Abstract PS3-03-15: Germline Genetic Testing Access and Survival Outcomes in Male Breast Cancer: A Veterans Affairs Cohort Analysis

Abstract Background Male breast cancer (MBC) accounts for ∼1%of breast cancers, with ∼2,800 new US cases in 2025. MBC has a higher germline mutation frequency than female breast cancer, mostly the result of a higher frequency of BRCA2 mutations in males (10-15%) compared to females (5-10%). NCCN guidelines and VA clinical pathways recommend genetic testing for all men with breast cancer given high mutation frequency and treatment implications. However, real-world genetic testing access and survival outcomes in veterans remain understudied. With >90% male patients, the Veteran Affairs (VA) represents the largest MBC cohort nationwide, providing a unique opportunity to evaluate genetic testing utilization and survival outcomes. Methods Veterans with MBC (2019-2025) were identified using VA Cancer Registry (site code C50). Patients receiving VA care were defined as having ≥2 visits with oncology services. Clinical notes were analyzed using natural language processing and large language model (Llama 3.3 70B) to extract germline genetic testing (GGT) access. GGT access proportion was compared for year 2019-2021 vs. 2022-2024. Overall survival (OS) analysis was conducted and outcomes by GGT access were compared. Results 523 Veterans with male breast cancer were identified. Mean age was 72 years, 61% were White, 28% were Black and 4% were Hispanic. 75% lived in urban areas. 520 (99.43%) were ER/PR+, 46 (8.8%) HER2+, and 3 (57%) triple negative. Of 523 veterans, 334 (63.9%) had access to germline genetic testing at VA over the course of their disease. Patient characteristics were similar between GGT groups. Five-year OS was 70.9% overall, with significant difference by GGT access (78.6% vs. 59.3%, p<0.001). Genetic testing access rates significantly increased from 56.5% (134/237) in 2019-2021 to 70.6% (192/272) in 2022-2024, representing a 14.1 percentage point improvement (p < 0.001, χ2 test). Conclusion The vast majority of veterans with MBC receive GGT, with increasing access over time. GGT access is associated with improved overall survival, suggesting potential benefits of access to comprehensive genetic evaluation. A more detailed covariate analysis is needed to further explore. Citation Format: C. Li, V. Patel, R. McShinsky, Z. Burningham, A. Chiba, S. Bushan, S. Trehan, M. Kelley, A. Halwani, S. V. Colonna. Germline Genetic Testing Access and Survival Outcomes in Male Breast Cancer: A Veterans Affairs Cohort Analysis [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS3-03-15.