Multiple trials confirm systemic T-DXd efficacy in HER2+ breast cancer with leptomeningeal/brain metastases, yet median LM survival remains 3-4 months, highlighting unmet needs. While systemic therapies improve survival, intracranial disease control remains limited due to poor BBB penetration. Preclinical data show no detectable T-DXd/DXd in CSF, though intrathecal trastuzumab demonstrates preliminary safety/efficacy in HER2+ LM.
This study evaluates intrathecal/intra-Ommaya T-DXd plus systemic therapy in active HER2+ meningeal/brain metastases, assessing safety, intracranial efficacy, and CSF/peripheral blood T-DXd distribution to clarify BBB penetration potential. Findings may guide novel therapeutic strategies for this high-need population.