New advances in DPYD genotype and risk of severe toxicity under capecitabineReport as inadecuate

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Deficiency in dihydropyrimidine dehydrogenase DPD enzyme is the main cause of severe and lethal fluoropyrimidine-related toxicity. Various approaches have been developed for DPD-deficiency screening, including DPYD genotyping and phenotyping. The goal of this prospective observational study was to perform exhaustive exome DPYD sequencing and to examine relationships between DPYD variants and toxicity in advanced breast cancer patients receiving capecitabine.


Two-hundred forty-three patients were analysed 88.5% capecitabine monotherapy. Grade 3 and grade 4 capecitabine-related digestive and-or neurologic and-or hemato-toxicities were observed in 10.3% and 2.1% of patients, respectively. DPYD exome, along with flanking intronic regions 3’UTR and 5’UTR, were sequenced on MiSeq Illumina. DPD phenotype was assessed by pre-treatment plasma uracil U and dihydrouracil UH2 measurement.


Among the 48 SNPs identified, 19 were located in coding regions, including 3 novel variations, each observed in a single patient among which, F100L and A26T, both pathogenic in silico. Combined analysis of deleterious variants *2A, I560S *13 and D949V showed significant association with grade 3–4 toxicity sensitivity 16.7%, positive predictive value PPV 71.4%, relative risk RR 6.7, p<0.001 but not with grade 4 toxicity. Considering additional deleterious coding variants D342G, S492L, R592W and F100L increased the sensitivity to 26.7% for grade 3–4 toxicity PPV 72.7%, RR 7.6, p<0.001, and was significantly associated with grade 4 toxicity sensitivity 60%, PPV 27.3%, RR 31.4, p = 0.001, suggesting the clinical relevance of extended targeted DPYD genotyping. As compared to extended genotype, combining genotyping 7 variants and phenotyping U>16 ng-ml did not substantially increase the sensitivity, while impairing PPV and RR.


Exploring an extended set of deleterious DPYD variants improves the performance of DPYD genotyping for predicting both grade 3–4 and grade 4 toxicities digestive and-or neurologic and-or hematotoxicities related to capecitabine, as compared to conventional genotyping restricted to consensual variants *2A, *13 and D949V.

Author: Marie-Christine Etienne-Grimaldi, Jean-Christophe Boyer, Christophe Beroud, Litaty Mbatchi, André van Kuilenburg, Christine Bobi



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