In patients with HR+/HER2− advanced breast tumors, cyclin-dependent kinase 4/6 inhibitors (CDK4/6 inhibitor), including palbociclib, ribociclib, and abemaciclib, have significantly improved the outcomes with a median PFS ranging from 14 to over 25 months [5,6,7,8,9]. The gene discussed is CDK4; the disease is breast neoplasm.