The effect of metastasis patterns on survival in male patients with different breast cancer subtypes: results from the Surveillance, Epidemiology, and End Results (SEER) database

BACKGROUND: Metastasis sites and breast cancer subtypes are important for breast cancer patients. This study aimed to assess possible relationships between them and their influence on prognosis in male breast cancer (MBC) patients. METHODS: We collected data on 2,983 patients with MBC from the Surveillance, Epidemiology, and End Results database, including 250 patients with M1 stage disease. Information on metastatic patterns was provided for bone, brain, liver, and lung metastases. MBC was classified into four subtypes: Her2−/HR+, Her2+/HR+, Her2+/HR−, and triple negative (TN). Univariate and multivariate logistic regression analysis were used to analyze the association, and Cox regression analyses were used to analyze prognosis. RESULTS: The bone was the most common metastatic site and the brain was the least common metastatic site. Patients with the Her2−/HR+ subtype had the highest proportion of metastatic disease, and Her2+/HR− patients had the lowest proportion. Univariate and multivariate logistic regression analyses showed that there were significant differences in distant metastasis patterns in patients with different subtypes. Men with the Her2+/HR+ or Her2−/HR+ subtypes with bone metastasis had better cancer specific survival (CSS), and those with the TN subtype had the worst CSS in all metastatic patterns. CONCLUSIONS: MBC subtypes are associated with different metastasis patterns and can have different effects on prognosis. This study might provide insights into a better understanding of MBC.