Combined versus sequential chemo-endocrine therapy in advanced prostate cancer: final results of a randomized Southwest Oncology Group study

Abstract

Cytotoxic chemotherapy has not provided survival benefit in metastatic prostate cancer, although it has been used most frequently in patients with far-advanced, refractory disease. To evaluate the effects of chemotherapy given earlier in the course of the disease, the Southwest Oncology Group (SWOG) performed a randomized trial between September 1982 and October 1986 comparing endocrine therapy (diethylstilbestrol [DES] or orchiectomy) alone followed by cyclophosphamide-Adriamycin (doxorubicin; Adria Laboratories, Columbus, OH) chemotherapy at progression versus initial combined chemo-endocrine therapy. One hundred forty-three patients were registered, and only six were declared ineligible. Patients on the combined chemo-endocrine therapy arm had a slightly higher response rate (63%) compared with endocrine therapy alone (48%). A log-linear model of tumor response and treatment arm adjusted for the stratification factors favored the combination arm (P = .059). Only three of 27 patients on the endocrine therapy alone arm had an objective partial response when crossed over to chemotherapy, while two others had stable disease. Despite the difference in initial response rate, time to treatment failure and survival were identical in the two treatment arms. Seventy-seven percent of patients on the initial endocrine therapy alone arm have died (median survival, 25.6 months) compared with 78% on the chemo-endocrine therapy arm (median survival, 22.0 months). No significant effect of treatment on survival was observed even after adjustment for the stratification variables in a Cox regression model. Exploratory survival analyses with patients on both arms combined did show a marginally significant time to treatment failure and survival advantage for patients treated with DES rather than orchiectomy as initial endocrine therapy. Eighty-six percent of patients treated by orchiectomy have died compared with only 65% of those treated with DES. These data do not support the addition of cytotoxic chemotherapy to initial endocrine therapy in patients with metastatic prostate cancer.