The increased immunogenicity induced by CDK 4/6 inhibitors contributes to these agents’ anti-tumor activity and is the prominent means by which they indirectly cause tumor cell death [14]. Food and Drug Administration (FDA) approved palbociclib in 2015 for advanced breast cancer and thus has become a powerful therapeutic tool for advanced, ER+ HER2- breast cancer treatment. This evidence concerns the gene ESR1 and neoplasm.