Phase II trial of oral cyclophosphamide, prednisone, and diethylstilbestrol for androgen-independent prostate carcinoma

BACKGROUND. The authors evaluated the combination of oral cyclophosphamide, oral prednisone, and diethylstilbestrol (DES) in patients with androgen-independent prostate carcinoma (AIPC). METHODS. Thirty-seven patients with prostate carcinoma refractory to androgen ablation who had undergone antiandrogen withdrawal (if previously treated with an antiandrogen) were enrolled in the current study. They were treated with oral cyclophosphamide 100 mg per day on Days 1-20, prednisone 10 mg per day continuously, and DES 1 mg continuously, on a 30-day cycle. Warfarin 1 mg per day was given as prophylaxis for thrombosis. Patient levels of prostate-specific antigen (PSA) were monitored on a monthly basis, with imaging studies every 3 months. Patients continued to receive therapy until disease progression or the occurrence of significant toxicity. The effect of therapy on the patient's quality of life was assessed using the Functional Assessment of Cancer Therapy-Prostate. RESULTS. Thirty-six patients were evaluable for response. Of the 36 patients, 15 (42%) had a 50% or greater decline in PSA levels from pretreatment levels and 1 patient (6%) with measurable disease had a partial response to therapy. The median duration of response was 4.5 months (range, 4-18 months). The overall median survival period was 16.4 months. The treatment was well tolerated, with only three patients removed from the study for toxicities associated with treatment. One patient, who had been treated for more than 24 months, developed acute leukemia. Quality of life evaluation in 17 patients showed a significant improvement in responders, whereas nonresponders had no deterioration while receiving therapy. CONCLUSIONS. Cyclophosphamide, prednisone, and DES represent a well tolerated, low-cost combination therapy with significant activity in the treatment of patients with AIPC.