Mortality in Medicare-aged Men with Metastatic Prostate Cancer After the Introduction of Androgen Receptor Pathway Inhibitors: A Population-Based Study

Objective To examine mortality and usage changes after the introduction of androgen receptor pathway inhibitors (ARPI) among older patients with metastatic prostate cancer covered by Medicare. Materials and Methods The study cohort, consisting of patients newly diagnosed with mPCa, was identified from the Surveillance, Epidemiology, and End Results (SEER)-Medicare Linked Database. The primary outcome was all-cause mortality with time zero at date of mPCa diagnosis. Patients were classified as pre-ARPI era if diagnosed with mPCa in 2006-2012 and ARPI era if diagnosed in 2013-2019. Mortality was summarized by unadjusted cumulative incidence and evaluated using covariate adjusted mortality hazard ratios (aHRs) from Cox proportional hazards regression modeling. Results This study included 9,625 patients diagnosed with mPCa (median age 78 years). 44.3% of patients with Medicaid Part D coverage were prescribed therapies in the ARPI era. Stratification by stage revealed that patients with M1a and M1b disease experienced significantly decreased mortality (aHRs: M1a 0.77, 95% CI 0.60-0.98, p=0.03; M1b 0.81, 0.77-0.86, p<0.01; M1c 0.90, 0.80-1.01; p=0.06). Conclusions Since the introduction of ARPIs, the uptake among Medicare patients was relatively high. While we observed a significant 20% lower mortality hazard among patients diagnosed with mPCa after 2013 when ARPIs were introduced, some of the improvement might have resulted from stage migration.