Trastuzumab uptake and its relation to efficacy in an animal model of HER2-positive breast cancer brain metastasis.

In models of HER2-positive breast cancer brain metastasis, trastuzumab efficacy does not appear to be limited by access to intracranial tumors. Anti-tumor activity improved with the addition of a brain-penetrant PI3K/mTOR inhibitor, suggesting that combining targeted therapies is a more effective strategy for treating HER2-positive breast cancer brain metastases. Survival was also extended in mice with Fo5 brain lesions treated with T-DM1.