Stereotactic Radiation & Abemaciclib in the Management of HR+/HER2- Breast Cancer Brain Metastases

Patients will receive single session SRS to intact brain metastases and post-operative cavities. For intact brain metastases, this will be 15 Gy to lesions between 31-40 mm, 18 Gy to 21- 30 mm, and 24 Gy to lesions measuring ≤ 20 mm.

Abemaciclib is an orally administered selective small-molecule inhibitor of CDK4 and CDK6 that is 14 times more potent against CDK4 than CDK6 in enzymatic assays that is approved for the treatment of advanced or metastatic breast cancers. Abemaciclib will be administered at a dose of 150 mg twice daily.

Abemaciclib will be administered with standard of care endocrine therapy. Endocrine therapy can consist of fulvestrant or an aromatase inhibitor. Dosing of concurrent endocrine therapy with abemaciclib should follow standard dosing and safety guidelines.