Clinical Implication of Subcategorizing T2 Category in Metaplastic Breast Cancer

In the tumor, node, metastasis staging system for metaplastic breast cancer (MBC), the T2 category, encompassing a border spectrum of tumor sizes than T1 category, curiously lacks subcategorization.

Using the Surveillance, Epidemiology, and End Results database, data of 767 women diagnosed as T2N0-2 MBC between 2004 and 2016 were analyzed. The optimal tumor size cutoff was determined using X-tile software to facilitate the subclassification of T2 tumors. A comparison of breast cancer-special survival (BCSS) was conducted across three subcategories, with a median follow-up duration of 44 months.

Of 767 patients, 136 (17.7%) died. Based on Kaplan-Meier analysis, 30 mm and 40 mm were selected as the cutoff values. Ten-year BCSS rate was 90.2% in patients with breast tumors ≤ 30 mm (T2a), 80.2% in patients with breast tumors ≤ 40 mm (T2b), and 68.2% in patients with breast tumors ≤ 50 mm (T2c) (log-rank p = 0.001). T2b (p = 0.009) and T2c (p < 0.001) subcategory showed worse BCSS than T2a subcategory. By multivariate analysis, T2b (T2a as reference, hazard ratio [HR], 1.610, p = 0.020) and T2c (HR, 1.981, p = 0.002) subcategory were significant independent prognostic factors of BCSS. By subgroup multivariate analysis, patients receiving breast-conserving surgery (BCS) plus radiotherapy (RT) had a better prognosis than that receiving total mastectomy (TM) in T2a stage. However, the prognosis was worse in BCS + RT group than TM group in T2c stage, while there was no difference between two groups in T2b stage.

Further stratification within the T2 category could enhance the precision of prognostic predictions and facilitate the customization of adjuvant treatments.