Although the addition of endocrine therapy to chemotherapy and anti-HER2-based neoadjuvant regimens does not improve the pathological complete response15,16, co-targeting the HER2 and the estrogen receptor pathway in HR-positive/HER2-positive BC is an effective strategy in the metastatic setting17,18 and the administration of adjuvant ET for 5–10 years in addition to chemotherapy and anti-HER2 treatment is standard in the adjuvant setting19. This evidence concerns the gene ERBB2 and breast cancer.