Anastrozole, Palbociclib, Trastuzumab and Pertuzumab in HR-positive, HER2-positive Metastatic Breast

This is a multicenter, phase I/II trial of anastrozole, palbociclib, trastuzumab, and pertuzumab is proposed as first-line therapy in metastatic hormone receptor-positive, HER2-positive breast cancer patients. In this phase I/II clinical trial, the researchers aim to establish the safety and efficacy of dual HER2 therapy in combination with palbociclib and anastrozole, which represents a novel and all biologic approach to the treatment of HR+, HER2+ metastatic breast cancer. Additionally, the researchers aim to examine potential biomarkers of response to palbociclib including cyclin D1, cyclin E1 and cyclin E2 expression levels, CDK 2, 4, and 6 levels, phosphorylated retinoblastoma expression and p16 levels. The researchers intend to use RNA sequencing to assess for other predictors of response in an unbiased manner to see if this correlates with inhibition of Ki-67 and phosphorylated retinoblastoma expression as well as evaluate for potential mechanisms of resistance.