MKI67 and breast cancer: In MonarchE phase III trial, abemaciclib (cyclin-dependent kinase 4 and 6 inhibitor plus ET demonstrated superior invasive DFS (iDFS) compared with ET alone (hazard ratio: 0.75; 95% CI, 0.60 to 0.93, p = 0.01), with 2-year iDFS rates of 92.2% versus 88.7%, respectively in patients with HR-positive, HER2 negative, high-risk (≥ 4 positive nodes; 1–3 nodes involved and at least one of the following: tumor size ≥5 cm, histologic grade 3, or central Ki-67 ≥20%) early BC, in adjuvant settings (106).