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.
