Palbociclib in Treating Patients With Metastatic HER-2 Positive Breast Cancer With Brain Metastasis

PRIMARY OBJECTIVES: I. To determine the radiographic response rate in the central nervous system (CNS) in patients with HER2-positive breast cancer who have brain metastasis treated with palbociclib. SECONDARY OBJECTIVES: I. To determine the progression-free survival (PFS) and overall survival (OS) in patients with HER2-positive breast cancer who have brain metastasis treated with palbociclib. II. To determine time to CNS progression in patients with HER2-positive breast cancer who have brain metastasis treated with palbociclib. III. To determine systemic overall response rate (ORR) in patients with HER2-positive breast cancer who have brain metastasis treated with palbociclib. IV. To determine the safety and tolerability of palbociclib in patients with and HER2-positive breast cancer. TERTIARY OBJECTIVES: I. To evaluate circulating tumor deoxyribonucleic acid (DNA) at baseline, 2 month and 4 months; particularly to assess cyclin D1 aberrations, and if this is predictive of responses. II. To evaluate genomic landscape of available CNS and non-CNS tumors, and describe any discordance. III. To evaluate cognitive function and quality of life at baseline, 2 and 4 months in patients receiving palbociclib. OUTLINE: Patients receive palbociclib orally (PO) daily on days 1-21. Courses repeat every 28 days in the absence of disease progression or unacceptable toxicity. Patients with HER2 positive breast cancer may also receive trastuzumab intravenously (IV) as standard of care concurrently with palbociclib. After completion of study treatment, patients are followed up at 3, 6, 9, and 12 months, and then every 6 months for up to 3 years.