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

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20 Applications to Gynecological Cancers

Anthony W. Fyles, Michael Milosevic, and Amit Oza

A. Fyles, MD; M. Milosevic, MD

Department of Radiation Oncology, Princess Margaret Hos- pital, 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

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 Announce- ment, 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

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 improv- ing 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, focus- ing 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 chemo- radiation 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 cisplatin- containing chemotherapy although benefit was also

CONTENTS

20.1 Introduction 303

20.2 Chemo-Radiation Using

Cytotoxic Agents in Cervical Cancer 303 20.2.1 Randomized Clinical Trials 303 20.2.2 Phase-I/II Chemo-Radiation Trials

of Cytotoxic Agents in Cervical Cancer 305 20.2.3 Phase-I/II Chemo-Radiation Trials

of Cytotoxic Agents in Vulvar Cancer 306 20.2.4 Chemo-Radiation in Endometrial Cancer 306 20.3 Biologically Targeted Treatment of the Tumor

Microenvironment in Gynecological Cancer 306 20.3.1 The Microenvironment in Cervical Cancer 306 20.3.2 Hypoxia-Targeted Treatment 308

20.4 Incorporating Molecularly Targeted Agents with Radiation/Chemotherapy

in Gynecological Malignancies 309 20.4.1 Carcinoma of the Cervix 310 20.4.2 EGFR and COX-2 Inhibitors 310 20.4.3 Vascular-Targeted Treatment and Anti-Angiogenic Agents 311 20.4.4 Pro-Apoptotic Agents 312

20.4.5 Targeted Agents in Endometrial Cancer 312 References 313

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seen in studies of other agents such as mitomycin C and 5-fluorouracil (5-FU). Not included in the meta- analysis 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

Fig. 20.1. Concomitant chemotherapy and radiation therapy for cancer of the uterine cervix 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

01 Platinum chemotherapy

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]

Subtotal (95% CI) 77.8 0.68 [0.60, 0.78]

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]

Subtotal (95% CI) 22.2 0.72 [0.56, 0.92]

Test for overall effect z=2.63 p=0.008

Total (95% CI) 100 0.69 [0.61, 0.77]

Test for overall effect z=6.25 p<0.00001

0.1 0.2 0.5 1 2 5 10

Favours control Favours treatment

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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. Eighty- three 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; Duenas- Gonzalez 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

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 Oncol- ogy 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). Grade- 3 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 topoi- somerase 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 recurrence- free. Although a randomized trial is planned, these results are difficult to compare with other chemo- radiation 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 resect- able 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-insti- tution and retrospective studies have shown similar good rates of response and control in advanced tumors, with outcome limited by significant co- morbidities 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; unfor- tunately, 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

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 progression- free 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, demon- strating the significant activity of both modalities.

Studies combining chemotherapy and radiation are underway. Many of these studies are using sequen- tial 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 physi- ological 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

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(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 factor- 1D (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 consump- tion exceeds supply. The new vessels that form have abnormal structure and architecture and are ineffi- cient 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-

cans (Jain 1987; Heldin et al. 2004). In general, tumors have a higher level of collagen then the sur- rounding normal tissue, and a pronounced inflam- matory 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 inflam- matory 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 gener- ally 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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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 sub- group 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 pre- sumed 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 cor- recting 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

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 Tumor vasculature 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

RT radiotherapy, IFP interstitial ﬂ uid pressure, dCT dynamic computed tomography, dMRI dynamic magnetic resonance imaging

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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 dis- appointing results have been attributed to drug levels that were inadequate to achieve sensitization, and the fact that some of the patients in these studies prob- ably 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; Lor- vidhaya 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 selec- tively kills the hypoxic cells in tumors that are resistant to the effects of radiotherapy, and also potenti- ates 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

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 avail- ability 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. Gener- ally, initial trials to assess toxicity and efficacy are conducted in patients who have recurrent or persis- tent 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 life- time 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 cau- tiously, 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 com- mence, 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, pro- apoptotic agents, and modulators of hypoxia.

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

0 1 2 3 4 5 6 7

Biomarkers at weeks 0, 2, 4 RT + Cisplatin Phase II: Imatinib 400 mg

Phase I: Imatinib 400 mg for escalating intervals

Time n=3

n=3 n=3

n=15

Fig. 20.2. Clinical trial design for integration of chemoradia- tion and biological targeted agents such as imatinib

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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 PDQ- NCI 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

with vascular-targeted treatments may improve local tumor control and overall survival. Antian- giogenic 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 contrast- enhanced 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 can- didates for combination with conventional cytotoxic

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therapy in this disease. They also have the theoreti- cal 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, tumor- specific 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 modu- lating 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 dis- rupted 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

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 inactiva- tion, causing cellular immortalization and transfor- mation. The proteosome inhibitor bortezomib inhib- its 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 perti- nent to cervical cancer. Bortezomib had no detect- able 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.

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