PD35-12: Association between use of second-generation antiandrogens and overall survival in patients with metastatic prostate cancer – a population-based study

Isaac Kim Jr.*, Providence, RI, Nikita Nikita, Joshua Banks, Scott Keith, Philadelphia, PA, Isaac Kim, New Haven, CT, Grace Lu-Yao, Philadelphia, PA

Introduction: Our previous study found a marginal survival improvement among patients diagnosed with metastatic prostate cancer (PCa) in the second-generation antiandrogen (SGA) era. When stratified by stage, only men with bone and visceral metastasis (M1b and M1c) experienced a statistically significant improvement in survival. We tested the hypothesis that use of SGAs is associated with selective survival among M1b and M1c patients only.

Methods: The study was composed of patients with newly diagnosed metastatic PCa identified from the Surveillance, Epidemiology, and End Results (SEER)-Medicare Linked Database. The primary outcome was overall survival (OS). Patients were classified to the pre-SGA era if diagnosed in 2004-2010 and post-SGA era if diagnosed in 2011-2016. We analyzed the association between use of SGA and overall survival by the Kaplan-Meier method, log-rank test, and Cox proportional hazards model.

Results: This study was composed of 7,791 patients (median age 76.73). Median OS improved by 2 months from 27.17 to 29.44 months in M1b patients (p=0.01) but did not significantly change in M1a and M1c patients (p=0.99 and p=0.77, respectively; Figure 1). Use of SGAs was uniformly distributed across M1a, M1b, and M1c patients (p=0.52; Table 1). In the post-SGA era, SGA use was significantly associated with increased OS among M1b patients only (hazard ratio 0.78; 95% CI 0.68-0.89) but not M1a and M1c patients (p=0.20 and p=0.32, respectively; Table 2).

Conclusions: Since the advent of SGAs in 2011, there has been a marginal overall survival improvement in patients with metastatic PCa. Survival improvements from SGAs were observed in M1b patients only. Further investigation is warranted.

Source of Funding: This study was funded by the AUA’s Summer Medical Student Fellowship and supported in part by the Cancer Center Support Grant to the Sidney Kimmel Cancer Center at Jefferson (5 P30 CA056036).