Real-World Treatment Patterns in Patients with Metastatic Castration-Sensitive Prostate Cancer in Japan: A Retrospective Health Administrative Data Analysis.

[INTRODUCTION] Since 2020, several androgen receptor signaling inhibitors (ARSIs) have been approved for use among patients with metastatic castration-sensitive prostate cancer (mCSPC) in Japan. To evaluate how these approvals may have changed the mCSPC treatment landscape in Japan, we analyzed treatment patterns and time to treatment discontinuation (TTD) since 2020 in patients with mCSPC.

[METHODS] This retrospective cohort study utilized data from the Medical Data Vision health administrative database between May 2020 and March 2024. Study endpoints were patient characteristics at baseline, first-line, and subsequent-line treatment patterns; TTD of first-line therapies; and TTD of first-line ARSIs. Patient characteristics were analyzed descriptively. Hazard ratios (HRs) for TTD between treatment classes were calculated using an inverse probability of treatment weight-adjusted Cox proportional hazards model.

[RESULTS] Overall, 8830 patients with mCSPC were identified. Treatment with androgen-deprivation therapy (ADT) plus ARSI increased during follow-up, while treatment with ADT plus nonsteroidal antiandrogens (NSAAs) decreased. Transition from first- to second-line therapy occurred in approximately 32% of patients. Patients who received first-line ADT plus ARSI had a lower risk of treatment discontinuation compared with patients who received first-line ADT alone (adjusted HR 0.62, 95% CI 0.59-0.65) or ADT plus NSAA (adjusted HR 0.50, 95% CI 0.48-0.52). Among ARSIs, ADT plus enzalutamide had the longest median TTD.

[CONCLUSION] Use of ARSIs for mCSPC is increasing, but ADT alone and ADT plus NSAA are still frequently used. The longer treatment duration among patients who received ARSIs indicates that treatment intensification with ARSIs is vital for mCSPC disease control.