Approximately 90% of patients with breast cancer are diagnosed with early breast cancer (EBC) and ~30% with HR+ disease experience distant relapse. Historical data estimate the 5-year invasive disease-free survival (IDFS) rate for the population at high-risk of recurrence based on clinicopathological features and high Ki-67 to be between 80% and 85% following completion of definitive locoregional therapy and chemotherapy. Abemaciclib is an oral, continuously dosed CDK4 & 6 inhibitor approved for use in HR+, HER2- advanced breast cancer. The efficacy and safety of abemaciclib in the metastatic setting supported Phase 3 evaluation in the adjuvant setting.
This open-label phase 3 study randomized (1:1) 5,637 patients with node-positive (N+), HR+, HER2-, high-risk EBC to standard of care (SOC) adjuvant endocrine therapy (ET) with or without abemaciclib (150 mg BID for 2 years). Women and men with ≥4 positive nodes, or 1-3 nodes and at least one of the following features: grade 3 disease, tumor size ≥5 cm, and/or central Ki-67 ≥20%, were eligible. The primary endpoint was IDFS per STEEP criteria and key secondary endpoints included distant recurrence-free survival, overall survival and safety. A preplanned efficacy interim analysis occurred after approximately 293 IDFS events.
The results of this efficacy interim analysis will be presented at the ESMO meeting September 2020 and published simultaneously.
Following the efficacy interim analysis, the associated conclusions will be presented at the meeting.