Fluoropyrimidine Tailored-dose Based on Uracil Concentration in Patients Treated for Digestive Carcinomas: Evaluation of Clinical Practice

Digestive carcinomas chemotherapies regimen are mostly based on fluoropyrimidine drugs (5-Fluorouracil (5-FU) or capecitabine). 5-FU is mainly catabolised by dihydropyrimidine dehydrogenase (DPD) and partial or complete DPD deficiency can cause severe adverse reactions. Different strategies have been proposed to predict DPD deficiency; the two main approaches are phenotyping the enzyme activity (directly or indirectly), or genotyping the four main polymorphisms associated with 5-FU-toxicity. In February 2018, the French medicines agency (Agence nationale de sécurité du médicament et des produits de santé, ANSM) recommended DPD genotyping for all patients receiving fluoropyrimidine-based treatment to improve its safety as compared to the European Medicines Agency (EMA)13 and others pharmacogenetics working group. In December 2018, a new guideline from the French cancer institute (Institut National Du Cancer, INCa) and the French health authority (Haute Autorité de Santé, HAS) recommended the measurement of the uracil blood level before genotyping DPD and dose adaptation if this level is greater than 16 ng/mL. The aim herein is to assess how this recommendation has been implemented in clinical routine. 5-FU displays a dose-response relationship regarding both its efficacy and its toxicity, did tailored-dose impair the treatment efficacy as it decreased the risk of toxicity? To address that matter we conducted a retrospective study to evaluate how fluoropyrimidine dosage is adapted to uracil concentration with an emphasis on how patients outcome were affected. We compared time to failure and overall survival between patients with an uracil concentration \ or = 16 ng/mL.