New treatment strategy for early hormone receptor-positive HER2-negative breast cancer: updated results of adjuvant abemaciclib trial in operable and locally advanced breast cancer

Abemaciclib is an oral inhibitor 4 and 6 (CDK4/6). Abemaciclib differs from other drugs in this group in suppression spectrum of cyclin-dependent kinases and is proven to improve survival rates in different treatment lines of metastatic breast cancer. In randomized clinical trials 3rd phase in patients with early hormone-dependent HR+ HER2 negative breast cancer high risk of progression abemaciclib in conjunction with hormone therapy significantly improves invasive disease-free survival (IDFS) and distant relapse-free survival (DRFS). Long- term outcome studies monarchE with 5 – year follow – up of patients showed that abemaciclib adding to ET increases 5-year IDFS from 76 to 83.6% (HR0.680; 95% CI 0.599 to 0.772; p <0.001) and 5-year DRFS from 79.2% to 86.0% (HR0.675; 95% CI 0.588 to 0.774; p <0.001). Adverse events of 3rd degree and higher are registrated in 45.5% of patients in abemaciclib group and in 12,7% in control group and mainly presented by neutropenia (18.6 and 0.7%) and diarrhea (7,6 and 0.1%). Toxicity profile was expected and controlled. The reasonable dose reduction of abemaciclib did not lead to deterioration of long-term treatment result.