The reported incidence of hematological adverse events associated with CDK4/6 inhibitors is low and the severity is milder: i) Neutropenia, palbociclib 79.5%, abemaciclib 80% and dalpiciclib 99%; ii) leucopenia, palbociclib 39%, abemaciclib 76.1% and dalpiciclib 98.3%; iii) anemia, palbociclib 24.1%, abemaciclib 62% and dalpiciclib 66.9%; and iv) thrombocytopenia, palbociclib 15.5%, abemaciclib 44.4% and dalpiciclib 53.3% (16,45,46). This evidence concerns the gene CDK4 and anemia.