Abi Race: A prospective, multicenter study of black (B) and white (W) patients (pts) with metastatic castrate resistant prostate cancer (mCRPC) treated with abiraterone acetate and prednisone (AAP).

Abstract

LBA5009 Background: Pivotal trials of AAP for patients with mCRPC enrolled few B pts, a population with a higher mortality from prostate cancer. Retrospective data suggests B pts may have higher PSA response rates than W pts treated with AAP for mCRPC. Therefore, we prospectively investigated AAP in B vs. W pts with mCRPC. Methods: Abi Race (NCT01940276) is a prospective, multicenter, parallel group study of AP in 100 men (50 B, 50 W) with mCRPC, self-identified by race. All pts received AA 1000 mg/D and P 10 mg/D (AAP) until disease progression or unacceptable adverse events (AE). The primary objective was radiographic progression-free survival (rPFS); key secondary endpoints include PSA kinetics and safety. Exploratory analyses include SNP, metabolomics and hormonal differences by race. Results: Baseline characteristics among pts were similar. The median rPFS for B and W pts was 16.8 months (mo) in each. However, PSA PFS varied by race; median PSA PFS for B and W pts were 16.6 and 11.5 mo [Table]. B pts also had numerically higher rates of ≥30%, ≥50% and ≥90% PSA decline [Table]. AEs were similar in frequency and severity by race including hypertension (42 vs 40%); however, fatigue was higher in W pts (40 vs 26%), and hypokalemia was higher in B pts (36 vs 18%). SNP profiling revealed differences in key genes involved in androgen metabolism and transport. Conclusions: This is the first prospective multicenter study by race of secondary hormonal therapy in mCRPC. B pts may have greater and more durable PSA response to AAP than W pts. SNP patterns vary by race and will be evaluated for prognostic significance. Further prospective studies in B pts are possible and needed to understand the impact of racial determinants on outcome of new hormonal regimens. Clinical trial information: NCT01940276. [Table: see text]