Detecting the expression of HRs and BCL2 via IHC can help identify luminal A-like subtypes of triple-positive breast cancers

Background Triple-positive breast cancer (TPBC) is a tumor that simultaneously expresses estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor-2 (HER2). Luminal A-like TPBC is a special subtype with a favorable prognosis but benefits less from HER2-targeted therapy. However, little is known about how to identify luminal A-like TPBCs. Therefore, our study aims to explore a clinically feasible method to identify luminal A-like TPBCs using immunohistochemical (IHC) markers. Methods Our cohort enrolled consecutive 190 patients with early-stage TPBCs diagnosed, treated and followed up in our hospital between 2013 and 2019. Patients whose IHC staining displayed ≥ 50% in both ER and PR scores and B-cell lymphoma 2 (BCL2) positivity were classified as cohort A ( n = 64), and the rest were enrolled in cohort B ( n = 126). Kaplan–Meier plotter and log-rank test were used to compare the survival difference between cohort A and cohort B and the efficacy of trastuzumab therapy in the two cohorts. Results The disease-free survival (DFS) of patients in cohort A was significantly better than in cohort B ( p = 0.031). In cohort A, there was no statistically significant difference in DFS between patients treated with trastuzumab and those without trastuzumab ( p = 0.663). While in cohort B, patients treated with trastuzumab had significantly better DFS than those without trastuzumab ( p = 0.032). Multivariate survival analysis showed that cohort A was associated with better DFS(95%CI 1.046–11.776, p = 0.042). Conclusion TPBCs consist of heterogeneous subtypes. Detecting the expression of ER, PR and BCL2 via IHC can help identify luminal A-like TPBCs. This study will enable individualized treatment of TPBCs.