CDK4 and chronic kidney disease: At the time of CDK4/6 inhibitor initiation, sCr was 1.25 mg/dL (normal range value 0.6-1.3mg/dL), corresponding to a 45 mL/min/1.73 m2 eGFR calculated by the 2021 CKD-EPI creatinine equation, without evidence of proteinuria (stage G3bA1 chronic kidney disease (CKD)).