Incidence and survival outcomes of early male breast cancer: a population-based comparison with early female breast cancer

Background: Male breast cancer (MBC) is a rare malignancy. We aimed to analyze the incidence trends, clinicopathological characteristics, and survival outcomes in early MBC comparison with early female breast cancer (FBC). Methods: We included eligible MBC and FBC patients with stage I-II disease in the Surveillance, Epidemiology, and End Results (SEER) database from 2000-2015. Joinpoint regression was used to evaluate the trends in age-adjusted incidence. A one-to-four propensity score matching (PSM) analysis was performed to reduce bias in a retrospective study. Survival outcomes were evaluated using Kaplan-Meier analyses with the log-rank test and Cox proportional hazards regression analysis. Results: Trends in the age-adjusted incidence rates of early MBC were stable [2000-2015, annual percentage change (APC) =0.50, 95% confidence interval (CI): -0.1 to 1.1, P=0.102]; however, the incidence of early FBC changed significantly over the time period (2000-2015, APC = 0.30, 95% CI: 0.0 to 0.6, P=0.045). In the matched cohort, unmarried status, higher grade, larger tumor size, and advanced lymph node (LN) status were associated with a higher risk of breast cancer death and death of any causes both in early MBC and FBC patients. The hormone receptor (HR) status was as a prognostic factor in FBC patients, but not in MBC. Early MBC had worse breast cancer-specific survival (BCSS) and overall survival (OS) than early FBC in stage I, stage II and HR-positive subgroup of patients. Conclusions: The biological behavior, clinicopathological features, and clinical outcomes of early MBC are different from that of FBC. Further studies on individualized treatment approaches in MBC are needed.