Analysis of the distinct features of metastasis male breast cancer and its effect on overall survival based on the SEER database compared with female breast cancer

BACKGROUND: Male breast cancer (MBC) is a rare disease and differs from female breast cancer (FBC) in clinicopathological and immune tissue types. Given the limited research on MBC due to its rarity, an understanding of the shared and distinct features of MBC and FBC is vital for formulating efficacious treatment strategies. METHODS: Data of patients diagnosed with metastatic breast cancer in the Surveillance, Epidemiology, and End Results (SEER) database from 2012 to 2017 were analysed. Chi-square test was used to compare clinicopathological characteristics between male and female patients. Kaplan-Meier analysis was utilized to compare differences in overall survival (OS). RESULTS: A total of 2,858 patients with MBC were studied, 134 of whom had distant metastasis. Compared with 8,698 patients with metastatic FBC, a higher proportion of metastatic MBC patients had tumors located in the center of the breast, received surgical treatment, and had bone + lung metastasis. Survival analysis revealed no difference in OS between metastatic MBC and FBC patients (P=0.27), but there was a significant difference in OS between metastatic and nonmetastatic MBC (P=0.004). Compared with metastatic FBC, MBC patients with bone metastasis alone, lung metastasis alone, liver metastasis alone, and bone + lung metastasis also had worse prognosis (P=0.021, 0.019, 0.024, 0.011, respectively). CONCLUSIONS: Metastatic MBC has unique clinicopathological disease features and patterns of metastasis. No significant difference between the survival of metastatic MBC and FBC patients was observed. Distant metastasis was an independent risk factor impacting the prognosis of MBC patients.