• Haruo Kato, Yosuke Furuya, Yoshiyuki Miyazawa, Takeshi Miyao, Takahiro Syuto, Masashi Nomura, Yoshitaka Sekine, Hidekazu Koike, Hiroshi Matsui, Yasuhiro Shibata, Kazuto Ito, and Kazuhiro Suzuki.
• Department of Urology, Gunma University Graduate School of Medicine, Gunma, Japan.
• Anticancer Res. 2016 Nov 1; 36 (11): 6141-6149.

Background/AimRecent studies have shown that an early prostate-specific antigen (PSA) response to androgen receptor (AR)-targeting agents in metastatic castration-resistant prostate cancer (mCRPC) is associated with a better prognosis. We analyzed early PSA response to enzalutamide and oncological outcomes to study their prognostic significance in the Japanese population.Patients And MethodsFifty-one patients with mCRPC (26 of pre-docetaxel and 25 of post-docetaxel status) were treated with enzalutamide. The PSA progression-free survival (PFS), radiographic PFS (rPFS) and overall survival (OS) were assessed. The association of rPFS and OS in patients with an early PSA response at 4 weeks after commencement of enzalutamide was studied.ResultsEarly PSA responses were significantly associated with a longer rPFS (median of 47.9 vs. 20.1 weeks, p<0.001, in patients exhibiting a 50% PSA response; median of 40.9 vs. 20.1 weeks, p=0.016, in patients exhibiting a 30% PSA response). OS was also significantly associated with an early PSA response (p=0.002 for patients exhibiting a 50% PSA response, p=0.003 for patients exhibiting a 30% PSA response). Multivariate analysis showed that the predictors of a 50% PSA response were an interval to mCRPC and a docetaxel treatment history, while the predictor of a 30% PSA response was a docetaxel treatment history. Furthermore, a 50% PSA response was independently prognostic of rPFS.ConclusionAn early PSA response to enzalutamide was significantly associated with a longer rPFS and OS. This information will aid in the management of patients treated with enzalutamide.Copyright© 2016 International Institute of Anticancer Research (Dr. John G. Delinassios), All rights reserved.

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