Enzalutamide in Chemotherapy-Naive Metastatic Castration-Resistant Prostate Cancer: An Asian Multiregional, Randomized Study

Introduction: Enzalutamide significantly improved clinical outcomes compared with placebo in patients with chemotherapy-naive metastatic castration-resistant prostate cancer (mCRPC) with disease progression despite androgen deprivation therapy (ADT) in the PREVAIL study. However, few patients from Asia were enrolled. Our study (NCT02294461) aimed to evaluate the safety and efficacy of enzalutamide in this disease setting in patients in mainland China, Korea, Taiwan, and Hong Kong. Methods: In this double-blind, phase III study, patients with asymptomatic/mildly symptomatic metastatic prostate cancer and disease progression despite ADT were randomized to enzalutamide (160 mg/day) or placebo. The primary endpoint was time to prostate-specific antigen (PSA) progression. Secondary endpoints included overall survival, radiographic progression-free survival, time to first skeletal-related event (SRE), time to initiation of cytotoxic chemotherapy, PSA response >= 50%, best overall soft-tissue response, and safety. Pre-planned interim analysis was scheduled following approximately 175 PSA-progression events (67% of targeted total of 261 events). An additional 5-year landmark analysis of overall survival, time to antineoplastic therapy, and safety was performed. Results: The double-blind study period was stopped after interim analysis owing to the benefit of enzalutamide over placebo. Overall, 388 patients were randomized (enzalutamide, n = 198; placebo, n = 190). Baseline characteristics were balanced between treatment groups. Enzalutamide significantly reduced risk of PSA progression vs placebo (hazard ratio 0.38; 95% CI 0.27-0.52; P < 0.0001). Median time to PSA progression was 8.31 months with enzalutamide and 2.86 months with placebo. Secondary endpoints, including 5-year overall survival, were significantly improved with enzalutamide, except time to first SRE. Adverse-event incidence was similar between enzalutamide and placebo. Fatigue was the most common drug-related adverse event in both treatment groups. Conclusion: Enzalutamide significantly reduced risk of PSA progression, improved secondary efficacy endpoints, and was well tolerated in chemotherapy-naive Asian patients with mCRPC with disease progression despite ADT.

Automated summary

This study aimed to evaluate the safety and efficacy of enzalutamide in Asian patients with mCRPC. The results showed that enzalutamide significantly reduced the risk of disease progression and improved secondary efficacy endpoints, with good tolerability.