A single 24-hour plasma sample does not predict the carboplatin AUC from carboplatin-paclitaxel combinations or from a high-dose carboplatin-thiotepa-cyclophosphamide regimen

Purpose: It has been observed that the area under the free carboplatin conc entration in plasma ultrafiltrate versus time curve (AUC) is related to tox icity and tumour response. For this reason, it can be important to measure the carboplatin AUC and subsequently adjust the dose to achieve a predefine d target AUG. The use of limited sampling strategies enables relatively sim ple measurement and calculation of actual carboplatin AUCs. Methods: We stu died the performance of a limited sampling model, based on a single 24-h sa mple (the Ghazal-Aswad model), in 52 patients who received carboplatin in t wo different chemotherapy regimens (a carboplatin-paclitaxel combination an d a high-dose carboplatin-thiotepa-cyclophosphamide combination). Results: The measured mean AUC in our population was 4.1 min . mg/ml (median 3.9, ra nge 1.9-6.3, SD 1.0 min . mg/ml). With the limited sampling model, the pred icted mean AUC was 4.4 min . mg/ml (median 4.2, range 2.4-8.4, SD 1.2 min m g/ml). Statistical analysis revealed that the model was slightly biased (MP E%, 6.5%), but imprecise (RMSE%, 20.6%) in our study population. Conclusion : Although easy and attractive to use, the Ghazal-Aswad formula is not prec ise enough to predict the carboplatin AUG, and needs to be evaluated prospe ctively in other patient populations.