Apalutamide and Abiraterone Acetate in African American and Caucasian Men With Metastatic Castrate Resistant Prostate Cancer

The primary goal is to prospectively estimate the median PFS of African American and Caucasian men with mCRPC taking apalutamide, abiraterone acetate, and prednisone. Secondary objectives include: PSA kinetics: to determine the duration of PSA response, time to nadir, and percent of men who achieve a PSA \< 0.1; Radiographic assessments: to estimate the rate of objective response and incidence of bone flares; Safety (NCI CTC v4.0) and tolerability, particularly incidence and grade of hypertension in the two populations. This is a non-comparative pilot open-label, parallel arm, multicenter study of apalutamide and abiraterone acetate in African American and Caucasian men with mCRPC. It is anticipated that 3 additional sites will be needed to accrue 100 subjects (50 African American and 50 Caucasian) over a 24 month accrual period. The study agents will be administerd at the following doses: apalutamide 240mg orally once daily, abiraterone acetate 1000mg orally once daily, and prednisone 5 mg BID in 4-week cycles throughout the treatment period. Fifty (50) patients will be enrolled in each group (AA and Caucasians). The proportion of patients who experience PSA decline of 30%, 50% and 90% will be estimated with exact 95% confidence intervals based on the binomial distribution will be computed. In addition, post therapy changes in PSA will be explored as a continuous outcome. The Kaplan-Meier product limit method will be used to estimate the rPFS, biochemical PFS and overall survival distributions.