Second primary breast cancer after diagnosis of breast cancer among male patients: An examination of population characteristics and overall survival

Male patients with breast cancer (BrC) have increased risk of developing 2nd-primary BrC (2nd-BrC). Given the relative rarity of male BrC, population-based registries are needed to analyze overall survival (OS) outcomes for these patients. Using the Surveillance, Epidemiology and End Results registry of patients diagnosed from 1975 to 2016, a cohort study of men whose only malignancy was BrC (BrCO; n = 6,475), and men who developed 2nd-BrC after initial BrC diagnosis (BrC-2; n = 85) was performed. The standardized incidence ratio (SIR) of 2nd-BrC, Kaplan-Meier OS and multivariable Cox regression modelling were performed. The SIR for 2nd-BrC was 32.95 (95%CI:[23.85–44.38],p