Background: Population-level data suggest that B men are more likely to be diagnosed and die from PC. In juxtaposition, across multiple treatments for advanced PC, studies suggest B men have better survival than W men, including with novel hormone therapies (NHTs) such as ENZA. Whether improved survival is driven by better clinical response is unknown as data on racial differences in treatment response for ENZA are limited. This study assessed real-world PSA outcomes (response and progression) of ENZA-treated B vs W CN PC pts in the US. Methods: This retrospective cohort study included PC pts who initiated ENZA in the IntrinsiQ Specialty Solutions urology electronic medical records database from Sept 1, 2014 to Feb 28, 2018. The index date was the first prescription for ENZA. Patients with evidence of prior chemotherapy and/or abiraterone were excluded. Baseline characteristics, PSA response (PSA decline ≥50% or ≥90%), and clinical progression-free survival (cPFS) were assessed by race. Kaplan-Meier and Cox models adjusting for baseline characteristics were used to estimate PSA response and cPFS. Results: The study included 214 B and 1,332 W CN PC pts. Black pts were younger and had a higher baseline median PSA than W pts. Charlson Comorbidity Index (CCI), median duration of therapy, follow-up time, and number of post-index PSA tests were similar between races. In adjusted analyses, the chances of pts achieving ≥50% PSA decline was similar, whereas a numerically higher trend was observed for ≥90% PSA decline in B pts (Table). In addition, B men had significantly better cPFS (hazard ratio [HR] 0.82; 95% confidence interval [CI] 0.68, 0.98; p=0.03) [Table]. Conclusions: This real-world study found similar PSA response in B and W CN PC pts treated with ENZA but suggests that B pts may have better cPFS than W pts. Further research is warranted to validate these findings.

^aMultivariate Cox proportional HR adjusted for baseline covariates age, region, marital status, year of ENZA initiation, CCI, baseline log PSA, pre-index treatments, and documentation of metastasis; ^bcPFS was defined as the earliest of the following: 1) ≥25% increase or an absolute increase of ≥2 ng/mL above the baseline (if all post-baseline PSA values are higher than baseline) or above the nadir; 2) change to second-line treatment; or 3) all-cause death. Ref, reference for HR calculation.