Validation of a limited sampling model for carboplatin in a high-dose chemotherapy combination

A limited sampling model for the estimation of the carboplatin area under the concentration versus time curve (AUC), as developed by Sørensen et al., was validated prospectively for the use in a high-dose combination chemotherapy schedule. The model allows an estimation of the AUC on the basis of only one timed plasma drug concentration, sampled at exactly 2.75 h after a 1-h carboplatin infusion. Pharmacokinetic curves were obtained from nine patients receiving carboplatin (400 mg/m2 per day) combined with cyclophosphamide (1500 mg/m2 per day), thiotepa (120 mg/m2 per day), and mesna (3 g/day) for 4 consecutive days. Peripheral blood stem-cell transplantation (PBSCT) was performed 3 days later to restore hematopoiesis. Using this combination of high doses, the model proved to be unbiased (MPE -3.40%; SE, 1.22%) and highly precise [root mean squared prediction error (RMSE), 5.15%; SE, 0.17%] for estimation of the AUC during 4 consecutive days. The validated limited sampling model provides a starting point for future pharmacokinetic studies in a larger population of patients, which might lead to more insight into the relationships with the pharmacodynamic outcome of carboplatin and may help in achieving more rational dosing of patients on the basis of an AUC determination.