In conclusion, DPD-deficiency is recognized to be a leading cause of severe fluoropyrimidine toxicity [6,17] and a recent prospective study has demonstrated that fluoropyrimidine dose-adjustment based on upfront DPYD *2A genotyping (dose reduced by >50% in heterozygous carriers) was feasible, cost-effective, and improved safety [43]. The gene discussed is DPYD; the disease is dihydropyrimidine dehydrogenase deficiency.