Abiraterone acetate plus prednisone in addition to androgen-deprivation therapy (ADT) was efficacious versus ADT alone in Japanese men with metastatic hormone-naïve prostate cancer. No new safety concerns were identified.

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286 Background: Patients with high-risk mHNPC have a poor prognosis. In Japan, mHNPC accounts for approximately 10% of newly diagnosed prostate cancers. AAP was approved for the treatment of castration-resistant prostate cancer in Japan in July 2014. We now report the clinical benefit of AAP with ADT in Japanese patients with newly diagnosed, high-risk mHNPC. Methods: Interim analysis of the multinational, randomized, double-blind, placebo-controlled, phase 3 study, LATITUDE, was previously reported at ASCO2017. We evaluated the superiority of AA 1g + P 5 mg + ADT (AAP group) to ADT+PBOs of AA and P (P group) in mHNPC with ≥ 2 of 3 risk factors (Gleason ≥ 8, ≥ 3 bone lesions, measurable visceral metastases) for the subgroup of Japanese patients. Results: Of 1199 total patients in LATITUDE trial, 70 patients were Japanese (AAP group, n = 35; P group, n = 35). The hazard ratio (HR) for overall survival in the AAP group versus the P group was 0.635 (95% confidence interval [CI], 0.152 to 2.659) and HR for radiographic progression-free survival was 0.219 (95%CI, 0.086 to 0.560). The incidence of adverse events (AE) was 97% (34/35) in both groups. AEs that occurred in the AAP group at a frequency ≥10% compared with the P group included hypertension, hypokalemia, rib fracture, hematuria and hyperbilirubinemia. The incidence of Grade 3 and 4 AEs was 66% in the AAP group and 20% in the P group. As a whole, efficacy and safety of Japanese patients in LATITUDE were shown to be consistent with those of overall population. Conclusions: AAP has shown a favorable risk/benefit balance and may serve as a new treatment option to improve the prognosis of Japanese mHNPC patients with high-risk prognostic factors. Clinical trial information: NCT01715285.

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