Validation of Capillary Microsampling for Therapeutic Drug Monitoring of CDK4/6 Inhibitors in Breast Cancer Patients (TDHOME)

Therapeutic drug monitoring (TDM) could serve as a valuable tool to minimize adverse events and maximize the efficacy of treatment in breast cancer patients receiving CDK4/6 inhibitors (ribociclib, abemaciclib, palbociclib). However, current TDM performed via venous blood draws can be inconvenient, especially for repeated sampling. This study aims to evaluate the reliability of capillary (fingertip) microsampling-which could be performed at home as a less invasive alternative to standard venous sampling for measuring residual drug concentrations. Five blood samples will be collected at a single time point during treatment, in accordance with the routine TDM schedule (the treatment duration will remain as per the prescribed CDK4/6 regimen): 4 capillary samples (using the VAMS Mitra device) including 2 samples collected by the study nurse who will train the patient to perform the 2 following samples him/herself; and 1 venous sample (5 mL heparinized tube).