Abiraterone (AA) and enzalutamide (ENZA) are increasingly being used in chemotherapy-naive patients with metastatic castration-resistant prostate cancer owing to efficacy and favorable toxicity. However, the order in which they should be administered has not been determined.
We retrospectively reviewed the records of chemotherapy-naive patients with metastatic castration-resistant prostate cancer who had received sequential treatment with either AA followed by ENZA (AA-ENZA) or the converse (ENZA-AA). Prostate-specific antigen (PSA) response rates (defined as ≥ 50% PSA decline from baseline), first-line progression-free survival (PFS), second-line PFS, combined PFS (defined as first-line PFS plus second-line PFS), and overall survival are compared between the 2 sequence groups.
A total of 97 patients received sequential treatment with AA and ENZA; 50 patients were in the AA-ENZA group, and 47 patients were in the ENZA-AA group. The PSA response rate to first-line treatment was not significantly different between AA (48%) and ENZA (51%) (P = .840). However, a significant difference was observed in the PSA response rate to second-line treatment (AA, 6.4% vs. ENZA, 30%; P = .004). The median combined PFS was not significantly different between sequence groups (hazard ratio, 0.71; 95% confidence interval, 0.46-1.08; log-rank P = .105). The order of addition also had no significant effect on median overall survival (hazard ratio, 0.98; 95% confidence interval, 0.64-1.52; log-rank P = .834).
With the exception of the second-line PSA response, there was no significant difference in clinical outcomes between the AA-ENZA and ENZA-AA groups. Our results might be useful reference in daily practice, especially for patients who do not have a suitable general condition for chemotherapy.
Clinical genitourinary cancer. 2017 Sep 23 [Epub ahead of print]
Nobuaki Matsubara, Yoko Yamada, Ken-Ichi Tabata, Takefumi Satoh, Naoto Kamiya, Hiroyoshi Suzuki, Takashi Kawahara, Hiroji Uemura, Akihiro Yano, Satoru Kawakami, Masafumi Otsuka, Satoshi Fukasawa
Department of Breast and Medical Oncology, National Cancer Center Hospital East, Chiba, Japan. Electronic address: ., Department of Breast and Medical Oncology, National Cancer Center Hospital East, Chiba, Japan., Department of Urology, Kitasato University School of Medicine, Kanagawa, Japan., Department of Urology, Toho University Sakura Medical Center, Chiba, Japan., Departments of Urology and Renal Transplantation, Yokohama City University Medical Center, Kanagawa, Japan., Department of Urology, Saitama Medical Center, Saitama Medical University, Saitama, Japan., Department of Urology, Chiba Cancer Center Hospital, Chiba, Japan.