Efficacy of androgen receptor signaling inhibitors in combination with androgen deprivation therapy for castration-sensitive metastatic prostate cancer: a retrospective analysis in a Japanese cohort.

BACKGROUND: This study aimed to evaluate the efficacy of androgen receptor signaling inhibitors (ARSIs) combined with androgen deprivation therapy (ADT) for treating castration-sensitive metastatic prostate cancer in Japanese patients, focusing on the effects on time to the development of castration-resistant prostate cancer (CRPC) and overall survival (OS).

METHODS: This retrospective muti-institutional analysis included 332 patients diagnosed with metastatic prostate cancer in Japan between 2018 and 2023. The patients were categorized into two groups: patients receiving ADT combined with ARSI (ARSI group) and those receiving ADT alone or with bicalutamide (ADT group). Data on demographics, treatments, and outcomes were compared using the Kaplan-Meier method with propensity score matching.

RESULTS: We found an increasing trend in ARSI use over time. The median time to CRPC was significantly longer in the ARSI group than in the ADT group (47.1 vs. 15.2 months, p < 0.001); however, no significant differences in OS were observed before or after propensity score matching. The 1-year-survival rate of patients in the ARSI group tended to be higher than that of patients in the ADT group in subgroups with high tumor volume (96.1% vs. 85.0%) and high Gleason grade (98.1% vs. 85.9%).

CONCLUSIONS: Adding ARSI to ADT extended the time to CRPC but did not significantly affect OS. However, it potentially suppressed the short-term risk of death in high-risk subgroups. This study highlights the need for further research to explore the characteristics of Japanese patients with metastatic prostate cancer in whom upfront ARSIs are effective.