CDK4 and breast cancer: Previous meta-study results show CDK4/6 improves OS in breast cancer patients (37), but OS data remain incomplete, only some studies of Ribociclib and Palbociclib have reported the results of OS, with risk reductions of 26% [HR 0.74 (95%CI: 0.65, 0.85), P<0.00001] and 17% [HR 0.83 (95%CI: 0.68, 1.02), P<0.00001], respectively.