Patterns in male and female breast cancer care: A comparative analysis of stage at presentation, treatment, and survival in the Veterans Health Administration.

Abstract

538 Background: Male breast cancer (MBC) is a rare disease that is often managed using treatment protocols derived from female breast cancer (FBC). Given its rarity, limited large-scale national cohort data exists to inform clinical treatment decisions for MBC. This study aims to compare contemporary treatment trends and survival outcomes for MBC and FBC within the Veterans Health Administration (VHA). Methods: We conducted a retrospective cohort study of patients diagnosed with MBC and FBC between 2000 and 2022 using national data from the VHA Cancer Cube registry. Demographics, tumor characteristics, treatment (surgery, chemotherapy, hormone therapy, and radiation), and survival were compared between MBC and FBC patients. Descriptive statistics and chi-square tests compared the cohorts. Kaplan-Meier methods and Cox proportional hazards regression model were utilized to examine overall survival (OS). Results: Of the 14,018 total patients who met inclusion criteria, only 13.9% (n=1952) were males. MBC patients were significantly more likely to get diagnosed at an older age (MBC 68.8 vs. FBC 60.0 years; p≤0.001) and present with stage III or IV disease (25.8% vs. 12.9%; p<0.001). Compared to FBC patients, MBC patients had significantly higher rates of receiving hormone therapy (56.8% vs. 51.6%; p<0.001) and lower rates of chemotherapy (34.3% vs. 37.4%; p=0.007), radiation (21.2% vs. 47.3%; p <0.001), and surgery (92.1% vs 93.0%; p=0.01). MBC patients were significantly less likely to undergo breast-conserving surgery (BCS) (11.2% vs. 52.0%; p <0.001) than FBC patients. In a Cox proportional hazard model including age and stratified by stage, MBC patients had reduced OS (6.9 vs. 19.0 years; p<0.001) and higher risk-adjusted hazard of all-cause mortality (adjusted hazard ratio 1.40, 95% CI 1.30-1.49). OS for MBC was lower than FBC across all stages (Table). Conclusions: Our national cohort study is the largest series of patients with MBC and FBC in the VHA population to date. We demonstrate that MBC patients present with advanced-stage cancer, are less likely to receive aggressive treatments, are less likely to undergo BCS, and have reduced OS across all stages, compared to FBC patients. Our findings highlight the need for further research to optimize outcomes of MBC patients. Stage and survival of the cohort. Clinical Stage All Patients (n=12066) Males(n =1952) Median Survival for Males (years) Females (n=12066) Median Survival for Females (years) P-value 0 2518 141 (7.2%) 12.3 2377 (19.7%) Not reached <0.001 I 5877 601 (30.8%) 9.8 5276 (43.7%) 20.2 II 3589 709 (36.3%) 7.1 2880 (23.9%) 17.5 III 1324 314 (16.1%) 5.4 1010 (8.4%) 10.6 IV 730 189 (9.7%) 1.9 541 (4.4%) 2.8