Artificial increase of uracilemia during fluoropyrimidine treatment can lead to DPD deficiency misinterpretation

Each year in France, >75 000 patients receive fluoropyrimidines, including 5-fluorouracil (5-FU) and its oral prodrug capecitabine (Xeloda), to treat digestive, breast and head and neck cancers.1 Among them, ∼20% will experience severe hematological and digestive toxicities and <2% will have a fatal outcome in the first two cycles. A part of these toxicities may result from a deficiency in dihydropyrimidine dehydrogenase (DPD) which catabolizes the endogenous uracil (U) into dihydrouracil (UH2) as well as 5-FU. In 2018, French Health Authorities [Haute Autorité de Santé (HAS) and Institut National du Cancer, (INCa)] recommended the evaluation of the enzymatic activity of DPD by measuring th…