This invention directed to methods for treating select RB-positive cancers and other Rb-positive abnormal cellular proliferative disorders using CDK4/6 inhibitors in specific dosing and combination or alternation regimes. In one aspect, treatments of select RB-positive cancers are disclosed using specific CDK4/6 inhibitors in combination or alternation with another chemotherapeutic, for example, an additional kinase inhibitor, PD-1 inhibitor, or BCL-2 inhibitor, or combination thereof.
