ERBB2 and breast cancer: Trastuzumab emtansine and trastuzumab deruxtecan have shown promise in treating ERBB2-positive metastatic BC; however, there is a paucity of data comparing the cardiotoxic effects among ADCs, of ADCs vs the standard-of-care trastuzumab-containing chemotherapy regimens, and the potential of ADCs as first-line therapy for both early-stage and metastatic BC.