The emerging predictive and prognostic role of HER2 in HER2-negative early breast cancer: a retrospective study.

Purpose: Many patients with early breast cancer (eBC) undergoing neoadjuvant chemotherapy do not achieve pathological complete response (pCR), which is a prognostic factor. We examined the role of HER2-low expression in predicting pCR and prognosis in HER2-negative eBC.

Methods: We evaluated patients with stage I-III HER2-negative BC, treated between 2013 and 2023 at The Royal Marsden NHS Foundation Trust, London.