ERBB2 and breast cancer: The CDK 4/6i abemaciclib was recently approved in the adjuvant setting based on the results of the MonarchE trial, which reported significant benefits in invasive disease-free survival (iDFS), when it was added to adjuvant AI therapy in patients with HR+, HER2− early high-risk BC (5-year iDFS rates: 83.6% vs. 76.0%, HR 0.680; 95% confidence interval 0.599–0.772) [19].