A prospective trial of apalutamide and abiraterone acetate plus prednisone in Black and White men with metastatic castrate-resistant prostate cancer.

Abstract

5015 Background: Abi Race was the first prospective parallel cohort study of abiraterone acetate plus prednisone (AAP) in Black and White men with metastatic castrate-resistant prostate cancer (mCRPC) and demonstrated greater prostate-specific antigen (PSA) response, time to PSA progression (TTP) and toxicity rates among Black patients (pts). We designed the PANTHER trial to estimate clinical outcomes among Black and White pts with mCRPC treated with apalutamide, abiraterone, plus prednisone. Methods: This parallel cohort multicenter study treated androgen receptor pathway inhibitor naïve mCRPC pts with oral apalutamide (240 mg/d), abiraterone (1000 mg/d) and prednisone (10 mg/d) (AAAP) continuously until disease progression, unacceptable toxicity or 2 years. The primary endpoint was radiographic progression free survival (rPFS); secondary endpoints were to estimate TTP, overall survival (OS) and best PSA response, among Black and White pts, separately. Exploratory endpoints included safety and correlative biomarkers of outcome by race and ancestry. Results: Between July 2017 and January 2021, we enrolled 43 Black and 50 White pts from 8 sites. Baseline prognostic characteristics were largely similar with some differences. We report an interim analysis as the pts are still followed for OS. At the time of the abstract submission, there were 18 and 36 rPFS events and 15 and 30 deaths in Black and White pts, respectively. We present the time to event endpoint rates at 12 and 24 mos and PSA declines for Black and White pts. Conclusions: We hypothesize that treatment with the combination of AAAP may result in clinical efficacy in Black men with mCRPC. Black pts were underrepresented in the phase III ACIS trial which compared AAP to AAAP and demonstrated longer rPFS but not OS. Further studies of AAAP combination therapy among Black men with advanced prostate cancer are needed to determine potential clinical benefits in this understudied population. Clinical trial information: NCT03098836 . [Table: see text]