Would you try abemaciclib in a woman on fulvestrant and palbociclib with good systemic control but progression in the brain?  

I believe this is a reasonable option as treatment of Brain metastasis remains challenging despite advances in the management of metastatic HR + breast cancer. Abemaciclib, currently approved for the treatment of  HR+ metastatic breast cancer (MBC), has been shown preclinically to cro...

Remember that fulvestrant does not cross the blood brain barrier. You can switch to tamoxifen as an alternative anti estrogen since it crosses, and since most postmenopausal patients in this day and age wouldn't have received it. Switching the CDK 4/6 inhibitor is reasonable as well. 

I think it isn't unreasonable to try this strategy, but it is important to note that the JPBO study was for patients that were CDK 4/6 naïve, so we don't have data for use of abemaciclib in patients who develop brain metastases on palbociclib.  There are now some case series that have been...

I think abemaciclib is a reasonable consideration. I would also recommend targeting PI3-kinase-Akt-mTOR pathway in this situation. Several of these inhibitors have good CNS penetration. Active PIK3CA mutations are found in approximately 30% of patients resistant to AI and PI3K inhibitors have higher...