Impact of Human Epidermal Growth Factor Receptor 2 (HER2) Low Status in Response to Neoadjuvant Chemotherapy in Early Breast Cancer
Fatima Regina Abreu Alves, Lúcia Gil, Leonor Vasconcelos de Matos, Ana Baleiras, Carolina Vasques, Maria Teresa Neves, André Ferreira, Mário Fontes-Sousa, Helena Miranda, Ana Martins
Abstract
In clinical practice, there is a binary distinction between human epidermal growth factor receptor 2 (HER2)-positive and HER2-negative (HER2−) breast cancer (BC). However, within HER2− disease, there is significant heterogeneity. Particularly, HER2− tumors that express some level of HER2 by immunohistochemistry (IHC) score 1+ or 2+/in situ hybridization (ISH) non-amplified are currently defined as HER2-low. This subgroup has shown distinct biological features compared to HER2-zero (HER2-0) BC and additionally novel antibody-drug conjugate therapies have demonstrated a potential and promising activity in HER2-low BC population. This study aims to evaluate the impact of HER2-low status in response to neoadjuvant chemotherapy (NACT) in HER2− BC being HER2-low and HER2-0 status.