Relationship between 5-fluorouracil exposure and outcome in patients receiving continuous venous infusion with or without concomitant radiotherapy

What is already known about this subjectDihydropyrimidine dehydrogenase (DPD) deficiency is currently evaluated as a means of identifying patients with a risk of toxicity during 5-fluorouracil (5-FU) treatment.Therapeutic drug monitoring (TDM) is a complementary tool already shown to be useful for doses of 1000 mg m−2 day−1.We carried out the first analysis of the concentration – effect relationships of 5-FU administered at a dose of 600 mg m−2 day−1 with concomitant radiotherapy.What this study addsNo relationship was found between exposure and toxicity for 5-FU administered at a dose of 600 mg m−2 day−1 with concomitant radiotherapy.The use of TDM to improve tolerance to this treatment protocol is not supported by our data.This study confirms the existence of an exposure – toxicity relationship for a dose of 1000 mg m−2 day−1 and has developed a simplified sampling strategy to make TDM easier to implement with this dose schedule