Background: There is emerging evidence that radiographic progression-free survival (rPFS) is highly correlated with overall survival (OS), potentially serving as an indicator of treatment outcome for castration-resistant prostate cancer (CRPC). The objective of this study is to assess rPFS and prostate specific antigen (PSA) response in sequential treatment using androgen signaling inhibitors (ASIs) including abiraterone and enzalutamide in newly diagnosed CRPC. Methods: Propensity score matching was performed to reduce bias by confounding factors between first-line ASIs. The primary endpoints of the study included rPFS, time to PSA progression (TTPP), and PSA response. Results: A paired-matched group of 184 patients were identified. From the initiation of first-line ASIs, there was no significant difference in rPFS, TTPP, and PSA response between treatment arms. From the initiation of second-line ASIs, enzalutamide following abiraterone consistently exhibited longer rPFS (median: 7 and 15 months, p = 0.04), TTPP, and better PSA response compared to the reverse, whereas OS did not reach significance (median: 14 and 23 months, p = 0.35). Conclusion: Although the effect of ASIs as the first line was similar, the extent of cross-resistance might differ towards less resistance in enzalutamide following abiraterone than the reverse.

Journal of clinical medicine. 2019 Aug 19*** epublish ***

Kazumasa Komura, Yuya Fujiwara, Taizo Uchimoto, Kenkichi Saito, Naoki Tanda, Tomohisa Matsunaga, Atsushi Ichihashi, Takeshi Tsutsumi, Takuya Tsujino, Yuki Yoshikawa, Yudai Nishimoto, Tomoaki Takai, Koichiro Minami, Kohei Taniguchi, Tomohito Tanaka, Hirofumi Uehara, Hajime Hirano, Hayahito Nomi, Naokazu Ibuki, Kiyoshi Takahara, Teruo Inamoto, Haruhito Azuma

Department of Urology, Osaka Medical College, Osaka 569-8686, Japan. ., Department of Urology, Osaka Medical College, Osaka 569-8686, Japan., Department of Urology, Saiseikai-Nakatsu Hospital, Osaka 530-0012, Japan., Department of Urology, Osaka Medical College Mishima-Minami Hospital, Osaka 569-0856, Japan., Department of Urology, Aijinkai-Takatsuki Hospital, Osaka 569-1192, Japan., Division of Urology, Department of Surgery, Brigham and Women’s Hospital, Boston, MA 02115, USA., Department of Urology, Hirakata Municipal Hospital, Osaka 573-1013, Japan., Translational Research Program, Osaka Medical College, Osaka 569-8686, Japan., Department of Urology, Fujita-Health University School of Medicine, Nagoya 470-1192, Japan.