Phase II trial of misonidazole (MISO) and cyclophosphamide (CYC) in metastatic renal cell carcinoma.

In animal models pre-treatment with misonidazole, a hypoxic cell radiosensitizer, enhances the antineoplastic effects of alkylating agent chemotherapy. Laboratory data suggest that hypoxic tumor cells may be more resistant to chemotherapy because of suboptimal drug delivery, reduced rates of cell division, or because hypoxia confers relative drug resistance. The therapeutic potential depends on the tumor type, doses of radiosensitizer and alkylating agent, the time interval between drug administration, and the ratio of sensitization of normal and malignant tissues. A Phase II trial of misonidazole and cyclophosphamide was initiated by the Eastern Cooperative Oncology Group to determine the response rate and toxicity in patients with metastatic renal cell cancer. Patients received 5 gm/m2 of misonidazole intravenously two hr before 1200 mg/m2 of cyclophosphamide every 3 wk. Patients with prior chemotherapy or radiotherapy received 1000 mg/m2 of cyclophosphamide. Misonidazole was discontinued after a total dose of 15 gm/m2. The median total misonidazole dose was 23.5 gm (range 4.5-34.5 gm). The median number of cyclophosphamide cycles was 2 (range 1-12). Of the 30 patients evaluable for response, only one patient had an objective partial response. Twenty-nine patients had stable or progressive disease. One patient remains on cyclophosphamide after 9 mo. Estimated median survival is 4.8 mo. There have been no lethal toxicities; however, 9 patients (25%) experienced life-threatening leukopenia and an additional 42% experienced severe hematologic toxicity. Eight patients had WBC less than 1000 on days 7-14 of cycle 1. Thrombocytopenia and grade 3 anemia occurred in 1 and 2 patients, respectively. Moderate or severe nausea and vomiting occurred in 47% and 19% of patients, respectively. Only 3 patients experienced severe neurotoxicity. Four additional patients had moderate neurotoxicity. In summary, misonidazole in this dosing schedule does not enhance the antitumor activity of cyclophosphamide in renal cell carcinoma.