Differences in male breast cancer outcomes by race/ethnicity in Florida and the United States: A population-based comparison of FCDS and SEER

Introduction Male breast cancer (MBC) is rare (<1% of U.S. cases) yet clinically important. Evidence on racial/ethnic differences is limited and often comes from single registries. We characterize sociodemographic, clinical, and treatment features of MBC and evaluate factors associated with overall survival (OS) in Florida and the broader United States in relation to race/ethnicity and nativity. Methods We performed a retrospective cohort study of the Florida Cancer Data System (FCDS, 1981-2020; N=1,878) and SEER 8 registries (1975-2022; N=4,754), including primary MBC (ICD-O-C56XX). We described sociodemographic variables (age, race/ethnicity; plus insurance/smoking in FCDS; marital status/area-level income in SEER), clinical features (grade, stage, ER/PR/HER2), and treatment types (surgery, chemotherapy, radiation). Registry-specific Cox models shared the same adjustment set (age, grade, stage, ER/PR/HER2, surgery, chemotherapy, radiation). Race/ethnicity was categorized as non-Hispanic White (NHW), non-Hispanic Black (NHB), and Hispanic. In FCDS, we also tested the moderating effect of nativity (U.S.-born vs non-U.S.-born) and the joint effect of race and nativity. Results In FCDS (n=1,878; 80% NHW, 12% NHB, 8% Hispanic; mean age 67.5 years), NHB men vs NHW and Hispanic were younger at diagnosis (61 vs 69 vs 67 years), had shorter OS (38 vs 59 vs 49 months), more high-grade tumors (56% vs 37% vs 38%), more distant stage (15% vs 7% vs 11%), and lower surgery rates (77% vs 90% vs 86%; all p<0.01); ER/PR/HER2 status did not differ by race/ethnicity. In SEER (n=4,754; 84% NHW, 11% NHB, 5% Hispanic; mean age 67.0 years), NHB men were younger (62 vs 68 vs 64 years), had shorter OS (54 vs 70 vs 63 months), more distant stage (14% vs 7% vs 11%), and lower surgery rates (84% vs 91% vs 89%; all p<0.01). NHB men had fewer ER-positive (92% vs 96% vs 94%) and PR-positive tumors (80% vs 89% vs 85%; p<0.01), while HER2 status did not vary by race/ethnicity. In multivariable models, race/ethnicity was not associated with OS in FCDS; however, among NHB men, non-U.S.-born had lower mortality than U.S.-born (HR 0.54; 95% CI 0.34-0.86; interaction p=0.01). In SEER, NHB men had higher mortality than NHW (HR 1.22; 95% CI 1.07-1.38). In both registries, older age, high grade, distant stage, and omission of surgery were independently associated with higher mortality (all p<0.01). Conclusion Across Florida and the United States, MBC OS is chiefly determined by age, grade, stage, and surgery. In SEER, NHB have higher adjusted mortality than NHW, an effect not seen in FCDS. In FCDS, nativity modifies risk among Black men: non-USB have lower mortality than USB. These findings support nativity-stratified surveillance and equity efforts to promote earlier diagnosis and consistent access to definitive surgery.