CDK Inhibition in HR-Positive, HER2-Negative Early-Stage Breast Cancer

Abemaciclib Shows Long-Term IDFS Benefit in HR+, HER2- Breast Cancer

Manali Bhave, MD, discusses the updated results of the MonarchE study of abemaciclib in patients with hormone receptor-positive, HER2-negative, breast cancer.

Manali A. Bhave, MD, assistant professor in the department of hematology and medical oncology at Emory University School of Medicine, discusses the updated results of the MonarchE study (NCT03155997) of abemaciclib in patients with hormone receptor-positive, HER2-negative, breast cancer.

The primary end point of the randomized phase 3 MonarchE trial of adjuvant endocrine therapy with abemaciclib (Verzenio) was invasive disease-free survival (IDFS) in the intent-to-treat (ITT) population. The updated results of a median 27-month follow-up showed that 90% of patients received abemaciclib for 2 years, and the 3-year IDFS was 88.8% with abemaciclib versus 83.4% with endocrine therapy alone, Bhave says.

The updated results analyzed the IDFS of patients with a high Ki-67 status. Cohort 1 enrolled patients regardless of Ki-67 status, while cohort 2 enrolled patients with a high Ki-67 status starting 1 year after cohort 1.

A Ki-67 of 20% or greater was found to be prognostic of high risk of disease recurrence, but abemaciclib showed benefit regardless of Ki-67 status. In the Ki-67–high population, there was a 4.5% absolute improvement in 2-year IDFS with abemaciclib. Ki-67­ status could serve as a biomarker for patients who will benefit from abemaciclib, according to Bhave.

TRANSCRIPTION:

0:08 | [In] the updated 27-month follow-up on these patients, in which 90% of patients actually completed the 2 years of abemaciclib, we did see that across the board, in cohort 1, there was an improvement in the IDFS. So, in the ITT population, we actually saw 3-year IDFS to be about 88.8% in patients with abemaciclib versus approximately 83% in patients who just received the standard endocrine therapy.

That benefit was actually higher if they had a Ki-67 that was 20% or greater. And those patients in that high-risk group with a Ki-67 of at least 20% actually had closer to about a 7% improvement in 3-year IDFS. So it looks like based off of the data, that Ki-67 was definitely prognostic of risk because patients with high Ki-67, overall, did slightly worse than those that had a low Ki-67, but may also be a marker to help us predict which patients absolutely benefit from the addition of abemaciclib to endocrine therapy.