In contrast, the new generation of HER2-targeted ADCs, such as trastuzumab deruxtecan (T-DXd), have shown impressive response rates and benefits in terms of progression-free (PFS) and overall survival (OS), compared to conventional chemotherapy, in HER2-low tumors, thus expanding the proportion of breast cancers accessible to HER2-targeted therapy [6, 7]. This evidence concerns the gene ERBB2 and breast cancer.