Making TDM work to optimize cancer chemotherapy: a multidisciplinary team approach

Several factors can limit the use of therapeutic drug monitoring (TDM) for cancer chemotherapeutic agents, including poorly defined concentration-effect relationships for many antineoplastic agents. This is further complicated by cancer being a highly heterogeneous group of diseases, each of which may have a unique concentration-effect relationship for any given drug or drug combination. Nonetheless, TDM clearly has the potential to improve the clinical use of antineoplastic agents, most of which have very narrow therapeutic indices and highly variable pharmacokinetics. A substantial body of literature accumulating during the past 15 years demonstrates relationships between systemic exposure to various anticancer drugs and their toxic or therapeutic effects. This review highlights selected studies that illustrate concentration-effect relationship for the antineoplastic effects of 5-fluorouracil, mercaptopurine, and methotrexate. A much larger number of pharmacodynamic studies have established the relationship between serum concentration and dose-limiting toxicities for anticancer agents, including epipodophyllotoxins, platinum compounds, camptothecin, anthracyclines, and antimetabolites. In this review we will focus on anticancer drugs for which the pharmacodynamics of antineoplastic effects have been elucidated. We will also address issues critical to the optimal use of TDM in a clinical setting, which requires effective participation by a multidisciplinary team of professionals.