Pharmacology-driven Dosing of Fluoropyrimidines in Cancer Patients

Multiplex amplification of each sample is performed in an individual well of a 24-well plate using a Mastercycler platform. Template and Platinum Taq Polymerase (Life Technologies, Carlsbad, California) are added to an analyte-specific amplification mix (AutoGenomics Inc., Carlsbad, California). After amplification, the plate is transferred into the Infinity analyzer (AutoGenomics Inc.), followed by primer extension and hybridization of detection primers to individual oligonucleotides arrayed on the Bio-FilmChip. After hybridization, the BioFilmChips are washed and scanned in the Infiniti optics module. The Autogenomics DPYD assay is used to detect the presence of the four risk alleles (IVS14+G\>A, c.1679T\>G, HapB3/c.1129-5923C\>G and c.2846A\>T).

Repeated PK plasma sampling is done in all patients receiving 5FU. Blood is taken from venipuncture into one 5 ml heparin tube and into one 3 ml EDTA tube for the analysis of 5FU steady-state plasma concentrations in every (2-weekly) treatment cycle. Special attention has to be paid not to take PK blood from the site of drug infusion. For 5FU, PK sampling is done two hours before the calculated end of the 5FU pump on day 3 of every treatment cycle. The quantitative 5FU exposure expressed as the area-under-the concentration-time curve in mg•h/L is calculated from the measured steady-state plasma concentrations of 5FU and the duration of 5FU infusion. In all patients, 5FU doses for the second and subsequent administrations are adjusted to target a 5FU AUC between 20 and 30 mg•h/L