Combined modality program with possible organ preservation for invasive bladder carcinoma: results of RTOG protocol 85-12. Int J Radiat Oncol Biol Phys 25:783790 Tester W, Porter A, Heaney J et al. (1996) Neoadjuvant combined modality therapy with possible organ preservation for invasive bladder cancer. J Clin Oncol 14:119126 Timmer PR, Hartlief HA, Hooijkaas JA (1985) Bladder cancer: pattern of recurrence in 142 patients. Int J Radiat Oncol Biol Phys 11:899905 Vaughn DJ, Manola J, Dreicer R et al. (2002) Phase II study of

302 paclitaxel plus carboplatin in patients with advanced carcinoma of the urothelium and renal dysfunction (E2896): a trial of the Eastern Cooperative Oncology Group. Cancer 95:10221027 Vaveris H, Delakas D, Anezinis P et al. (1997) Concurrent platinum and docetaxel chemotherapy and external radical radiotherapy in patients with invasive transitional cell bladder carcinoma. A preliminary report of tolerance and local control. Anticancer Res 17:47714780 Vieweg J, Gschwend JE, Herr HW, Fair WR (1999) The impact of primary stage on survival in patients with lymph node positive bladder cancer. J Urol 161:7276 Waehre H, Ous S, Klevmark B et al. (1993) A bladder cancer multi-institutional experience with total cystectomy for muscle invasive bladder cancer. Cancer 72:30443051 Wallace DM, Bloom HJ (1976) The management of deeply infiltrating (T3) bladder carcinoma: controlled trial of radical radiotherapy versus preoperative radiotherapy and radical cystectomy. Br J Urol 48:587594 Weiss C, Roedel F, Wolf I et al. (2005) Combined-modality treatment and organ-preservation in bladder cancer. Do molecular markers predict outcome? Strahlenther Onkol 181:213222 Wishnow KI, Tenney DM (1991) Will Rogers and the results

J. Dunst et al. of radical cystectomy for invasive bladder cancer. Urol Clin North Am 18:529537 Yu WS, Sagerman RH, Chung CT et al. (1985) Bladder carcinoma: experience with radical and preoperative radiotherapy in 421 patients. Cancer 56:12931299 Zapatero A, Martin de Vidales C, Marin A et al. (2000) Invasive bladder cancer: a single-institution experience with bladder-sparing approach. Int J Cancer 90:287294 Zietman A, Skinner E (2005) Quality of life after radical treatment for invasive bladder cancer. Semin Radiat Oncol 15:5559 Zietman AL, Shipley WU, Kaufman DS (1993) The combination of cis-platinum based chemotherapy and radiation in the treatment of muscle-invading transitional cell cancer of the bladder. Int J Radiat Oncol Biol Phys 27:161170 Zietman AL, Kaufman DS, Shipley WU et al. (1997) Phase I/II trial of transurethral surgery plus cisplatin and radiation therapy followed either by selective bladder preservation or radical cystectomy for patients with muscle-invading bladder cancer but without hydronephrosis. Int J Radiat Oncol Biol Phys (Suppl 2):abstract 42 Zincke H, Patterson DE, Utz DC, Benson RC Jr (1985) Pelvic lymphadenectomy and radical cystectomy for transitional cell carcinoma of the bladder with pelvic nodal disease. Br J Urol 57:156159

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20 Applications to Gynecological Cancers Anthony W. Fyles, Michael Milosevic, and Amit Oza

CONTENTS 20.1 20.2 20.2.1 20.2.2 20.2.3 20.2.4 20.3 20.3.1 20.3.2 20.4

20.4.1 20.4.2 20.4.3 20.4.4 20.4.5

Introduction 303 Chemo-Radiation Using Cytotoxic Agents in Cervical Cancer 303 Randomized Clinical Trials 303 Phase-I/II Chemo-Radiation Trials of Cytotoxic Agents in Cervical Cancer 305 Phase-I/II Chemo-Radiation Trials of Cytotoxic Agents in Vulvar Cancer 306 Chemo-Radiation in Endometrial Cancer 306 Biologically Targeted Treatment of the Tumor Microenvironment in Gynecological Cancer 306 The Microenvironment in Cervical Cancer 306 Hypoxia-Targeted Treatment 308 Incorporating Molecularly Targeted Agents with Radiation/Chemotherapy in Gynecological Malignancies 309 Carcinoma of the Cervix 310 EGFR and COX-2 Inhibitors 310 Vascular-Targeted Treatment and Anti-Angiogenic Agents 311 Pro-Apoptotic Agents 312 Targeted Agents in Endometrial Cancer 312 References 313

20.1 Introduction Since the publication of five randomized trials of platinum-containing chemo-radiation in women with cervical cancer in 1999, and the accompanying National Cancer Institute (NCI) Clinical Announcement, combined treatment has become the standard of care in this disease (Rose et al. 1999; Whitney et al. 1999; Morris et al. 1999; Keys et al. 1999; Peters et al. 2000). In women with vulvar cancer, trials of chemo-radiation for locally advanced tumors have shown good response rates, consistent with their A. Fyles, MD; M. Milosevic, MD Department of Radiation Oncology, Princess Margaret Hospital, 610 University Avenue, Toronto, ON M5G 2M9, Canada A. Oza, MD Department of Medical Oncology and Haematology, Princess Margaret Hospital, 610 University Avenue, Toronto, ON M5G 2M9, Canada

similar histology and etiology to cervix tumors. Despite this, local and distant relapse continue to be significant problems, particularly for patients with bulky tumors; hence, the interest in improving combined modality treatment, ideally without further increasing toxicity. Current areas of interest in gynecological cancers include combinations of novel agents and standard chemo-radiation, including cytotoxics and biologically targeted agents. These targets may be microenvironmental (e.g., tumor hypoxia and interstitial hypertension; angiogenesis), growth factors such as epidermal growth factor (EGF), or, for example, can be directed against epigenetic events such as DNA methylation. In this chapter we review current and upcoming trials investigating new chemo-radiation protocols for women with gynecological cancers, focusing specifically on cervix and vulvar cancer, where combined treatment is most frequently used. We begin by discussing prospective studies of cytotoxic agents in combination with radiation, followed by a review of hypoxia-targeted agents, and finish with an update of current and proposed studies of biologically targeted agents in combination with radiation and chemo-radiation.

20.2 Chemo-Radiation Using Cytotoxic Agents in Cervical Cancer 20.2.1 Randomized Clinical Trials A recent meta-analysis of randomized chemoradiation trials in cervical cancer demonstrated a 10% absolute survival improvement, largely due to improved pelvic control, but with a suggestion of improved distant relapse (Fig. 20.1; Green et al. 2005). Most of these trials used concurrent cisplatincontaining chemotherapy although benefit was also

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304

Review: Concomitant chemotherapy and radiation therapy for cancer of the uterine cervix Comparsion: 01 Concomitant chemoradiotherapy versus radiotherapy Outcome: 01 Survival by type of chemotherapy Study

Treatment n/N

Control n/N

Peto Odds ratio 99% CI

Weight Peto Odds Ratio (%) 99% CI

Eifel 2004

59/194

102/195

15.0

0.48 [0.32, 0.71]

Keys 1999

27/183

49/186

6.4

0.54 [0.29, 0.99]

Leborgne 2000

42/75

39/78

5.4

1.19 [0.61, 2.31]

Onishi 1999

10/18

8/15

0.7

1.40 [0.21, 9.21]

Pearcey 2002

49/127

52/126

9.2

0.88 [0.53, 1.46]

Peters 2000

21/127

36/116

4.8

0.51 [0.25, 1.03]

Rose 1999

116/349

89/177

16.4

0.60 [0.41, 0.88]

Tseng 1997

23/60

22/62

4.0

1.39 [0.64, 2.99]

Whitney 1999

79/177

108/191

15.9

0.74 [0.50, 1.09]

77.8

0.68 [0.60, 0.78]

01 Platinum chemotherapy

Subtotal (95% CI) Test for heterogeneity chi-square=21.98 df=8 p=0.006 |==62.4% Test for overall effect z=5.68 p<0.00001 02 Non-platinum chemotherapy Hernandez 1991

21/36

6/18

1.9

2.01 [0.65, 6.24]

Lorvidhaya 2003

68/238

98/450

11.6

0.62 [0.39, 0.97]

Roberts 2000

20/78

30/82

4.3

0.67 [0.32, 1.41]

Wong 1999

21/110

34/110

4.4

0.73 [0.35, 1.51]

22.2

0.72 [0.56, 0.92]

100

0.69 [0.61, 0.77]

Subtotal (95% CI) Test for heterogeneity chi-square=6.30 df=3 p=0.10 |==52.4% Test for overall effect z=2.63 p=0.008 Total (95% CI) Test for heterogeneity chi-square=27.71 df=12 p=0.006 |==56.7% Test for overall effect z=6.25 p<0.00001 0.1 0.2 0.5 Favours treatment

1

2 5 10 Favours control

Fig. 20.1. Concomitant chemotherapy and radiation therapy for cancer of the uterine cervix

seen in studies of other agents such as mitomycin C and 5-fluorouracil (5-FU). Not included in the metaanalysis was a recent randomized study comparing infusional 5-FU vs cisplatin that was stopped early due to an increased risk of relapse in the 5-FU arm (Lanciano et al. 2005; note that there have been no direct comparisons of different cisplatin regimens such as cisplatin alone vs cisplatin and 5-FU). The benefit of chemo-radiation was at an increased cost in acute toxicity, particularly hematological, as well as nausea and vomiting, which are usually manageable with suitable supportive care. Weekly

cisplatin is felt to be associated with lesser toxicity than cisplatin/5FU [particularly gastrointestinal (GI)] and appears to be the favored regimen (Lukka and Johnston 2004). There was uncertainty about the risk of increased late toxicity (Maduro et al. 2003) and a patient-based meta-analysis is underway for an upcoming Cochrane review. These results would suggest that the current policy of cisplatin alone on a weekly basis, or with 5-FU given every 3 weeks, is reasonable and associated with significant benefits and manageable toxicity; however, despite these improvements, patients

Applications to Gynecological Cancers

with advanced disease continue to exhibit high rates of local and distant failure, indicating the need for further improvements in combined-modality therapy while avoiding excessive toxicity. With radiation treatment, late complications involving bowel and bladder are typically dose-limiting, yet may not become evident for months to years following treatment. This pattern poses significant challenges for phase-I/II clinical trial design and follow-up of chemo-radiation protocols, particularly with regard to interim analyses and dose-escalation schemes. As a result, investigators have adopted novel designs for these studies, including delayed assessment of interim end points, to allow the development of any late effects, and escalation of drug duration as well as dose, particularly for oral agents given on a daily basis. These and other issues are highlighted in the following sections.

20.2.2 Phase-I/II Chemo-Radiation Trials of Cytotoxic Agents in Cervical Cancer A number of prospective trials exploring cytotoxic agents in addition to cisplatin chemo-radiation have been undertaken, as well as trials evaluating different platinum compounds such as carboplatin. An interesting randomized phase-II trial comparing weekly cisplatin chemo-radiotherapy with cisplatin (40 mg/m2) and gemcitabine (125 mg/m2) prior to radical hysterectomy was recently reported. Eightythree women with stage-IB to stage-IIB disease were entered, with a 55% pathological complete response (CR) in the cisplatin arm compared with 77.5% (p=0.02) in the cisplatin-gemcitabine group. Toxicity was greater with cisplatingemcitabine, predominantly hematological and gastrointestinal, with only 63% of the cisplatingemcitabine group completing the planned six cycles, compared with 82% of the cisplatin group (p=0.01; DuenasGonzalez et al. 2005). In locally advanced disease a dose-escalation trial recommended the same doses of weekly gemcitabine and cisplatin, with manageable toxicity (<20% grades 3 or 4) and a 78% CR rate at a median follow-up of 26 months (Zarba et al. 2003). These studies suggest that gemcitabine has radiosensitizing properties in cervical cancer, in keeping with pre-clinical data and consistent with other tumor sites. Another active combination in recurrent disease is the tubulin inhibitor paclitaxel and cisplatin or carboplatin, which has been tested in combination

305

with radiation in several trials. Chen et al. (1997) established the tolerability of a weekly dose of 50 mg/m2 of paclitaxel in addition to cisplatin at a low dose of 50 mg/m2 every 3 weeks. A phase-I trial using cisplatin (with a lower than standard dose of 30 mg/m2 weekly) also found that 50 mg/m2 of weekly paclitaxel was the maximum tolerated dose (MTD), with diarrhea as the dose-limiting toxicity (DLT; Pignata et al. 2000). A Gynecologic Oncology Group (GOG) trial recently reported an MTD of 40 mg/m2 paclitaxel weekly with the same dose of weekly cisplatin (Di Silvestro et al. 2005). Grade3 to grade-4 neutropenia and GI toxicity was seen in 11 and 37% of patients. A phase-I dose escalation study in 15 women with advanced disease and negative para-aortic nodes found an MTD for weekly carboplatin of area under the curve (AUC) 2.5 when combined with weekly paclitaxel (50 mg/m2), with predominantly hematological toxicity. At a median of 17 months the 2-year progression-free survival (PFS) was estimated to be 80% (Rao et al. 2005). In contrast, a small trial found that weekly carboplatin (AUC 2) and paclitaxel at a dose of 60 mg/ m2 was associated with grade-3 diarrhea in three of six patients after only four cycles (De Vos et al. 2004). Weekly paclitaxel added to vinorelbine was also poorly tolerated with significant neutropenia (Mundt et al. 2001). A trial of the oral 5-FU prodrug capecitabine defined an MTD of 450 mg/m2 twice daily in addition to weekly cisplatin with DLTs of diarrhea and cytopenias. Of concern were 3 of 13 patients with late grade-3 toxicities (Stokes et al. 2005). The topoisomerase inhibitor topotecan has been assessed in addition to radiation and cisplatin and appears to be well tolerated (Padilla et al. 2005). A MTD of 15 mg/m2 of weekly vinorelbine with weekly cisplatin and radiotherapy was found in one trial (Mundt et al. 2004). A combination of ifosfamide and cisplatin was evaluated in 44 patients during brachytherapy (two courses) and following radiation (four courses) (Vrdoljak et al. 2005). Acute toxicity was acceptable (25% grade-3 and 11% grade-4 leukopenia) but late complications were seen in 16% of women. At a median of 34 months 84% of them were recurrencefree. Although a randomized trial is planned, these results are difficult to compare with other chemoradiation protocols due to the omission of chemotherapy during external radiation. These results suggest that adding gemcitabine to cisplatin may be the most promising option, based on the encouraging response rates and manageable

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toxicity. A phase-III study has recently been completed and awaits analysis. Cisplatin and taxanes together appear to be associated with more frequent side effects, which may limit its use in clinical practice. Combinations of other agents with cisplatin will require further investigation to assess activity as well as toxicity.

20.2.3 Phase-I/II Chemo-Radiation Trials of Cytotoxic Agents in Vulvar Cancer There have been fewer prospective chemo-radiation trials in women with vulvar cancer, and most have focused on advanced disease. A GOG trial evaluated pre-operative cisplatin and 5-FU chemo-radiotherapy in 71 women with advanced vulvar cancer using split-course radiation to 47.5 Gy (Moore et al. 1998). A 47% clinical CR rate was seen, and 67% of patients were disease-free at a median of 45 months. Grade-3 or grade-4 skin and mucosal toxicity was seen in 54% of patients. In another pre-operative trial, 46 women with advanced nodal disease (N2/N3) were treated with a similar chemo-radiation schedule (Montana et al. 2000). Thirty-eight patients (83%) had resectable nodal disease following treatment, including two with pulmonary metastases. Of 37 women who underwent node dissection (the other patient had a vulvectomy alone), negative nodes were found in 15 patients. Twelve patients were alive and free of disease at a median of 78 months. Other single-institution and retrospective studies have shown similar good rates of response and control in advanced tumors, with outcome limited by significant comorbidities in this frequently elderly population. Although many of these studies used cisplatin and 5-FU in combination with radiation, many centers are using weekly cisplatin alone, based on the cervical cancer chemo-radiation data and in an effort to reduce toxicities; however, randomized studies to demonstrate the efficacy of a combined-modality approach are badly needed.

20.2.4 Chemo-Radiation in Endometrial Cancer Endometrial cancer is treated very successfully with surgery and radiation when diagnosed early; unfortunately, advanced disease is still often seen and in this setting treatment outcome is poorer. Randall et al. (2006) have recently reported the results of a

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pivotal phase-III study in 422 patients with advanced (stage III or IV) endometrial cancer who underwent debulking surgery with less than 2 cm of residual disease, and were subsequently randomized to chemotherapy with doxorubicin and cisplatin or whole abdominal radiation. This study demonstrated a significant improvement in overall and progressionfree survival, favoring chemotherapy. Interestingly, even though all patients had advanced disease, 42% of those treated with radiation and 55% of those who received chemotherapy were alive at 5 years, demonstrating the significant activity of both modalities. Studies combining chemotherapy and radiation are underway. Many of these studies are using sequential treatment, but concurrent therapy needs to be explored in this setting as well.

20.3 Biologically Targeted Treatment of the Tumor Microenvironment in Gynecological Cancer 20.3.1 The Microenvironment in Cervical Cancer The microenvironment in which cancer cells exist is abnormal, and is a potential target for novel drugs designed to enhance the cytotoxic effects of radiotherapy or more conventional chemotherapy. This has been explored in cervical cancer, and is a strong focus of ongoing new drug development. The microenvironment refers to the physiological and biochemical state of the extracellular space that surrounds the malignant cells, which is determined mainly by the tumor vasculature and interstitial matrix. The cellular and extracellular compartments are tightly coupled: aspects of the microenvironment are known to influence cell proliferation, gene expression, metastatic potential and response to treatment, whereas cytokines produced by malignant cells are important in the development and ongoing remodeling of the vasculature and interstitium (Heldin et al. 2004; Hicklin and Ellis 2005); therefore, treatment strategies that target the microenvironment, or the underlying structural and functional abnormalities that influence it, have the potential to alter clinical behavior and improve cure rates in many tumors including cervical cancer. Our discussion will focus on the abnormal tumor vasculature in cervical cancer, hypoxia, and elevated interstitial fluid pressure

Applications to Gynecological Cancers

(IFP), including hypoxia-targeted and vascular-targeted treatment strategies. Angiogenesis is necessary for invasive tumor growth and the development of metastases (Folkman 2002). The vasculature is induced and remodeled as tumors grow by a variety of paracrine growth factors that are secreted by malignant cells, as well as by normal tissue cells such as fibroblasts within the tumor (Hicklin and Ellis 2005). The most important of these is vascular endothelial growth factor (VEGF), which is a strong promoter of endothelial cell proliferation, migration, and survival. Hypoxia, through activation of the hypoxia inducible factor1D (HIF-1D) signaling cascade, is an important determinant of VEGF expression. It is likely that microregions of hypoxia and increased VEGF levels develop early in tumor growth as oxygen consumption exceeds supply. The new vessels that form have abnormal structure and architecture and are inefficient at delivering oxygen and other nutrients (Jain 1988, 2005; Vaupel 2004). This abnormal vasculature, coupled with other factors such as anemia (Harrison and Blackwell 2004) and transient tumor blood flow fluctuations (Brown 1979), results in profoundly hypoxic regions in some tumors. Clinically significant levels of hypoxia have been measured in cervical cancer using needle-electrode techniques, nitroimidazole drugs that bind in hypoxic regions or endogenous tissue-bound or circulating proteins that are upregulated by hypoxia (Lyng et al. 2000; Fyles et al. 2002; Airley et al. 2003; Nordsmark et al. 2003; Burri et al. 2003). In general, cervical cancer hypoxia has been associated with more aggressive malignant phenotypes (Hockel et al. 1996, 1999), higher rates of metastatic disease (Lyng et al. 2000; Fyles et al. 2002), and higher recurrence rates regardless of whether treatment is with radiation or surgery (Hockel et al. 1996). Our study has now accrued almost 300 patients who underwent needle-electrode oxygen measurements prior to treatment. The results demonstrated hypoxic regions with pO2 values <5 mmHg in most tumors. Profound hypoxia (>50% of the tumor oxygen readings <5 mmHg) was associated with a higher rate of radiographically detected lymph node metastases at diagnosis and lower disease-free survival in node-negative patients treated with radiotherapy alone, independent of other prognostic factors (Fyles et al. 2002). The extracellular, extravascular space is also abnormal in tumors. It is comprised of cross-linked collagen and elastin surrounded by fluid and macromolecules, including hyaluronate and proteogly-

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cans (Jain 1987; Heldin et al. 2004). In general, tumors have a higher level of collagen then the surrounding normal tissue, and a pronounced inflammatory cell infiltrate. Integrins bind the cellular components of the interstitium to the collagen-elastin matrix, and may play a role in cellular signaling (Wiig et al. 2003). Cytokines released by inflammatory cells are important in tumor growth and progression. For example, platelet-derived growth factor (PDGF) has been shown to modulate angiogenesis by recruiting VEGF-producing fibroblasts, enhancing endothelial cell survival and promoting pericyte coverage and stability of newly formed vessels (Dong et al. 2004). The abnormal vasculature and interstitium in tumors together result in elevated IFP. High capillary permeability and a lack of functional intratumoral lymphatics lead to accumulation of fluid in the interstitium, distention of the elastic interstitial matrix, and elevation of the pressure above normal atmospheric levels (Baxter and Jain 1989). In most cases, IFP is equal to the average capillary pressure and variability in IFP among tumors mainly reflects difference in capillary flow resistance. High IFP may contribute to the development of transient blood flow and hypoxia in tumors through a vascular destabilizing effect (Mollica et al. 2003), and has been implicated as a cause of impaired drug delivery. In our cervical cancer study, there was no relationship between IFP and tumor oxygenation; however, elevated IFP was an important independent prognostic factor for disease-free survival, pelvic recurrence, and distant metastatic recurrence following treatment with radiotherapy (Milosevic et al. 2001). It has been suggested that IFP provides a marker of relative vascular complexity in tumors (Jain 2005), and that changes in IFP after antiangiogenic or vascular-disrupting treatments might provide a clinically useful indication of biological response (Jain 2001). It is clear from these studies that the abnormal microenvironment in cervical cancer contributes to the failure of existing treatments, which generally consist of radical hysterectomy for small, early stage tumors, and radiotherapy with concurrent chemotherapy for more advanced disease; therefore, pharmacological agents that either target hypoxia directly, the upstream regulators of angiogenesis or the abnormal tumor vasculature, have the potential to improve patient outcome when used in combination with radiation and cytotoxic chemotherapy. The most promising of these targeted treatments are summarized in Table 20.1.

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308 Table 20.1. Pharmacologic targets in the cervix cancer microenvironment Target

Agent

Mechanism

Biologic response assessment

Hypoxia

Erythropoietin

Correction of anemia Increased O2-carrying capacity

Hemoglobin Tumor pO2

Nitroimidazoles

Hypoxic cell radiation sensitization

Mitomycin C

Hypoxic cell cytotoxin

Tirapazamine

Hypoxic cell cytotoxin

Bevacizumab

Inhibition of angiogenesis Vascular normalization Vascular sensitivity to RT

IFP dCT, dMRI

VEGF tyrosine kinase inhibitors

Inhibition of angiogenesis Vascular normalization Vascular sensitivity to RT

IFP dCT, dMRI

PDGF tyrosine kinase inhibitors

Inhibition of angiogenesis

IFP

Tumor vasculature

RT radiotherapy, IFP interstitial ﬂuid pressure, dCT dynamic computed tomography, dMRI dynamic magnetic resonance imaging

20.3.2 Hypoxia-Targeted Treatment Several pharmacological strategies have been proposed for overcoming the adverse effects of tumor hypoxia in patients with cervical cancer, including the correction of anemia with erythropoietin, radiation sensitization of hypoxic cells using nitroimidazole compounds, and direct killing of hypoxic cells with mitomycin C or tirapazamine. There is substantial clinical evidence to indicate that anemia prior to and especially during radiotherapy for cervical cancer is associated with poorer patient outcome (Harrison and Blackwell 2004; Winter et al. 2004). The underlying mechanism is not known, although it is possible that the lower oxygen carrying capacity of blood in anemic patients contributes to the development of tumor hypoxia, radiation resistance, and angiogenesis. An important question is whether or not the normalization of hemoglobin levels either by transfusion or with recombinant human erythropoietin overcomes the adverse consequences of anemia and improves patient survival. In the only randomized study to date that has addressed this issue, transfusion to maintain hemoglobin levels above 120 g/l during radiotherapy was associated with better local tumor control than transfusion for hemoglobin levels <100 g/l (Bush et al. 1978); however, this result was based on a subgroup analysis, as not all patients were transfused; nor did the randomization control for tumor size,

which is an important predictor of both anemia and poor patient outcome, making the results difficult to interpret. Erythropoietin has been shown to increase hemoglobin levels and improve the quality of life of cancer patients when administered weekly before and during radiation or chemotherapy. A large intergroup randomized study was designed to test the benefit of maintaining hemoglobin levels >120 g/l throughout treatment in patients with advanced cervical cancer, but was closed prematurely because of an excess risk of thrombosis, and new information linking erythropoietin to inferior patient outcome in other randomized studies (Leyland-Jones et al. 2003; Henke et al. 2003). This latter effect was presumed to be due to direct stimulation of erythropoietin receptors on cancer cells and tumor blood vessels. At this point, the role that anemia plays in the development of cervical cancer hypoxia is not known, nor is there conclusive evidence to indicate that correcting anemia improves patient outcome. Patients should be transfused to ameliorate the symptoms of profound anemia and maximize quality of life during treatment, or should be involved in clinical studies designed to better define the relative benefits and risk of erythropoietin in this clinical setting. The nitroimidazole family of drugs has been shown in numerous preclinical studies to sensitize hypoxic cells to radiation (Tannock et al. 2005). They undergo reductive metabolism in hypoxic regions of tumors and mimic the effect of oxygen. There are at least six phase-III studies in which

Applications to Gynecological Cancers

patients with advanced disease were randomized to receive a nitroimidazole with or without standard radiotherapy (Dische et al. 1984, 1993; Overgaard et al. 1989; Okkan et al. 1996; Grigsby et al. 1999; Chan et al. 2004). Misonidazole was the most commonly used drug in these studies; all pre-dated the modern era of radiotherapy and concurrent cisplatin chemotherapy. Only one of the six showed improved patient outcome (Dische et al. 1993). In addition, two meta-analyses, which pooled the results from these studies, found no difference in local tumor control or patient survival (Overgaard 1994; Dayes and Abuzallouf 2005). Neurotoxicity was significantly higher in nitroimidazole-treated patients. These disappointing results have been attributed to drug levels that were inadequate to achieve sensitization, and the fact that some of the patients in these studies probably had relatively well oxygenated tumors and could not have benefited from the treatment. In general, the nitroimidazoles have fallen out of favor in cervical cancer, being displaced by enthusiasm for drugs that are directly cytotoxic under hypoxic conditions. Mitomycin C and tirapazamine are examples of hypoxia-activated drugs that have been studied in patients with gynecological cancer; both undergo reduction in the absence of oxygen to form reactive compounds that cause DNA damage and inhibit DNA repair, as reviewed in Chap. 5. There have been numerous phase-I to phase-II studies of radiotherapy and concurrent mitomycin C (with or without other drugs such as 5-FU) in cervix and vulvar cancers. In addition, there have been at least two phase-III studies of radiotherapy plus mitomycin C vs radiotherapy alone in locally advanced cervical cancer. These studies demonstrated improved disease-free survival and a reduction in the risk of distant recurrence, with no apparent difference in late treatment complications (Roberts et al. 2000; Lorvidhaya et al. 2003); however, other studies have identified unacceptably high rates of late GI toxicity when mitomycin C is combined with radiotherapy to treat cervical cancer (Rakovitch et al. 1997). Tirapazamine is the most promising hypoxic-cell cytotoxic drug currently in clinical testing. It selectively kills the hypoxic cells in tumors that are resistant to the effects of radiotherapy, and also potentiates cisplatin cytotoxicity (Brown 1993). A phase-I study has demonstrated the feasibility and safety of using radiotherapy plus cisplatin and tirapazamine every 3 weeks to treat cervical cancer (Craighead et al. 2000). An ongoing phase-I to phase-II study is evaluating weekly dosing, which is more relevant to current clinical practice and should maximize

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the potential for interaction among the three therapeutic modalities. A phase-III intergroup study will begin shortly.

20.4 Incorporating Molecularly Targeted Agents with Radiation/Chemotherapy in Gynecological Malignancies We are now in an era of rationally designed molecularly targeted therapy against cancer. Targeted agents are increasingly used, either as single agents or in combination with chemotherapy and radiation. The choice of agents and combinations is dependent on understanding the biology of the cancer and availability of anticancer agents. There is also increasing understanding of the biological effects of radiation on intracellular molecular pathways that will lead to the development of logical synergistic combinations with targeted agents (Prise et al. 2005). To a large extent, current developments in cancer treatment have been to identify biologically active agents, define activity as a single agent, and then empirically combine these with active chemotherapeutic agents or radiation. The burden of identifying improved activity and balancing this with acceptable toxicity is therefore critically dependent on trial design. Generally, initial trials to assess toxicity and efficacy are conducted in patients who have recurrent or persistent disease following standard therapy. Once toxicity in these phase-I trials has been defined, activity can be assessed in phase-II settings, or combined with chemotherapy or radiation in disease specific phase-I/II studies; therefore, implementation of novel therapies is highly dependent on the effectiveness of «standard» chemotherapy or radiation. Paradoxically, adding a targeted agent to a regimen that has proven effectiveness in treating cancer is more challenging and needs to ensure that the outcome of therapy will not be compromised or toxicity increased significantly. The limitations imposed by normal tissue toxicity further add to the complexity. Radiation, much more than chemotherapy or molecularly targeted agents, has a narrower cumulative lifetime normal tissue tolerance which, if exceeded, may result in a significant increase in side effects. In addition, late radiation toxicity, which is seen 6 months or longer after completing treatment, is a significant concern particularly when treating tumors such as cervical cancer where this risk with standard radiation alone is at the high end of what is considered

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to be clinically acceptable. As a consequence, trials assessing the potential to combine chemotherapy or molecularly targeted agents with radiation need to be used with primary radiation therapy, rather than treatment for recurrent disease. While this is likely to yield greater improvement in outcome (as de novo tumors are perhaps not as resistant to treatment as those that recur following exposure to radiation or chemotherapy), this presents unique challenges to ensure studies are designed to assess both toxicity and efficacy, without compromising the results achieved with standard therapy; hence, these studies incorporate elements from phases-I, phases-II, and phases-III trial design. The more «treatable» a tumor is with conventional therapy, the greater the challenge in designing appropriate early phase trials in that setting. Previous chapters in this book have detailed the rationale and many of the current targeted agents in combination with chemotherapy and radiation. This section considers some of the practical aspects of current and planned implementation of targeted therapy in conjunction with radiation in gynecological cancer. Adding targeted therapy to radiation and chemotherapy requires careful attention to the patient population being treated and rigorous trial design. The end points of the clinical trial are an important factor in this consideration, with attention to clinical outcomes (response, disease control) as well as assessment of toxicity. Increasingly, pharmacokinetic and pharmacodynamic end points are incorporated in early-phase clinical trials. The ability to assess changes in pharmacodynamic end points in gynecological malignancies, such as cervical and vulvar carcinoma, following administration of a targeted agent with or without radiation allows a more selective and rational approach to therapy possible. Clinical trials incorporating targeted agents are underway in many gynecological cancers, although most of the activity at present is in carcinoma of the cervix. There are some trials that have been conducted in endometrial cancers that may prove to be interesting for future development with radiation. There has been little activity in looking at targeted agents in carcinoma of the vulva to date.

20.4.1 Carcinoma of the Cervix Patients who receive radiation for carcinoma of the cervix predominantly have curable disease. Our approach to incorporating novel agents in this set-

ting is to select patients who are at higher risk of treatment failure (advanced stage, bulky disease, hypoxic tumors) and introduce the novel agent cautiously, at lower doses and gradually increasing the duration of exposure. The novel agent is commenced 2 weeks prior to commencing chemo-radiation as a single agent, with clinical and pharmacodynamic assessment. Once chemotherapy and radiation commence, the novel agent is administered concurrently, incrementally, 1 week at a time. During this entire period, careful attention is paid to assessment of local and systemic toxicity. Longer-term follow-up is essential for assessment of delayed toxicities. This is illustrated in Fig. 20.2, as an example, using the PDGF inhibitor imatinib. Some of the biologically rational targets in gynecological cancer include EGF receptor (EGFR) inhibition, anti-angiogenics, proapoptotic agents, and modulators of hypoxia. Phase I: Imatinib 400 mg for escalating intervals n=3 n=3 n=3 n=3 n=3 Phase II: Imatinib 400 mg n=15 RT + Cisplatin Time 0

1

2

3

4

5

6

7

Biomarkers at weeks 0, 2, 4 Fig. 20.2. Clinical trial design for integration of chemoradiation and biological targeted agents such as imatinib

20.4.2 EGFR and COX-2 Inhibitors The general principles of combining therapy using EGFR inhibitors with chemotherapy and radiation have been described in Chap. 8. The EGFR inhibition either with monoclonal antibodies (cetuximab) or small molecule tyrosine kinase inhibitors (erlotinib, gefitinib) has already demonstrated improvement in progression-free and overall survival in colorectal, lung, and pancreatic cancers. Cetuximab therapy has been shown to significantly improve survival when added to radiation in head and neck cancer (Bonner et al. 2004). Carcinoma of the cervix would seem to be an appropriate disease setting where there is a good

Applications to Gynecological Cancers

biological rationale to improve outcome using EGFR inhibitors. The EGFR is frequently over expressed in squamous cell malignancies. The EGFR over expression is seen in up to 70% of cervical cancers. Mathur et al. (2001) have demonstrated increasing EGFR expression with the transition from cervical intra-epithelial neoplasia to malignancy. Gaffney et al. (2003) correlated EGFR expression of cervical tumors with inferior outcome following treatment. Cyclooxygenase-2 (COX-2) over expression has been reported in cervix cancers in association with locally advanced stage, distant metastasis, and poor survival (Ryu et al. 2000; Gaffney et al. 2001; Kim et al. 2003). Kim et al. (2004) also demonstrated, in a separate study, the negative outcome associated with tumor EGFR expression and suggest worsening outcome if there was co-expression of COX-2. At present, there are only two trials investigating EGFR inhibition in this disease, according to PDQNCI Clinical Trials Database: one looking at cetuximab with cisplatin in patients with recurrent disease and another investigating cetuximab/cisplatin and radiation as a phase-I trial in patients with stages-IB to stage-IVA disease. These trials will assess the tolerability and feasibility of adding an EGFR targeting agent to chemo-radiation or chemotherapy alone in cervical cancer. If promising, the next step will be to design appropriate phase-III studies. A recently reported phase-I/II trial of concurrent cisplatin and 5-FU chemo-radiation in addition to celecoxib 400 mg twice daily in cervical cancer demonstrated an increased risk of acute complications (Gaffney et al. 2005). Few of the toxicities were directly attributable to the celecoxib and most were hematological, suggesting that the combination of 5-FU with cisplatin may have contributed to the toxicity seen. This again highlights the importance of toxicity as an end point for trials of biologically targeted agents in addition to chemo-radiation.

20.4.3 Vascular-Targeted Treatment and Anti-Angiogenic Agents Targeting the angiogenic pathway is an increasingly important therapeutic strategy for cancer. Many of the microenvironmental abnormalities that have been associated with a poor prognosis in patients with cervix cancer, like hypoxia and high IFP, are a reflection of the chaotic and dysfunctional tumor vasculature; therefore, therapeutic strategies that combine radiation and concurrent chemotherapy

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with vascular-targeted treatments may improve local tumor control and overall survival. Antiangiogenic therapy has been shown in laboratory and clinical studies to increase tumor oxygenation (Lee et al. 2000), reduce IFP (Willett et al. 2004), and reduce capillary permeability (Morgan et al. 2003); however, there is also evidence to indicate higher levels of tumor hypoxia with these agents. Jain (2005) has hypothesized that antiangiogenic treatment causes time-dependent normalization of the tumor vasculature and that an optimal window exists when vascular efficiency is maximal. If so, the timing of how antiangiogenic treatment is combined with conventional radiation and chemotherapy in patients with cervix cancer may be critical to assuring maximal improvement in outcome. This implies the need to incorporate biological monitoring of the tumor microenvironment into future studies of these agents. The IFP may be useful in this regard given our clinical results, as may dynamic contrastenhanced imaging measurements of vascular permeability (Morgan et al. 2003). Angiogenesis associated with VEGF expression was reported in cervical intraepithelial neoplasia and cervical cancer (Dai et al. 2005) and VEGF expression is a poor prognostic factor, particularly in combination with EGFR over expression (Gaffney et al. 2005); thus, targeting VEGF and angiogenesis in carcinoma of the cervix would be rational, and if this improves the disorganized vasculature and reduces hypoxia and IFP, would potentially improve clinical outcome with radiation and chemotherapy. The agent that is most advanced in clinical development is bevacizumab, a humanized monoclonal antibody against VEGF. Bevacizumab has been shown to improve outcome in colorectal and lung cancers, and is currently being evaluated in many other malignancies. These studies have identified some of the toxicities that may arise with bevacizumab therapy, particularly a higher than expected rate of hemorrhage and bowel perforation. Late-radiation GI toxicity occurs in 5–10% of cervix cancer patients treated with conventional radiation and chemotherapy (Bachtiary et al. 2005), which raises concern about the safety of adding bevacizumab. At present, there is one trial underway evaluating bevacizumab in women with recurrent or metastatic cervical cancer, but none in combination with radiation or chemotherapy. The tyrosine kinase VEGF inhibitors do not appear to have the same high risk of GI side effects as bevacizumab, making them more attractive candidates for combination with conventional cytotoxic

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therapy in this disease. They also have the theoretical advantage of inhibiting other tyrosine kinase domains including PDGF, which plays a central role in vascular and lymphatic development (Pietras et al. 2001; Bergers et al. 2003). Inhibition of PDGF has been associated with reductions in IFP, tumorspecific increases in drug uptake and greater chemotherapy cytotoxicity (Pietras et al. 2001, 2002). There are many different anti-angiogenics currently in development. Our group has organized a clinical trial with sorafenib, in women with high risk cervical cancer being treated with chemotherapy and radiation. Sorafenib is a multitargeted tyrosine kinase inhibitor that has potent anti-angiogenic properties. This trial will assess the safety and tolerability of the combination with cisplatin and radiation in a phase-I setting, and also assess the pharmacodynamic changes on tissue oxygenation and IFP. Overall, there is a strong rationale based on preclinical and clinical data for combining antiangiogenic drugs with radiation and cisplatin in the treatment of cervical cancer. The immediate challenge is to develop clinical studies to define the optimal dosing and sequencing of these three therapeutic modalities, and the benefit of angiogenesis inhibition in this disease, while assuring patient safety particularly with respect to the late complications. Early monitoring of novel biological efficacy and toxicity end points will need to be an important component of these studies if timely results are to be obtained in an expeditious manner.

20.4.4 Pro-Apoptotic Agents Tumor resistance is commonly caused by a loss of the tumor cell’s ability to enter apoptosis; therefore, modulation of specific molecular pathways leading to increased cell death could widen the therapeutic window. Enhancing apoptotic cell death by modulating the survival pathway and combining this with radiation induced cell killing may be synergistic. This may be more relevant in cervical cancer as the normal apoptotic signaling pathways may be disrupted by the human papilloma virus (HPV) genome (Hougardy et al. 2005). The extrinsic apoptotic pathway is initiated by activation of death receptors on the cell membrane. Apoptosis is triggered by binding of tumor necrosis factor (TNF) receptor super family ligands such as TNF related apoptosis inducing ligand – TRAIL – to their cognate receptors. Normal keratinocytes are relatively resistant

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to recombinant TRAIL suggesting a wide therapeutic window that can be exploited for death receptor targeted therapy. At present, recombinant TRAIL has completed phase-I trials and is currently being evaluated in phase-II and combination phase-I studies. Combinations with radiation would be appropriate to consider. The proteosome also plays an important role in apoptosis by regulating intracellular protein degradation. The HPV targets the ubiquitin-proteosome system: the viral oncoproteins E6 and E7 target host tumor-suppressor gene products p53 and pRB for accelerated proteosomal degradation and inactivation, causing cellular immortalization and transformation. The proteosome inhibitor bortezomib inhibits radiation induced activation of nuclear factor kB (NFkB), with reduced tumor growth and enhanced radiosensitivity. This effect is further enhanced when combined with chemotherapy. Our group assessed the impact of bortezomib in colorectal cancer, and although we found that this agent is inactive in metastatic colorectal cancer, there were some interesting pharmacodynamic observations that may be pertinent to cervical cancer. Bortezomib had no detectable effect on NFkB, but a significant accumulation of HIF-1D was seen relative to carbonic anhydrase IX. This suggests that proteasome inhibition alters the response to tumor hypoxia (Mackay et al. 2005). This observation warrants assessment of bortezomib in combination with radiation and chemotherapy.

20.4.5 Targeted Agents in Endometrial Cancer Despite being the commonest gynecological cancer, there are few trials incorporating targeted agents with radiation in this malignancy; however targeted agents alone have been used in endometrial cancer with some success. We have conducted a phase-II clinical trial with single agent erlotinib, an EGFR tyrosine kinase inhibitor, in women with recurrent or metastatic disease who were chemotherapy naïve. Overexpression of EGFR is seen in up to 70–80% of endometrial cancers. Our results demonstrated an overall objective response rate of 12.5%, and a 21% response rate in EGFR positive tumors (Jasas et al. 2004). To put these results in context, endometrial cancer was at least as responsive, if not more, as lung or pancreatic cancers, for which erlotinib has been licensed. This also raises the attractive possibility of combining erlotinib with chemotherapy, radiation, or both in this disease.

Applications to Gynecological Cancers

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314 Jain RK (1988) Determinants of tumor blood flow: a review. Cancer Res 48:2641–2658 Jain RK (2001) Normalizing tumor vasculature with antiangiogenic therapy: a new paradigm for combination therapy. Nat Med 7:987–989 Jain RK (2005) Normalization of tumor vasculature: an emerging concept in a antiangiogenic therapy. Science 307:58–62 Jasas KV et al (2004) Phase II study of erlotinib (OSA-774) in women with recurrent or metastatic endometrial cancer: NCIC CTG IND 148 (Abstract). J Clin Oncol 22 (Suppl):453s Keys H et al (1999) Cisplatin, radiation, and adjuvant hysterectomy compared with radiation and adjuvant hysterectomy for bulky stage IB cervical carcinoma. N Engl J Med 340:1154–1161 Kim GE et al (2004) Synchronous coexpression of epidermal growth factor receptor and cyclooxygenase-2 in carcinomas of the uterine cervix: a potential predictor of poor survival. Clin Cancer Res 10:1366–1374 Kim HJ et al (2003) High cyclooxygenase-2 expression is related with distant metastasis in cervical cancer treated with radiotherapy. Int J Radiat Oncol Biol Phys 55:16–20 Lanciano R et al (2005) A randomized comparison of weekly cisplatin or protracted venous infusion of fluorouracil in combination with pelvic radiation in advanced cervix cancer: a Gynecologic Oncology Group Study. J Clin Oncol 23, epub Leborgne F, Leborgne JH, Doldan R, Zubizarreta E, Ortega B, Maisonneuve J, Museti E, Hekimian L, Mezzera J (1997) Induction chemotherapy and radiotherapy of advanced cancer of the cervic: a pilot study and phase III randomized trials. Int J Radiat Oncol Biol Phys. 37(2):343–350 Lee C et al (2000) Anti-vascular endothelial growth factor treatment augments tumor radiation response under normoxic and hypoxic conditions. Cancer Res 60:5565–5570 Leyland-Jones B (2003) Breast cancer trial with erythropoietin terminated unexpectedly. Lancet Oncol 4:459–460 Lorvidhaya V et al (2003) Concurrent mitomycin C, 5-fluorouracil, and radiotherapy in the treatment of locally advanced carcinoma of the cervix: a randomized trial. Int J Radiat Oncol Biol Phys 55:1226–1232 Lukka H, Johnston M (2004) Concurrent cisplatin-based chemotherapy plus radiotherapy for cervical cancer: a metaanalysis. Clin Oncol (R Coll Radiol) 16:160–161 Lyng H et al (2000) Disease control of uterine cervical cancer: relationships to tumor oxygen tension, vascular density, cell density, and frequency of mitosis and apoptosis measured before treatment and during radiotherapy. Clin Cancer Res 6:1104–1112 Mackay H et al (2005) A phase II trial with pharmacodynamic endpoints of the proteasome inhibitor bortezomib in patients with metastatic colorectal cancer. Clin Cancer Res 11:5526–5533 Maduro JH et al (2003) Acute and long-term toxicity following radiotherapy alone or in combination with chemotherapy for locally advanced cervical cancer. Cancer Treat Rev 29:471–488 Mathur SP et al (2001) Human papilloma virus (HPV)-E6/E7 and epidermal growth factor receptor (EGF-R) protein levels in cervical cancer and cervical intraepithelial neoplasia (CIN). Am J Reprod Immunol 46:280–287 Milosevic M et al (2001) Interstitial fluid pressure predicts survival in patients with cervix cancer independent of clinical prognostic factors and tumor oxygen measurements. Cancer Res 61:6400–6405

A. W. Fyles et al. Mollica FR, Jain RK, Netti PA (2003) A model for temporal heterogeneities of tumor blood flow. Microvasc Res 65:56–60 Montana GS et al (2000) Preoperative chemo-radiation for carcinoma of the vulva with N2/N3 nodes: a gynecologic oncology group study. Int J Radiat Oncol Biol Phys 48:1007–1013 Moore DH et al (1998) Preoperative chemoradiation for advanced vulvar cancer: a phase II study of the Gynecologic Oncology Group. Int J Radiat Oncol Biol Phys 42:79–85 Morgan B et al (2003) Dynamic contrast-enhanced magnetic resonance imaging as a biomarker for the pharmacological response of PTK787/ZK 222584, an inhibitor of the vascular endothelial growth factor receptor tyrosine kinases, in patients with advanced colorectal cancer and liver metastases: results from two phase I studies. J Clin Oncol 21:3955–3964 Morris M et al (1999) Pelvic radiation with concurrent chemotherapy compared with pelvic and para-aortic radiation for high-risk cervical cancer. N Engl J Med 340:1137–1143 Mundt AJ et al (2001) Phase I trial of concomitant vinorelbine, paclitaxel, and pelvic irradiation in cervical carcinoma and other advanced pelvic malignancies. Gynecol Oncol 82:333–337 Mundt AJ et al (2004) Phase I trial of concomitant vinorelbine, cisplatin, and pelvic irradiation in cervical carcinoma and other advanced pelvic malignancies. Gynecol Oncol 92:801–805 Nordsmark M et al (2003) Measurements of hypoxia using pimonidazole and polarographic oxygen-sensitive electrodes in human cervix carcinomas. Radiother Oncol 67:35–44 Okkan S et al (1996) A randomised study of ornidazole as a radiosensitiser in carcinoma of the cervix: long term results. Br J Cancer 74 (Suppl 27):S282–S286 Onishi T, Ohishi Y, Imagawa K, Ohmoto Y, Murata K (1999) An assessment of the immunological environment based on intratumoral cytokine production in renal carcinoma. BJU Int. 83(4):488–492 Overgaard J (1994) Clinical evaluation of nitroimidazoles as modifiers of hypoxia in solid tumors. Oncol Res 6:509– 510 Overgaard J et al (1989) Misonidazole combined with radiotherapy in the treatment of carcinoma of the uterine cervix. Int J Radiat Oncol Biol Phys 16:1069–1072 Padilla LA, Mitchell SK, Carson LF (2005) Phase I study of topotecan continuous infusion and weekly cisplatin with radiation therapy for locally advanced/recurrent cervical cancer. Proc Am Soc Clin Oncol, Abstract 5129 Pearcey R, Brundage M. Drouin P, Jeffrey J, Johnston D, Lukka H. MacLean G, Souhami L, Stuart G, Tu D (2002) Phase III trial comparing radical radiotherapy with and without cisplatin chemotherapy in patients with advanced squamous cell cancer of the cervix. J Clin Oncol. 20(4):891–893 Peters WA III et al (2000) Concurrent chemotherapy and pelvic radiation therapy compared with pelvic radiation therapy alone as adjuvant therapy after radical surgery in high-risk early-stage cancer of the cervix. J Clin Oncol 18:1606–1613 Pietras K et al (2001) Inhibition of platelet-derived growth factor receptors reduces interstitial hypertension and increases transcapillary transport in tumors. Cancer Res 61:2929–2934 Pietras K et al (2002) Inhibition of PDGF receptor signaling in

Applications to Gynecological Cancers tumor stroma enhances antitumor effect of chemotherapy. Cancer Res 62:5476–5484 Pignata S et al (2000) Phase I study with weekly cisplatin-paclitaxel and concurrent radiotherapy in patients with carcinoma of the cervix uteri. Ann Oncol 11:455–459 Prise KM et al (2005) New insights on cell death from radiation exposure. Lancet Oncol 6:520–528 Rakovitch E et al (1997) Role of mitomycin C in the development of late bowel toxicity following chemoradiation for locally advanced carcinoma of the cervix. Int J Radiat Oncol Biol Phys 38:979–987 Randall ME et al (2006) Randomized phase III trial of wholeabdominal irradiation versus doxorubicin and cisplatin chemotherapy in advanced endometrial carcinoma: a Gynecologic Oncology Group Study. J Clin Oncol 24:36– 44 Rao GG et al (2005) Phase I clinical trial of weekly paclitaxel, weekly carboplatin, and concurrent radiotherapy for primary cervical cancer. Gynecol Oncol 96:168–172 Roberts KB et al (2000) Interim results of a randomized trial of mitomycin C as an adjunct to radical radiotherapy in the treatment of locally advanced squamous-cell carcinoma of the cervix. Int J Cancer 90:206–223 Rose P et al (1999) Concurrent cisplatin-based radiotherapy and chemotherapy for locally advanced cervical cancer. N Engl J Med 340:1144–1153 Ryu HS et al (2000) High cyclooxygenase-2 expression in stage IB cervical cancer with lymph node metastasis or parametrial invasion. Gynecol Oncol 76:320–325 Stokes Z et al (2005) Phase one dose finding study of capecitabine (Xeloda), radiotherapy and cisplatin in the treatment of locally advanced squamous cervical cancer. Gynecol Oncol 97:790–795 Tannock IF et al (2005) The basic science of oncology, 4th edn. McGraw-Hill, Toronto, p 555

315 Tseng CJ, Chang CT, Lai CH, Soong YK, Hong JH, Tang SG, Hsueh S. (1997) A randomized trial on concurrent chemoradiotherapy versus radiotherapy in advanced carcinoma of the uterine cervix. Gynecol Oncol. 66(1):52–58 Vaupel P (2004) Tumor microenvironmental physiology and its implication for radiation oncology. Semin Radiat Oncol 14:198–206 Vrdoljak E et al (2005) Concomitant chemobrachyradiotherapy with ifosfamide and cisplatin followed by consolidation chemotherapy in locally advanced squamous cell carcinoma of the uterine cervix: results of a phase II study. Int J Radiat Oncol Biol Phys 61:824–829 Whitney CW et al (1999) Randomized comparison of fluorouracil plus cisplatin versus hydroxyurea as an adjunct to radiation therapy in stage IIB–IVA carcinoma of the cervix with negative para-aortic lymph nodes: a Gynecologic Oncology Group and Southwest Oncology Group study. J Clin Oncol 17:1339–1348 Wiig H, Rubin K, Reed RK (2003) New and active role of the interstitium in control of interstitial fluid pressure: potential therapeutic consequences. Acta Anaesthesiol Scand 47:111–121 Willett CG et al (2004) Direct evidence that the VEGF-specific antibody bevacizumab has antivascular effects in human rectal cancer. Nat Med 10:145–147 Winter WE et al (2004) Association of hemoglobin level with survival in cervical carcinoma patients treated with concurrent cisplatin and radiotherapy: a Gynecologic Oncology Group Study. Gynecol Oncol 94:495–501 Wong LC, Ngan HY, Cheung AN, Cheng DK, Ng TY, Choy DT. (1999) Chemoradiation and adjuvant chemotherapy in cervical cancer. J Clin Oncol. 17(7):2055–2060 Zarba JJ et al (2003) A phase I-II study of weekly cisplatin and gemcitabine with concurrent radiotherapy in locally advanced cervical carcinoma. Ann Oncol 14:1285–1290

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21 Early and Late Treatment-Induced Toxicity Wolfgang Dörr, Dorothea Riesenbeck, and Carsten Nieder

CONTENTS 21.1 21.2 21.2.1 21.2.2 21.2.3 21.2.3.1 21.2.3.2 21.2.4 21.2.4.1 21.2.4.2 21.2.5 21.3 21.3.1 21.3.2 21.3.3 21.3.3.1 21.3.3.2 21.3.3.3 21.3.3.4

Introduction 317 Early Side Effects 319 Pathogenesis 319 Radiobiological Parameters 320 Impact of Cytotoxic Treatment 321 Conventional Cytotoxic Drugs 321 Emerging Strategies 321 Biological Intervention and Supportive Care 322 Stimulation of Proliferation 322 Amifostine, Selenium, Superoxide Dismutase 323 Supportive Measures 324 Late Sequelae of Cancer Therapy 326 Pathogenesis 326 Radiobiological Parameters 327 Impact of Cytotoxic Treatment 327 Conventional Cytotoxic Drugs 327 Emerging Strategies 327 Biological Intervention 328 Supportive Care 328 References 329

non-malignant structures within the tumor, such as blood vessels or connective tissues, areas at the tumor margins, and also organs and structures traversed by the radiation beams. The volume of normal tissues receiving radiation doses that may eventually result in clinically manifest morbidity hence can be substantially larger than the tumor volume. These normal tissue responses are based mainly on the cytotoxic effects of ionizing radiation resulting in clonogenic cell death. This, however, does not only include cell kill by mitotic death, but also induction of differentiation, e.g., in fibroblasts, or induction of apoptotic processes, e.g., in endothelial cells. As already defined in 1936 by Holthusen, the optimum radiation dose is the dose associated with a small, generally accepted incidence of severe side effects in cured patients (Fig. 21.1); therefore, manifestation of severe side effects per se must

tumor control Frequency [%]

Malignant tumors, by definition, infiltrate the surrounding normal tissue structures; therefore, it is inevitable that the target volume of curative radiotherapy of solid tumors includes a significant volume of normal tissues, which are exposed to toxicity-inducing radiation doses. In addition, areas of suspected microscopic spread and safety margins accounting for organ- and patient motion are to be included. In principle, normal tissues refers to

thera pe u wind tic ow

100

21.1 Introduction

side effects

complicationfree cure 0

W. Dörr, DVM, PhD Professor, Medical Faculty Carl Gustav Carus, University of Technology Dresden, Fetscherstrasse 74, PF 58, 01307 Dresden, Germany D. Riesenbeck, MD Klinik für Strahlentherapie und Radioonkologie, Marienhospital Herne, Ruhr-Universität Bochum, Hölkeskampring 40, 44625 Herne, Germany C. Nieder, MD Department of Radiation Oncology, Klinikum rechts der Isar der Technischen Universität München, Ismaninger Strasse 22, 81675 München, Germany

Dose [Gy]

Fig. 21.1. Dose dependence of tumor control and side effects. Tumor control probability (TCP) and side effects (normal tissue complication probability, NTCP) of cancer therapy are represented by sigmoid dose–effect curves. The overlay of both curves results in the dose–effect relationship for complicationfree tumor cures, which initially increases, but subsequently decreases, when the side effects become a dominating factor. This results in a therapeutic window with a width that depends on the position of the TCP- and NTCP curve at the abscissa. (Adapted and modiﬁed from Holthusen 1936)

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not be considered a consequence of a wrong treatment strategy but is the price to pay for a maximum chance of tumor cure. Radiation-induced side effects in general, besides a possible systemic inflammatory response, only occur within the irradiated volume. In contrast, systemic treatment with cytotoxic drugs will eventually affect entire organs if accumulation of the drug occurs, or the entire body through widespread distribution. This results in a reduction of the residual compensatory

capacity of the individual organs and tissues. It must be emphasized that such a reduction has to be taken into account if the volume effect, which is well known for radiotherapy (Hopewell and Trott 2000; Hopewell 1997), is to be exploited during the treatment, e.g., for lung, liver, or kidneys. With modern delivery techniques, volumesparing high-dose treatment of, for example, earlystage lung cancer results in very low complication rates (Zimmermann et al. 2005).

Table 21.1. Examples of recently published acute esophageal toxicity studies Reference

Patients and treatment

No. of Study end point patients

Kim et al. (2005)

Lung cancer, with or without CTx, all cRT

124

tGrade 3 toxicity Significant risk factors: concurrent CTx; (RTOG) V60 >30% (risk 6% without concurrent CTx and 11% with concurrent CTx when V60 ≤30%)

Belderbos et al. Lung cancer, with or without CTx, dose per fraction (2005) 2.25–2.75 Gy

156

tGrade 2 toxicity Significant risk factors: concurrent CTx; (RTOG) volume receiving >35 Gy

36

tGrade 2 toxicity Significant risk factors: volume receiv(RTOG) ing >50 Gy; low pretreatment body mass index

Patel et al. (2004)

Lung cancer, concurrent CTx, hyperfractionated RT

Results

Table 21.2. Examples of recent lung toxicity studies Reference

Patients and treatment

No. of Study details patients

Results

Tsujino et al. (2003)

SCLC and NSCLC, concurrent CTx

71

Paired organ analysisa

V20 significant risk factor for RP, mean V20 in patients without RP was 20%

Claude et al. (2004)

NSCLC (also post-operative), 64% had previous CTx

90

Paired organ analysisa

V20, V30, and MLD sign. risk factors for RP and V20 in patients without RP was 12% (MLD 10 vs 13 Gy with RP)

Hernando et al. SCLC and NSCLC, most patients 201 had previous CTx, some con(2001) current

Paired organ analy- V20, V30, and MLD sign. risk factors sisa for RP and RP rate was 16% for MLD 11–20 Gy and 27% for 21–30 Gy

Graham et al. (1999)

NSCLC, 42% had some type of CTx

99

Paired organ analy- V20 significant risk factor for RP, V20 <22% caused <10% RP, RP rate was sisa 9% for MLD 11–20 Gy and 24% for 21–30 Gy

Willner et al. (2003)

SCLC and NSCLC, concurrent CTx in all but 1 patient

49

Both paired and separate organ analysis

Lee et al. (2003)

Esophageal cancer, preoperative RCT

61

Paired organ analy- V20 significant risk factor for RP, unfasisa vorable results when V20 t20%

RP correlated to high dose volume, V10–40, and MLD of ipsilateral lung; less pronounced effects were seen for the whole lung

SCLC, small cell lung cancer; NSCLC, non-small cell lung cancer; CTx, chemotherapy; RCT; combined radio- and chemotherapy; V20, lung volume receiving at least 20 Gy; RP, radiation pneumonitis; MLD, mean lung dose. aBoth lungs were considered as a single organ. Note that the gross tumor volume is usually excluded. Differences exist between planning algorithms and dose calculation, e.g., inhomogeneity correction.

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The same principle of optimum treatment resulting in complication-free cure applies for curative multimodality therapy, with combination of drugs and radiation, which has been shown to be advantageous over treatment with a single modality for a variety of malignancies, as illustrated in this volume. It appears from clinical data that toxicity to the mucosa of the aerodigestive tract and intestine and to the lungs is often the limiting factor in aggressive multimodal regimens. Data related to esophageal toxicity are summarized in Table 21.1. Table 21.2 shows examples of recent lung toxicity data. With regard to the mechanism of action, it must be differentiated between those drugs with direct cytostatic or cytotoxic effects, and those which affect specific physiological targets (growth factor receptors, vascularization, etc.) within tumors, thus indirectly inhibiting tumor growth and/or proliferation. While the former affect all proliferating cells within the body, the latter may be associated with specific side effects in the parental tissue of the tumor or other tissues, which express the same target. The same applies for pro-drugs, which are metabolically activated within the tumor and possibly the respective normal tissue. Radiation itself is a cytotoxic agent that results in normal tissue reactions. The impact of a combination of irradiation with cytostatic or cytotoxic substances on these normal tissue reactions is highly dependent on the pathogenesis of the radiation effects; therefore, the general pathogenesis of radiation effects are briefly summarized. Toxicity is frequently associated with specific drugs alone, without a combination with radiation. Examples are oto- and nephrotoxicity of cisplatin, or cardiotoxicity of adriamycin. These specific effects, which add to the potential modification of radiation sequelae, are not considered in this chapter. Side effects of radiotherapy that occur during or shortly after, i.e., within 90 days after the onset of the treatment, are referred to as early or acute complications. In contrast, normal tissue sequelae observed at later time intervals of months to years are depicted as chronic or late side effects. The cutoff time of 90 days has been chosen arbitrarily; however, early and late normal tissue effects of irradiation follow different biological principles, and are influenced by different radiobiological parameters; hence, the impact of additional cytotoxic treatment is likely to be based on different mechanisms in early and late responding tissues, and approaches for the amelioration of these side effects in consequence may be different. Therefore,

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early and late normal tissue sequelae are considered separately in this chapter. It has to be noted that the combination of radiotherapy with novel drugs, particularly those targeting biological mechanisms in tumors, may significantly alter the “normal” pathological changes seen after radiotherapy or conventional radiochemotherapy. This, in consequence, may completely change the clinical manifestation and pathology of side effects, but also the time course, particularly of late radiation sequelae; hence, in addition to sufficient preclinical testing in relevant animal models, a systematic and sufficiently long follow-up must be requested for all trials testing such biological targeting strategies. It must also be emphasized that any approach for prevention of normal tissue effects of multimodality treatment as well as of radiotherapy alone is highly dependent on the organs and tissues at risk. Similarly, the supportive care to be applied is closely related to the existing or expected morbidity; therefore, the present chapter focuses on few examples, which may relate not only to individual organs, but may be more generally applied, rather than giving a detailed and comprehensive overview of individual preventive approaches.

21.2 Early Side Effects 21.2.1 Pathogenesis Early radiation effects are usually seen in tissues with a permanent, more or less rapid, cell turnover, such as surface epithelia of the skin or the gastrointestinal tract, or hematopoietic tissue. The pathogenesis of these early reactions is closely related to the proliferative organization of the tissues, with a stringently regulated balance between cell production in the germinal tissue compartment and cell loss from the post-mitotic, functional compartments. Cell production is based on a stem cell population, in which cells on average divide into one stem cell and one transit cell (Fig. 21.2); the latter undergo a limited number of amplifying divisions before differentiation. Radiation impacts on cell production by sterilization (clonogenic, mitotic cell death) of proliferating cells, predominantly of stem cells. In contrast, cell loss, based on the physiological life span of the functional cells and hence largely

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lial cells, macrophages, etc. These changes can be directly induced by the radiation exposure, or indirectly, by the epithelial changes. Interactions with the epithelial response are currently unclear, but an influence on clinical symptoms, like pain, is obvious.

Fig. 21.2. Hierarchical proliferative organization of turnover tissues. The entire cell production in turnover tissues is based on tissue stem cells. A stem cell division on average results in one stem cell daughter and one transit cell daughter. This guarantees a constant stem cell number through all cell generations. The transit cells can undergo a limited number of divisions in order to amplify the cellular output per stem cell division. After differentiation, the post-mitotic, functional cells are eventually lost. The lifespan of the functional cells is tissue speciﬁc.

independent of radiation exposure, continues at its normal rate. It has to be noted that the sterilized proliferating cells usually undergo a limited number of so-called abortive divisions before terminal differentiation. As a consequence of the imbalance between cell production and loss, progressive hypoplasia develops, which eventually can result in a complete loss of cells. Clinical effects are observed, if cell density falls below a tissue-specific, minimum cell number, and hence after a tissue-specific but dose-independent latent time (Fig. 21.3). Besides the lifespan of the functional cells, this latency is also substantially influenced by the efficacy of the above-mentioned abortive divisions of the sterilized cells, which represent a significant residual cell production. Reactions of different severity, like dry or moist skin desquamation, are related to different threshold cell numbers. Healing of early effects, particularly in surface epithelia, occurs mainly on the basis of surviving cells within the irradiated volume; therefore, the time to tissue restoration clearly increases with decreasing numbers of surviving stem cells, i.e., with radiation dose. In other tissues, such as bone marrow, migrating stem cells originating from nonirradiated tissue volumes significantly contribute to tissue healing. Besides this cellular component of the early reactions, further effects are observed, ranging from vascular, inflammatory changes to increased expression of molecules such as cytokines, adhesion molecules, prostaglandins, and others in endothe-

21.2.2 Radiobiological Parameters The dominating treatment-related factor of early radiation effects to fractionated radiotherapy is the overall treatment time (Dörr 2003a,b; Hopewell et al. 2003). A reduction, for example, in accelerated radiotherapy regimens, results in a significant aggravation of acute reactions. This has been best demonstrated for oral mucositis, which represents one of the most important, frequently dose-limiting early complications. The time factor in earlyresponding tissues is based on a complex reorganization of the proliferative structure, which is summarized as “repopulation” (Dörr 1997). One of the main mechanisms, which is also relevant for the influence of additional cytostatic treatment, is the acceleration of the proliferation of surviving cells within the tissue, which also impacts on the efficacy of the abortive divisions once these cells are

Fig. 21.3. Changes in relative cell numbers during early radiation effects. The relative cell number in a turnover tissue is shown after irradiation alone (solid line) and in combination with cytostatic/-toxic drug treatment (dashed line). A clinical effect is seen after cell counts fall below a threshold cell number. The rate at which cells are lost deﬁnes the latent time, before the effect becomes manifest. With irradiation alone, this rate is tissue dependent, and independent of dose. With combined treatment, an increase in the rate of cell loss is seen, resulting in a shortening of the latent time. Regeneration, and hence the time to clinical healing as well as to complete restoration of cell numbers, is based on the number of surviving cells. Both are prolonged after combined treatment, as cell kill is more pronounced.

Early and Late Treatment-Induced Toxicity

sterilized. The basis is the reduction in overall cell numbers, i.e., tissue hypoplasia, on the one hand, but also the reduction of the stem cell compartment, as an autoregulatory process, on the other hand. The regulation of these proliferative changes remains unclear, but a number of factors have recently been identified that seem to contribute. In oral mucosa, the most prominent is keratinocyte growth factor (KGF), which seems to stimulate stem cell proliferation as well as abortive divisions and to modify differentiation of the cells (Dörr 2003b). In oral mucosa (Kase 2001), significant changes have also been observed in the expression of epidermal growth factor (EGF) and its receptor (EGFR). Inhibition experiments, however, suggested that the EGF/ EGFR system seems to be involved in the regulation of transit/abortive divisions, and not in stem cell proliferation (Fehrmann and Dörr 2005). In the hematopoietic system, a variety of cytokines, such as granulocyte-colony stimulating factor (GCSF) or granulocyte-macrophage-colony stimulating factor (GM-CSF), has been identified that influence repopulation and also post-treatment healing (Ganser and Karthaus 1996; Lord 2001). For most other early responding tissues, no data on the factors regulating proliferation and/or reconstitution are available. Besides the overall treatment time, a minor but significant effect of dose per fraction can be demonstrated in early-responding tissues (Dörr and Hendry 2001).

21.2.3 Impact of Cytotoxic Treatment 21.2.3.1 Conventional Cytotoxic Drugs The effect of cytostatic or cytotoxic drugs on these proliferating tissues follows similar mechanisms, i.e., sterilization of proliferating cells resulting in progressive hypoplasia. As a consequence of druginduced (stem) cell kill and hypoplasia, repopulation processes may also be influenced by chemotherapy (Tannock 1996; Nishimura 2004). In neoadjuvant regimens, stimulation of normal tissue repopulation can result in an increased normal tissue tolerance to the subsequent radiotherapy series. This has been clearly demonstrated in experimental studies in oral mucosa (Dörr et al. 2005a). As a result of the additional cell kill by cytotoxic drugs, the time to tissue healing is usually prolonged compared with radiotherapy alone.

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Some chemotherapeutic drugs, such as 5-fluorouracil (5-FU) or cisplatin, have been shown to significantly reduce the latent time to early normal tissue effects, e.g., in oral mucosa in experimental (Dörr et al. 2005b) and precise clinical studies, based on daily scoring of the reactions (W. Dörr et al., in preparation). As the latency is defined by the lifespan of the post-mitotic cells and the abortive divisions of sterilized cells, these drugs seem to affect either or both of these parameters (Fig. 21.2).

21.2.3.2 Emerging Strategies In recent years, a variety of novel strategies for the therapy of solid tumors have been proposed, most of which are summarized in the individual chapters of this book. Any of these strategies also bears the risk of affecting normal tissues, particularly the parental tissue of the tumor, which may be dependent on the same biological targets as the tumor itself. This chapter focuses on two of the most prominent approaches, inhibition of EGFR and vascular targeting by inhibition of the vascular endothelial growth factor (VEGF) receptor. Two approaches have been developed for inhibition of EGFR: specific tyrosine kinase inhibitors and inhibiting antibodies, such as C225 (cetuximab). Only few clinical data are available for normal tissue effects of treatment with EGFR antagonists, which include cetuximab-related toxicities, such as acneiform skin rash and hypersensitivity reactions (Burtness 2005). Association of early radiation reactions, such as oral mucositis, with changes in the expression of EGF and EGFR, as demonstrated in preclinical studies (Kase 2001; Dörr 2003a), render this tissue a potential target for EGFR inhibition; however, detailed studies using a tyrosine kinase inhibitor (Fehrmann and Dörr 2005) did not show an effect on the mucosal response to fractionated radiotherapy. Further studies are required into the effect of other EGFR antagonists on early radiation effects. With the exception of wound healing, angiogenesis is a rare event in normal tissues; hence, no interactions of anti-VEGF strategies with normal tissue reactions might be expected. However, no data are available on the quality and the time course of healing after tumor surgery. Moreover, the drugs developed for VEGF inhibition may act on more than one target, and may also influence non-angiogenic functions of vasculature and endothelial cells, and hence may indirectly affect normal tissue effects.

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In general, it must be postulated that any novel approach for biological targeting should be tested not only in relevant tumor models, but also in normal tissue models, at least the parental tissue of the tumor entity which is targeted. For this purpose, clinically relevant end points, and clinically relevant radio- and radiochemotherapy protocols must be applied.

21.2.4 Biological Intervention and Supportive Care Biological interventions and any other supportive care aiming at a reduction of early side effects of tumor therapy are independent of the induction of these side effects either by radiation or by chemotherapy, as both operate through cell kill as the main mechanism; however, it must be noted that a combination of both agents usually aggravates early morbidity and hence may be associated with a stronger necessity for interventions. For early effects, strategies for biological conditioning mainly aim at a stimulation of proliferation, as impaired cell production is the major pathogenetic factor. Besides this, substances such as amifostine or selenium have been suggested, on the basis of their potential for radical scavenging, for amelioration of (early) normal tissue side effects of irradiation. As many chemotherapeutic agents also act, directly or indirectly, through radicals, this approach for normal tissue sparing may also be relevant for combined radiochemotherapy; however, it must be emphasized that tumor effects of both radiation and chemotherapeutic drugs are similarly based on generation of radicals, and a systemic radical scavenging approach hence may also reduce tumor cell kill.

21.2.4.1 Stimulation of Proliferation Initial approaches for intervention in pathophysiological regulatory pathways of early normal tissue effects of irradiation were developed for the hematopoietic system. In this tissue, the hierarchical proliferative structure, with stem and early progenitor cells to terminally differentiated cells, can be more readily studied than in other tissues, and hence a variety of factors acting at the individual differentiation levels of the cellular hierarchy have been established (Lord 2001); of these, G-CSF and GM-CSF have been introduced into clinical treat-

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ment of therapy-induced neutropenia (Ganser and Karthaus 1996; Lord 2001). Administration of these factors, however, may indirectly also affect radiation sequelae other than in the hematopoietic system, by mobilization of hematopoietic stem cells from the bone marrow into the circulation, which may in turn migrate into sites damaged by irradiation and modify the radiation response. This has recently been illustrated, e.g., for oral mucosa (Dörr et al. 2005c,d) and salivary glands (Coppes et al. 2005). A proof for an indirect effect of the growth factors rather than a direct effect in the individual tissues is given by a similar efficacy of transplantation of bone marrow cells without growth factor treatment (Dörr et al. 2005c,d). Studies of biological conditioning in tissues other than the hematopoietic system are scarce. In skin, early investigations aimed at an increase in proliferation rates by removal of superficial skin material in mice by hair plucking. This did result in increased cell production, but no change in the response to single-dose irradiation (Hegazy and Fowler 1973). No fractionation studies were performed. A similar approach was tested in mouse oral mucosa, where silver nitrate as a mild astringent was used topically to remove superficial material (Dörr and Kummermehr 1992). A clear proliferative response was found, which, however, like in skin, was not associated with a change in the response to single radiation doses. Only when fractionated irradiation was administered, a reduction in mucosal effects was observed, indicating an effect on repopulation processes in the tissue. In clinical studies with accelerated fractionation (Maciejewski et al. 1991), a similar protective effect was seen, which, however, was missing in a study with conventional daily fractionation (Dörr et al. 1995); therefore, this method currently cannot be recommended for clinical use. Recently, growth factors specific for normal tissues have been suggested for biological targeting of normal tissues, besides hematopoietic growth factors mentioned above (Lord 2001; Parvez et al. 2005). One prominent example is KGF (Dörr 2003b) in its recombinant human form (palifermin). In numerous and detailed preclinical studies in mouse oral mucosa, a high efficacy for reducing oral mucositis induced by single dose irradiation (Dörr et al. 2001) as well as by fractionated irradiation (Dörr et al. 2002; Dörr et al. 2005e) and radiochemotherapy (Dörr et al. 2005b) was demonstrated, which depended on the administration protocol (Dörr et al. 2005a) and dosage (Dörr et al. 2005e) of the

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drug. In a clinical randomized phase-III study with high-dose radiochemotherapy as a conditioning treatment for stem cell transplantation in patients with hematological diseases (Spielberger et al. 2004), a highly significant effect was found, which was the basis for FDA approval of this growth factor for this indication in 2004 (FDA 2004). Currently, studies with radiochemotherapy for head and neck and lung malignancies are ongoing. One major prerequisite for clinical administration of biological targeting strategies aimed at a stimulation of proliferation in normal tissues, particularly for early responses, is selectivity for the normal cells without effects on tumor cells. This may be, except for very superficial tumors, of minor importance for local administration, but must be a major concern for systemic treatment, e.g., with growth factors; therefore, potential tumor effects must be tested. For this purpose, preclinical studies in relevant tumor models, with relevant fractionation protocols and relevant end points, must precede and/or supplement clinical studies.

21.2.4.2 Amifostine, Selenium, Superoxide Dismutase Amifostine (WR2721) was tested for its potential to reduce early treatment-related morbidity in a variety of clinical studies and for a variety of tissues and organs, with conflicting results (Andreassen et al. 2003; Grdina et al. 2002). So far, the only approved indication is amelioration of salivary gland effects of radiotherapy, and a recent followup of a prospective, randomized phase-III trial in head and neck cancer patients has confirmed these results (Wassermann et al. 2005). A protective effect on oral mucosa, postulated from a number of preclinical (Cassatt et al. 2003a, 2005) and clinical studies (e.g., Antonadou et al. 2002; Bourhis et al. 2000; Bourhis and Rosine 2002; Haddad et al. 2003; Suntharalingam et al. 2004), could not be confirmed in larger, randomized, placebo-controlled studies (Brizel et al. 2000), in one of which even an aggravation of oral mucositis was observed (Buentzel et al. 2005). When administered to patients with nonsmall cell lung cancer undergoing hyperfractionated radiotherapy plus cisplatin and etoposide in a randomized trial (n=62), intravenous amifostine significantly reduced esophageal toxicity, severe pneumonitis, and neutropenic fever (Komaki et al. 2004). Comparable results in such patients

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(n=68, conventional radiotherapy plus paclitaxel or carboplatin) were found by Antonadou et al. (2003). Intravenous administration of amifostine, the usually applied route, is associated with significant side effects, including nausea, emesis, and severe hypotension (Antonadou et al. 2002; Bourhis et al. 2000; Bourhis and Rosine 2002); therefore, subcutaneous application, with reduced and mainly local side effects, was suggested. Preclinical studies showed that this route of administration was similarly effective (Cassatt et al. 2003b, 2005). Results from first, small clinical studies demonstrated a superior toxicity profile compared with intravenous administration (Thorstadt et al. 2004; WernerWasik et al. 2005). In a recent preclinical study on oral mucosa with fractionated irradiation over 1 week, a significant reduction of oral mucositis by amifostine was demonstrated (W. Dörr et al., in preparation). In contrast, when fractionated irradiation was applied daily for 2 weeks, amifostine was effective only if given in week 1, but no further effect was observed with continued administration in week 2. These results indicate that the protective effect of amifostine on oral mucosa is largely independent of radical scavenging, as similar amounts of radicals are produced and scavenged in either week 1 or 2 of radiation treatment. The selectivity of amifostine, i.e., a potential risk of stimulation of tumor cell growth, is still subject to discussion (Andreassen et al. 2003; Bourhis et al. 2004; Lindegaard and Grau 2000). Sufficient follow-up and analysis of the available clinical trials with this drug must assist to solve this open question. Selenium, another radical scavenging drug, has similarly been suggested for amelioration of normal tissue effects of radio- or radiochemotherapy (Breccia et al. 1969; Bruns et al. 2003, 2004; Sagowski et al. 2005; Weiss et al. 1992). When tested preclinically in oral mucosa (Dörr and Gehrisch 2005), a dependence of the efficacy on the timing of selenium administration similar to amifostine has been observed. These findings with radical scavenging agents point towards a possible mechanism of action: shortening of the lag time before the onset of repopulation might explain the observed dependence of efficacy on the pattern of administration, and this may be related to a reduction of oxidative stress in the initial treatment phase; however, this hypothesis has to be tested in further investigations.

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As another antioxidant approach, administration of superoxide dismutase, has also been tested in experimental models (Carpenter et al. 2005; Epperly et al. 2004). Clinical trials are required to validate this concept.

21.2.5 Supportive Measures In general, similar principles apply for supportive therapy of early normal tissue effects if radiotherapy is administered with or without chemotherapy or any other additional treatment; hence, accepted guidelines for supportive care during and after radiotherapy (oral and dental care, avoidance of toxins such as tobacco and alcohol, placement of percutaneous endoscopic gastrostomy, feeding tubes, and central venous access lines, hydration, prevention of infec-

tions, diarrhea treatment, pain relief, monitoring of performance status, and body weight as well as blood counts, etc.) may be adopted for combination treatments (Rubenstein et al. 2004; Sonis et al. 2004), and no specific supportive measures are discussed here. It is noteworthy that treatment breaks may have a detrimental effect on outcome and that early initiation of comprehensive supportive care is warranted. With regard to the head and neck mucosa, several recent randomized trials have failed to define a new standard of care (Table 21.3). The positive trials of oral tocopherol oil, zinc sulfate, or GM-CSF were too small to draw definitive conclusions. Furthermore, validated scoring systems and precise definition of additional measures, as well as size of the mucosal areas exposed to therapeutic radiation doses, are a pre-requisite for such trials. G-CSF has been previously evaluated in 263 patients with stage-III/IV head and neck cancer in a multicenter randomized trial

Table 21.3. Recent randomized controlled clinical trials of supportive measures (head and neck mucosa) Reference

Patient population

No. of patients

Strategy

Results

Su et al. (2004)

Head and neck cancer, RT only

58

Oral aloe vera gel vs placebo, double blind

No significant benefit

Trotti et al. (2004)

Head and neck cancer, RT or RCT

545

Antimicrobial peptide iseganan oral vs placebo, double blind

No significant benefit

Stokman et al. (2003)

Head and neck cancer, RT only

65

Polymyxin E/tobramycin/amphotericin B No significant benefit lozenges vs placebo, double blind

El-Sayed et al. (2002)

Head and neck cancer, RT only

137

Bacitracin/clotrimazole/gentamicin lozenge vs placebo, double blind

No significant benefit

Bairati et al. (2005)

Head and neck cancer, RT only

540

Oral tocopherol plus E-carotene vs placebo, double blind

Significant reduction of acute toxicity but no QOL improvementb

Ferreira et al. (2004)

Oropharynx and oral cavity cancer, RT only

54

Oral tocopherol oil solution vs placebo, double blind

Significant reduction of symptomatic mucositis and pain

Ertekin et al. (2004)

Head and neck cancer, RT only

30

Oral zinc sulphate vs placebo

Significant reduction of degree of mucositis and shortening of confluent mucositis

Saarilahti et al. (2002)

Head and neck cancer, RT only

40

GM-CSF vs sucralfate mouthwashes, double blind

Significantly improved mucositis healing, less opioids, and interruption

Masucci et al. (2005)

Oropharynx and oral cavity cancer, RT only

61a

GM-CSF s.c. vs conventional mucositis treatment

Higher rate of reduction in mucositis grade

RT, radiotherapy; RCT, combined radio- and chemotherapy; GM-CSF, granulocyte-macrophage-colony stimulating factor; QOL, quality of life. a In contrast to the other trials using prophylactic treatment, patients started supportive care agent after having reached a certain, pre-deﬁned level of mucositis. b Tocopherol capsules without E-carotene did not reduce acute toxicity; intervention arm had higher local relapse rate.

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(Staar et al. 2001). Treatment was simultaneous radiochemotherapy in arm A and radiotherapy alone in arm B. In both arms there was a second randomization for prophylactic use of G-CSF to prevent mucosal toxicity. Radiotherapy followed a concomitant boost concept up to 69.9 Gy. In week 1 and 5, two cycles of 5FU and carboplatin were administered. Subcutaneous G-CSF treatment was given on days 15–19. Patients with G-CSF showed reduced acute mucosal toxicities (p=0.066). Unfortunately, this statement is not supported by presentation of data in greater detail; however, in both treatment arms G-CSF was associated with significantly worse local-regional control. This was more pronounced in the radiotherapy alone group. In multivariate analysis, inferior prognosis after G-CSF was confirmed. Although this was not end point of the study, the results do not encourage use of G-CSF in such settings.

Recommendations for the use of antiemetics (5HT3 antagonists, steroids, dopamine, etc.) were recently published by the Multinational Association of Supportive Care in Cancer (Maranzano et al. 2005) and can also be found on websites such as www.asco.org. With regard to gastrointestinal toxicity, Table 21.4 suggests that dietary counseling might be a valuable instrument. Pharmacological prevention trials have not resulted in a generally accepted recommendation to date; however, it must be noted that the combination of radiotherapy with chemotherapy or novel agents is less well studied, although it may aggravate early radiation effects, and therefore necessitate more intensive supportive approaches. Also they may change the pattern of early side effects, for example with acne-like skin reactions after antibody therapy, which may then require appropriate treatment.

Table 21.4. Recent randomized controlled clinical trials of supportive measures (acute gastrointestinal toxicity from pelvic radiotherapy) Reference

Patient population

No. of patients

Strategy

Results

Kozelsky et al. (2003)

Pelvic RT

129

Oral glutamine vs placebo, double blind

No significant benefit

Martenson et al. (2000)

Pelvic RT

123

Oral sucralfate vs placebo, double blind

Aggravation of some symptoms

Stellamans et al. (2002)

Pelvic RT

108

Oral sucralfate vs placebo, double blind

No significant benefit

Martin et al. (2002)

Adjuvant pelvic RT

56

Oral papain/trypsin/chymotrypsin No significant benefit vs placebo, double blind

Hombrink et al. (2000)

Pelvic or abdominal RT

176

Oral smectite vs placebo, double blind

No significant benefit

Resbeut et al. (1997)

Pelvic RT

153

Oral mesalazine (5-ASA) vs placebo, double blind

No significant benefit

Baughan et al. (1993)

Pelvic RT

73

Oral mesalazine (5-ASA) vs placebo, double blind

Aggravation of some symptoms

Kilic et al. (2000)

Pelvic RT

87

Oral sulfasalazine vs placebo, double blind

Significant reduction in acute enteritis rates and LENT-SOMA scores

Kilic et al. (2001)

Pelvic RT

31

Oral sulfasalazine vs placebo, double blind

Significant reduction in GI toxicity G_2,but no difference in endoscopic and histopathological findings

205

Amifostine i.v.

Significant reduction in lower GI tract and bladder toxicity

111

Dietary counseling vs protein sup- Improved outcome with both plements vs ad libitum food intake interventions, sustained effects with dietary counseling

Athanassiou et al. Pelvic RT (2003) Ravasco et al. 2005)

Colorectal cancer, pre-operative RCT

RT, radiotherapy; RCT, combined radio- and chemotherapy.

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21.3 Late Sequelae of Cancer Therapy 21.3.1 Pathogenesis Late effects of multimodal cancer therapy are essentially seen in all organs, with organ-specific manifestations and their respective clinical consequences. They occur after a latent time of months to years, are progressive, and are usually irreversible. Their pathomechanisms, however, follow some general principles, which are discussed briefly. Treatment effects on organ-specific parenchymal cells usually result in cell death, which, however, in most tissues does occur before the cells attempt to divide, i.e., with a significant time delay. If a substantial number of cells are lost, the remaining cells can be triggered into proliferation, which, in turn, further accelerates the cell loss. This has been depicted as the f lexibility in late-responding organs and tissues (Michalowski 1981; Stewart and van der Kogel 2002; Wheldon et al. 1982). Besides parenchymal cells, the vasculo-connective tissue must be considered as a target for late radiation effects (Dörr 1998; Dörr and Hendry 2001; Dörr and Herrmann 2003; Rodemann 2003). It has clearly been demonstrated that irradiation of vascular endothelial cells results in loss of capillaries (Fajardo et al. 2001; Hopewell et al. 1993), which may be associated with radiation-induced apoptosis. The impairment of blood supply significantly contributes to the development of late hypoplasia and atrophy. The development of telangiectasia (Fajardo et al. 2001), with a still unknown biological basis, represents a cosmetic problem in skin, but their vulnerability may have major relevance in hollow organs such as urinary bladder or intestine, or in the brain. One further component of late radiation sequelae is the fibroblast-collagen system. It has been demonstrated very well (Burger et al. 1998; Rodemann and Bamberg 1995; Rodemann 2003) that irradiation of mitotic fibroblasts causes differentiation into postmitotic fibrocytes. Transforming growth factor ß (TGF-ß) has been identified as one key player in these processes (Hakenjos et al. 2000; Rodemann 2003). The latter, however, remain metabolically active and can produce a significantly larger amount of collagen over a substantial time interval. This is the major basis for late radiation-induced fibrotic changes.

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Although the contribution of these individual components varies between organs, they are regularly found in all late radiation-induced changes. Each of the components can be affected by additional cytotoxic treatments. The latent time for chronic radiation effects is clearly depending on the aggressiveness of the treatment, i.e., radiation dose. This is related mainly to an accelerated loss of capillaries and collagen production if more cells are affected, but also to stimulated loss of parenchymal cells. In addition to the pathogenesis of these generic late effects, a second mechanism must be considered, resulting in consequential late effects (Dörr and Hendry 2001). This is based on an impairment of the barrier and protective function against mechanical and/or chemical stress of the earlyresponding tissue component during the early response, and hence is seen in organs with protective surface epithelia, such as the intestine, the oral mucosa, and skin sites with mechanical stress, but also in the urinary bladder and the lungs (Dörr and Hendry 2001). The loss of protection during the early response facilitates mechanical or chemical traumata (Fig. 21.4), in addition to the direct radiation effect, to the target structures for the late radiation response, i.e., mainly vasculature and connective tissue. These consequential changes usually cannot be distinguished from generic late sequelae on the basis of their morphology or pathology.

Fig. 21.4. Impact of chemotherapy or novel drugs on radiation pathogenesis. Radiation pathogenesis of early epithelial, generic late, and consequential late effects was adapted from Dörr and Hendry (2001). Chemotherapy and novel drugs impact on proliferating cells in the epithelium, and aggravate early radiation effects, thus also resulting in increased additional trauma and further consequential effects. Moreover, novel drugs, but also chemotherapy, may affect the targets for late radiation effects directly, and hence add to generic late effects.

Early and Late Treatment-Induced Toxicity

The extent of the additional trauma correlates with the severity of the early response. It has to be noted that the consequential component of a chronic treatment response follows the radiobiological principles of acute effects described in Sect. 21.2.2, i.e., gross dependence on overall treatment time and minor effects of dose fractionation, rather than those for late effects (see Sect. 21.3.2). The combination of radiotherapy with conventional cytotoxic or cytostatic drugs is expected to aggravate predominantly the effects in proliferating turnover tissues, i.e., epithelia, and hence to elevate the consequential component of the late effects (Fig. 21.4). Similarly, novel drugs may affect late effects through this mechanism; the latter, moreover, may also directly affect the target structures for late effects, which is less pronounced with conventional chemotherapeutic drugs.

21.3.2 Radiobiological Parameters The major radiobiological factor of the radiation tolerance of late-responding normal tissues is the effect of dose per fraction (Joiner and Bentzen 2002; Thames and Hendry 1987). The total dose, which can be applied to induce a given reaction, significantly increases with a reduction of the dose per fraction (hyperfractionation), associated with an increase in the number of fractions. In turn, with a given total dose, the reduction in dose per fraction will reduce the incidence of the reaction, i.e., ameliorate late effects. In experimental studies, where complete dose effect curves can be generated, this fractionation effect results in a shift of the dose effect curves towards higher doses (Joiner and Bentzen 2002). A therapeutic gain can hence be achieved, as the response of tumors to changes in dose per fraction is only minor compared with those in late-responding tissues. A quantitative measure of the fractionation effect, i.e., the shift in isoeffective doses, is the DE-ratio (unit: Gy) of the linear quadratic model of radiation effects (Thames et al. 1982; Thames and Hendry 1987; Joiner and Bentzen 2002). The higher the D E, the less sensitive is a tissue to changes in dose per fraction, i.e. the less pronounced is the fractionation effect. It has to be noted that the linear-quadratic model was developed to describe the radiation dose-effect, for single and fractionated doses, on cell survival, usually measured by a colony-forming assay in cell

327

culture (Thames and Hendry 1987). For this, it was assumed that radiation induced two types of lesions: primarily cytolethal or only sublethal lesions. The latter must interact in time and space for cell killing. With recovery of such lesions between fractions, they are not available for interaction with newly produced lesions by the next fraction, and the efficacy by the total dose decreases. Currently, it is clear, that the frequently quoted assumption that these lesions are represented by DNA double-strand breaks (lethal) and single-strand breaks (sublethal, two single-strand breaks must form a double-strand break) is not justified. The linear-quadratic model, particularly if applied to radiation effects in vivo, should be exclusively considered a (simple) mathematical equation to describe the fractionation effect, without any mechanistic background, although DNA repair obviously contributes to the fractionation effect, depicted as recovery. The time factor for late-responding tissues depends on the contribution of the consequential component to the overall effect, but is usually of minor relevance.

21.3.3 Impact of Cytotoxic Treatment 21.3.3.1 Conventional Cytotoxic Drugs The combination of cytotoxic drugs with radiation yields additional cell kill, which can affect all three target structures for late effects, i.e., parenchymal cells, vascular endothelium, and fibroblasts (Fig. 21.4). This will result in an aggravation of the late radiation response. As mentioned above, the latent time to the clinical manifestation of chronic radiation sequelae depends on the aggressiveness of the treatment; therefore, combination of radiotherapy with cytotoxic drugs, and hence additional cell kill, usually results in a shortened latent time.

21.3.3.2 Emerging Strategies No data are available for the impact of unconventional strategies, applied to affect biological targets in tumors, on late-responding tissues. It must be assumed, however, that if general cellular functions are attacked, which are present in the target cells for late effects as well as in tumors, aggravation of

W. Dörr et al.

328

chronic treatment effects is possible; hence, clinical trials with sufficient follow-up are required. It must be emphasized, however, that approaches to interfere with recovery processes may affect mainly late-responding tissues, rather than tumors, because of the differences in the capacity for recovery; hence, these strategies may result in significantly increased late complications, but only a minor increase in the tumor effect of the treatment; therefore, there is a risk for a reduction of the therapeutic efficacy, instead of a therapeutic gain.

21.3.3.3 Biological Intervention Interventions with cytoprotective efficacy, such as the antioxidants mentioned for early radiation effects, are considered to be similarly effective for late effects, if given at the time of irradiation. This, however, is only true if the protection occurs at the cellular level, and not through interaction with, for example, repopulation processes. This has, for example, been demonstrated for amelioration of CNS changes by amifostine (Nieder et al. 2004), possibly resulting from a reduction of the vascular component of the radiation effect; however, no evidence from conclusive clinical results is available. With regard to consequential late effects, any strategy effective in reducing the corresponding early effect will also be effective in ameliorating the consequential component and hence the total late reaction. Experimentally, this has been shown in the urinary bladder in mice: Impairment of the barrier function has been identified as the major mechanism of the early radiation effects. Prevention of the loss or restoration of the barrier function was achieved by topical administration of glycosaminoglycans, administered at very early time points. This intervention during the early reaction significantly reduced the manifestation for chronic radiation sequelae (Dörr et al. 1998, 2000). In rat intestine, the synthetic somatostatin analog octreotide was applied during the earlyresponse phase, which also resulted in a reduction of chronic structural changes (Wang et al. 1999, 2001). This implies that the inhibitor of exocrine pancreatic secretion, which causes the additional, chemical trauma during the early phase, could be used to reduce consequential late reactions. In general, late radiation effects are irreversible. For decades they were considered as a passive consequence of radiation exposure and the associated events and hence cannot be modified once the initial

treatment has happened. Molecular biology studies in recent years, however, have revealed that between the primary radiation effects and the clinical manifestation of the chronic sequelae, i.e., during the (clinical) latent time, very dynamic processes occur that include interactions between the cell types (Dörr 1998; Rodemann 2003). This processing of the tissue damage not only includes the target cells mentioned above, but also involves inflammatory changes, the immune system, and other factors. This knowledge opens the door for the development of biological strategies to interfere with these processes, i.e., for biological targeting in late responding normal tissues; however, so far, all these approaches are strictly experimental or lack clinical evidence. It must be assumed that the efficacy in the individual patient in general depends on various factors, such as the stage of fibrosis progression, the size of the lesion, but also on vascular changes, such as diabetes and arteriosclerosis. Pentoxifylline, which interferes with inflammatory processes, has been tested for its ability to interfere with late radiation effects, as recently reviewed by Nieder et al. (2005b). Whether combinations with tocopherol are truly superior to monotherapy is still an unanswered question. Encouraging data were published for radiation proctitis/enteritis (Hille et al. 2005) and superficial fibrosis (Delanian et al. 2005). Current evidence suggests that long-term medication might be needed for this chronic conditions. Conclusive clinical data, however, are required. In patients with cutaneous fibrosis, low-dose interferon-J given over 1 year resulted in regression of fibrosis and ulcerations (Gottlober et al. 2001). Further studies into the efficacy of this approach are required. Recently, it has been demonstrated in rats that insulin-like growth factor-1 has a potential to increase the latent time for radiation-induced CNS effects (Nieder et al. 2002). In a pre-clinical followup study, in combination with amifostine, a 7% increase in isoeffective doses was observed (Nieder et al. 2005a). Currently, the active search for new compounds that are capable of preventing radiation-induced side effects continues (Cotrim et al. 2005; Dittmann et al. 2005).

21.3.3.4 Supportive Care Cancer survivors are at increased risk of several serious late effects affecting their organ functions,

Early and Late Treatment-Induced Toxicity

quality of life, and social functioning (Kirwan et al. 2003; Maduro et al. 2003; Campbell et al. 2004; Duke et al. 2005; Ginsberg and Womer 2005). These complex issues, which have been reviewed in detail in the articles cited above, include cardiovascular diseases and neurocognitive deficits (Heflin et al. 2005; Prosnitz et al. 2005; Welzel et al. 2005); therefore, continuous monitoring and early intervention are recommended (DemarkWahnefried et al. 2005). The vast majority of supportive measures with regard to late normal tissue effects of multimodal cancer therapy are symptomatic or induced to compensate for functional deficits. These symptoms, e.g., of lung fibrosis, cardiac damage, kidney dysfunction, bowel stenosis, etc., are largely independent of the initiating agent, i.e., radiation, drugs, or other diseases, and represent the common end stage of injury in the individual organ. The supportive strategies hence are the subject of the respective medical discipline. Management might involve pharmacological treatment (e.g., of xerostomia and fibrosis), dietary counseling and supplements, nutritional support, physical therapies for lymph edema (Cheville et al. 2003; Badger et al. 2004), psychosocial support (Kash et al. 2005), and others.

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22 Feasibility of Combined Chemo- and Radiation Treatment in Elderly/Comorbid Patients Hans Geinitz

CONTENTS 22.1 22.2 22.3 22.4 22.4.1 22.4.2 22.4.3 22.4.4 22.4.5 22.4.6 22.4.7 22.5

Introduction 333 Demographics 333 Comorbidity and Organ Function 334 Clinical Studies of Radio-chemotherapy in the Elderly 334 Head and Neck Cancer 334 Oesophageal Cancer 335 Lung Cancer 335 Rectal and Anal Cancer 337 Bladder Cancer 338 Carcinoma of the Vulva 338 Glioblastoma Multiforme 338 Conclusion 339 References 339

22.1 Introduction There is growing evidence from retrospective studies that radiation therapy in elderly patients is effective and well tolerated (Geinitz et al. 2005; Baumann 1998; Pignon et al. 1996, 1997, 1998). Most of the patients treated within these studies received radiation therapy either as the sole anti tumour agent or in conjunction with surgery in a neoadjuvant or adjuvant fashion. Only a few analyses deal with combined chemo- and radiation treatment in elderly patients. Large prospectively conducted studies assessing the safety and effectiveness of combined radio-chemotherapy in elderly patients are lacking. On the other hand, the evidence for the superiority of radio-chemotherapy over radiation therapy alone in the elderly is limited since many study protocols either definitively exclude patients above the age of 70 years from participation or the contributing phy-

H. Geinitz, MD Department of Radiation Oncology, Klinikum rechts der Isar der Technischen Universität München, Ismaninger Strasse 22, 81675 Munich, Germany

sicians are not willing to enter these patients on the trial. The underrepresentation of elderly patients in cancer-treatment trials is still an unsolved problem (Hutchins et al. 1999). Older patients tend to be less often screened and subsequently more often present with advanced disease (Clark et al. 2004; Berkman et al. 1994). Disease staging is often carried out less accurately than in younger patients with malignant diseases (Wylie et al. 1998; Yancik and Ries 1994). Lastly, elderly patients are more often treated inadequately or not treated at all (Merchant et al. 1996; Berkman et al. 1994; Samet et al. 1986). The reasons for these age-related variations are not entirely clear. Patient’s preferences and physician’s attitudes play a major role and are influenced by the fear of excessive treatment toxicity as well as the common belief that cancer in the aged is in general less aggressive than in their younger counterparts (Berkman et al. 1994). Recent advances in supportive cancer therapy may not have been acknowledged by elderly persons as well as their primary care physicians.

22.2 Demographics In the next decades oncologists will be confronted more and more with cancer in the elderly. Life expectancy has steadily increased in industrial countries over the past 100 years. With advancing age, cancer incidence and cancer death arise in a near exponential fashion (Geinitz et al. 1999). In the United States the total number of newly diagnosed cancer in persons aged 75 years or older is expected to increase nearly threefold from 389,000 in the year 2000 to 1,102,000 in the year 2050, a rise from 30 to 42% of the cancer population aged 75 years or older (Edwards et al. 2002). The further life expectancy of a 70-year-old woman in Germany is still 15.7 years, and that of a 70-year-old man is 12.8 years (Federal Statistical Office of Germany, life

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table 2002/2004; www.destatis.de). These time spans are too long to a priori choose a palliative therapy regime in patients whose malignant tumours are potentially curable with radio- or radio-chemotherapy. Most cancer recurrences occur within 25 years after treatment. Since there is no unequivocal data that malignant tumours are per se less aggressive with advanced age, recurrences will be experienced also by the elderly patient with all the negative consequences on the patient's quality of life.

22.3 Comorbidity and Organ Function Comorbidity and organ function are important cofactors that must be taken into account when assessing the indication for radio-chemotherapy. The prevalence of comorbid disease increases with age and organ capacity (renal, pulmonary and liver function) usually decreases with age (Ogle et al. 2000). The influence of concomitant disease on acute or late radiation toxicity has not yet been studied in great detail, but some investigators report that diabetes mellitus or hypertension have a negative impact on radiation side effects (Herold et al. 1999; Boehler et al. 1992). There is evidence that decreased pulmonary function limits the tolerated radiation dose to the lung (Mehta 2005). Concomitant disease as well as decreased organ capacity could impair the clearance of chemotherapeutic substances and consequently lead to toxic plasma- and/or tissue concentrations. Furthermore, concomitant disease might be more important to the overall prognosis of the patient than the malignant disease itself. Comorbidity- and organ-functioning scores might further help assigning the indication to radio-chemotherapy in elderly patients (Charlson et al. 1987).

22.4 Clinical Studies of Radio-chemotherapy in the Elderly Clinical studies of radio-chemotherapy in the elderly are rare. Since the effects of radio-chemotherapy on the elderly are not very well known, study protocols often include lower radiation doses and/or less toxic chemotherapy protocols in this population than in younger patients (Jeremic et al. 1999a; Allal et al. 1999).

22.4.1 Head and Neck Cancer Kodaira et al. (2005) carried out a phase-I trial in 15 elderly (>70 years) or medically unfit patients with head and neck cancer that were treated with combined radio-chemotherapy. Patients had to have an Eastern Cooperative Oncology Group (ECOG) performance status of 0–2 and adequate organ function. In previously untreated patients radiation therapy was applied to a total dose of 60–66 Gy to the primary tumour and 66–70 Gy to involved cervical lymph nodes in 2-Gy fractions. Patients who had received radiation therapy to the neck before (n=5) were treated to doses of at least 39.4 Gy to the primary lesion in 1.8-Gy fractions with the cumulative dose of both radiation schedules not exceeding 100 Gy. Docetaxel was administered concomitantly once weekly over five consecutive weeks. The starting dose was 10 mg/m 2 which was escalated by 2 mg/ m2 following the treatment of at least three consecutive patients until a grade-3 toxicity occurred (with the exception of side effects concerning mucosa, skin and nausea which had to be at least grade 4). No patient experienced any grade-3 or higher haematological toxicity. Six patients developed grade-3 mucositis and 3 patients grade-4 mucositis, all of them in the 14-mg/m 2 dose group; thus, the recommended docetaxel dose was 12 mg/m2 weekly over five consecutive weeks. An Italian group prospectively evaluated postoperative radio-chemotherapy in 40 elderly patients with head and neck cancer and a high risk for loco-regional recurrence (Airoldi et al. 2004). Patients 70 years or older with an ECOG performance status of 0–2 who have had curative resection for squamous cell carcinoma of the oral cavity, oropharynx, hypopharynx or larynx were entered on this trial. A total dose of 54 Gy was applied to regions at risk of microscopic disease and a dose of 64.8 Gy was given for positive margins or extracapsular nodal extension. Carboplatin was administered 4560 min prior to irradiation at a dose of 30 mg/m2 on days 1–5 of weeks 1, 3, and 5. Treatment was administered on an outpatient basis and 80% of the patients received all three cycles of chemotherapy. Grade-3 toxicity was observed for mucositis (25%), neutropaenia (15%), dermatitis (5%), and thrombocytopaenia (2.5%). No grade-4 toxicity occurred. One case of moderate osteoradionecrosis occurred as a late side effect. The 3-year local control rate was 79% and 3-year overall survival was 64%. These data compared favourably to matched controls 70 years or older who received postoperative radio-

Feasibility of Combined Chemo- and Radiation Treatment in Elderly/Comorbid Patients

therapy alone in the same institution (3-year local control 64%, 3-year overall survival 52%). Quality of life (Functional Assessment of Cancer Therapy) declined minimally during therapy (from 85.7 to 81.4) and fully recovered by 12 months (87.1). Ampil et al. (2001) retrospectively analysed 10 patients aged 65 years or older who received combined radio-chemotherapy for advanced (stage III/ IV) head and neck cancer. Neoadjuvant chemotherapy consisted of cisplatin (20 mg/m 2 day-1 on days 1–5), 5-FU 800 mg/m2 24 h-1 continuously days 1–4) and etoposide (60 mg/m 2 day-1 on days 1– 3). This regimen was repeated every 21 days for three cycles. Conventionally fractionated radiation therapy began concomitant to the second cycle of chemotherapy. A total dose of 45–70 Gy was delivered to the primary tumour and upper neck, the lower neck was treated to 45–50 Gy. Three of 10 patients experienced a grade-3 acute toxicity and 1 patient a grade 3 late side effect. The local failure rate was 30% with a 3-year survival of 30%.

22.4.2 Oesophageal Cancer The Roswell Park Cancer Institute reviewed their experience with combined radio-chemotherapy in patients aged 70 years or older with oesophageal cancer (Nallapareddy et al. 2005). Data on 30 patients were available. Radiation doses ranged from 45 to 64.8 Gy in 1.8-Gy daily fractions. Various chemotherapy regimens were applied on an outpatient basis. 5-FU continuous infusion was used in 26 patients at a median dose of 1220 mg/m2 per week. In 13 patients it was combined with cisplatin (27–36 mg/ m2 per week) and in 8 patients with oxaliplatin (31– 46 mg/m2 per week). Four patients received paclitaxel (50–80 mg/m2 per week). The following grade-3 or grade-4 toxicities were observed: haematological 17%; febrile neutropaenia 13%; mucositis 40%; dehydration/diarrhoea that required hospitalisation 50%; pulmonary 20%; cardiac 7%; and neuropathy 7%. Median survival was 10 months; 6 patients died of local recurrence and 7 of metastatic disease. A Japanese group analysed the efficacy and toxicity of concurrent radio-chemotherapy in 22 patients with oesophageal cancer aged 75 years or older (Uno et al. 2004). Patients had to have a Karnofsky performance status of at least 70 and no serious comorbidity. Total radiation doses ranged from 50 to 65 Gy conventionally fractionated. Different chemotherapy protocols were applied concurrently with radia-

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tion therapy, the most common (n=12) was a combination of cisplatin (15 mg/m2, five consecutive days) and 5-FU (500 mg/m2 as continuous infusion 5 days/week). Four patients received lower doses of cisplatin and/or 5-FU, 1 patient received a combination of carboplatin and 5-FU and 5 patients received 5-FU alone. Two patients experienced grade-3 neutropaenia, and no grade-4 toxicity was observed. The median survival was 9 months; 13 patients died of local recurrence and 4 of distant metastasis. A study by Rice et al. (2005) analysed retrospectively the outcome and operative mortality in 74 patients aged 70 years or older with cancer of the oesophagus. Patients received either preoperative radio-chemotherapy (group I; n=35) or no neoadjuvant treatment (group II; n=39). The elderly were compared with patients younger than 70 years who received radio-chemotherapy before oesophagectomy (group III; n=165). Neoadjuvant treatment was not reported on in detail. Patients received total doses of 4550 Gy in 1.8-Gy daily fractions along with chemotherapy which was mostly administered concomitantly. Chemotherapy typically included 5-FU plus a platinum agent but taxanes were also frequently incorporated into the treatment regimen. Perioperative mortality was not significantly increased in elderly patients with neoadjuvant treatment as compared with the other groups (3%). Except for the use of more perioperative blood transfusions and a higher rate in atrial arrhythmias in pre-treated elderly patients, postoperative complications were similar between groups. The authors did not report on toxicity during neoadjuvant treatment. Overall survival of elderly patients with preoperative radio-chemotherapy did not differ significantly from that of younger pre-treated patients.

22.4.3 Lung Cancer Approximately 67% of all new lung cancer cases in the United States are diagnosed in persons 65 years and older, and about 31% of the cases in persons >75 years (Edwards et al. 2002). Schild et al. (2003) retrospectively analysed toxicity and outcome data for 63 patients >70 years who were treated within a North Central Treatment Group phase-III trial. The trial compared bid radiochemotherapy (60 Gy, 1.5 Gy bid, 2-week break after 30 Gy) with once daily radio-chemotherapy (60 Gy, 2 Gy) for the treatment of stage IIIA-B non-smallcell lung cancer. In both treatment arms etoposide

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100 mg/m2 and cisplatin 30 mg/m2 were applied on days 1–3 and days 28–30. Study participants had to have an ECOG performance status of 0 or 1 and adequate haematological, renal and pulmonary function. Elderly patients experienced significantly more grade-4 or grade-5 haematological side effects (78 vs 56%) and more grade-4 or grade-5 pneumonitis (6 vs 1%). No difference in grade-4 or grade-5 oesophagitis was observed. Survival did not differ between age groups. The 2- and 5-year survival rates were 36 and 13%, respectively, in elderly patients and 39 and 18%, respectively, in patients younger than 70 years. Yuen et al. (2000) performed a retrospective analysis for 50 patients >70 years who participated in the phase-III Intergroup trial 00096 for limited-stage small cell lung cancer. Patients received cisplatin 60 mg/m2, day 1, and etoposide 120 mg/m 2, days 1– 3, for four cycles and either once or twice daily concurrent thoracic radiotherapy to 45 Gy. Grade-4 to grade-5 haematological toxicity (84 vs 61%; p<0.001) and fatal toxicity (10 vs 1%; p=0.01) occurred more often in patients >70 years despite the fact that they received all four cycles of chemotherapy less frequently than younger patients. Fatal toxicity in the elderly was related to infection (2 patients), pulmonary toxicity (1 patient), hemorrhage (1 patient), and coagulation (1 patient). There was no difference in the frequencies of grade-3 or grade-4 oesophagitis between age groups. Response rate, time to local failure and duration of response did not differ between groups. Overall survival at 5 years was significantly lower for elderly patients (16 vs 22%). A group from Osaka conducted a multicenter phaseII study of 38 patients 76 years or older with medically inoperable or unresectable stage-I to stage-III nonsmall-cell lung cancer (Atagi et al. 2000). Patients with ECOG performance status 0–2 and adequate organ function received conventionally fractionated thoracic radiotherapy (mediastinum, hilar region, primary tumour with or without supraclavicular fossa) to a dose of 40 Gy and a subsequent boost to the primary tumour and involved lymph nodes of 10–20 Gy. Carboplatin 30 mg/m2 on days 1–5 was given concurrently during weeks 1–4. The following grade-3 or grade-4 haematological toxicity was observed: leucopenia (71%); thrombocytopaenia (29%); and anaemia (34%). No grade-3 or grade4 oesophagitis was observed but 2 patients died because of pneumonitis (5%). For stage-III patients 2-year survival was 21% and for stage-I/II patients 3-year survival was 69%. Jeremic et al. (1999a) studied a hyperfractionated accelerated radiation therapy regimen with concur-

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rent carboplatin/oral etoposide in 58 elderly patients >70 years with stage-III non-small-cell lung cancer and a Karnofsky performance status of >70. In this phase-II trial radiation therapy was given to a total dose of 51 Gy in 34 fractions over 3.5 weeks. Carboplatin (400 mg/m2) was administered intravenously on days 1 and 29, and etoposide (50 mg/m 2) was given orally on days 1–21 and 29–42. The haematological, oesophageal and bronchopulmonary acute grade-3 or grade-4 toxicities amounted to 22, 7 and 4%, respectively. No grade-3 or grade-4 late toxicity was observed. In 55 evaluable patients the median survival time was 10 months and the 2- and 5-year survival rate was 24 and 9%, respectively. The 5-year local control rate was 13%. The authors state that the observed toxicity was lower than anticipated, but that on the other hand, the efficacy was inferior to (more aggressive) combined radio-chemotherapy in younger patients. Another phase-II study by the same investigators evaluated a palliative radio-chemotherapy protocol in 50 patients >70 years with stage-IV non-smallcell lung cancer (Jeremic et al. 1999b). Study entry criteria required a Karnofsky performance status of at least 70. Low-dose hypofractionated radiation therapy was given to the mediastinum and primary tumour to a total dose of 14 Gy in two 7-Gy fractions on days 1 and 8. Chemotherapy consisted of carboplatin (300 mg/m2) on days 1 and 29 and oral etoposide (50 mg/m2) days 1–21 and 29–42. Combined modality treatment was administered totally on an outpatient basis. Grade-3 haematological side effects were observed in 19% of the patients. Nonhaematological grade-3 toxicity comprised oesophagitis (19%) and bronchopulmonary side effects (9%). No grade-4 or grade-5 toxicity occurred. The median overall survival was 7 months. Cough, haemoptysis and chest pain improved in 60, 75 and 68% of cases, respectively. The authors state that symptom improvement in their study was similar to that observed in various chemotherapy studies using more aggressive protocols. A randomized multicenter study of the Japan Clinical Oncology Group (JCOG9812) in elderly patients with locally advanced non-small-cell lung cancer was prematurely closed because of a high rate of treatment related deaths (Atagi et al. 2005). Patients aged 71 years or older with stage-III non-small-cell lung cancer were randomised either to conventionally fractionated radiation therapy of 60 Gy to the primary tumour (RT) or to the same radiation treatment with concomitant carboplatin 30 mg/m2 per fraction up to the first 20 fractions (CRT). Treatment tech-

Feasibility of Combined Chemo- and Radiation Treatment in Elderly/Comorbid Patients

niques were simple and consisted of anterior/posterior opposed fields up to 40 Gy and bilateral oblique fields thereafter. No lung heterogeneity corrections were used. Forty-six patients were randomised. No patient in the RT arm had grade-4 haematological toxicity and 2 (9%) and 4 (17%) patients in the CRT arm experienced grade-4 leucocytopaenia and neutropaenia, respectively. Grade-3/4 subacute lung toxicity was observed in two patients in the RT arm and 4 patients in the CRT arm. Four patients died as a result of radiation pneumonitis, one in the RT arm and 3 in the CRT arm. Post-hoc quality assurance revealed a major protocol violation in 60% of the cases, and in 7% the dose constraints to the lung were violated. In the latter group were two of the patients who died from radiation pneumonitis. A new trial (JCOG0301) with prospective quality assurance was activated in September 2003.

22.4.4 Rectal and Anal Cancer Although the 1990 NIH consensus recommended adjuvant radio-chemotherapy for stage-II and stageIII rectal cancer without an upper age limit, this recommendation was far from being accepted for the wide majority of elderly patients treated in the 1990s (Neugut et al. 2002; Schrag et al. 2001). Neugut et al. (2002) carried out a populationbased study on the use of adjuvant chemotherapy and radiation therapy for rectal cancer among patients 65 years or older who were diagnosed between 1992 and 1995. A total of 983 patients with stage-II and 824 patients with stage-III disease who had received surgery were identified in the Surveillance, Epidemiology, and End-Results (SEER) Medicare data base. Of the total population 28% received surgery alone, 11% received surgery plus radiation therapy, 14% received surgery plus adjuvant 5-FU and 37% received surgery with radiation plus adjuvant 5-FU chemotherapy. Of the patients with combined radio-chemotherapy 89% received treatment postsurgically, 10% presurgically and 1% pre- and postsurgically. Age was inversely associated with receiving combined adjuvant therapy as were high comorbidity scores. The number of involved lymph nodes increased the odds of radio-chemotherapy. The cumulative mortality was lower among patients receiving radiation plus 5-FU than among patients treated with surgery alone (47 vs 54%, respectively; p<0.01). This was confirmed in multivariate analysis. When stratified by age a significant sur-

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vival benefit was found for stage-III patients only: patients receiving radio-chemotherapy had a 29% risk reduction in overall mortality at 5 years. Another SEER study by Schrag et al. (2001) on 1411 patients aged 65 years or older with resected stage-II or stage-III rectal cancer disclosed similar results concerning the under-usage of adjuvant radio-chemotherapy: only 42% of the entire cohort received chemotherapy and radiation. Age was the strongest determinant of treatment: 60% of patients aged 65–69 years; 52% aged 70–75 years; 36% aged 75–79 years; 23% aged 80–84 years; and 12% aged 85 years or older received radio-chemotherapy. During the 5 years of diagnosis (1992–1996) the proportion of patients that received combined adjuvant treatment merely increased by 1% (from 42 to 43%). A study group from Leeds evaluated a low-dose radiochemotherapy protocol in 16 elderly (77–91 years) frail patients with anal carcinoma (Charnley et al. 2005). Patients not suitable for full-dose radio-chemotherapy due to low performance status or comorbidity were treated with 30 Gy in 15 fractions to the gross tumour volume plus a 3-cm margin. Concurrent chemotherapy comprised 5-FU 600 mg/m2 24 h-1 continuous infusion on days 1–4. All 16 patients completed treatment as planned. Only 1 patient experienced grade-3 skin toxicity. The local control at a median follow-up of 16 months was 73%. Overall survival was 69% and disease-specific survival 86%. Allal et al. (1999) et al. reported on 42 patients aged 75 years or older that received either radiotherapy alone (RT; n=21) or radio-chemotherapy (RT-CT; n=21) for anal carcinoma. Radiation therapy was administered in two sequential courses, the first with a median dose of 39.6 Gy in 22 fractions to the pelvis, the second with a median dose of 20 Gy in 10 fractions as a boost to the tumour region. Median interval between the two courses was 43 days. Chemotherapy consisted of mitomycin C 9.5 mg/m2 on day 1 and 5-FU 600 mg/m2 24 h-1 continuously on days 1–4. Because of toxicity 11 patients required an unplanned treatment break (4 in the RT and 7 in the RTCT group). Acute grade-3 toxicity was 54% (53% in the RT group and 55% in the RTCT group). No grade-4 or grade-5 acute toxicity occurred in either group. Five of 35 patients available for long term follow-up experienced grade-3 to grade-4 late complications all observed in female patients in the RTCT group. The 5-year local control rate was 78.5% (73 and 83% for the RT and RTCT groups, respectively; p=0.36). The 5- and 8-year overall survival rates were 54 and 36% without differences between treatment groups.

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A research group from Rome analysed 17 patients aged 75 years or older who received radio-chemotherapy for anorectal cancer (Valentini et al. 1997). Patients had to have an ECOG performance status <2 and adequate bone marrow, renal, liver, cardiovascular and pulmonary function. Ten patients had rectal cancer and 7 patients anal cancer. Radiation therapy was applied according to treatment indication and site of disease: patients with rectal carcinoma who were treated in curative intent received preoperatively 38 Gy to the pelvis in 1.8-Gy fractions, patients with rectal carcinoma treated in palliative intent received two courses of 24 Gy to the pelvis with a 4- to 5-week interval and patients with anal carcinoma received two courses of 24 Gy to the pelvis with a 4- to 5-week split, followed by a boost of 15 Gy in 3 patients. Concomitant chemotherapy consisted of mitomycin C 10 mg/m 2 on day 1 and 5FU 1000 mg/m2 continuous infusion an days 1–4. Acute grade-3 toxicity occurred in 3 patients. No severe late toxicity developed during 26 months of follow-up. None of the resected patients with rectal cancer (n=4) and none of the patients with anal carcinoma treated in curative intent developed local or distant failure during follow-up.

22.4.5 Bladder Cancer Goffin et al. (2004) reviewed their data on patients aged 70 years or older who received radio-chemotherapy for T2–T4 bladder cancer. Three different protocols were applied: Seven patients received radiation therapy to a total dose of 44 Gy with 3 Gy bid on days 1, 3, 15, 17, then 2.5 Gy bid on days 63, 65, 77, 79 with concurrent cisplatin (15 mg/m 2) and 5-FU (400 mg/m2) on days 1–3, 15–17, 63–65 and 77–79. Six patients were treated with conventionally fractionated radiation therapy to doses of 52–60 Gy with concurrent cisplatin (20–30 mg/m2 weekly during radiation). One patient received 40.8 Gy in a bid regimen with concurrent cisplatin, metothrexate and vinblastine. Six of 14 patients experienced grade-3 or grade-4 toxicity including 1 patient with cisplatin/hydration-induced heart failure. The median survival was 19 months; 5 patients had local recurrences and 7 patients developed distant metastasis. A study by Patel et al. (2005) analysed toxicity and outcome of concurrent radio-chemotherapy in a cohort of 14 patients with urothelial carcinoma that were not considered candidates for cystectomy or platin-based therapy because of low perfor-

mance and/or advanced comorbidity. Median age was 80 years (46–88 years); 9 patients had localized disease and 5 patients advanced disease. The 3D target volume encompassed the primary and draining lymph nodes with a subsequent boost to the primary tumour. Median radiotherapy dose was 63 Gy (40–68.4 Gy) at 1.8–2.5 Gy per fraction. Chemotherapy consisted of capecitabine 1200 mg/ m2 day-1 to 1800 mg/m2 day-1 Monday through Friday throughout radiation therapy. All patients underwent transurethral resection before radiochemotherapy. Grade-3 toxicity comprised predominately diarrhoea (3 patients; 29%) and dehydration (3 patients). One patient experienced grade-3 infection. No grade-4 or grade-5 toxicity was observed. The overall response rate was 85%. Follow-up was too short to draw conclusions on local control and survival.

22.4.6 Carcinoma of the Vulva Cunningham et al. (1997) reported on 14 patients with advanced vulvar carcinoma who were not candidates for standard radical vulvectomy that were submitted to combined radio-chemotherapy. Median age was 68 years. Patients were treated with a dose of 45–50 Gy to the pelvis and the total doses to the vulva with or without groins ranged from 50 to 65 Gy. Chemotherapy was administered in the first and last weeks of radiotherapy and consisted of 5-FU 1000 mg/m2 24 h-1 continuous infusion over 96 h and cisplatin 50 mg/m2 on day 1. Two patients experienced grade-3 toxicity and radiation therapy had to be stopped prematurely. One patient died during therapy due to congestive heart failure and aspiration pneumonia. No significant myelosuppression, sepsis, renal, or gastrointestinal toxicity was observed. One grade-4 delayed complication occurred (small bowel obstruction). After a median follow-up of 26 months 4 patients with partial response died (three of them due to progressive disease), and of the 9 patients with complete response, 5 died (only one of them due to vulvar cancer).

22.4.7 Glioblastoma Multiforme Treatment of glioblastoma multiforme in the elderly is a matter of debate. Age is a critical and independent prognostic factor in patients with malig-

Feasibility of Combined Chemo- and Radiation Treatment in Elderly/Comorbid Patients

nant glioma (DeAngelis 2000). In elderly patients in good clinical condition standard fractionated or short course hypofractionated radiation therapy are offered in some institutions, depending on the extent of prior tumour resection; however, those elderly patients with extensive tumours that cannot be resected, who are in poor clinical condition, may not be treated with radiation therapy at all. The limiting factor in these patients is their extremely poor outcome and short survival from tumour progression (DeAngelis 2000). A prospective study analysed the outcome of sequential radiation and chemotherapy in 79 patients aged 65 years or older (Brandes et al. 2003). Patients had to have a Karnofsky performance status >60 to enter the study and their residual disease after surgery had to measure <2 cm. All patients received radiation therapy to the gross tumour volume and oedema plus a 2-cm margin to a total dose of 59.4 Gy in 1.8Gy daily fractions. Patients treated between 1993 and 1995 received no further treatment. Patients who were enrolled between 1995 and 1997 received adjuvant chemotherapy with lomustine 110 mg/m2 on day 1, procarbazine 60 mg/m2 on days 8–21, and vincristine 1.4 mg/m2 on days 8 and 29 (PCV) every 8 weeks. Patients enrolled between 1997 and 2000 were treated with adjuvant temozolomide 150 mg/ m2 for 5 days every 28 days. Chemotherapy was carried out until disease progression or occurrence of grade-3 to grade-4 non-haematological toxicity. The incidence of grade-3 thrombopaenia and leukopenia was 10 and 4.4%, respectively, for PCV therapy and 1.7 and 6%, respectively, for temozolomide. Median time to disease progression and median overall survival for all patients was 7.2 and 12.5 months, respectively. Patients with adjuvant temozolomide therapy had a significantly better time to disease progression as compared with the other groups and a better overall survival as compared with patients who received radiation therapy alone.

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has yet to be determined. Before submitting elderly patients to radio-chemotherapy organ functioning and comorbid disease should be assessed thoroughly. During therapy the nutritional and hydration status, blood cell counts and signs of infection should be monitored closely with supportive measures being applied early in the course of combined modality treatment. In two prospective studies cisplatin-based radiochemotherapy was applied to elderly patients with lung cancer in comparable dosage as in their younger counterparts (Schild et al. 2003; Yuen et al. 2000). Retrospective analyses of these studies disclosed more grade-4, and in one study more grade-5, toxicity in patients 70 years or older, although study entry criteria selected only those patients who had a good performance status and adequate organ functioning. In a randomised prospective Japanese trial on elderly patients with lung cancer an unacceptably high rate of treatment-related deaths was found in the combined radio-chemotherapy arm, although poor treatment quality might have contributed to this outcome (Atagi et al. 2005). Until further data accumulates, the indication to aggressive combined radio-chemotherapy in elderly patients, especially those with lung cancer, should be given with caution and treatment should be carried out under close surveillance. With regard to the steady aging of the population in industrial countries, the paucity of studies analysing the feasibility and effectiveness of radio-chemotherapy in elderly patients is hardly understandable. Combined efforts of medical oncology and radiation oncology should be made to enter elderly patients with cancer into specially designed clinical trials. These trials should also include quality of life as a major outcome parameter.

References 22.5 Conclusion The amount of clinical data for combined radio-chemotherapy in elderly patients is limited. Specially designed treatment protocols that used reduced radiation doses or low-intensity chemotherapy were feasible in selected patients beyond 70 years with acceptable toxicity; however, the superiority of these protocols over radiation therapy as sole modality

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340 elderly patients with locally advanced non-small cell lung cancer. Jpn J Clin Oncol 30:59–64 Atagi S, Kawahara M, Tamura T et al (2005) Standard thoracic radiotherapy with or without concurrent daily lowdose carboplatin in elderly patients with locally advanced non-small cell lung cancer: a phase III trial of the Japan Clinical Oncology Group (JCOG9812). Jpn J Clin Oncol 35:195–201 Baumann M (1998) Is curative radiation therapy in elderly patients limited by increased normal tissue toxicity? Radiother Oncol 46:225–227 Berkman B, Rohan B, Sampson S (1994) Myths and biases related to cancer in the elderly. Cancer 74:2004–2008 Boehler FK, Rhomberg W, Doringer W (1992) Hypertension as risk factor for radiation induced side-effects in breast cancer. Strahlenther Onkol 168:344–349 Brandes AA, Vastola F, Basso U et al (2003) A prospective study on glioblastoma in the elderly. Cancer 97:657–662 Charlson ME, Pompei P, Ales KL et al. (1987) A new method of classifying prognostic comorbidity in longitudinal studies: development and validation. J Chronic Dis 40:373–383 Charnley N, Choudhury A, Chesser P et al (2005) Effective treatment of anal cancer in the elderly with low-dose chemotherapy. Br J Cancer 92:1221–1225 Clark AJ, Stockton D, Elder A et al (2004) Assessment of outcomes after colorectal cancer resection in the elderly as a rationale for screening and early detection. Br J Surg 91:1345–1351 Cunningham MJ, Goyer RP, Gibbons SK et al (1997) Primary radiation, cisplatin, and 5-fluorouracil for advanced squamous carcinoma of the vulva. Gynecol Oncol 66:258–261 DeAngelis LM (2000) Radiotherapy of the brain in elderly patients. Arbiter. Eur J Cancer 36:451–452 Edwards B, Howe HL, Ries L et al (2002) Annual report to the nation on the status of cancer, 1973–1999, featuring implications of age and aging on U.S. cancer burden. Cancer 94:2766–2792 Geinitz H, Zimmermann FB, Molls M (1999) Strahlentherapie des alten Patienten. Verträglichkeit und Ergebnisse der Strahlentherapie älterer Personen. Strahlenther Onkol 175(3):119–127 Geinitz H, Zimmermann F, Thamm R et al (2005) 3-D conformal radiation therapy for prostate cancer in elderly patients. Radiother Oncol 76:27–34 Goffin JR, Rajan R, Souhami L (2004) Tolerance of radiotherapy and chemotherapy in elderly patients with bladder cancer. Am J Clin Oncol 27:172–177 Herold DM, Hanlon AL, Hanks GE (1999) Diabetes mellitus: a predictor for late radiation morbidity. Int J Radiat Oncol Biol Phys 43(3):475–479 Hutchins LF, Unger JM, Crowley JJ et al (1999) Underrepresentation of patients 65 years of age or older in cancer-treatment trials. N Engl J Med 341:2061–2067 Jeremic B, Shibamoto Y, Milicic B et al (1999a) A phase II study of concurrent accelerated hyperfractionated radiotherapy and carboplatin/oral etoposide for elderly patients with stage III non-small-cell lung cancer. Int J Radiat Oncol Biol Phys 44:343–348 Jeremic B, Shibamoto Y, Milicic B et al (1999b) Short-term chemotherapy and palliative radiotherapy for elderly patients with stage IV non-small cell lung cancer: a phase II study. Lung Cancer 24:1–9 Kodaira T, Fuwa N, Furutani K et al (2005) Phase I trial of

H. Geinitz weekly docetaxel and concurrent radiotherapy for head and neck cancer in elderly patients or patients with complications. Jpn J Clin Oncol 35:173–176 Mehta V (2005) Radiation pneumonitis and pulmonary fibrosis in non-small-cell lung cancer: pulmonary function, prediction and prevention. Int J Radiat Oncol Biol Phys 63:5–24 Merchant TE, McCormick B, Yahalom J et al (1996) The influence of older age on breast cancer treatment decisions and outcome. Int J Radiat Oncol Biol Phys 34:565–570 Nallapareddy S, Wilding GE, Yang G et al (2005) Chemoradiation is a tolerable therapy for older adults with esophageal cancer. Anticancer Res 25:3055–3060 Neugut AI, Fleischauer AT, Sundararajan V et al (2002) Use of adjuvant chemotherapy and radiation therapy for rectal cancer among the elderly: a population-based study. J Clin Oncol 20:2643–2650 Ogle KS, Swanson GM, Woods N et al (2000) Cancer and comorbidity: redefining chronic diseases. Cancer 88:653–663 Patel B, Forman J, Fontana J et al (2005) A single institution experience with concurrent capecitabine and radiation therapy in weak and/or elderly patients with urothelial cancer. Int J Radiat Oncol Biol Phys 62:1332–1338 Pignon T, Horiot JC, Van den BW et al (1996) No age limit for radical radiotherapy in head and neck tumours. Eur J Cancer 32A:2075–2081 Pignon T, Horiot JC, Bolla M et al (1997) Age is not a limiting factor for radical radiotherapy in pelvic malignancies. Radiother Oncol 42:107–120 Pignon T, Gregor A, Schaake KC et al (1998) Age has no impact on acute and late toxicity of curative thoracic radiotherapy. Radiother Oncol 46:239–248 Rice DC, Correa AM, Vaporciyan AA et al (2005) Preoperative chemoradiotherapy prior to esophagectomy in elderly patients is not associated with increased morbidity. Ann Thorac Surg 79:391–397 Samet J, Hunt WC, Key C et al (1986) Choice of cancer therapy varies with age of patient. J Am Med Assoc 255:3385–3390 Schild SE, Stella PS, Geyer SM et al (2003) The outcome of combined-modality therapy for stage III non-small-cell lung cancer in the elderly. J Clin Oncol 21:3201–3206 Schrag D, Gelfand SE, Bach PB et al (2001) Who gets adjuvant treatment for stage II and III rectal cancer? Insight from surveillance, epidemiology, and end results–Medicare. J Clin Oncol 19:3712–3718 Uno T, Isobe K, Kawakami H et al (2004) Efficacy and toxicities of concurrent chemoradiation for elderly patients with esophageal cancer. Anticancer Res 24:2483–2486 Valentini V, Morganti AG, Luzi S et al (1997) Is chemoradiation feasible in elderly patients? A study of 17 patients with anorectal carcinoma. Cancer 80:1387–1392 Wylie JP, Cowan RA, Deakin DP (1998) The role of radiotherapy in the treatment of localised intermediate and high grade non-Hodgkin’s lymphoma in elderly patients. Radiother Oncol 49:9–14 Yancik R, Ries L (1994) Cancer in older persons. Magnitude of the problem: How do we apply what we know? Cancer 74:1995–2003 Yuen AR, Zou G, Turrisi AT et al (2000) Similar outcome of elderly patients in Intergroup Trial 0096. Cisplatin, etoposide, and thoracic radiotherapy administered once or twice daily in limited small cell lung carcinoma. Cancer 89:1953–1960

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341

Subject Index

A Acute toxicity – cystitis 295 – esophagitis 318 – gastrointestinal 325 – lung 318 Additivity 6 Akt, see PKB Alpha/beta ratio 327 Amifostine 323 Anal cancer 279 – in elderly patients 337 Anastrozole 254 Anemia 308 Angiogenesis 45, 103, 117 Angiostatin 103 Anticonvulsants 167 Antiemetics 325 Antimetabolites 19 Apoptosis 12, 37, 312 AQ4N 79 Astrocytoma 166 – anaplastic 166 – high grade 166 – low grade 166 – pilocytic 166 Ataxia telangiectasia mutated (ATM) 128 Auger electron 151

B Bax 39 Bcl-2 39 Bevacizumab 110, 220, 278 Bladder cancer 285 – in elderly patients 338 Blood-brain barrier 165 Bortezomib 312 Brain metastases 141, 180 – and motexaﬁn-gadolinium 141 – and temozolomide 144, 181 Brain tumors, see CNS tumors Breast cancer 251 – locally advanced breast cancer 260 – neoadjuvant chemotherapy 260 5-Bromo-2’-deoxyuridine (BrdU) 24

C Camptothecins 54 Capecitabine 29, 220

– in breast cancer 262 – in rectal cancer 274 Carboxylesterase 29 Carboplatin 96 Carmustine 168 Cell cycle 11, 25, 131 Central nervous system (CNS) tumors 60, 139, 165 – recurrent CNS tumors 176 Cervical cancer 303 Cetuximab 118, 221, 243, 277, 321 Chemosensitivity testing 14 Chitosan 157 Cisplatin 93 Comorbidity 334 Complications, see acute and late toxicity Consequential late effects 326 Convection-enhanced delivery 169 Cytidine deaminase 29 Cytochrome P450 enzymes 166

D Dendrimer 159 Deoxyribonucleicacid (DNA) 10 – DNA array 153 – DNA damage 10 – DNA-dependent protein kinase 128 – DNA repair 10, 117 – DNA topoisomerase 53 Dihydrofolate reductase 22 Docetaxel 36 Dose density of chemotherapy 276 Doxorubicin 257 Ductal carcinoma in situ of the breast 252

E 4EBP1 130 Endostatin 103 Endothelial cells 108, 131, 152, 326 Ependymoma 178 Epidermal growth factor (EGF) 115 – EGF receptors (EGFR) 115 – EGFR inhibitors 115 – EGFR inhibitors and mTOR inhibitors 134 – EGFR inhibitors in cervical cancer 311 – EGFR inhibitors in colorectal cancer 277 Epipodophyllotoxin 56 ErbB, see EGFR ERCC1 93 Erlotinib 118, 221, 243, 312

342 Endometrial cancer 306 Erythropoietin 308 Esophageal cancer 58, 197 – esophagogastric junction adenocarcinoma 197, 207 – in elderly patients 335 Etanidazole 69 Etoposide 54 Everolimus 127 Excision repair cross-complementing 1, see ERCC1 Exemestane 254

F Fibroblast collagen system 326 Fibroblast growth factor (FGF) 103 5-Fluorouracil (5-FU) 19, 26 – in rectal cancer 267 – continuous infusion 269 Fractionation sensitivity 6, 327 Ftorafur 28

G Gadolinium-neutron capture therapy 143 Gastric cancer 207 Gastrointestinal toxicity 325 Geﬁtinib 118, 242 Gemcitabine 21, 29, 218, 305 Gene-directed enzyme-prodrug therapy 74 Gene therapy 151, 176 Glioblastoma multiforme (GBM) 143, 166 – and motexaﬁn-gadolinium 143 – and temozolomide 145 – in elderly patients 338 Gluthatione S-transferase 174 Granulocyte colony-stimulating factor (G-CSF) 322 Granulocyte macrophage colony-stimulating factor (GM-CSF) 322

H Head and neck tumors 61, 187 – in elderly patients 324 HER2 in breast cancer 259 Hormonal ablation 14 – in breast cancer 254 – with mTOR inhibitors 133 – with radiation therapy 14 Hydroxyurea 24, 168 Hypopharynx cancer 189 Hypoxia 9, 44, 67, 108, 130, 306 – acute 67 – chronic 67 – hypoxia-inducible factor-1 (HIF-1) 82, 83, 130, 307 I Imatinib 134, 310 Immune response 46 Immunotherapy 176 Insulin-like growth factor receptor 128 Integrins 152, 155, 307 Intercellular adhesion molecule (ICAM)-1 152, 155 Interstitial ﬂuid pressure 306

Subject Index Irinotecan 54, 277 Isobologram 6

K Keratinocyte growth factor (KGF) 321, 322

L Lapatinib 118 Larynx cancer 188 Late toxicity 326 – bladder 295 Letrozole 254 Leucovorin 269 Levamisol 269 Linear quadratic model 327 Liposomes 157 Liver metastases from rectal cancer 276 Lung cancer, see NSCLC and SCLC Lung toxicity 318 Lymphangiogenesis 104

M Mammalian target of rapamycin (mTOR) 127 – mTOR inhibitors 127 Matrix metalloproteinase inhibitor 103 Medulloblastoma 179 Meningioma 180 Methotrexate 22 Methyl-guanine methyl transferase (MGMT) 143, 146, 174 Metronomic chemotherapy 5 Micelles 157 Microenvironment – in cervical cancer 306 Microtubules 37 Misonidazole 69, 309 Mitomycin C 75, 309 Mitotic spindle 37 Motexaﬁn-gadolinium 139

N Nanoparticles 157 Nasopharynx cancer 190 Neoantigens 152 Neovascularization 152 Nimorazole 69 Nitroimidazoles 69 Nitrosoureas 168 Non-small cell lung cancer (NSCLC) 56, 231 – in elderly patients 335 Normal tissues 317 Nucleoside 24

O O-6 benzylguanine 144 Oligoastrocytoma 166 Oligodendroglioma 166, 178 Oropharynx cancer 187 Oxaliplatin 97, 276

Subject Index Oxidative damage 72 Oxygenation 44 Oxygen diffusion 67

P Paclitaxel 36, 219 – in breast cancer 257 – in cervical cancer 305 Pancreatic cancer 215 PCV 339 Pemetrexed 30, 110 Pentoxifylline 328 P-glycoprotein 169 Pimonidazole 69 Phosphatidyl-inositol 3-kinase (PI3K) 128 Platelet-derived growth factor (PDGF) 103, 307 Poly-ADP-ribose polymerase 1 (PARP-1) 146, 174 Polyethylene glycol (PEG) 158 Polyglycolic acid (PGA) 158 Polylactic acid (PLA) 158 Polylacticglycolic acid (PLGA) 158 Polymers 159 – synthetic polymers 159 Porﬁromycin 75 Positron emission tomography (PET) – in lung cancer 232 Procarbazine 168 Prodrug 28, 79 – gene-directed enzyme-prodrug therapy 74 Programmed cell death, see apoptosis Protein kinase B (PKB, Akt) 128 Proteomics 154 Proteosome 312 Protracted drug exposure 13, 27 Protracted venous infusion 27 PTEN 129 Pyrimidine analogs 19 P21 39 P53 25, 39 PR-104 74

R Radiation-induced neoantigens 152 Radiation-inducible gene therapy 151 Radiation sensitivity 6 Radical scavenging agents 323 Radiolysis of water 79 Radiosensitization 6 Rapamycin 127, 133 Rectal cancer 59, 267 – in elderly patients 337 Redox cycling 72 Repopulation 8, 320

343 S Selenium 323 Serial analysis of gene expression (SAGE) 153 Side effects, see acute and late toxicity Single nucleotide polymorphisms 15 Small cell lung cancer (SCLC) 57, 243 – in elderly patients 336 Sorafenib 312 Spatial interaction 8 Stem cells 319 – hematopoietic 322 Sub-additivity 6 Suicide genes 176 Superoxide dismutase 324 Supportive measures 324, 328 Supra-additivity 6 Sustained drug release 159 Synergism 6 S-1 28

T Tamoxifen 254, 258 Taxanes 35 Temozolomide 143, 169 Temsirolimus 127 Texaphyrins 140 Therapeutic gain 5 Thioredoxin reductase 140 Thymidylate synthase (TS) 21 Tirapazamine 76, 309 Topoisomerases 53 Topoisomerase inhibitors 54 Topotecan 54 Toxicity, see acute and late toxicity TRAIL 312 Transforming growth factor (TGF) beta 326 Trastuzumab 259, 262 Treatment monitoring 14 Tumor cell kill 3 Tumor vasculature 68

U UFT 28 Uterine cancer, see cervical and endometrial cancer

V Vascular-disrupting agents 153 Vascular endothelial growth factor (VEGF) 68, 103, 131, 307 – VEGF inhibitors 105 – VEGF receptors 105 Vasculature 131 Vulvar cancer 306 – in elderly patients 338

List of Contributors

345

List of Contributors

G-One Ahn, PhD Division of Radiation and Cancer Biology Department of Radiation Oncology Stanford School of Medicine 269 Campus Drive Center for Clinical Science and Research, Rm 1255 Stanford, CA 94305-5152 USA

J. Martin Brown, PhD Division of Radiation and Cancer Biology Department of Radiation Oncology Stanford School of Medicine 269 Campus Drive Center for Clinical Science and Research, Rm 1255 Stanford, CA 94305-5152 USA

K. K. Ang, MD PhD Professor, Departments of Experimental Radiation Oncology and Radiation Oncology The University of Texas M. D. Anderson Cancer Center 1515 Holcombe Blvd. Houston, TX 77030-4009 USA

Björn L. D. M. Brücher, MD Department of Surgery Klinikum rechts der Isar der Technischen Universität München Ismaninger Straße 22 81675 München Germany

Nicolaus H. Andratschke, MD Department of Radiation Oncology Klinikum rechts der Isar der Technischen Universität München Ismaninger Straße 22 81675 München Germany Michael Bastasch, MD Department of Radiation Oncology The University of Texas Southwestern Medical Center at Dallas 5801 Forest Park Rd. Dallas, TX 75390-9183 USA

Thomas A. Buchholz, MD Department of Radiation Oncology The University of Texas M. D. Anderson Cancer Center 1515 Holcombe Blvd. Houston, TX 77030 USA Seungtaek Choi, MD Department of Radiation Oncology The University of Texas M.D. Anderson Center 1515 Holcombe Blvd. Dallas, Texas 77030 USA

Claus Belka, MD Department of Radiation Oncology University Hospital Eberhard-Karls Universität Tübingen Hoppe-Seyler-Strasse 3 72076 Tübingen Germany

Hak Choy, MD Professor and Chairman Nancy B. and Jake L. Hamon distinguished Chair in Therapeutic Oncology Research Department of Radiation Oncology The University of Texas Southwestern Medical Center at Dallas 5801 Forest Park Rd. Dallas, TX 75390-9183 USA

Jean Bourhis, MD Professor, Head of Radiation Oncology Department Institut Gustave Roussy 39, rue Camille Desmoulins 94805 Villejuif Cedex France

Christopher H. Crane, MD Department of Radiation Oncology, Box 97 The University of Texas M. D. Anderson Cancer Center 1515 Holcombe Blvd. Houston, TX 77030 USA

List of Contributors

346

Wolfgang Dörr, DVM PhD Professor, Medical Faculty Carl Gustav Carus University of Technology Dresden Fetscherstrasse 74, PF 58 01307 Dresden Germany

Paul Harari, MD Jack Fowler Professor, Department of Human Oncology University of Wisconsin Hospital Medical School 600 Highland Avenue, K4 312-3684 Madison, WI 53792 USA

Jürgen Dunst, MD Professor, Department of Radiation Oncology University Hospital Schleswig-Holstein Campus Lübeck Ratzeburger Allee 160 23538 Lübeck Germany

Hiroshi Harada, MD Department of Radiation Oncology and Image-Applied Therapy Kyoto University Graduate School of Medicine Kyoto 606-8507 Japan

Douglas B. Evans, MD Department of Surgical Oncology The University of Texas M. D. Anderson Cancer Center 1515 Holcombe Blvd. Houston, TX 77030 USA

Ghazal Hariri Department of Radiation Oncology School of Medicine Vanderbilt University 11611 21st Ave. South Nashville, TN 37232 USA

Jochen Fleckenstein, MD Department of Radiotherapy and Radiation Oncology Saarland University Medical School 66421 Homburg Germany Anthony Fyles, MD Department of Radiation Oncology Princess Margaret Hospital 610 University Ave. Toronto, ON M5G 2M9 Canada Hans Geinitz, MD Department of Radiation Oncology Klinikum rechts der Isar der Technischen Universität München Ismaninger Straße 22 81675 München Germany Mark R. Gilbert, MD Department of Neuro-Oncology The University of Texas M.D. Anderson Cancer Center 1515 Holcombe Blvd. Houston, TX 77030 USA Dennis E. Hallahan, MD B-902 Vanderbilt Clinic Vanderbilt University 1301 22nd Ave South Nashville, TN 37232-5671 USA Zhaozhong Han, PhD Department of Radiation Oncology Vanderbilt University School of Medicine 11611 21st Ave. South Nashville, TN 37232 USA

Masahiro Hiraoka, MD PhD Department of Radiation Oncology and Image-Applied Therapy Kyoto University Graduate School of Medicine Kyoto 606-8507 Japan Deepak Khuntia, MD Assistant Professor Department of Human Oncology University of Wisconsin 600 Highland Avenue, K4 312-3684 Madison, WI 53792 USA Guido Lammering, MD PhD Department of Radiation Oncology and Laboratory of Experimental Radiation Oncology (Maastro Clinic and Lab), University Maastricht Postbus 4446 6401 CX Heerlen The Netherlands Zhongxing Liao, MD Associate Professor, Department of Experimental Radiation Oncology The University of Texas M. D. Anderson Cancer Center 1515 Holcombe Blvd. Houston, TX 77030-4009 USA Florian Lordick, MD 3rd Department of Internal Medicine (Hematology/Medical Oncology) Klinikum rechts der Isar der Technischen Universität München Ismaninger Str. 22 81675 Munich Germany

List of Contributors

347

Kathryn A. Mason, MS Department of Experimental Radiation Oncology The University of Texas M. D. Anderson Cancer Center 1515 Holcombe Blvd., Box 066 Houston, TX 77030-4009 USA

Dorothea Riesenbeck, MD Klinik für Strahlentherapie und Radioonkologie Marienhospital Herne, Ruhr-Universität Bochum Hölkeskampring 40 44625 Herne Germany

Luka Milas, MD PhD Professor, Department of Experimental Radiation Oncology The University of Texas M. D. Anderson Cancer Center 1515 Holcombe Blvd., Box 066 Houston, TX 77030-4009 USA

Claus Rödel, MD Klinik und Poliklinik für Strahlentherapie Universitätsklinikum Erlangen Postfach 2306 Universitätsstrasse 27 91054 Erlangen Germany

Michael Milosevic, MD Department of Radiation Oncology Princess Margaret Hospital 610 University Ave. Toronto, ON M5G 2M9 Canada

Christian Rübe, MD PhD Head of the Department of Radiotherapy and Radiation Oncology Saarland University Medical School 66421 Homburg Germany

Minesh P. Mehta, MD Department of Human Oncology University of Wisconsin Hospital Medical School 600 Highland Avenue, K4 312-3684 Madison, WI 53792 USA

Jann N. Sarkaria, MD Assistant Professor Department of Oncology Mayo Clinic College of Medicine 200 First Street SW Rochester, MN 55905 USA

Michael Molls, MD Professor and Chairman, Department of Radiation Oncology Klinikum rechts der Isar der Technischen Universität München Ismaninger Straße 22 81675 München Germany

Rolf Sauer, MD Professor, Direktor der Strahlenklinik Universitätsklinikum Erlangen Postfach 2306 Universitätsstrasse 27 91054 Erlangen Germany

Carsten Nieder, MD Department of Radiation Oncology Klinikum rechts der Isar der Technischen Universität München Ismaninger Straße 22 81675 München Germany Amit Oza, MD Department of Medical Oncology and Haematology Princess Margaret Hospital 610 University Ave. Toronto, ON M5G 2M9 Canada Peter W. T. Pisters, MD Department of Surgical Oncology The University of Texas M. D. Anderson Cancer Center 1515 Holcombe Blvd. Houston, TX 77030 USA

Keiko Shibuya, MD Department of Radiation Oncology and Image-Applied Therapy Kyoto University Graduate School of Medicine Kyoto 606-8507 Japan Howard D. Thames, PhD Department of Biomathematics/Biostatistics The University of Texas M. D. Anderson Cancer Center 1515 Holcombe Blvd. Houston, TX 77030 USA Anne M. Traynor, MD Assistant Professor Department of Medicine University of Wisconsin 600 Highland Avenue, K4 312-3684 Madison, WI 53792 USA

List of Contributors

348

Gauri Varadhachary, MD Gastrointestinal Medical Oncology, Box 426 The University of Texas M. D. Anderson Cancer Center 1515 Holcombe Blvd. Houston, TX 77030 USA

Anthony Zietman, MD Department of Radiation Oncology Massachusetts General Hospital Harvard Medical School 101 Blossom Street Boston, MA 02114 USA

Robert A. Wolff, MD Gastrointestinal Medical Oncology, Box 426 The University of Texas M. D. Anderson Cancer Center 1515 Holcombe Blvd. Houston, TX 77030 USA

Frank Zimmermann, MD Department of Radiation Oncology Klinikum rechts der Isar der Technischen Universität München Ismaninger Str. 22 81675 München Germany

List of Contributors

349

Medical Radiology

Diagnostic Imaging and Radiation Oncology Titles in the series already published

Radiation Oncology Lung Cancer Edited by C.W. Scarantino Innovations in Radiation Oncology Edited by H. R. Withers and L. J. Peters Radiation Therapy of Head and Neck Cancer Edited by G. E. Laramore Gastrointestinal Cancer – Radiation Therapy Edited by R.R. Dobelbower, Jr. Radiation Exposure and Occupational Risks Edited by E. Scherer, C. Streffer, and K.-R. Trott Radiation Therapy of Benign Diseases A Clinical Guide

S. E. Order and S. S. Donaldson

Interventional Radiation Therapy Techniques – Brachytherapy Edited by R. Sauer Radiopathology of Organs and Tissues Edited by E. Scherer, C. Streffer, and K.-R. Trott Concomitant Continuous Infusion Chemotherapy and Radiation Edited by M. Rotman and C. J. Rosenthal Intraoperative Radiotherapy – Clinical Experiences and Results Edited by F. A. Calvo, M. Santos, and L.W. Brady Radiotherapy of Intraocular and Orbital Tumors Edited by W. E. Alberti and R. H. Sagerman Interstitial and Intracavitary Thermoradiotherapy Edited by M. H. Seegenschmiedt and R. Sauer Non-Disseminated Breast Cancer Controversial Issues in Management

Edited by G. H. Fletcher and S.H. Levitt

Current Topics in Clinical Radiobiology of Tumors Edited by H.-P. Beck-Bornholdt

Practical Approaches to Cancer Invasion and Metastases

Progress and Perspectives in the Treatment of Lung Cancer A Compendium of Radiation Edited by P. Van Houtte, Oncologists’ Responses to 40 Histories J. Klastersky, and P. Rocmans Edited by A. R. Kagan with the Combined Modality Therapy of Assistance of R. J. Steckel Central Nervous System Tumors Edited by Z. Petrovich, L. W. Brady, Radiation Therapy in Pediatric Oncology M. L. Apuzzo, and M. Bamberg Edited by J. R. Cassady Age-Related Macular Degeneration

Radiation Therapy Physics Edited by A. R. Smith

Current Treatment Concepts

Late Sequelae in Oncology Edited by J. Dunst and R. Sauer Mediastinal Tumors. Update Edited by D. E. Wood and C. R. Thomas, Jr.

1995

Thermoradiotherapy and Thermochemotherapy Volume 1: Biology, Physiology, and Physics Volume 2: Clinical Applications Edited by M.H. Seegenschmiedt, P. Fessenden, and C.C. Vernon Carcinoma of the Prostate Innovations in Management

Edited by Z. Petrovich, L. Baert, and L.W. Brady

Radiation Oncology of Gynecological Cancers Edited by H.W. Vahrson Carcinoma of the Bladder Innovations in Management

Edited by Z. Petrovich, L. Baert, and L.W. Brady

Blood Perfusion and Microenvironment of Human Tumors Implications for Clinical Radiooncology

Edited by M. Molls and P. Vaupel

Radiation Therapy of Benign Diseases A Clinical Guide

2nd Revised Edition S. E. Order and S. S. Donaldson

Carcinoma of the Kidney and Testis, and Rare Urologic Malignancies Innovations in Management

Edited by Z. Petrovich, L. Baert, and L.W. Brady

Edited by W. A. Alberti, G. Richard, and R. H. Sagerman

Radiotherapy of Intraocular and Orbital Tumors 2nd Revised Edition Edited by R. H. Sagerman, and W. E. Alberti Modiﬁcation of Radiation Response Cytokines, Growth Factors, and Other Biolgical Targets

Edited by C. Nieder, L. Milas, and K. K. Ang

Radiation Oncology for Cure and Palliation R. G. Parker, N. A. Janjan, and M. T. Selch Clinical Target Volumes in Conformal and Intensity Modulated Radiation Therapy A Clinical Guide to Cancer Treatment

Edited by V. Grégoire, P. Scalliet, and K. K. Ang

Advances in Radiation Oncology in Lung Cancer Edited by Branislav Jeremi´c New Technologies in Radiation Oncology Edited by W. Schlegel, T. Bortfeld, and A.-L. Grosu Technical Basis of Radiation Therapy Practical Clinical Applications 4th Revised Edition Edited by S. H. Levitt, J. A. Purdy, C. A. Perez, and S. Vijayakumar Multimodal Concepts for Integration of Cytotoxic Drugs Edited by J. M. Brown, M. P. Mehta, and C. Nieder

123

350

Subject Index

Medical Radiology

Diagnostic Imaging and Radiation Oncology Titles in the series already published

Diagnostic Imaging

Orthopedic Imaging Techniques and Applications

Edited by A. M. Davies and H. Pettersson

Innovations in Diagnostic Imaging Edited by J. H. Anderson Radiology of the Upper Urinary Tract Edited by E. K. Lang The Thymus - Diagnostic Imaging, Functions, and Pathologic Anatomy Edited by E. Walter, E. Willich, and W. R. Webb Interventional Neuroradiology Edited by A. Valavanis Radiology of the Pancreas Edited by A. L. Baert, co-edited by G. Delorme Radiology of the Lower Urinary Tract Edited by E. K. Lang Magnetic Resonance Angiography Edited by I. P. Arlart, G. M. Bongartz, and G. Marchal Contrast-Enhanced MRI of the Breast S. Heywang-Köbrunner and R. Beck

Radiology of the Female Pelvic Organs Edited by E. K.Lang Magnetic Resonance of the Heart and Great Vessels Clinical Applications

Edited by J. Bogaert, A.J. Duerinckx, and F. E. Rademakers

Modern Head and Neck Imaging Edited by S. K. Mukherji and J. A. Castelijns Radiological Imaging of Endocrine Diseases Edited by J. N. Bruneton in collaboration with B. Padovani and M.-Y. Mourou Trends in Contrast Media Edited by H. S. Thomsen, R. N. Muller, and R. F. Mattrey Functional MRI Edited by C. T. W. Moonen and P. A. Bandettini

Spiral CT of the Chest Radiology of the Pancreas Edited by M. Rémy-Jardin and J. Rémy 2nd Revised Edition Radiological Diagnosis of Breast Diseases Edited by A. L. Baert Edited by M. Friedrich Co-edited by G. Delorme and E.A. Sickles and L. Van Hoe Radiology of the Trauma Edited by M. Heller and A. Fink

Emergency Pediatric Radiology Edited by H. Carty

Biliary Tract Radiology Edited by P. Rossi, co-edited by M. Brezi

Spiral CT of the Abdomen Edited by F. Terrier, M. Grossholz, and C. D. Becker

Radiological Imaging of Sports Injuries Edited by C. Masciocchi

Liver Malignancies

Modern Imaging of the Alimentary Tube Edited by A. R. Margulis Diagnosis and Therapy of Spinal Tumors Edited by P. R. Algra, J. Valk, and J. J. Heimans Interventional Magnetic Resonance Imaging Edited by J.F. Debatin and G. Adam Abdominal and Pelvic MRI Edited by A. Heuck and M. Reiser

Diagnostic and Interventional Radiology

Edited by C. Bartolozzi and R. Lencioni

Medical Imaging of the Spleen Edited by A. M. De Schepper and F. Vanhoenacker Radiology of Peripheral Vascular Diseases Edited by E. Zeitler Diagnostic Nuclear Medicine Edited by C. Schiepers

Radiology of Blunt Trauma of the Chest P. Schnyder and M. Wintermark Portal Hypertension Diagnostic Imaging-Guided Therapy

Edited by P. Rossi Co-edited by P. Ricci and L. Broglia

Recent Advances in Diagnostic Neuroradiology Edited by Ph. Demaerel Virtual Endoscopy and Related 3D Techniques Edited by P. Rogalla, J. Terwisscha Van Scheltinga, and B. Hamm Multislice CT Edited by M. F. Reiser, M. Takahashi, M. Modic, and R. Bruening Pediatric Uroradiology Edited by R. Fotter Transfontanellar Doppler Imaging in Neonates A. Couture and C. Veyrac Radiology of AIDS A Practical Approach Edited by J.W.A.J. Reeders and P.C. Goodman CT of the Peritoneum Armando Rossi and Giorgio Rossi Magnetic Resonance Angiography 2nd Revised Edition Edited by I. P. Arlart, G. M. Bongratz, and G. Marchal Pediatric Chest Imaging Edited by Javier Lucaya and Janet L. Strife Applications of Sonography in Head and Neck Pathology Edited by J. N. Bruneton in collaboration with C. Raffaelli and O. Dassonville Imaging of the Larynx Edited by R. Hermans 3D Image Processing Techniques and Clinical Applications Edited by D. Caramella and C. Bartolozzi Imaging of Orbital and Visual Pathway Pathology Edited by W. S. Müller-Forell

Subject Index

351

Medical Radiology

Diagnostic Imaging and Radiation Oncology Titles in the series already published

Pediatric ENT Radiology Edited by S. J. King and A. E. Boothroyd

Interventional Radiology in Cancer Edited by A. Adam, R. F. Dondelinger, and P. R. Mueller

Multidetector-Row CT Angiography Edited by C. Catalano and R. Passariello

Radiological Imaging of the Small Intestine Edited by N. C. Gourtsoyiannis

Duplex and Color Doppler Imaging of the Venous System Edited by G. H. Mostbeck

Paediatric Musculoskeletal Diseases With an Emphasis on Ultrasound Edited by D. Wilson

Imaging of the Knee

Multidetector-Row CT of the Thorax Edited by U. J. Schoepf

Contrast Media in Ultrasonography Basic Principles and Clinical Applications Edited by Emilio Quaia

Techniques and Applications

Edited by A. M. Davies and V. N. Cassar-Pullicino

Perinatal Imaging From Ultrasound to MR Imaging Edited by Fred E. Avni Radiological Imaging of the Neonatal Chest Edited by V. Donoghue Diagnostic and Interventional Radiology in Liver Transplantation Edited by E. Bücheler, V. Nicolas, C. E. Broelsch, X. Rogiers, and G. Krupski Radiology of Osteoporosis Edited by S. Grampp Imaging Pelvic Floor Disorders Edited by C. I. Bartram and J. O. L. DeLancey Associate Editors: S. Halligan, F. M. Kelvin, and J. Stoker Imaging of the Pancreas Cystic and Rare Tumors Edited by C. Procacci and A. J. Megibow High Resolution Sonography of the Peripheral Nervous System Edited by S. Peer and G. Bodner Imaging of the Foot and Ankle Techniques and Applications Edited by A. M. Davies, R. W. Whitehouse, and J. P. R. Jenkins Radiology Imaging of the Ureter Edited by F. Joffre, Ph. Otal, and M. Soulie Imaging of the Shoulder Techniques and Applications Edited by A. M. Davies and J. Hodler Radiology of the Petrous Bone Edited by M. Lemmerling and S. S. Kollias

Functional Imaging of the Chest Edited by H.-U. Kauczor Radiology of the Pharynx and the Esophagus Edited by O. Ekberg Radiological Imaging in Hematological Malignancies Edited by A. Guermazi Imaging and Intervention in Abdominal Trauma Edited by R. F. Dondelinger Multislice CT 2nd Revised Edition Edited by M. F. Reiser, M. Takahashi, M. Modic, and C. R. Becker Intracranial Vascular Malformations and Aneurysms From Diagnostic Work-Up to Endovascular Therapy Edited by M. Forsting Radiology and Imaing of the Colon Edited by A. H. Chapman Coronary Radiology Edited by M. Oudkerk Dynamic Contrast-Enhanced Magnetic Resonance Imaging in Oncology Edited by A. Jackson, D. L. Buckley, and G. J. M. Parker Imaging in Treatment Planning for Sinonasal Diseases Edited by R. Maroldi and P. Nicolai Clinical Cardiac MRI With Interactive CD-ROM Edited by J. Bogaert, S. Dymarkowski, and A. M. Taylor Focal Liver Lesions Detection, Characterization, Ablation Edited by R. Lencioni, D. Cioni, and C. Bartolozzi

MR Imaging in White Matter Diseases of the Brain and Spinal Cord Edited by M. Filippi, N. De Stefano, V. Dousset, and J. C. McGowan Diagnostic Nuclear Medicine 2nd Revised Edition Edited by C. Schiepers Imaging of the Kidney Cancer Edited by A. Guermazi Magnetic Resonance Imaging in Ischemic Stroke Edited by R. von Kummer and T. Back Imaging of the Hip & Bony Pelvis Techniques and Applications

Edited by A. M. Davies, K. J. Johnson, and R. W. Whitehouse

Imaging of Occupational and Environmental Disorders of the Chest Edited by P. A. Gevenois and P. De Vuyst Contrast Media Safety Issues and ESUR Guidelines

Edited by H. S. Thomsen

Virtual Colonoscopy A Practical Guide

Edited by P. Lefere and S. Gryspeerdt

Vascular Embolotherapy A Comprehensive Approach

Volume 1 Edited by J. Golzarian. Co-edited by S. Sun and M. J. Sharafuddin

Vascular Embolotherapy A Comprehensive Approach

Volume 2 Edited by J. Golzarian. Co-edited by S. Sun and M. J. Sharafuddin

123

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