Real world clinical outcomes of palbociclib in hormone receptor positive (HR+) metastatic breast cancer (MBC) patients.

e13034Background: Palbociclib (PA), a CDK4/CDK6 inhibitor, has been shown in clinical trials to prolong progression free survival (PFS) in HR+/Her-2 negative MBC when combined with an aromatase inhibitor (AI) or fulvestrant (FULV). This study assessed real world outcomes of HR+ MBC patients (pts) treated with PA/endocrine therapy (ET). Methods: This is a retrospective, single institution review of HR+ MBC pts treated with PA plus either an AI or FULV from 2015-2017. The primary outcome was progression-free survival (PFS) as assessed by the clinician based on radiological and/or clinical criteria. Tolerability and observed toxicities with PA and overall survival (OS)—defined as date of initial PA treatment to date of death— were also evaluated as secondary outcomes. Results: 411 women with HR+ MBC who received PA were identified. 94% were HER-2 negative. Median and average follow up duration were 10.2 and 11.3 months, respectively. 55% received PA/letrozole (LTZ), 6% PA/other AI, and 38% PA/FULV. PA/ET was...