Most radiolabeled biological samples require extensive sample preparation to reduce quenching interference before quantification of radioactivity is possible. Clearly, a more rapid and simple method ensuring a constant count rate and optimal counting efficiency has important advantages. We report on the development and analytical method validation of a rapid and simple combustion method to quantify [3H]docetaxel excreted in human feces and urine. A 3-day validation procedure was performed; quality control (QC) samples, prepared in blank feces and urine, were combusted 5 times and aliquots of the produced tritiated combustion water were counted in a liquid scintillation counter. The validation runs demonstrated adequate precision (below 7.6%) across all QC levels. Sensitivity at the lowest QC level was excellent and recovery of radioactivity constant (ranging from 85 to 91.8%). Clinical applicability of the method was tested in a cancer patient receiving docetaxel and a tracer amount of [3H]docetaxel; during the first 72 h after [3H]docetaxel infusion, 60% of total radioactivity was excreted in the collected feces and urine, which is within the expected range. Combustion of tritiated feces and urine samples is a simple, rapid, sensitive, precise and reproducible method with high recovery. It can be applied to quantify [3H]docetaxel excretion after i.v. administration.

Combustion method, Docetaxel, Liquid scintillation counting, Tritium, Validation,
Anti-Cancer Drugs
Erasmus MC: University Medical Center Rotterdam

Engels, F.K, Buijs, D, Loos, W.J, Verweij, J, Bakker, W.H, & Krenning, E.P. (2006). Quantification of [3H]docetaxel in feces and urine: Development and validation of a combustion method. Anti-Cancer Drugs, 17(1), 63–67. doi:10.1097/01.cad.0000185183.57357.c2