Background: In the phase 3 PREVAIL trial, enzalutamide (ENZA), an androgen receptor inhibitor, improved overall survival (OS) and radiographic progression-free survival (rPFS) relative to placebo (PBO) in chemotherapy-naïve men with mCRPC. Methods: PREVAIL randomized 1,717 patients (pts) with asymptomatic or minimally symptomatic chemotherapy-naïve mCRPC 1:1 to ENZA 160 mg daily or PBO. Coprimary endpoints were OS and rPFS. This prespecified analysis evaluated the impact of age (≥ 75 vs < 75 years) on efficacy and safety. Results: In PREVAIL, 609 (35%) pts were aged ≥ 75 years. This older subset had several poorer baseline prognostics relative to those aged < 75 years: worse ECOG performance status (ECOG 1: 45.0% vs 24.7%), higher prostate-specific antigen (PSA; 73.3 vs 37.3 ng/mL) and more cardiovascular disease (26.9% vs 16.5%). In both older and younger pts, ENZA improved OS, rPFS and time to PSA progression (Table). Pts aged ≥ 75 years in both the ENZA and PBO groups combined had a higher rate of grade ≥ 3 adverse events (46% vs 37% in younger pts) and among enzalutamide-treated men more older pts reported falls (any grade; ENZA 19% and PBO 8%) than younger pts (ENZA 7% and PBO 4%). Fewer pts ≥ 75 years received subsequent antineoplastic therapies. Conclusions: In PREVAIL, efficacy outcomes in elderly (≥ 75 years) and younger (< 75 years) pts with chemotherapy-naïve mCRPC were comparable and pts consistently benefited from ENZA treatment. Safety with ENZA was similar in both age groups, although older pts reported a higher incidence of falls and received fewer subsequent antineoplastic therapies. Clinical trial information: NCT01212991

NYR = not yet reached; mo = months.