ERBB2 and breast cancer: A clinical trial called TUXEDO-1[28] found that endpoints related to patients with brain metastases from HER2 + breast cancer receiving T-DXd met the predicted outcomes and no new adverse events were observed, which is consistent with the results of the brain metastasis subgroup analyses in our study, confirming the high extracranial activity of trastuzumab deruxtecan in HER2 + breast cancer.