Safety and efficacy of apalutamide in Japanese patients with metastatic castration-sensitive prostate cancer receiving androgen deprivation therapy: Final report for the Japanese subpopulation analysis of the randomized, placebo-controlled, phase III TITAN study

Objectives: The TITAN study is a randomized, double-blind, placebo-controlled, multinational trial that evaluated apalutamide with androgen deprivation therapy in patients with metastatic castration-sensitive prostate cancer. At the first interim analysis in the Japanese subpopulation (median follow-up 25.7 months), there was an improvement in overall survival and radiological progression-free survival with apalutamide versus placebo. Here, we report the final analysis results for the Japanese subpopulation. Methods: Patients were randomized 1:1 to receive apalutamide 240 mg or placebo. After the first interim analysis, protocol treatment was unblinded, and crossover was allowed. Efficacy and safety were evaluated in the preplanned, event-driven final analysis. Results: Fifty-one patients were Japanese (apalutamide n = 28; placebo n = 23). After a median follow-up of 46.0 months, the median overall survival was not reached neither in the apalutamide nor the placebo group; the hazard ratio was 0.45, favoring apalutamide, which was consistent with the overall population. Hazard ratios for time to cytotoxic chemotherapy (0.39), time to pain progression (0.87), and time to chronic opioid use (0.82) also favored apalutamide and were comparable with those of the overall population. Time to prostate-specific antigen progression and progression-free survival 2, respectively, was favored in the apalutamide group (0.21 and 0.44). Apalutamide was associated with higher incidences of rash and fracture in the Japanese subpopulation compared with the overall population. Conclusions: The efficacy of apalutamide with androgen deprivation therapy in Japanese patients was consistent with efficacy demonstrated in the overall population. No new safety concerns emerged with long-term follow-up.