Toxicity/Benefit Ratio Optimization of Chemotherapy in Colorectal Cancer (CRC) Patients by Determination of Individual Genotypic Determinants

This study intends to optimize a fluorouracil/irinotecan chemotherapy regimen by the identification of individual thymidylate synthase (TS) and UDP-glucuronosyltransferase 1 (UGT1A1) polymorphisms before the first administration. The results of this identification determine the chemotherapy type: high-dose irinotecan or not.