Multi-institutional evaluation of the clinical outcomes and genomic correlates of African Americans with metastatic castration-sensitive prostate cancer (mCSPC).

Abstract

17 Background: Prostate cancer incidence and mortality is higher in African American (AA) as compared with non-AA men. The outcomes of mCSPC have significantly improved through treatment intensification yet, AA representation in those studies was suboptimal. We aimed to report the clinical, treatment outcomes and genomic data of AA men with mCSPC. Methods: Retrospective analysis of consecutive AA men with mCSPC at six Academic Institutions. The primary objective was to report the baseline characteristics and treatment patterns of mCSPC AA patients. The secondary objectives included the germline and somatic data and the clinical outcomes including PSA response, progression-free survival and subsequent treatments. Results: A total of 71 patients, median age 63 years (range, 41-84) with 58% Gleason 8-10, initial PSA of 69.8 ng/mL (0.02-7650), 59% with de-novo and 55% with high-volume (CHAARTED criteria; 20% visceral) disease, were included in this analysis. Twenty-two patients (31%) were treated with androgen deprivation therapy (ADT; 67% prior to year 2017), while 24%, 45% and 3% received docetaxel (median 6 cycles), abiraterone acetate and enzalutamide, respectively. Two patients received triplet therapy with ADT/docetaxel plus abiraterone or enzalutamide. Undetectable PSA was achieved in 35% after a median of 8.9 months (1.8-22.3). Among patients with mCSPC who received radiation therapy to prostate (n = 8), 89% had low volume disease. At time of cut off, thirty-two patients developed CRPC and the estimated median time to CRPC was 2.9 years (95% CI, 1.6-4.2). Subsequent therapies (n = 29) included abiraterone acetate (41%), enzalutamide (24%), bicalutamide (10%), radium-223 (7%), chemotherapy (7%), sipuleucel-T (3%) and others (7%). Five patients (8%) had pathogenic germline alterations (n = 2 BRCA1; n = 1 HOXB13, PALB2 and PMS2). Additionally, the most common somatic alterations among tested patients (n = 27) included CDK12, SPOP, TMPRSS2-ERG fusion, and TP53, all in 11% frequency. Of note, n = 2 BRCA1 and n = 1 high MSI/TMB. Conclusions: In one of the largest reported cohorts to our knowledge, mCSPC AA presented with a high number of de-novo and high-volume disease and might harbor a different germline and somatic genomic profile. The outcomes were comparable to contemporary phase III trials with treatment intensification, yet 31% were treated with ADT. Despite the known limitations associated with retrospective analysis, these data support prior observations where AA might have better initial PSA responses to ADT-based strategies compared with Caucasians, requiring further validation.