Efficacy and safety of abiraterone acetate plus prednisone in Japanese patients with newly diagnosed, metastatic hormone-naïve prostate cancer: a subgroup analysis of LATITUDE, a randomized, double-blind, placebo-controlled, Phase 3 study.

Objectives: To evaluate the efficacy and safety of abiraterone acetate plus prednisone (AAP) plus androgen-deprivation therapy (ADT) in Japanese subgroup with newly diagnosed, metastatic hormone-naïve prostate cancer (mHNPC) from Phase 3, randomized, global LATITUDE study.

Methods: Men with mHNPC having ≥2 of 3 high-risk factors (Gleason score ≥8, ≥3 bone lesions or measurable visceral metastases) randomly received abiraterone acetate 1000-mg+ prednisone 5-mg+ADT (AAP group) or ADT+Placebos (Placebo group). Coprimary endpoints were overall survival (OS) and radiographic progression-free survival (rPFS).

Results: Of total 1199 patients in the LATITUDE study, 70 (5.8%) were Japanese (n = 35 each in the AAP and placebo group). After a median follow-up of 35.02 months (range: 2.5-42.3), median OS was not reached in both AAP group and placebo group (HR: 0.635; 95% CI, 0.152-2.659) and the median length of rPFS was not reached in the AAP group and was 22 months in the placebo group (HR:0.219; 95% CI, 0.086-0.560). The most frequently reported adverse events (>20% in either group) in the Japanese subgroup were hypertension, nasopharyngitis, weight increased, hypokalemia, hot flush, back pain, hyperglycemia, ALT and AST elevation. The incidence of Grade 3 or 4 adverse events was 65.7% (23/35) in the AAP group and 20% (7/35) in the placebo group. The efficacy and safety findings of Japanese subgroup were consistent with that of the overall study population.

Conclusion: Treatment with AAP plus ADT has shown a positive risk-benefit balance and may serve as a new treatment option to improve the prognosis of Japanese mHNPC patients with high-risk features.