The impact of homologous recombination repair (HRR) gene mutation status on treatment (tx) patterns and clinical outcomes among patients (pts) with metastatic castrationresistant prostate cancer (mCRPC) in the United States (US).

97 Background: There is a paucity of evidence that evaluates the impact of HRR mutation status on clinical outcomes in pts with mCRPC. This study assessed the real-world (rw) progression-free survival (rwPFS) based on HRR mutation status (HRR mutated [HRRm]), HRR wild type (HRRwt) among pts with mCRPC in the US. Methods: Data from pts with mCRPC initiating first line (1L) tx between 2016 and 2019 and known HRR status based on germline or tumor testing were retrospectively abstracted from medical charts by physicians in the US from 2021–2022. Pt demographic and clinical characteristics were summarized descriptively across subgroups by HRR status (HRRm vs HRRwt). HRRm was defined as a mutation in at least 1 of 12 genes of interest ( BRCA1, BRCA2, PALB2, ATM, ATR, CHEK2, FANCA, MLH1, MRE11A, NBN, RAD51C, CDK12), regardless of test type. RwPFS on 1L mCRPC tx was compared among pts with HRRm vs HRRwt genes and BRCA1/2 HRRm vs HRRwt genes using the Kaplan–Meier method and log-rank test. Results: A total of 80 physicians contributed data from charts of 130 pts (N=51 HRRm and N=79 HRRwt). Among pts with HRRm genes, 34 (67%) were positive for BRCA1 or BRCA2 mutations. In pts with known timing of testing (n=88), 33% were tested prior to initiation of 1L therapy and 67% after initiation of 1L therapy. In the 1L setting, novel hormonal therapy (NHT) was utilized in 29% of pts with HRRm vs 58% with HRRwt genes (P<0.01). Chemotherapy was utilized in 43% of pts with HRRm vs 34% with HRRwt genes (P=0.40); docetaxel was the most common agent, utilized in 26% vs 27% of pts with HRRm vs HRRwt genes. Median rwPFS on 1L tx was 19 months (95% CI: 11–NE) vs 31 months (95% CI: 23–NE), P=0.11, for pts with HRRm vs HRRwt genes, respectively. RwPFS for pts with BRCA1/2 HRRm genes (N=34) vs HRRwt genes was 19 months (95% CI: 11–NE) vs 31 months (95% CI: 23–NE), P=0.17. Conclusions: In this rw study, genomic testing was performed frequently in later stages of metastatic disease. Pts with HRRm genes had numerically shorter rwPFS on 1L standard therapies compared with HRRwt pts. While unmet needs exist to optimize mCRPC txs and prolong disease progression irrespective of HRRm mutation status, further studies are warranted to further elucidate the prognostic role of HRRm and BRCA1/2 mutations on clinical outcomes.