Personalization of oral small molecule anticancer drug doses based on
individual patient blood drug levels, also known as therapeutic drug
monitoring or TDM, has the potential to significantly improve the
effectiveness of treatment by maximizing drug efficacy and minimize
toxicity. However, this option has not yet been widely embraced by the
oncology community. Some reasons for this include increased logistical
complexity of dose individualization, the lack of clinical laboratories
that measure small molecule drug concentrations in support of patient
care, and the lack of reimbursement of costs. However, the main obstacle
may be the lack of studies clearly demonstrating that monitoring of oral
small molecule anticancer drug levels actually improves clinical
outcomes. Without unequivocal evidence in support of TDM-guided dose
individualization, especially demonstration of improved survival with
TDM in randomized controlled trials, wide acceptance of this approach by
oncologists and reimbursement by insurance companies is unlikely, and
patients may continue to suffer as a result of receiving incorrect drug
doses. This article reviews the current status of therapeutic drug
monitoring of oral small molecule drugs in oncology and intends to
provide strategic insights into the design of studies for evaluating the
utility of TDM in this clinical context.