5-fluorouracil (5-FU) and its prodrug capecitabine are Fluoropyrimidines, widely used in colorectal cancer. The prevention of adverse effects related to severe toxicity Fluoropyrimidines essentially involves pre-therapeutic screening for dihydropyrimidine dehydrogenase (DPD) deficiency, which must be carried out systematically before starting treatment with fluorouracil or since the joint HAS/I...