Overall survival (OS) in patients (pts) with metastatic hormone-sensitive prostate cancer (mHSPC) treated with enzalutamide (ENZA) + androgen deprivation therapy (ADT) by high or low disease volume and progression to mHSPC (M0 at diagnosis) or de novo mHSPC (M1 at diagnosis): Post hoc analysis of the phase 3 ARCHES trial.

Abstract

115 Background: In ARCHES (NCT02677896), ENZA + ADT improved radiographic progression-free survival, OS, and other key secondary endpoints vs placebo (PBO) + ADT for pts with mHSPC (also known as metastatic castration-sensitive prostate cancer). Final OS results confirmed a long-term survival benefit with ENZA + ADT (hazard ratio [HR] 0.66; 95% confidence interval [CI] 0.53, 0.81; p<0.0001). We present post hoc analyses of OS by disease volume and progression to M1 HSPC after initial diagnosis with localized disease (M0) or presentation of de novo mHSPC at initial diagnosis (M1). Methods: Pts with mHSPC (N=1150) were randomized 1:1 to ENZA (160 mg/day) + ADT (n=574) or PBO + ADT (n=576), stratified by disease volume and prior docetaxel use. After unblinding, 180 (31.3%) PBO + ADT-treated pts crossed over to open-label ENZA + ADT. High disease volume was defined per CHAARTED criteria. Medical profiles of pts assessed as MX/unknown metastasis at initial diagnosis (n=213) were further reviewed centrally and adjudicated as having either M0 or M1 disease. Median OS and HRs were estimated by Kaplan-Meier methods and Cox proportional hazards, respectively. Results: Median treatment duration was 40.2 months (mo) for ENZA + ADT and 13.8 mo for PBO + ADT. Inclusive of crossover, 401 (69.6%) PBO + ADT pts had subsequent life-prolonging therapy. OS benefits with ENZA + ADT were seen in all disease volume and M0/M1 populations at a similar magnitude to the overall population (Table). Median OS was not reached in most populations except PBO + ADT pts with high disease volume (45.9 mo; 95% CI 40.1, not estimable [NE]) or high disease volume and M1 disease (43.4 mo; 95% CI 36.4, 49.7) and ENZA + ADT pts with high disease volume and M0 disease (54.2 mo; 95% CI 54.2, NE). Conclusions: Our post hoc analysis demonstrates consistent long-term survival benefit with ENZA + ADT vs PBO + ADT across pts with mHSPC with high and low disease volumes and M0 or M1 disease at initial diagnosis, despite substantial treatment crossover and subsequent therapy use in PBO + ADT pts.[Table: see text]