ERBB2 and breast cancer: It may also represent a new option for endocrine-resistant hormone receptor-positive/HER2-negative metastatic BC, since it has recently shown a longer PFS and a statistically significant OS compared to standard chemotherapy (capecitabine, eribulin, vinorelbine or gemcitabine) after CDK4/6 inhibitors and 2 to 4 previous lines of chemotherapy (26).