Clinical relevance of TNM staging system according to breast cancer (BC) subtypes.

Abstract

632 Background: Understanding recent advances of tumor biology allow us to divide breast cancer (BC) into at least five subtypes. Different therapeutic approaches are needed based on these molecular subtypes. There has been reported that the association between nodal spread and tumor size was disrupted in BRCA related BC and triple negative breast cancer (TNBC) shows characteristically early relapse and poor prognosis. Therefore, the AJCC TNM staging system might not be equally effective as a prognostic indicator for all subtypes of BC. The aim of our study was to evaluate the usefulness of the TNM staging according to BC subtypes. Methods: We conducted a retrospective analysis of medical records of patients with histologically confirmed invasive BC who received curative surgery at Samsung Medical Center from 2000 to 2004. Relapse-free survivals (RFS) according to TNM stage were analyzed based on BC subtypes. Results: Of the 2,428 patients who had received surgery, 1,879 invasive BC patients who were available clinicopathologic data including immunohistochemical stainings were included. These patients were analyzed according to three subtypes; HR (hormone receptor)+, HER2+, and triple- negative (ER-/PgR-/HER2-) groups. As the stage was advanced, the slope of each stage of the Kaplan-Meier survival curves for RFS in patients with HR+ and HER2+ steadily steepened. In contrast, RFS curves merged from stage I to stage IIIA in TNBC patients without separation. There was only wide separation of RFS curves between stage I-IIIA and stage IIIB-IIIC in TNBC. Staging effect was more profound in HER2+ than in HR+ patients. At stage I and II, the HER2+ and TNBC had significantly worse outcomes than HR+ patients. The RFS curve of TNBC patients at stage III was in between HR+ and HER2+ patients. When the stage III was sub-analyzed, stage IIIA TNBC patients did not have a worse outcome than other subtypes, which is similar to those with HR+ patients. At stages IIIB and IIIC, the TNBC had worse outcomes than HR+ and similar to those with HER2+ patients. Conclusions: The currently used TNM staging system might not be enough for encompassing the tumor biology and for predicting clinical outcomes to make therapeutic decisions for all breast cancers, especially for TNBC patients. No significant financial relationships to disclose.