Retrospective studies of an antibody-drug conjugate, trastuzumab deruxtecan, in patients with HER2 breast cancer and NM showed initial evidence of activity, and more recently, the DEBBRAH trial included patients with both BM and NM, and the published data showed excellent responses in patients with BM while the data for NM is awaited [73]. This evidence concerns the gene ERBB2 and breast carcinoma.