George DJ, et al. - Abiraterone acetate and prednisone (AAP) was prospectively investigated in black (B) vs white (W) patients with metastatic castrate resistant prostate cancer (mCRPC) in this first prospective multicenter study by race of secondary hormonal therapy in mCRPC. Compared to W patients, B patients could exhibit greater and more durable PSA response to AAP. Variation in SNP patterns by race was noted and these patterns will be evaluated for prognostic significance.

Methods

• Researchers performed a prospective, multicenter, parallel group study [Abi Race (NCT01940276)] in 100 men (50 B, 50 W) with mCRPC, self-identified by race.
• Until disease progression or unacceptable adverse events (AE), they administered AA 1000 mg/D and P 10 mg/D (AAP) to all patients.
• Radiographic progression-free survival (rPFS) was assessed as the primary endpoint; PSA kinetics and safety were included as key secondary endpoints.
• SNP, metabolomics and hormonal differences by race were included in the exploratory analyses.

Results

• Patients were similar regarding baseline characteristics.
• For B and W patients, the median rPFS was 16.8 months in each.
• However, variation in PSA PFS by race was observed; for B and W patients, median PSA PFS were 16.6 and 11.5 months, respectively.
• B patients also displayed numerically higher rates of ≥ 30%, ≥ 50% and ≥ 90% PSA decline.
• AEs were similar in frequency and severity by race, including hypertension (42% vs 40%); however, W patients displayed higher fatigue (40% vs 26%), and B patients displayed higher hypokalemia (36% vs 18%).
• Key genes involved in androgen metabolism and transport showed differences in SNP profiling.