LBA-10 ARCHES – EFFICACY OF ANDROGEN DEPRIVATION THERAPY WITH ENZALUTAMIDE OR PLACEBO IN METASTATIC HORMONE-SENSITIVE PROSTATE CANCER: PROSTATE-SPECIFIC ANTIGEN RESULTS

INTRODUCTION AND OBJECTIVES:Potent androgen receptor inhibitor enzalutamide (ENZA) provides benefit in men with castration-resistant prostate cancer (CRPC). ARCHES, a multinational, double-blind, placebo (PBO)-controlled, Phase 3 study (NCT02677896), examined the efficacy of ENZA with androgen deprivation therapy (ADT) in men with metastatic hormone-sensitive prostate cancer (mHSPC). As an important marker of prostate cancer, here we report prostate-specific antigen (PSA) results for ARCHES.METHODS:Patients (pts) with mHSPC were randomized 1:1 to ENZA (160 mg/day) + ADT or PBO + ADT, stratified by disease volume and prior docetaxel. Up to 3 months of ADT (≤6 months if with docetaxel) with no radiographic disease progression or rising PSA levels prior to day 1 was allowed. The primary endpoint was radiographic progression-free survival (rPFS) [scans assessed centrally] or death within 24 weeks of treatment discontinuation. Pre-specified analyses included rPFS (overall and by baseline PSA levels), time to P...