The Prognostic Impact of HER2 Status and Survival Outcomes in Metastatic Triple Negative Breast Cancer

Abstract

Background/Aim: This study investigated the prognostic impact of human epidermal growth factor-2 receptor (HER2) status on the survival of patients with metastatic triple-negative breast cancer (TNBC). Patients and Methods: This multicenter, retrospective study included 168 patients diagnosed with recurrent or de novo metastatic TNBC between April 2013 and September 2024. Patients were categorized into two groups: HER2- negative (n=121, 72%) and HER2-low (n=47, 28%). Clinicopathological features and survival outcomes were compared between groups. Results: The median follow-up was 44 months [95% confidence interval (CI)=35.7-52.2]. All patients received systemic chemotherapy as part of their first-line treatment. The median progression-free survival (PFS) in all patients was 9 months (95%CI=7.7-10.3 months). The median overall survival (OS) in all patients was 22 months (95%CI=17.4-26.5 months). Higher Ki67 value at diagnosis was a significant poor prognostic factor for median OS (29 months vs. 15 months, p<0.001). HER2-negative patients had significantly worse median OS than HER2-low patients (19 months vs. 33 months, p=0.026). In multivariate analysis, the HER2-low group had significantly longer median OS than the HER2-negative group [hazard ratio=0.64 (95%CI=0.42-0.98), p=0.040]. Conclusion: HER2-low expression was associated with significantly improved survival compared with HER2-negative status in metastatic TNBC. These findings highlight HER2 status as a potential prognostic factor, particularly relevant in settings with limited access to novel therapies such as immunotherapy or antibody-drug conjugates.