The efficacy of ethinylestradiol for castration-resistant prostate cancer

Abstract

We analyzed the efficacy of ethinylestradiol as estrogen therapy on Castration-resistant Prostate Cancer (CRPC). The study was conducted on 14 patients who were diagnosed as having CRPC and who were being prescribed ethinylestradiol (1.5-2.0 mg/day) with aspirin (100 mg/day) and an LH-RH agonist in our hospital from August 2011. All patients had already been treated with a combined androgen blockade (CAB), 8 patients had been treated with docetaxel, 9 patients with tegafur-uracil, 4 patients with estramustine phosphate sodium. Age and prostate-specific antigen (PSA) at prescription of ethinylestradiol was 55-85 (median 75.5) and 0.784-508.7 ng/ml (median 4.842 ng/ml). Thirteen patients (92.9%) achieved a decline in PSA, 8 patients (57.1%) achieved a decline in PSA > 50%. Time to progression was 0-18 months (median 7 months), and there were no severe adverse events including venous thromboembolic diseases. Oral ethinylestradiol administration may have efficacy for CRPC without severe adverse events. Ethinylestradiol may be one of the selective drugs for CRPC patients who do not wish to undergo intravenous chemotherapy or become resistant to docetaxel.