Clinical relevance of TNM staging system according to breast cancer subtypes

Background: There has been reported that the association between nodal spread and tumor size was disrupted in triple-negative breast cancer (TNBC) and it showed characteristically early relapse. The TNM (tumor-node-metastasis) staging system might not be equally effective as a prognostic indicator for all subtypes. The aim of our study was to evaluate the usefulness of the staging according to subtypes. Patients and methods: We conducted a retrospective analysis of invasive breast cancer patients who received curative surgery at Samsung Medical Center from 2000 to 2004. Relapse-free survivals (RFS) by stage were analyzed. Results: Thousand eight hundred and seventy-nine patients who were available clinicopathologic data were included. These patients were divided into three subtypes: hormone receptor (HR)+, human epidermal growth factor receptor 2+, and triple negative groups. As the stage became more advanced, the slope of each stage of the RFS curves of patients with HR+ and HER2+ steadily increased. In contrast, RFS curves intermingled and showed overlap from stage 1 to 3A in TNBC patients. There was only wide separation of RFS curves between stage 1-3A and 3B-3C in TNBC. Conclusions: The current TNM staging system might not be enough for encompassing the tumor biology and for predicting outcomes to make therapeutic decisions for all BCs, especially for TNBC patients.