Creatinine clearance as a predictor of ultrafilterable platinum disposition in cancer patients treated with cisplatin: relationship between peak ultrafilterable platinum plasma levels and nephrotoxicity.

Ultrafilterable platinum (UP) disposition was studied in 22 cancer patients receiving their first course of cisplatin (50 to 140 mg/m2) by two-hour infusion. UP plasma and urinary platinum levels were quantitated using a high-performance liquid chromatographic (HPLC) assay, which was selective for cisplatin and active platinum metabolites. Creatinine clearance was determined in all patients at the time of the pharmacokinetic studies and ranged from 58 to 214 mL/min. Creatinine clearance was a poor predictor of UP disposition in patients, probably as a consequence of the complex renal clearance mechanism for UP in the human kidney, which involves both tubular secretion and reabsorption. However, the peak plasma level of UP was closely related to the area under curve (AUC) of UP (r2 = .831), P less than .0001) and was significantly correlated with the decline in creatinine clearance observed after four courses of cisplatin therapy to 12 of the patients (r2 = .727, P less than .005). Cisplatin dose and the AUC of UP were less satisfactory predictors of the change in creatinine clearance with four courses of therapy (r2 = .488, P less than .025 and r2 = .623, P less than .005). The large interpatient variability in all the parameters of cisplatin disposition measured in this study suggested that there may be a role for individualization of cisplatin dosage based on a peak level obtained in the first course of therapy. Longer term infusion of cisplatin could also be justified.