We provide updated results (median follow-up duration: 20.4 months) of a retrospective study on the effectiveness of trastuzumab deruxtecan (T-DXd) in patients with human epidermal growth factor receptor 2-positive (HER2+) breast cancer with brain metastases (BM) and/or leptomeningeal disease (ROSET-BM). The gene discussed is ERBB2; the disease is breast carcinoma.