CDK4 and neoplasm: In this type of tumor, CDK4/6 inhibitors palbociclib, ribociclib, and abemaciclib have shown an improvement in progression-free survival (PFS) when combined with endocrine therapy (ET) [2,3,4]; therefore, a combination of ET and a CDK4/6 inhibitor serves as the standard of care in advanced or metastatic cases.