DPYD genotype-guided fluoropyrimidines dose: is it ready for prime time?

For over 50 years, fluoropyrimidines have been the cornerstone of anticancer drugs for various types of solid cancers. Treatment with these drugs -5-fluorouracil (FU) and its oral prodrugs, capecitabine and tegafur -is generally well-tolerated, except in a small proportion of patients who develop severe and life-threatening early toxicity. This toxicity is mainly associated with a deficiency of the primary fluoropyrimidine detoxifying enzyme, dihydropryrimidine dehydrogenase (DPD) [1]. The drug labels of FU and capecitabine state DPD deficiency as a contraindication, but they give no warning for the 3-8% of the population who are partially DPD deficient.