Luminal breast cancer classification according to proliferative indices: clinicopathological characteristics and short-term survival analysis

The classification of luminal breast cancer has been a popular topic regarding its heterogeneity with distinct biological features and clinical outcomes. This study aimed to assess the power of proliferative indices (Ki67 and histological grade) to determine various clinicopathological characteristics and survival in luminal disease. A total of 541 patients with stage I-III luminal breast cancer were enrolled. Subtypes were determined using proliferative indices and were compared with clinicopathological variables and short-term survival. The significance of various treatments was evaluated in a subgroup of pN0 (lymph node negative) patients. Histological grade, independent of other variables, was a better predictor in the ER/PR+, human epidermal growth factor receptor 2 (Her-2) subgroup (p = 0.011) and the pN0 subgroup (p = 0.044) compared with Ki67, which only showed significance in the ER/PR+, Her-2 subgroup (p = 0.008). Neither grade nor Ki67 was associated with outcomes in the luminal Her-2 class. In pN0 patients, various treatments did not show significance in short-term survival. Histological grade outperformed Ki67 as a determinant for the stratification of luminal class regarding short-term survival. Chemotherapy most likely did not provide additional benefit to pN0 patients with luminal breast cancer compared with endocrine therapy.