Abstract CT313: An exploratory analysis of efficacy and safety of abiraterone acetate (AA) in black patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) without prior chemotherapy (ctx)

Abstract

Abstract Background Black pts are underrepresented in prostate cancer (PC) trials but have the highest incidence of and mortality rates from PC of any group. Aberrant activation of androgen receptor signaling in black pts may contribute to more aggressive PC. Abiraterone inhibits persistent androgen synthesis and prolongs survival in pts with mCRPC. We previously demonstrated that clinical outcomes and tolerability of AA are similar in black and non-black pts with mCRPC post-docetaxel. Herein, we explore the efficacy and safety of AA in black pts with mCRPC with no prior ctx. Methods COU-AA-302 (NCT00887198) is a randomized, double-blind phase 3 trial of AA (1000 mg + prednisone [P] 5 mg po BID) vs placebo + P in pts with mCRPC with no prior ctx. We evaluated prostate- specific antigen (PSA) response (≥ 50% and ≥ 90% decline from baseline), time to PSA progression (TTPP), and radiographic progression-free survival (rPFS) in black pts treated with AA + P vs placebo + P. Results 28/1088 (2.6%) pts were black and their median ages were 69 and 68 years for the AA and P groups, respectively. PSA response rate and median TTPP and rPFS were higher with AA vs P (Table). Clinical outcomesBlack pt populationOverall populationAA (n = 15)P (n = 13)AA (n = 546)P (n = 542)PSA response rate, n (%)≥ 50% decline8 (53.3)3 (23.1)336 (61.5)129 (23.8)≥ 90% decline8 (53.3)0 (0)168 (30.8)41 (7.6)TTPPMedian (95% CI)16.6 (3.75-NE)5.6 (1.87-16.49)11.1 (8.48-11.24)5.6 (5.39-5.59)HR (95% CI)0.428 (0.151-1.214)0.501 (0.432-0.581)rPFSMedian (95% CI)16.5 (5.49-NE)13.7 (3.71-NE)16.5 (13.77-16.76)8.3 (8.02-9.43)HR (95% CI)1.032 (0.312-3.412)0.525 (0.449-0.615)CI, confidence interval; NE, not estimable. Grade 3/4 treatment-emergent adverse events (TEAEs) occurring in 2 or more black pts were hypertension (4), dyspnea (2), anemia (2), syncope (2), and hypokalemia (2) in the AA group, and hypertension (2) in the P group. One pt in the AA group discontinued due to gastrointestinal hemorrhage. No TEAE-related deaths were reported. Conclusions Black pts experienced clinical benefit from AA with a safety profile similar to that of the overall study population, though low accrual of black pts limits our ability to draw formal conclusions. Additional studies of AA in black pts are under way to understand the benefit in this population (NCT01735396 and NCT01940276). Citation Format: Eleni Efstathiou, Hari Deshpande, Daniel George, Anthony M. Joshua, Mary-Ellen Taplin, Thomas W. Griffin, Anil Londhe, Mary Todd, Arturo Molina. An exploratory analysis of efficacy and safety of abiraterone acetate (AA) in black patients (pts) with metastatic castration-resistant prostate cancer (mCRPC) without prior chemotherapy (ctx). [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr CT313. doi:10.1158/1538-7445.AM2014-CT313