Effects of HER2 status on the prognosis of male breast cancer: a population-based study.

Objective: This study was designed to analyze the effects of human epidermal growth factor receptor-2 (HER2) status on the prognosis of male breast cancer (MBC). Methods: The SEER database was used to identify MBC patients diagnosed between 2010 and 2015. Patients were divided into HER2-negative and HER2-positive groups and chi-square test was used to compare the demographics. Propensity score matching (PSM) was used to remove confounding factors. The log-rank test was used to compare the overall survival (OS) and disease-specific survival (DSS) between the two groups. Univariate and multivariate Cox regression analyses were used to evaluate the effects of different variables on the prognosis of MBC patients. Subgroup analysis was conducted by using R software to explore the benefit of OS and DSS in the subgroup of MBC patients. Results: In the matched cohort, the log-rank test showed that there was a longer OS (P=0.044) in the HER2-negative group, and the 4-year OS rate in HER2-negative patients was significantly improved (P=0.008), but there was no difference in the DSS (P=0.408) and the 4-year DSS rates (P=0.198) between the two groups. Univariate and multivariate Cox regression also showed that the HER2 status did not independently associate with DSS (P=0.444). Subgroup analysis showed that HER2-negative patients experienced a longer OS in the subgroup of tumors 2-4 cm in size, no distant metastasis and who had received radiotherapy, but none of subgroup was found a significant difference in DSS between different HER2 status. Conclusion: This study identified that HER2 status had a clear influence on OS in patients with MBC, and there was a longer OS and a higher 4-year OS rate in the HER2-negative group. In addition, we observed that HER2 status had no significant effect on DSS in patients with MBC.