Clinicopathological features and prognostic implications of HER2-low in early-stage male breast cancer: A retrospective analysis.

Abstract

e12518 Background: The clinicopathological and prognostic features of HER2-low female breast cancer (BC) have been widely studied. Current knowledge suggests that HER2-low could be identified as a special entity for treatment. However, limited research has focused on the HER2-low subtype in early-stage male breast cancer. Methods: This retrospective study screened male BC cases from all breast cancer patients at a single institution between January 2010 and September 2023. Early-stage cases with non-HER2-positive tumors were included and categorized into HER2-low and HER2-zero groups. Clinicopathological features were collected and compared between the two groups. The primary endpoints were disease-free survival (DFS) and overall survival (OS). Statistical analysis was conducted using descriptive statistics, the Kaplan-Meier method with the Log-rank test, and the Cox proportional hazards model to evaluate differences in DFS and OS between the groups. Results: A total of 99 early-stage non-HER2-positive male BC cases were identified, with 41 classified as HER2-low and 58 as HER2-zero, and these cases were included in the final analysis. Regarding the clinicopathological features, the HER2-low subgroup exhibited higher androgen receptor (AR) expression (P = 0.003). Regarding survival outcomes, no significant difference was observed in DFS (P = 0.1), but the HER2-low subgroup had a significantly longer OS compared to the HER2-zero subgroup (P = 0.01). Multivariate analysis identified age and TNM stage as independent prognostic factors for DFS, while age and HER2-low were independent prognostic factors for OS. Conclusions: HER2-low population in early-stage male BC had a different clinicopathological feature and prognostic role compared to HER2-zero counterparts. The HER2-low subgroup had a better OS compared to the HER2-zero subgroup, and HER2-low was determined as an independent prognostic factor for OS, but not for DFS.