Biomarker-directed therapy in black and white men with metastatic castration-resistant prostate cancer (mCRPC).

5013 Background: Black men have been underrepresented in large-scale molecular prostate cancer (PC) surveys, despite having higher PC incidence and mortality. Since molecular profiling to guide the use of targeted agents is increasingly important in mCRPC, we compared precision medicine data and utilization in a cohort of black and white men with mCRPC. Methods: The PROMISE precision medicine database is an academic collaboration to compile clinical and genomic data from men with PC. All patients have had germline and/or somatic genetic testing performed. Eligibility criteria for this analysis included a diagnosis of mCRPC with available race and biomarker data. The primary outcome was the proportion of non-Hispanic black (NHB) and non-Hispanic white (NHW) men with actionable molecular data, defined as the presence of mismatch repair deficiency (MMRd/MSI-H), homologous recombination repair deficiency (HRRd), tumor mutational burden (TMB) ≥ 10 mut/MB, or AR-V7. Secondary outcomes included the proportion of NHB and NHW men with other alterations, the type and timing of genomic testing performed, and the use of targeted therapy. Results: A total of 962 mCRPC patients (21.2% NHB; 78.8% NHW) met inclusion criteria of 1619 in the overall database. Median age (NHB/NHW) was 61/63; 77.5/68.8% had Gleason 8-10; 52.5/56.7% presented with de novo metastatic disease (33.8/29.9% LN, 36.2/32.2% bone and 8.3/6.1% viscera). The median time from diagnosis to first molecular result was 56.3 mo for NHB v 58.7 mo for NHW (p = 0.45). Use of blood-based molecular testing was more common in NHB men (48.7% v 36.4%, p < 0.001). Overall, 32.8% of NHB men harbored actionable molecular data compared to 30.3% of NHW men (Table). MMRd/MSI-H was more common in NHB men (9.1 v 4.9%, p = 0.04). Other than PTEN (12.7/23.8% NHB/NHW, p = 0.0001), no significant differences were seen in the 15 most frequently mutated genes, including TP53, AR, CDK12, RB1, and PIK3CA. Tumor suppressor co-mutations (PTEN/TP53/RB1) were found in 13.1% of NHB and 18.0% NHW (p = 0.13). Delivery of targeted therapy was reported in 19.6% of NHB and 23.7% of NHW men (p = 0.25) after a median of 2 CRPC lines. Median OS from development of mCRPC was 41.5 mo (95% CI, 34.7-51.3) and 44.7 mo (95% CI, 41.1-51.5) for NHB and NHW men, respectively (p = 0.14). Conclusions: In a real-world mCRPC molecular profiling cohort, we found similar overall rates of actionable molecular alterations in NHB and NHW men, but higher rates of MMRd/MSI-H and lower frequency of PTEN alterations in NHB men. We did not find differences in delivery of targeted therapy. [Table: see text]