Real-World Longitudinal Treatment Outcomes for Patients with Metastatic Castration-Sensitive Prostate Cancer in Japan

INTRODUCTION: With recent approvals in Japan, identifying optimal first-line therapy for metastatic castration-sensitive prostate cancer (mCSPC) is critical. We evaluated real-world outcomes of androgen-deprivation therapy (ADT) plus androgen receptor signaling inhibitors (ARSIs) as first-line therapies using prostate-specific antigen (PSA) responses and treatment duration. METHODS: This retrospective study used the Medical Data Vision database (May 2020-April 2024). The study population included males with mCSPC, with two cohorts: cohort 1 (with PSA data); cohort 2 (all eligible patients). PRIMARY ENDPOINT: cumulative incidence of ≥ 90% PSA reduction (PSA90) during the first-line period. Secondary endpoints: PSA50; PSA ≤ 0.2 ng/mL; time to PSA progression (TTPP); time-to-treatment discontinuation (TTD). Endpoints were estimated using the Kaplan-Meier method evaluated using the Cox proportional hazards model, adjusted for baseline characteristics. RESULTS: In cohort 1 (n = 1306), cumulative PSA90 response rates were higher with ADT + ARSI ± docetaxel (ARSI-based treatments) than with ADT alone or ADT + nonsteroidal antiandrogens (NSAAs) (at 3 months: ADT alone, 63.2%; ADT + NSAAs, 69.3%; ADT + enzalutamide, 91.8%; ADT + apalutamide, 90.9%; ADT + abiraterone, 90.7%; ADT + darolutamide + docetaxel, 81.2%). Cumulative PSA50 and PSA ≤ 0.2 ng/mL response rates were consistent with PSA90 findings. Median TTPP was longer for ARSI-based treatments versus ADT alone and ADT + NSAA. No significant differences were observed among ARSI-based treatments across these PSA-related endpoints. In cohort 2 (n = 11,737), the median TTD was longer for ARSI-based treatments versus ADT alone and ADT + NSAAs. Notably, ADT + apalutamide showed a shorter median TTD than other ARSI-based treatments. CONCLUSION: Compared with ADT alone or ADT + NSAA, ARSI-based treatments showed faster PSA declines and longer treatment durations. While ARSI-based treatments demonstrated similar PSA-lowering effects, differences in treatment continuation likely reflect real-world clinical management influenced by not only PSA response but also adverse events and patient characteristics.