Dihydropyrimidine Dehydrogenase Phenotyping Using Pretreatment Uracil: A Note of Caution Based on a Large Prospective Clinical Study

Mirjam de With*, Jonathan Knikman, Femke M. de Man, Carin A.T.C. Lunenburg, Linda M. Henricks, André B.P. van Kuilenburg, Jan G. Maring, Maurice C. van Staveren, Niels de Vries, Hilde Rosing, Jos H. Beijnen, Dick Pluim, Anil Modak, Alex L.T. Imholz, Ron H.N. van Schaik, Jan H.M. Schellens, Hans Gelderblom, Annemieke Cats, Henk Jan Guchelaar, Ron H.J. MathijssenJesse J. Swen, Didier Meulendijks

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

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In clinical practice, 25–30% of the patients treated with fluoropyrimidines experience severe fluoropyrimidine-related toxicity. Extensively clinically validated DPYD genotyping tests are available to identify patients at risk of severe toxicity due to decreased activity of dihydropyrimidine dehydrogenase (DPD), the rate limiting enzyme in fluoropyrimidine metabolism. In April 2020, the European Medicines Agency recommended that, as an alternative for DPYD genotype-based testing for DPD deficiency, also phenotype testing based on pretreatment plasma uracil levels is a suitable method to identify patients with DPD deficiency. Although the evidence for genotype-directed dosing of fluoropyrimidines is substantial, the level of evidence supporting plasma uracil levels to predict DPD activity in clinical practice is limited. Notwithstanding this, uracil-based phenotyping is now used in clinical practice in various countries in Europe. We aimed to determine the value of pretreatment uracil levels in predicting DPD deficiency and severe treatment-related toxicity. To this end, we determined pretreatment uracil levels in 955 patients with cancer, and assessed the correlation with DPD activity in peripheral blood mononuclear cells (PBMCs) and fluoropyrimidine-related severe toxicity. We identified substantial issues concerning the use of pretreatment uracil in clinical practice, including large between-center study differences in measured pretreatment uracil levels, most likely as a result of pre-analytical factors. Importantly, we were not able to correlate pretreatment uracil levels with DPD activity nor were uracil levels predictive of severe treatment-related toxicity. We urge that robust clinical validation should first be performed before pretreatment plasma uracil levels are used in clinical practice as part of a dosing strategy for fluoropyrimidines.

Original languageEnglish
Pages (from-to)62-68
Number of pages7
JournalClinical Pharmacology and Therapeutics
Issue number1
Early online date9 Apr 2022
Publication statusPublished - Jul 2022

Bibliographical note

Funding Information:
C.A.T.C.L. was supported by an unrestricted grant from Roche Pharmaceuticals. L.M.H., C.A.T.C.L., and this study were sponsored by the Dutch Cancer Society (Alpe‐d’HuZes/KWF‐fund NKI2013‐6249). There was no involvement from any of the funding sources in the study design, data collection, analysis, or interpretation of the data.

Publisher Copyright:
© 2022 The Authors. Clinical Pharmacology & Therapeutics published by Wiley Periodicals LLC on behalf of American Society for Clinical Pharmacology and Therapeutics.


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