Phase I evaluation of carboplatin by use of a dosing strategy based on a targeted area under the platinum concentration-versus-time curve and individual glomerular filtration rate in cats with tumors.

Abstract

OBJECTIVE: To determine whether a carboplatin dose calculation that is based on a targeted area under the concentration-versus-time curve (AUC(Target)) and individual glomerular filtration rate (GFR) accurately predicts carboplatin-associated myelotoxicoses in tumor-bearing cats, and to determine the maximum tolerated AUC(Target). ANIMALS: 32 cats with tumors. PROCEDURES: In each cat, plasma clearance of technetium Tc 99m-labeled diethylenetriaminepentaacetic acid was measured to assess GFR. Carboplatin was administered IV. The dose was calculated by use of an equation as follows: Dose = AUC(Target) x 2.6 x GFR x body weight. Initial AUC(Target) was 2.0 min.mg.mL(-1) and was increased in increments of 0.50 min.mg.mL(-1) in cohorts of 3 cats. To assess myelotoxic effects, CBCs were performed weekly for > or = 4 weeks. Following identification of the maximum tolerated AUC(Target), additional cats were treated at that AUC(Target) and plasma platinum concentrations were measured in 6 cats. RESULTS: The AUC(Target) values ranged from 2.0 to 3.0 min.mg.mL(-1). Neutropenia was the dose-limiting toxicosis, and the maximum tolerated AUC(Target) was 2.75 min.mg.mL(-1). Nineteen cats received this dose of carboplatin; 13 became neutropenic, but only 1 developed severe neutropenia (< 500 neutrophils/microL), and none had neutropenia-associated clinical signs. In the cats that had plasma platinum concentration determined, the difference between AUC(Target) and the measured value ranged from -0.23 to 0.31 min.mg.mL(-1) (median, 0.20 min.mg.mL(-1)). CONCLUSIONS AND CLINICAL RELEVANCE: In cats, carboplatin-associated myelotoxicoses were accurately and uniformly predicted by use of the proposed dosing strategy. The maximum tolerated AUC(Target) for a single dose of carboplatin was 2.75 min.mg.mL(-1).