Applications and challenges in therapeutic drug monitoring of cancer treatment: A review

Most anticancer agents show wide variability in pharmacokinetics (PK) and have a narrow therapeutic index which makes fixed dosing suboptimal. To achieve the best therapeutic outcomes with these agents, many studies have postulated using PK or therapeutic drug monitoring (TDM)-guided dosing. However, multiple factors contribute to the variability in PKs making the application of TDM in practice challenging. Also, despite the known association with clinical outcomes, standard guidelines on PK-guided dosing are lacking for most agents. Understanding the factors that contribute to PK variability and their impact is essential for dose individualization. The purpose of this review is to discuss the factors that contribute to the PK variability of anticancer agents and the challenges faced in practice when individualizing doses for certain widely used agents. Searching the literature has identified several gaps and efforts are needed to ensure better targeting of cancer therapeutics.