A phase I study of palbociclib (PALBO) plus everolimus (EVE) and exemestane (EXE) in hormone-receptor positive (HR+)/HER2- metastatic breast cancer (MBC) after progression on a CDK4/6 inhibitor (CDK4/6i): safety, tolerability and pharmacokinetic (PK) analysis

1068Background: Although adding a CDK4/6i to endocrine therapy (ET) has proved to prolong progression-free survival in patients (pts) with HR+/HER2- MBC, it is unclear if continuing a CDK4/6i, toge...