Ethinylestradiol improves prostate-specific antigen levels in pretreated castration-resistant prostate cancer patients.

BACKGROUND Ethinylestradiol was used as palliative treatment for patients with advanced prostate cancer (PCa). However, its use has declined after the development of combined androgen blockade. In the present study, we analyzed the effects of ethinylestradiol on pretreated castration-resistant PCa patients. PATIENTS AND METHODS Twenty-four Japanese patients were orally administered ethinylestradiol at a dose of 1.5 mg/day and prostate-specific antigen (PSA) was examined. We retrospectively analyzed the proportion of patients achieving a decline in PSA of >50% and progression-free and overall survival rates. RESULTS All patients had already been treated with combined androgen blockade followed by one or more salvage therapies. Median follow-up time was 227 (range: 42-1490) days and median ethinylestradiol treatment time was 195 (range: 3-791) days. The proportion of patients achieving a decline in PSA >50% was 70%. Median progression-free survival was estimated as 300 days. At the end of the follow-up period, one patient had died from PCa. Adverse events occurred in three patients, namely elevation of liver enzymes, anorexia, and heart failure in one patient each. CONCLUSION Oral ethinylestradiol administration may be useful for treatment of advanced castration-resistant PCa after salvage therapy with a high PSA response rate and low adverse event rate.