New therapeutic option for patients with high-risk HR-positive, HER2-negative breast cancer
Abemaciclib in combination with standard adjuvant endocrine therapy (ET) achieved its primary objective in the MonarchE study: an increase in invasive disease-free survival (iDFS), significantly decreasing the risk of breast cancer recurrence or death compared to adjuvant TE alone.
Abemaciclib is an oral target therapy that inhibits the enzymes CDK4 and CDK6 and has showed a statistically significant reduction in the recurrence rate of high-risk breast cancer with positive (RH +) and negative HER2 (HER2-) hormone receptor. The safety profile was consistent with that observed in other studies in the MONARCH clinical program.
These results are from a previously planned interim analysis of MonarchE phase III, a multicenter, randomized and open clinical trial involving 5,637 patients with initial high-risk breast cancer, RH +, HER2-. Randomization was carried out 1:1 for abemaciclib (150 mg dose twice daily) in combination with TE or TE alone.
The abemaciclib treatment arm continued for 2 years or until patients meet the discontinuation criteria. Standard hormone therapy was administered for a minimum of 5 years, if considered to be clinically appropriate.
The main objective was disease-free invasive disease (iDFS), which in monarchE is defined as the period of time before any cancer returns or the patient’s death. Secondary objectives include long-distance recurrence-free survival, overall survival, safety, pharmacokinetics and health outcomes.
High risk was specifically defined as women (in any state of menopause) and men with resected initial breast cancer HR + and HER2-, with ≥ 4 positive axillary lymph nodes confirmed by pathology (pLN) or 1 to 3 pLN affected with at least one of the risk characteristics:
• primary size of the invasive tumor ≥5 cm;
• histological grade 3;
• Ki-67 ≥ 20%.
MonarchE will continue until the end date, estimated for June 2027. At the time of the interim analysis, the SLDi results are considered definitive. All patients in the study will be followed up to primary analysis and beyond in order to assess overall survival and other parameters.
Abemaciclib is indicated for the treatment of patients with advanced or metastatic breast cancer for HR +, HER2-:
1. in combination with an aromatase inhibitor for the treatment of postmenopausal women as initial hormone therapy;
2. in combination with fulvestrant for women with disease progression after hormone therapy;
3. as monotherapy for the treatment of adult patients with disease progression after hormonal treatment and previous chemotherapy in the metastatic context.