Radiation with or without Antiandrogen Therapy in Recurrent Prostate Cancer.

BACKGROUND: Salvage radiation therapy is often necessary in men who have undergone radical prostatectomy and have evidence of prostate-cancer recurrence signaled by a persistently or recurrently elevated prostate-specific antigen (PSA) level. Whether antiandrogen therapy with radiation therapy will further improve cancer control and prolong overall survival is unknown. METHODS: In a double-blind, placebo-controlled trial conducted from 1998 through 2003, we assigned 760 eligible patients who had undergone prostatectomy with a lymphadenectomy and had disease, as assessed on pathological testing, with a tumor stage of T2 (confined to the prostate but with a positive surgical margin) or T3 (with histologic extension beyond the prostatic capsule), no nodal involvement, and a detectable PSA level of 0.2 to 4.0 ng per milliliter to undergo radiation therapy and receive either antiandrogen therapy (24 months of bicalutamide at a dose of 150 mg daily) or daily placebo tablets during and after radiation therapy. The primary end point was the rate of overall survival. RESULTS: The median follow-up among the surviving patients was 13 years. The actuarial rate of overall survival at 12 years was 76.3% in the bicalutamide group, as compared with 71.3% in the placebo group (hazard ratio for death, 0.77; 95% confidence interval, 0.59 to 0.99; P=0.04). The 12-year incidence of death from prostate cancer, as assessed by means of central review, was 5.8% in the bicalutamide group, as compared with 13.4% in the placebo group (P<0.001). The cumulative incidence of metastatic prostate cancer at 12 years was 14.5% in the bicalutamide group, as compared with 23.0% in the placebo group (P=0.005). The incidence of late adverse events associated with radiation therapy was similar in the two groups. Gynecomastia was recorded in 69.7% of the patients in the bicalutamide group, as compared with 10.9% of those in the placebo group (P<0.001). CONCLUSIONS: The addition of 24 months of antiandrogen therapy with daily bicalutamide to salvage radiation therapy resulted in significantly higher rates of long-term overall survival and lower incidences of metastatic prostate cancer and death from prostate cancer than radiation therapy plus placebo. (Funded by the National Cancer Institute and AstraZeneca; RTOG 9601 ClinicalTrials.gov number, NCT00002874 .).

Recombinant Newcastle disease viruses expressing immunological checkpoint inhibitors induce a pro-inflammatory state and enhance tumor-specific immune responses in two murine models of cancer.

Introduction: Tumor microenvironments are immunosuppressive due to progressive accumulation of mutations in cancer cells that can drive expression of a range of inhibitory ligands and cytokines, and recruitment of immunomodulatory cells, including myeloid-derived suppressor cells (MDSC), tumor-associated macrophages, and regulatory T cells (Tregs). Methods: To reverse this immunosuppression, we engineered mesogenic Newcastle disease virus (NDV) to express immunological checkpoint inhibitors anti-cytotoxic T lymphocyte antigen-4 and soluble programmed death protein-1. Results: Intratumoral administration of recombinant NDV (rNDV) to mice bearing intradermal B16-F10 melanomas or subcutaneous CT26LacZ colon carcinomas led to significant changes in the tumor-infiltrating lymphocyte profiles. Vectorizing immunological checkpoint inhibitors in NDV increased activation of intratumoral natural killer cells and cytotoxic T cells and decreased Tregs and MDSCs, suggesting induction of a pro-inflammatory state with greater infiltration of activated CD8+ T cells. These notable changes translated to higher ratios of activated effector/suppressor tumor-infiltrating lymphocytes in both cancer models, which is a promising prognostic marker. Whereas all rNDV-treated groups showed evidence of tumor regression and increased survival in the CT26LacZ and B16-F10, only treatment with NDV expressing immunological checkpoint blockades led to complete responses compared to tumors treated with NDV only. Discussion: These data demonstrated that NDV expressing immunological checkpoint inhibitors could reverse the immunosuppressive state of tumor microenvironments and enhance tumor-specific T cell responses.

AAV-Vectored Expression of the Vascular Normalizing Agents 3TSR and Fc3TSR, and the Anti-Angiogenic Bevacizumab Extends Survival in a Murine Model of End-Stage Epithelial Ovarian Carcinoma.

Epithelial ovarian cancer is the deadliest gynecological malignancy. The lack of effective treatments highlights the need for novel therapeutic interventions. The aim of this study was to investigate whether sustained adeno-associated virus (AAV) vector-mediated expression of vascular normalizing agents 3TSR and Fc3TSR and the antiangiogenic monoclonal antibody, Bevacizumab, with or without oncolytic virus treatment would improve survival in an orthotopic syngeneic mouse model of epithelial ovarian carcinoma. AAV vectors were administered 40 days post-tumor implantation and combined with oncolytic avian orthoavulavirus-1 (AOaV-1) 20 days later, at the peak of AAV-transgene expression, to ascertain whether survival could be extended. Flow cytometry conducted on blood samples, taken at an acute time point post-AOaV-1 administration (36 h), revealed a significant increase in activated NK cells in the blood of all mice that received AOaV-1. T cell analysis revealed a significant increase in CD8+ tumor specific T cells in the blood of AAV-Bevacizumab+AOaV-1 treated mice compared to control mice 10 days post AOaV-1 administration. Immunohistochemical staining of primary tumors harvested from a subset of mice euthanized 90 days post tumor implantation, when mice typically have large primary tumors, secondary peritoneal lesions, and extensive ascites fluid production, revealed that AAV-3TSR, AAV-Fc3TSR+AOaV-1, or AAV-Bevacizumab+AOaV-1 treated mice had significantly more tumor-infiltrating CD8+ T cells than PBS controls. Despite AAV-mediated transgene expression waning faster in tumor-bearing mice than in non-tumor bearing mice, all three of the AAV therapies significantly extended survival compared to control mice; with AAV-Bevacizumab performing the best in this model. However, combining AAV therapies with a single dose of AOaV-1 did not lead to significant extensions in survival compared to AAV therapies on their own, suggesting that additional doses of AOaV-1 may be required to improve efficacy in this model. These results suggest that vectorizing anti-angiogenic and vascular normalizing agents is a viable therapeutic option that warrants further investigation, including optimizing combination therapies.

Combining vanadyl sulfate with Newcastle disease virus potentiates rapid innate immune-mediated regression with curative potential in murine cancer models.

The avian paramyxovirus, Newcastle disease virus (NDV), is a promising oncolytic agent that has been shown to be safe and effective in a variety of pre-clinical cancer models and human clinical trials. NDV preferentially replicates in tumor cells due to signaling defects in apoptotic and antiviral pathways acquired during the transformation process and is a potent immunostimulatory agent. However, when used as a monotherapy NDV lacks the ability to consistently generate durable remissions. Here we investigate the use of viral sensitizer-mediated combination therapy to enhance the anti-neoplastic efficacy of NDV. Intratumoral injection of vanadyl sulfate, a pan-inhibitor of protein tyrosine phosphatases, in combination with NDV significantly increased the number and activation status of natural killer (NK) cells in the tumor microenvironment, concomitant with increased expression of interferon-ß, granulocyte-macrophage colony-stimulating factor, and monocyte chemoattractant protein-1, leading to rapid tumor regression and long-term cures in mice bearing syngeneic B16-F10 melanomas. The anti-tumor efficacy of this combination therapy was abrogated when NK cells were depleted and when interferon-ß expression was transiently suppressed. Tumor-specific CD8+ T cell responses were not detected, nor were mice whose tumors regressed protected from re-challenge. This suggested efficacy of the combination therapy predominantly relied on the innate immune system. Importantly, efficacy was not limited to melanoma; it was also demonstrated in a murine prostate cancer model. Taken together, these results suggest that combining NDV with vanadyl sulfate potentiates an innate immune response that can potentiate rapid clearance of tumors, with type I interferon signaling and NK cells being important mechanisms of action.

Intranasal vaccination with a Newcastle disease virus-vectored vaccine protects hamsters from SARS-CoV-2 infection and disease.

The pandemic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the cause of coronavirus disease 2019 (COVID-19). Worldwide efforts are being made to develop vaccines to mitigate this pandemic. We engineered two recombinant Newcastle disease virus (NDV) vectors expressing either the full-length SARS-CoV-2 spike protein (NDV-FLS) or a version with a 19 amino acid deletion at the carboxy terminus (NDV-Δ19S). Hamsters receiving two doses (prime-boost) of NDV-FLS developed a robust SARS-CoV-2-neutralizing antibody response, with elimination of infectious virus in the lungs and minimal lung pathology at five days post-challenge. Single-dose vaccination with NDV-FLS significantly reduced SARS-CoV-2 replication in the lungs but only mildly decreased lung inflammation. NDV-Δ19S-treated hamsters had a moderate decrease in SARS-CoV-2 titers in lungs and presented with severe microscopic lesions, suggesting that truncation of the spike protein was a less effective strategy. In summary, NDV-vectored vaccines represent a viable option for protection against COVID-19.

Tumour vasculature: Friend or foe of oncolytic viruses?

In the past two decades there have been substantial advances in understanding the anti-cancer mechanisms of oncolytic viruses (OVs). OVs can mediate their effects directly, by preferentially infecting and killing tumour cells. Additionally, OVs can indirectly generate anti-tumour immune responses. These differing mechanisms have led to a paradoxical divergence in strategies employed to further increase the potency of oncolytic virotherapies. On one hand, the tumour neovasculature is seen as a vital lifeline to the survival of the tumour, leading some to use OVs to target the tumour vasculature in hopes to starve cancers. Therapeutics causing vascular collapse can potentiate tumour hypoxia, nutrient restriction and pro-inflammatory cytokine release, which has shown promise in oncological studies. On the other hand, the same vasculature plays an important role for the dissemination of OVs, trafficking of effector cells and other therapeutics, which has prompted researchers to find ways of normalizing the vasculature to enhance infiltration of leukocytes and delivery of therapeutic agents. This article describes the recent developments of therapies aimed to shut down versus normalize tumour vasculature in order to inform researchers striving to optimize OV-based therapies.

Effect of bisphosphonates on pain and quality of life in patients with bone metastases.

Bone is the most common organ for tumor metastasis, especially in patients with cancers of the breast or prostate. Bone metastases disrupt skeletal metabolism and result in considerable skeletal morbidity, including intractable, chronic bone pain, hypercalcemia of malignancy, pathologic fracture and spinal-cord compression. In addition to the chronic pain caused by bone metastases, skeletal-related events (SREs) such as pathologic fractures and spinal-cord compression can result in acute increases in pain. These effects can severely impair mobility and contribute to a general decrease in quality of life. Palliative options to treat bone metastases include radiotherapy, analgesics, surgery and bisphosphonates. These drugs bind to the surface of the bone and impair osteoclast-mediated bone resorption, and reduce the tumor-associated osteolysis that is initiated by the development of skeletal metastases. In addition to preventing SREs, bisphosphonates can palliate bone pain caused by a variety of solid tumors. This Review summarizes the clinical trial data of bisphosphonates for the prevention of SREs and the palliation of bone pain. Among these agents, nitrogen-containing bisphosphonates are recognized as the most effective, and zoledronic acid has demonstrated the broadest clinical utility.

Natural history of malignant bone disease in breast cancer and the use of cumulative mean functions to measure skeletal morbidity.

BACKGROUND: Bone metastases are a common cause of skeletal morbidity in patients with advanced cancer. The pattern of skeletal morbidity is complex, and the number of skeletal complications is influenced by the duration of survival. Because many patients with cancer die before trial completion, there is a need for survival-adjusted methods to accurately assess the effects of treatment on skeletal morbidity. METHODS: Recently, a survival-adjusted cumulative mean function model has been generated that can provide an intuitive graphic representation of skeletal morbidity throughout a study. This model was applied to the placebo-control arm of a pamidronate study in patients with malignant bone disease from breast cancer. RESULTS: Analysis by bone lesion location showed that spinal metastases were associated with the highest cumulative mean incidence of skeletal-related events (SREs), followed by chest and pelvic metastases. Metastases located in the extremities were associated with an intermediate incidence of SREs, and those in the skull were associated with the lowest incidence of SREs. CONCLUSION: Application of this model to data from the placebo arm of this trial revealed important insight into the natural history of skeletal morbidity in patients with bone metastases. Based on these observations, treatment for the prevention of SREs is warranted regardless of lesion location except for metastases on the skull.

Combining Vascular Normalization with an Oncolytic Virus Enhances Immunotherapy in a Preclinical Model of Advanced-Stage Ovarian Cancer.

PURPOSE: Intravenous delivery of oncolytic viruses often leads to tumor vascular shutdown, resulting in decreased tumor perfusion and elevated tumor hypoxia. We hypothesized that using 3TSR to normalize tumor vasculature prior to administration of an oncolytic Newcastle disease virus (NDV) would enhance virus delivery and trafficking of immunologic cell subsets to the tumor core, resulting in systemically enhanced immunotherapy and regression of advanced-stage epithelial ovarian cancer (EOC). EXPERIMENTAL DESIGN: Using an orthotopic, syngeneic mouse model of advanced-stage EOC, we pretreated mice with 3TSR (4 mg/kg per day) alone or followed by combination with fusogenic NDV(F3aa) (1.0 × 108 plaque-forming units). RESULTS: Treatment with 3TSR normalized tumor vasculature, enhanced blood perfusion of primary EOC tumors, and induced disease regression. Animals treated with combination therapy had the greatest reduction in primary tumor mass, ascites accumulation, and secondary lesions (50% of mice were completely devoid of peritoneal metastases). Combining 3TSR + NDV(F3aa) led to enhanced trafficking of immunologic cells into the primary tumor core. CONCLUSIONS: We have shown, for the first time, that NDV, like other oncolytic viruses, is a potent mediator of acute vascular shutdown and that preventing this through vascular normalization can promote regression in a preclinical model of advanced-stage ovarian cancer. This challenges the current focus on induction of intravascular thrombosis as a requisite for successful oncolytic virotherapy.See related commentary by Bykov and Zamarin, p. 1446.

An optimized clinical regimen for the oncolytic virus PV701.

PURPOSE: Previous phase 1 trials of i.v.-administered PV701 have shown this virus to be well-tolerated with toxicity primarily associated with the first dose. Our hypothesis, based on preclinical evidence, was that patient tolerability could be improved by slowing the i.v. infusion rate, and that this approach would allow for the safe administration of higher doses. Additionally, this phase 1 trial was the first to measure PV701 clearance. EXPERIMENTAL DESIGN: For the first dose, a 3-h infusion was used compared with the 10- and 30-min infusions administered in the two previous trials. Subsequent doses were infused over 1 h. Six doses were given per 3-week cycle. Escalation of the first dose was done separately from the escalation of doses 2 to 6. Viral clearance was determined using whole blood reverse transcription-PCR. RESULTS: Eighteen patients with advanced chemorefractory cancer were enrolled. The first dose was safely escalated to 24x10(9) plaque-forming units/m2 and doses 2 to 6 were safely escalated to 120x10(9) plaque-forming units/m2. Tolerability was improved compared with the rapid bolus dosing used previously with the elimination of severe flu-like symptoms. Furthermore, infusion reactions were markedly decreased in this trial compared with previous PV701 trials. The presence of neutralizing antibodies did not significantly affect PV701 clearance. Four major and two minor tumor responses were observed. CONCLUSIONS: Using slow infusion, patient tolerability was improved, while the first dose was safely escalated relative to two previous PV701 trials. Based on improved tolerability and encouraging signs of activity, this slow infusion regimen was selected for further PV701 clinical development.

Production and Purification of High-Titer Newcastle Disease Virus for Use in Preclinical Mouse Models of Cancer.

Newcastle disease virus (NDV) is a single-stranded, negative-sense RNA virus in the Paramyxoviridae family. Although primarily an avian pathogen, NDV is a potent oncolytic virus that has been shown to be safe and effective in a variety of preclinical cancer models and human clinical trials. To produce virus for oncolytic trials, NDV is commonly amplified in embryonated chicken eggs and purified from the allantoic fluid. Conventional methods for purifying virus from allantoic fluid often result in relatively low-titer preparations containing high levels of impurities, including immunogenic chicken host cell proteins from allantoic fluid. However, large quantities of virus need to be delivered intravenously to administer oncolytic NDV systemically to mice. This route of administration requires virus preparations that are both highly concentrated (to enable delivery of small volumes) and highly pure (to limit toxic effects from contaminants). Given the accumulation of promising preclinical and clinical data demonstrating the efficacy of NDV as an oncolytic agent, strategies for increasing the titer and purity of NDV preparations are sorely needed to allow for effective intravenous administration in mice. Here, we describe an optimized protocol for the rescue, production, and purification of high-titer in vivo-grade NDV for preclinical studies in mouse models.

Overview of phase I studies of intravenous administration of PV701, an oncolytic virus.

PV701 is an attenuated, non-recombinant, oncolytic strain of Newcastle disease virus that displays preclinical intravenous (i.v.) efficacy. PV701 selectively lyses tumor cells versus normal cells based on tumor-specific defects in the interferon-mediated antiviral response. In three phase I trials in 113 patients, the effects of dose, schedule and i.v. infusion rate were evaluated. Three types of adverse events were seen: flu-like, tumor-site-specific and those occurring during infusion. The first PV701 dose desensitized the patient to the side effects of further doses, allowing a 5- to 10-fold increase in the maximum-tolerated dose for subsequent doses compared with the first dose. Tumor responses were first noted at the higher doses achieved using desensitization. In 95 evaluable patients, there were ten responses (six major and four minor), with five of these responses occurring in the most recent trial of 18 patients that employed desensitization, high repeat doses and a slower infusion rate. Phase II studies are planned.

Efficacy of bisphosphonates in the management of skeletal complications of bone metastases and selection of clinical endpoints.

Bisphosphonates are the current standard of palliative care for patients with bone lesions from breast cancer and multiple myeloma. This article discusses the selection of endpoints and statistical methods used to assess clinical efficacy of bisphosphonate therapies in patients with bone metastases. Recent studies of pamidronate and zoledronic acid have set the standards for the design and conduct of multicenter, randomized, placebo-controlled trials to assess the clinical benefit of bisphosphonates in patients with bone metastases. Studies of zoledronic acid have demonstrated objective, significant, and enduring benefits in patients with a broad range of primary cancers, including prostate cancer, using robust clinical endpoints. Other bisphosphonates, including clodronate, have been investigated for the treatment of bone metastases, but these studies have been relatively small. This review first considers issues of trial design and analysis, with particular emphasis on the statistical requirements for the rigorous analysis of multiple events occurring in the same patient, and then reviews the results of bisphosphonate trials in patients with breast or prostate cancers metastatic to bone in the light of these statistical considerations.

Immunotherapy for prostate cancer: lessons from responses to tumor-associated antigens.

Prostate cancer (PCa) is the most common cancer in men and the second most common cause of cancer-related death in men. In recent years, novel therapeutic options for PCa have been developed and studied extensively in clinical trials. Sipuleucel-T is the first cell-based immunotherapeutic vaccine for treatment of cancer. This vaccine consists of autologous mononuclear cells stimulated and loaded with an immunostimulatory fusion protein containing the prostate tumor antigen prostate acid posphatase. The choice of antigen might be key for the efficiency of cell-based immunotherapy. Depending on the treatment strategy, target antigens should be immunogenic, abundantly expressed by tumor cells, and preferably functionally important for the tumor to prevent loss of antigen expression. Autoimmune responses have been reported against several antigens expressed in the prostate, indicating that PCa is a suitable target for immunotherapy. In this review, we will discuss PCa antigens that exhibit immunogenic features and/or have been targeted in immunotherapeutic settings with promising results, and we highlight the hurdles and opportunities for cancer immunotherapy.

Possible survival benefits from zoledronic acid treatment in patients with bone metastases from solid tumours and poor prognostic features-An exploratory analysis of placebo-controlled trials.

BACKGROUND: Zoledronic acid (ZOL) is an important component of therapy for patients with metastatic bone disease (MBD) to reduce the risk of skeletal-related events (SREs). We evaluated overall survival (OS) in patients with MBD secondary to solid tumours included in placebocontrolled ZOL trials. PATIENTS AND METHODS: Exploratory analyses were performed using databases from three randomised trials of ZOL versus placebo. 1126 patients (ZOL, n=731; placebo, n=395) with complete baseline data for 18 predefined parameters were evaluated for OS. Relative risks (RRs) with 95% confidence intervals were assessed using stratified and adjusted Cox regression models. Baseline covariates defining patient populations with significantly different effects of ZOL treatment on OS (identified by stepwise backward elimination) were included in multivariate models. RESULTS: Although OS was similar between the overall treatment groups, ZOL significantly improved OS in the subset of patients (n=423; 38%) with elevated baseline NTX (≥100 nmol/mmol creatinine; RR, 0.692; P=.0028). Notably, this effect was independent of SRE prevention. Additional covariates associated with OS benefits with ZOL (e.g., low albumin, SRE history, elevated lactate dehydrogenase, shorter cancer duration) were characteristic of advanced disease. CONCLUSION: These exploratory analyses suggest a beneficial effect of ZOL on OS in patients with highly aggressive or advanced MBD.

Zoledronic acid and survival in patients with metastatic bone disease from lung cancer and elevated markers of osteoclast activity.

INTRODUCTION: Bone metastases from non-small cell lung cancer (NSCLC) are associated with skeletal-related events (SREs) and elevated levels of N-telopeptide of type I collagen (NTX) in some patients. Zoledronic acid (ZOL) reduces SRE risk and NTX levels. METHODS: To assess effects of baseline variables, including NTX levels (normal = NTX < 64 nmol/mmol creatinine; high = NTX > or = 64 nmol/mmol creatinine), on treatment effects in NSCLC patients, a retrospective analysis was performed in NSCLC patients with bone metastases (N = 382) treated with ZOL or placebo every 3 weeks in a 21-month randomized clinical trial in patients with NSCLC or other solid tumors. Cox proportional hazards models assessed relative risks (RRs) of SREs, bone lesion progression, and death. Multivariate models analyzed covariate effects on survival. RESULTS: For both placebo- and ZOL-treated patients, high baseline NTX correlated with increased SRE risk (p = 0.068 and 0.012, respectively). Although high versus normal baseline NTX correlated with more than twofold increased risks of bone lesion progression and death in the placebo group (p = 0.039 and 0.001, respectively), correlations were weaker in the ZOL group (RR = 1.38; p = 0.0186 and RR = 1.27; p = 0.142, respectively), suggesting an interaction effect of ZOL and baseline NTX. Among patients with high baseline NTX, ZOL significantly reduced the RR of death by 35% versus placebo (p = 0.024). Per multivariate analysis, ZOL treatment (p = 0.005), higher lymphocyte count (p = 0.011), performance status 0 to 1 (p = 0.012), and absence of narcotic use (p = 0.016) correlated with improved survival. CONCLUSIONS: This retrospective analysis revealed statistically significant correlations between ZOL and increased survival versus placebo in NSCLC patients and high baseline NTX levels.

Survival-adjusted multiple-event analysis for the evaluation of treatment effects of zoledronic Acid in patients with bone metastases from solid tumors.

Bone metastasis causes significant pain and morbidity and is characterized by multiple skeletal-related events (SREs), including fractures, spinal cord compression, and the requirement for radiation or surgery to bone. Analysis of such a composite endpoint provides insight into the clinical impact of the disease. However, SREs typically occur in a complex pattern. Recently, zoledronic acid (4 mg) was approved for the treatment of bone metastases secondary to all solid tumors and primary bone lesions from multiple myeloma based on significant benefits from first-event and skeletal morbidity rate analyses. However, multiple-event methods can provide information about the risk of SREs over the entire course of follow-up and address interpatient variation in event rates and temporal trends. Moreover, multiple-event methodology can adjust for survival, which has an effect on SRE incidence. Herein we present a survival-adjusted multiple-event analysis of the cumulative incidence of radiation to bone (a homogenous endpoint) and SREs (a composite endpoint) in 3 large, randomized clinical trials of zoledronic acid (4 mg) in patients with prostate cancer, lung cancer and other solid tumors, or breast cancer. In patients with prostate cancer, zoledronic acid significantly reduced the cumulative incidence of SREs compared with placebo (P = 0.002) as it did among patients with lung cancer and other solid tumors (P = 0.025). In patients with breast cancer, zoledronic acid significantly reduced the cumulative incidence of SREs compared with pamidronate 90 mg over 25 months (P = 0.050). These results are consistent with those obtained using established methods, supporting the validity of the survival-adjusted cumulative mean function for assessing benefits during bisphosphonate therapy.

A phase II trial of ZD1839 (Iressa) 750 mg per day, an oral epidermal growth factor receptor-tyrosine kinase inhibitor, in patients with metastatic colorectal cancer.

PURPOSE: The epidermal growth factor receptor (EGFR) appears relevant in the pathogenesis and progression of colorectal cancer. After completing a phase I pharmacodynamic trial of ZD1839, we undertook a dose expansion trial to examine the antitumour efficacy and adverse effect profile of this agent in a homogeneous group of patients with metastatic colorectal cancer (CRC). EXPERIMENTAL DESIGN: Eligible patients with metastatic or recurrent CRC received ZD1839 750 mg daily by mouth. This dose was selected based on a phase I trial conducted by the National Cancer Institute of Canada Clinical Trials Group (NCIC CTG). Treatment was continued until unacceptable toxicity or disease progression. RESULTS: Twenty-eight patients were enrolled at three NCIC CTG centers. Twenty-three patients had received prior chemotherapy; 12 patients had received three or more regimens. No objective responses were observed in 24 evaluable patients, although 8 patients had stable disease (median duration of 2.2 months). The most frequent drug related adverse events were diarrhea, rash and nausea. Eleven patients required dosing modification (hold or reduction), while 3 patients discontinued therapy because of toxicity. There were no treatment related deaths. CONCLUSIONS: ZD1839, when given at 750 mg/day to patients with pre-treated metastatic colorectal cancer, does not result in significant tumor regression.