A Randomized, Double-Blind, Placebo-Controlled, Phase 3 Study of Nonsteroidal Aromatase Inhibitors (Anastrozole or Letrozole) Plus LY2835219, a CDK4/6 Inhibitor, or Placebo in Postmenopausal Women With Hormone Receptor-Positive, HER2-Negative Locoregionally Recurrent or Metastatic Breast Cancer With No Prior Systemic Therapy in This Disease Setting

The main purpose of this study is to evaluate how effective nonsteroidal aromatase inhibitors (NSAI) plus abemaciclib are in postmenopausal women with breast cancer. Participants will be randomized to abemaciclib or placebo in a 2:1 ratio. Overall survival data and the clinical study report (CSR) are not being shared due to immaturity of the data that mandates continued blinding of the trial.