Neoadjuvant Chemotherapy (NC) Response in Patients with Breast Cancer According to Immunohistochemical Intrinsic Subtypes (IHC)

Introduction: Breast cancer is heterogeneous, with different responses to NC even within similar histology and stages. Objective: To evaluate clinical/pathological response to NC according to different tumor subtypes in Mexican breast cancer patients. Patients and methods: Retrospective study of patients with breast cancer stages II-III, and complete immunohistochemistry (IHC), such as hormonal receptors HER2 and Ki67, treated with NC and surgery. Descriptive and comparative analyses between different intrinsic subtypes were performed. Results: A total of 117 patients were included with 48.6 +/- 10.6 years of age, stage II (24%), and III (76%). We identified 20 (17.1%) cases of luminal A, 37 (31.6%) luminal B HER2-, 13 (11.1%) luminal B HER2+, 12 (10.3%) HER2+, and 35 (29.9%) triple negative. Clinical complete response (tumor and lymph nodes) in luminal A was 10%, in luminal B HER2-10.8%, luminal B HER2+ 15.4%, HER2+ 25%, and in triple negative 14.3%. Conservative surgeries were done in 9 (7.7%) patients. There is a weak positive association between Ki67 expression and tumor clinical response. Pathological complete response occurred in 8 (6.83%) cases, being more frequent in luminal B HER2+ patients (23%). Conclusions: Pathological complete responses were more often in luminal B HER2+ cases.