Comparison of procarbazine, imidazole-carboxyamide and cyclophosphamide in relapsing patients with advanced carcinoma of the prostate

In this third cooperative chemotherapy trial 165 patients with histologically confirmed, relapsing clinical stage D cancer were randomized to receive either imidazole-carboxamide, procarbazine or cyclophosphamide. All patients had received and failed previous hormonal therapy. Patients whose disease progressed after 12 weeks on initial therapy were crossed over or randomized to receive an alternate drug. There were 129 patients available for comparison of treatments. The objective response rates (partial regression plus stable disease) were 26 per cent for cyclophosphamide, 27 per cent for imidazole-carboxamide and 14 per cent for procarbazine. Subjective responses were noted in pain relief, improvement in performance status and weight gain. Procarbazine was associated with excessive toxicity, resulting in many patients (28 per cent) discontinuing therapy within the first 3 weeks and closure of this particular arm of the study. The regimen of initial imidazole-carboxamide therapy with a later cross-over to cyclophosphamide when the disease continues to progress is associated with the longest increase in survival. Imidazole-carboxamide and cyclophosphamide appear to be active agents in advanced prostatic cancer and are worthy of continued use in this disease.