Data Analyst The Life Raft Group Star Tannery, Virginia, United States
Objective: Therapeutic drug monitoring (TDM) of imatinib in GIST provides actionable information beyond standard dosing but must be interpreted cautiously. We sought to develop a clinical algorithm that incorporates plasma level testing without compromising patient safety, while identifying patients receiving subtherapeutic exposure.
Methods: We designed a stepwise decision algorithm for patients with imatinib-sensitive GIST (excluding resistant genotypes such as PDGFRA D842V). The algorithm respects three core principles: (1) maintain the standard 400 mg dose when tolerated, (2) avoid dose reduction based solely on plasma level, and (3) ensure plasma levels remain above a personalized therapeutic threshold in the absence of unacceptable side effects. Personalized thresholds (800–1100 ng/mL) were defined from trial data and real-world studies.
Results: The algorithm begins with standard 400 mg dosing of imatinib. If toxicity is tolerable and plasma levels fall below the personalized threshold, dose escalation is considered. Dose reductions occur only with clinically significant toxicity and are independent of plasma levels. Thresholds from 800 to 1100 ng/mL are chosen based on treatment timing, tolerance, and clinical judgment.
Conclusion: This algorithm offers a safe and practical method to integrate imatinib plasma level testing into clinical care. It balances evidence-based thresholds with individualized patient factors to optimize long-term response while reducing toxicity risk.
