In targeted anti-HER2 therapy for metastatic breast cancer setting, DS8201-A-J101, DESTINY-Breast04 and DESTINY-Breast06 studies showed that trastuzumab deruxtecan (T-DXd, DS-8201a) provide a novel treatment strategy for patients with low HER2 expression (11, 12). Here, ERBB2 is linked to breast carcinoma.