Background: Despite more aggressive prostate cancer (PCa) at presentation and higher mortality in real world, B pts with metastatic hormone resistant PCa did not have inferior outcomes than W pts when both were enrolled in clinical trials (PMID: 33951180). In the phase 3 S1216 trial, treatment with Ort, a novel CYP17 axis inhibitor, significantly improved progression-free survival (PFS) but not overall survival (OS) compared to bicalutamide (Bic) in pts with mHSPC receiving ADT. This trial enrolled the greatest number of B pts in a phase 3 trial in this setting to-date. We hypothesized that given comparable access to care as experienced in a clinical trial, outcomes in B pts would be similar to those of W pts in the mHSPC setting. Methods: Eligibility: Pts with mHSPC were enrolled. Only pts self-identifying as B or W were included in this analysis. PFS and OS for each group were estimated using Kaplan-Meier method. A multivariate analysis (MVA) adjusting for disease characteristics was conducted using a Cox proportional hazards model. Results: Among 1279 participants, 135 (10.6%) were B; 1077 (84.2%) were W. B and W were equally distributed between treatment arms, and had respectively similar proportion of pts with Gleason score ≥8 (61.3 vs 62.1%), Zubrod score ≥2 (5.1 vs 3.4%) and extensive disease (48.1 vs 48.7%). However, B pts, as compared to W, were younger (65.8 vs 68.4 yrs, p=0.001) and had a higher median baseline PSA (54.7 vs 26.7 ng/mL; p<0.001). PSA responses (≤ 0.2 ng/mL) at month 7 were similar in both groups (p=0.296). Overall, B vs W had similar median PFS (2.3 vs 2.9 yrs, p=0.71) and OS (5.5 vs 6.3 yrs, p=0.65). MVA confirmed similar PFS and OS after adjusting for known prognostic factors (Table). No interaction between race and treatment was observed (P-value interaction PFS= 0.77 and OS= 0.91). Conclusions: We demonstrate that even though B pts present with more aggressive disease in mHSPC setting, they did not have statistically significant worse OS and PFS than W pts and treatment effect was also similar for both racial groups. Equitable access to care may negate historical differences in outcomes among B vs W pts with advanced PCa. Funding: NIH/NCI/NCTN grant U10CA180888, U10CA180819; and Millennium Pharmaceuticals (Takeda Oncology). Univariate and MVA of PFS and OS.

¹HR = Hazard Ratio, CI = Confidence Interval