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

Daniel J. George Duke Cancer Institute Center for Prostate and Urologic Cancers, Durham, NC info_outline Daniel J. George, Susan Halabi, Mark T. Fleming, Elisabeth I. Heath, Ronald F. Tutrone, Linda Sutton, Young E. Whang, Brian E. Lewis, Michael Sandon Humeniuk, William R. Berry, Michael Roger Harrison, Julia Hurrelbrink, Kellie Shobe, Julia Rasmussen, Monika Anand, Marco Reyes-Martinez, Lauren Howard, Steven R. Patierno, Jennifer A Freedman, Andrew J. Armstrong

Authors Daniel J. George Duke Cancer Institute Center for Prostate and Urologic Cancers, Durham, NC info_outline Daniel J. George, Susan Halabi, Mark T. Fleming, Elisabeth I. Heath, Ronald F. Tutrone, Linda Sutton, Young E. Whang, Brian E. Lewis, Michael Sandon Humeniuk, William R. Berry, Michael Roger Harrison, Julia Hurrelbrink, Kellie Shobe, Julia Rasmussen, Monika Anand, Marco Reyes-Martinez, Lauren Howard, Steven R. Patierno, Jennifer A Freedman, Andrew J. Armstrong Organizations Duke Cancer Institute Center for Prostate and Urologic Cancers, Durham, NC, Duke Cancer Institute Center for Prostate and Urologic Cancers, Duke University School of Medicine, Durham, NC, Virginia Oncology Associates, U.S. Oncology Research, Norfolk, VA, Barbara Ann Karmanos Cancer Institute, Detroit, MI, Chesapeake Urologic Research Associates, Towson, MD, Duke Cancer Network, Duke University, Durham, NC, University of North Carolina, Chapel Hill, NC, Tulane University, New Orleans, LA, Gibbs Cancer Center, Spartanburg, SC, Duke Cancer Center, Durham, NC, Duke University School of Medicine, Durham, NC, Duke Cancer Institute, Durham, NC, Duke University, Durham, NC, Duke Cancer Institute Center for Prostate & Urologic Cancers, Durham, NC Abstract Disclosures Research Funding Pharmaceutical/Biotech Company Janssen, DOD CDMRP 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. Endpoint Black men (95% CI) White men (95% CI) 12 mo rPFS rate 79% (68, 92) 51% (39, 67) 24 mo rPFS rate 63% (50, 80) 38% (26, 55) 12 mo TTP rate 81% (69, 94) 59% (43, 80) 24 mo TTP rate 59% (46, 77) 39% (25, 60) 12 mo OS rate 95% (89, 100) 84% (73, 97) 24 mo OS rate 83% (74, 95) 65% (52, 80) >50% PSA decline 40 (93%) 34 (68%) No PSA decline 1 (2.3%) 7 (14%) PSA decline to < 0.1 ng/mL 21 (49%) 14 (28%)

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