Assessment of Interpatient and Intrapatient Variability of Dasatinib and Imatinib Concentrations in Patients With Chronic Myeloid Leukemia via Volumetric Absorptive Microsampling at Home

Background: Therapeutic drug monitoring (TDM) of tyrosine kinase inhibitors (TKIs) may optimize treatment outcomes in chronic myeloid leukemia (CML). Conventional blood sampling is invasive and logistically demanding, whereas finger-prick microsampling, such as volumetric absorptive microsampling (VAMS), offers a less invasive, patient-centric alternative that can be performed at home, which is particularly relevant for trough-level monitoring and frequent sampling. This study evaluated the feasibility of VAMS-based home-sampling for dasatinib and imatinib in patients with CML and assessed interindividual and intraindividual variability in trough levels. Methods: Patients were trained to collect replicate capillary VAMS samples at their home immediately before TKI intake, every 3 days, on 4 occasions. Collected samples were returned to the laboratory via prepaid mail. In addition, participants completed a questionnaire to assess the user-friendliness and feasibility of home-sampling. Results: Forty-nine patients were included (dasatinib, 32; imatinib, 17), and 47 sets of VAMS samples were received. Ninety percent of the home-collected VAMS samples were of good quality, with an acceptable analytical variability between replicates. Most participants reported a positive experience with home-sampling. The results confirmed large interpatient variations in dasatinib and imatinib trough levels and demonstrated that within a patient, trough levels may vary substantially, particularly for dasatinib. Conclusions: Home-based VAMS sampling for dasatinib and imatinib TDM in patients with CML is feasible, well received, and reliable. The observed interpatient and intrapatient variability in trough levels underscores the potential clinical value of TDM in guiding individualized therapy and in the longitudinal monitoring of patients.