These results, presented in spite of their significance, are the result of a retrospective study that is subject, as a minimum, to selection bias. It therefore seemed important to make a prospective study, centered on digestive cancers. The prospective nature will limit selection bias and restriction to digestive cancers in which fluoropyrimidines have a main function and limit confunding biases. The selection of the first and second lines of palliative chemotherapy will increase the population studied and thus the power of the statistical analysis.