Therapeutic drug monitoring of etoposide in a 14-day infusion for non-small-cell lung cancer

Individualised Cancer Chemotherapy: Strategies and Performance of Prospective Studies on Therapeutic Drug Monitoring with Dose Adaptation

Therapeutic drug monitoring (TDM) is increasingly used in clinical practice for the optimisation of drug treatment. Although pharmacokinetic variability is an established factor involved in the variation of therapeutic outcome of many chemotherapeutic agents, the use of TDM in the field of oncology has been limited thus far. An important reason for this is that a therapeutic index for most anticancer agents has not been established; however, in the last 20 years, relationships between plasma drug concentrations and clinical outcome have been defined for various chemotherapeutic agents. Several attempts have been made to use these relationships for optimising the administration of chemotherapeutics by applying pharmacokinetically guided dosage. These prospective studies, individualising chemotherapy dose during therapy based on measured drug concentrations, are discussed in this review. We focus on the way a target value is defined, the methodologies used for dose adaptation and the way the performance of the dose-adaptation approach is evaluated. Furthermore, attention is paid to the results of the studies and the applicability of the strategies in clinical practice. It can be concluded that TDM may contribute to improving cancer chemotherapy in terms of patient outcome and survival and should therefore be further investigated.

Therapeutic drug monitoring in 21-day oral etoposide treatment for lung cancer

We aimed to determine whether or not therapeutic drug monitoring is applicable to 21-day oral etoposide treatment for lung cancer. As the starting dose, a 25-mg capsule of etoposide was taken orally three times daily (75 mg/body). To achieve the target concentration range of 1.0 to 1.5 micrograms/ml, the dose was changed to two (50 mg/body) or four (100 mg/body) times a day from day 5, depending on the mean concentration obtained on days 3 and 4 (Cbefore). The mean concentration was calculated by use of a limited sampling model we constructed previously. Among 26 courses in 15 patients, two patients experienced grade 4 leukopenia plus neutropenia, and one of them died on day 20. Because nausea/emesis prevented the planned dose escalation in one patient, we excluded two courses of this patient from the pharmacokinetic analysis of dose modification. Among 5 courses with dose reduction, the Cbefore of 1.7 +/- 0.1 (microgram/ml, mean +/- SE) was decreased to 1.3 +/- 0.2 after day 5 (Cafter). Among 7 courses with dose escalation, the Cbefore of 0.9 +/- 0.0 was increased to the Cafter of 1.2 +/- 0.1. Among the remaining 12 courses without dose modification, the Cbefore and the Cafter were 1.2 +/- 0.0 and 1.3 +/- 0.1, respectively. Hematologic toxicities tended to correlate with the drug concentration. TDM is thus applicable to oral etoposide given according to this schedule, and a larger study is now needed to confirm that the therapeutic efficacy is improved by introducing TDM.