Poorer breast cancer survival outcomes in males than females might be attributable to tumor subtype

Background & Aims: Substantial controversy exists regarding the differences in tumor subtypes between male breast cancer (MBC) and female breast cancer (FBC). This is the largest population-based study to compare MBC and FBC patients. Methods: Using data obtained by the Surveillance, Epidemiology, and End Results (SEER) program from 2010-2012, a retrospective, population-based cohort study was conducted to investigate tumor subtype-specific differences in various characteristics, overall survival (OS) and breast cancer-specific mortality (BCSM) between males and females. Results: In all, 181,814 BC patients (1,516 male and 180,298 female) were eligible for this study. The male patients were more likely to be black, older, and have lower histological grades, more advanced stages, larger tumors, more lymph node and distant metastases and human epidermal growth factor receptor 2 (HER2)-negative tumors (each p<0.05). A matched analysis showed that the 2-year OS was 91.2% and 93.7% and that the BCSM was 2.2% and 2.5% for male and female patients, respectively. The univariate analysis showed that male triple-negative (TN), hormone receptor (HoR)-positive/HER2-positive and HoR-positive/HER2-negative patients had poorer OS (p <0.01). Meanwhile, the HoR-positive/HER2-positive and TN subtypes were associated with a higher BCSM in MBC patients (p<0.01). The multivariate analysis revealed that TN MBC patients had poorer OS and BCSM (p<0.05). Simultaneously, the results showed that male patients in the HoR-positive/HER2-negative subgroup were less likely to die of BC when adjusting for other factors (p<0.05). Conclusions: The analysis of 2-year OS and BCSM among the BC subtypes showed clear differences between MBC and FBC patients with the TN subtype; these differences warrant further investigation