Recently, the results of the phase 2 DAISY trial [26], evaluating the efficacy of T-DXd in patients with HER2+, HER2-low, and HER2- metastatic BC revealed that, although T-DXd efficacy increased when HER2 expression was high, a mild activity was also observed in patients with HER2− tumors. Here, ERBB2 is linked to breast cancer.