Summary
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.