Therapeutic Drug Monitoring of Oral Targeted Anticancer Drugs: Achievements, Experiences, Challenges, and the Path Forward

Background: – The introduction of oral targeted anticancer drugs has revolutionized anticancer treatments. Exposure to these drugs is often affected by individual, disease, or drug characteristics. As a result, these drugs often show high interpatient variability in drug exposure. Therapeutic drug monitoring (TDM) is a useful tool for addressing the underlying problems of this variability: unnecessary toxicity and suboptimal efficacy. In this overview article, the authors discuss achievements, experiences, and current challenges of TDM for oral targeted anticancer drugs in clinical practice and highlight directions for future research.Methods: – PubMed was searched for relevant clinical studies on TDM of oral targeted anticancer drugs.Results: – TDM for oral targeted anticancer drugs should be routinely conducted when exposure–response or exposure–toxicity relationships are established to avoid underexposure or overexposure, and on indication, to achieve reasonable drug exposure in individual cases when exposure is suspected to be outside the therapeutic index. The current challenges in supporting TDM for oral targeted anticancer drugs include the absence of compelling prospective evidence on clinical outcomes and the paucity of pharmacokinetic data for newly approved drugs. Future studies should address these issues.Conclusions: – Advancing TDM of oral targeted anticancer drugs requires finding the right drugs, the right patients, the right drug exposure targets, the right sampling methods, and the right evidence. Addressing these issues can facilitate clinical implementation and ensure that TDM can be applied for both older and newly approved oral targeted anticancer drugs.