Oral ethinylestradiol in castration-resistant prostate cancer: a 10-year experience

Objectives: To describe our 10-year experience with the use of oral ethinylestradiol in the treatment of metastatic castration-resistant prostate cancer.

Methods: From February 2000 to April 2010, 116 patients with a metastatic castration-resistant prostate cancer were prospectively submitted to oral ethinylestradiol monotherapy. Inclusion criteria were: diagnosis of castration-resistant prostate cancer after failure of at least two lines of androgen deprivation therapy and radiological evidence of metastases. Exclusion criteria were: symptomatic cases with a European Cooperative Oncology Group score >2 and severe or uncontrolled cardiovascular diseases. At inclusion in the study, all patients discontinued the previous androgen deprivation therapy and started oral ethinylestradiol at the daily dose of 1 mg. Aspirin (100 mg/daily) was concomitantly given.

Results: The median ethinylestradiol therapy duration was 15.9 months (range 8-36 months), whereas the median follow up of patients was 28 months (range 13-36 months). During ethinylestradiol therapy, a confirmed prostate-specific antigen response was found in 79 patients (70.5%). The median time to prostate-specific antigen progression was 15.10 months (95% confidence interval 13.24-18.76 months). A toxicity requiring treatment cessation was observed in 26 patients (23.2%) at a median time of 16 months (mainly thromboembolism).

Conclusions: Our 10-year experience shows that ethinylestradiol provides a prostate-specific antigen response in a high percentage of patients with metastatic castration-resistant prostate cancer. Cardiovascular toxicity can be managed through accurate patient selection, close follow up and a concomitant anticoagulation therapy.