Patterns of Recurrence and Survival Outcomes of HER2-Low Expression in Early-Stage Breast Cancer

To characterize site-specific recurrence patterns and survival outcomes of patients with human epidermal growth factor receptor 2 (HER2)-low breast cancer.

This retrospective cohort study included patients diagnosed with early-stage breast cancer at a single institution in China from January 2010 to December 2020. Patterns of the first site of recurrence were compared between patients with HER2-low and HER2-0 tumors using competing risks regression analysis. Disease-free survival (DFS) and overall survival (OS) were evaluated using Kaplan-Meier method.

A total of 2055 patients were analyzed (median follow-up 52.3 months), comprising 1102 (53.6%) patients with HER2-low and 953 (46.4%) with HER2-0 tumors. Patients with HER2-0 tumors had a significantly higher 5-year cumulative incidence of visceral recurrence than those with HER2-low tumors (7.20% vs. 4.50%; P = .046), especially for the lung recurrence (4.16% vs. 2.81%; P = .044). In the hormone receptor (HoR)-positive subgroup, HER2-low patients had a significantly higher risk of local recurrence (10-year cumulative incidence rate, 7.58% vs. 2.61%; P = .013) but a relatively lower risk of contralateral breast cancer (10-year cumulative incidence rate, 0.90% vs. 4.53%; P = .044) compared with HER2-0 patients. Nevertheless, there were no significant differences between the HER2-0 and HER2-low patients regarding the time to all sites of recurrence after adjusting other potential risk factors (all P > .05), DFS (P = .763), and OS (P = .106).

Site-specific recurrence patterns differ between HER2-low and HER2-0 patients. However, it does not support that HER2-low breast cancer is a distinct prognostic subtype.