Influence of prior oral ethinylestradiol use on the efficacy of enzalutamide for the treatment of castration‐resistant prostate cancer in men. (8th March 2018)

• Record Type: Journal Article
• Authors: Hakariya, Tomoaki; Shida, Yohei; Tsurusaki, Toshifumi; Watanabe, Junichi; Furukawa, Masataka; Matsuya, Fukuzo; Miyata, Yasuyoshi; Sakai, Hideki
• Is Part Of: International journal of urology. Volume 25:Number 5(2018)
• Page Start: 464
• Page End: 470
• Publication Date: 2018-03-08
• Subjects: castration‐resistant prostate cancer -- docetaxel -- enzalutamide -- ethinylestradiol; Urology -- Periodicals; Genitourinary organs -- Periodicals; Urologic Diseases -- Periodicals; 616.6005
• DOI: 10.1111/iju.13542
• Languages: English
• ISSNs: 0919-8172

Abstract

Abstract : Objective: To elucidate the effect of prior use of ethinylestradiol on enzalutamide treatment for men with castration‐resistant prostate cancer. Methods: We retrospectively analyzed data from 99 consecutive patients (median age 72 years, range 50–88 years) treated with enzalutamide for castration‐resistant prostate cancer between May 2014 and November 2015 after receiving several lines of hormonal therapy. Results: A total of 45 patients were given ethinylestradiol before enzalutamide. The prostate‐specific antigen response rate (decline in prostate‐specific antigen >50% from baseline) of patients receiving ethinylestradiol and enzalutamide were 51.1% and 41.4%, respectively. Cross‐resistance between ethinylestradiol and enzalutamide was clearly observed in the setting of pre‐docetaxel. In multivariate analysis, the T stage and number of therapies before enzalutamide were the only significant predictors of prostate‐specific antigen response to enzalutamide. However, in patients treated pre‐docetaxel use, prior use of ethinylestradiol was a significant predictor of prostate‐specific antigen response to enzalutamide, whereas ethinylestradiol did not affect the overall survival of these patients. Conclusions: Cross‐resistance between ethinylestradiol and enzalutamide in the setting of pre‐docetaxel therapy seems to be evident. Therefore, ethinylestradiol should be used prudently before enzalutamide in this setting.