Dataset from MONARCH 2: A Randomized, Double-Blind, Placebo-Controlled, Phase 3 Study of Fulvestrant With or Without Abemaciclib, a CDK4/6 Inhibitor, for Women With Hormone Receptor Positive, HER2 Negative Locally Advanced or Metastatic Breast Cancer

The main purpose of this study is to compare progression-free survival for women with hormone receptor positive (HR+), human epidermal growth factor receptor (HER2) negative advanced breast cancer receiving either abemaciclib + fulvestrant or fulvestrant alone. Participants will be randomized to abemaciclib or placebo in a 2:1 ratio. The study will last about 9 months for each participant. For the endocrine naïve cohort, all participants will received abemaciclib + fulvestrant.