Abstract
Background Male breast cancer (MBC) is rare, comprising a small proportion of all breast cancer cases. Despite its rarity, MBC carries significant clinical implications due to delayed diagnosis and poorer outcomes compared to female breast cancer (FBC). This study used the CDC Wide-Ranging Online Data for Epidemiologic Research (WONDER) database to evaluate demographic differences and temporal trends in MBC mortality in the U.S. from 1999 to 2020. Methods We performed a retrospective, population-based analysis of MBC mortality using the CDC WONDER database (1999-2020). MBC deaths in males aged ≥20 years were identified using the ICD-10 code C50. Mortality rates were age-adjusted and stratified by race and state. Temporal trends were assessed using joinpoint analysis and linear regression. State-level regression models evaluated geographic disparities, and heatmaps were used to visualize the results. Multivariable regression identified factors associated with mortality variation. Results We identified 13,286 MBC-related deaths. Mortality rates significantly decreased from 1999 to 2007 (annual percent change, or APC = -4.2%, p = 0.03), but plateaued after 2013 (APC = -1.8%, p = 0.46). Data for non-White groups were suppressed due to small sample sizes, while trends in White males were consistently analyzed. States with significantly higher mortality rates than the national average included Georgia (β = 0.73) and Indiana (β = 0.74). The multivariable model showed excellent fit (R² = 0.889). We observed geographic disparities in early detection and healthcare access. Conclusion MBC mortality decreased over the past 20 years, with notable progress before 2007, but plateaued thereafter. Geographic differences persist, with some states showing disproportionately high mortality rates. Disparities in early detection and healthcare access may explain these differences, and the lack of data for non-White populations limits comprehensive assessment. Public health initiatives, male-inclusive clinical trials, and increased awareness are essential for improving early detection and reducing MBC mortality.