ERBB2 and leptomeningeal metastasis: In a case series of eight patients with heavily pre-treated HER2-positive metastatic breast cancer and progressing LMD, all eight patients derived clinical benefit from T-DXd, and four (50%) patients had an objective partial response based on evaluations using the European Organization for Research and Treatment of Cancer (EORTC)/Response Assessment in Neuro-Oncology for Leptomeningeal Metastasis (RANO-LM) Revised Scorecard32.