A retrospective study of breast cancer subtypes: the risk of relapse and the relations with treatments

Immunohistochemical markers are often used to classify breast cancer into subtypes that are biologically distinct and behave differently. The aim of this study was to estimate relapse for patients with the major subtypes of breast cancer as classified using immunohistochemical assay and to investigate the patterns of benefit from the therapies over the past years. The study population included primary, operable 2,118 breast cancer patients, all non-specific infiltrative ductal carcinoma, with the median age of 53.2 years. All patients underwent local and/or systemic treatments. The clinicopathological characteristics and clinical outcomes were retrospectively reviewed. The expression of estrogen receptor (ER), progesterone receptor, human epidermal growth factor receptor 2 (HER2), epidermal growth factor receptor (EGFR), and cytokeratin 5/6 were analyzed by immunohistochemistry. All patients were classified into the following categories: luminal A, luminal B, HER2 overexpressing, basal-like, and unclassified subtypes. Ki-67 was detected in luminal A subtype. The median follow-up time was 67.9 months. Luminal A tumors had the lowest rate of relapse (12.7%, P