Body-Surface Area–Based Dosing Does Not Increase Accuracy of Predicting Cisplatin Exposure

Abstract

PURPOSE: Most anticancer drugs are dosed based on body-surface area (BSA) to reduce interindividual variability of drug effects. We evaluated the relevance of this concept for cisplatin by analyzing cisplatin pharmacokinetics obtained in prospective studies in a large patient population. PATIENTS AND METHODS: Data were obtained from 268 adult patients (163 males/105 females; median age, 54 years [range, 21 to 74 years]) with advanced solid tumors treated in phase I/II trials with cisplatin monotherapy or combination chemotherapy with etoposide, irinotecan, topotecan, or docetaxel. Cisplatin was administered either weekly (n = 93) or once every 3 weeks (n = 175) at dose levels of 50 to 100 mg/m2 (3-hour infusion). Analysis of 485 complete courses was based on measurement of total and non–protein-bound cisplatin in plasma by atomic absorption spectrometry. RESULTS: No pharmacokinetic interaction was found between cisplatin and the anticancer drugs used in combination therapies. A linear correlation was observed between area under the curves of unbound and total cisplatin (r = 0.63). The mean plasma clearance of unbound cisplatin (CLfree) was 57.1 ± 14.7 L/h (range, 31.0 to 116 L/h), with an interpatient variability of 25.6%. BSA varied between 1.43 and 2.40 m2 (mean, 1.86 ± 0.19 m2), with an interpatient variability of 10.4%. When CLfree was corrected for BSA, interindividual variability remained in the same order (23.6 v 25.6%). Only a weak correlation was found between CLfree and BSA (r = 0.42). Intrapatient variability in CLfree, calculated from 90 patients was 12.1% ± 7.8% (range, 0.30% to 32.7%). CONCLUSION: In view of the high interpatient variability in CLfree relative to variation in observed BSA, no rationale for continuing BSA-based dosing was found. We recommend fixed-dosing regimens for cisplatin.