China ARCHES: A Phase 3 Trial of Enzalutamide vs Placebo in Metastatic Hormone-Sensitive Prostate Cancer

Purpose: This study evaluated the efficacy and safety of enzalutamide vs placebo, both combined with androgen deprivation therapy, in Chinese men with metastatic hormone-sensitive prostate cancer. Materials and Methods: Patients were randomized 2:1 to enzalutamide 160 mg/day or placebo, both in combination with androgen deprivation therapy. The primary trial end point was the time to prostate-specific antigen progression. Selected secondary end points included radiographic progression-free survival, time to castration resistance, time to initiation of new antineoplastic therapy, undetectable prostate-specific antigen (<0.2 ng/mL) rate among patients with detectable levels at baseline, and safety. Results: From September 11, 2019, to November 18, 2022, 180 patients were randomized to treatment (enzalutamide: n = 120; placebo: n = 60). Baseline characteristics were balanced between the treatment arms. Median treatment duration in the enzalutamide vs the placebo arm was 25.66 vs 15.11 months. After 63 prostate-specific antigen progression events (enzalutamide: n = 23; placebo: n = 40), enzalutamide significantly reduced the hazard for prostate-specific antigen progression by 87% (hazard ratio: 0.130; 95% confidence interval: 0.076, 0.222; P < .0001) vs placebo. Radiographic progression-free survival, time to castration resistance, and achievement of undetectable prostate-specific antigen levels were increased with enzalutamide vs placebo, while treatment-emergent adverse event rates were similar. Serious and grade 3 to 4 treatment-emergent adverse events occurred in 35.3% and 52.1%, respectively, of enzalutamide recipients vs 20.3% and 39.0%, respectively, of placebo recipients. Conclusions: In Chinese men with metastatic hormone-sensitive prostate cancer, enzalutamide significantly reduced the hazard for prostate-specific antigen progression vs placebo when combined with androgen deprivation therapy. The China ARCHES (NCT04076059) results were consistent with those of the global ARCHES study (NCT02677896).