Escalation of adjuvant endocrine therapy for early hormone-dependent HER2-negative breast cancer: to whom, when and why?

This review presents the evolution of adjuvant endocrine therapy for early hormone-dependent HER2-negative breast cancer, describes late relapse phenomenon, provides clinical rationale for escalation of treatment, analyzes the key stages of the metastatic cascade, and provides a scientific rationale for the introduction of CDK4/6 inhibitors into adjuvant treatment regimens. The main results of two large randomized studies of therapy including abemaciclib (MonarchE) and ribociclib (NATALEE) in patients with early stages of hormone-dependent HER2-negative breast cancer are presented; the oncological results of escalation of treatment and the safety of therapy are assessed.