Pharmacogenetic variants in the DPYD, TYMS, CDA and MTHFR genes are clinically significant predictors of fluoropyrimidine toxicity

Abstract

Background:Fluoropyrimidine drugs are extensively used for the treatment of solid cancers. However, adverse drug reactions are a major clinical problem, often necessitating treatment discontinuation. The aim of this study was to identify pharmacogenetic markers predicting fluoropyrimidine toxicity.Methods:Toxicity in the first four cycles of 5-fluorouracil or capecitabine-based chemotherapy were recorded for a series of 430 patients. The association between demographic variables, DPYD, DPYS, TYMS, MTHFR, CDA genotypes, and toxicity were analysed using logistic regression models.Results:Four DPYD sequence variants (c.1905+1G>A, c.2846A>T, c.1601G>A and c.1679T>G) were found in 6% of the cohort and were significantly associated with grade 3–4 toxicity (P<0.0001). The TYMS 3′-untranslated region del/del genotype substantially increased the risk of severe toxicity (P=0.0123, odds ratio (OR)=3.08, 95% confidence interval (CI): 1.38–6.87). For patients treated with capecitabine, a MTHFR c.1298CC homozygous variant genotype predicted hand–foot syndrome (P=4.1 × 10−6, OR=9.99, 95% CI: 3.84–27.8). The linked CDA c.−92A>G and CDA c.−451C>T variants predicted grade 2–4 diarrhoea (P=0.0055, OR=2.3, 95% CI: 1.3–4.2 and P=0.0082, OR=2.3, 95% CI: 1.3–4.2, respectively).Conclusion:We have identified a panel of clinically useful pharmacogenetic markers predicting toxicity to fluoropyrimidine therapy. Dose reduction should be considered in patients carrying these sequence variants.

Clinical validity of a DPYD‐based pharmacogenetic test to predict severe toxicity to fluoropyrimidines

“…19 Clues that other DPYD genetic polymorphisms (DPYDrs2297595, DPYD-rs1801160, DPYD-rs1801158, DPYDrs1801159, and DPYD-rs17376848) could have a role in the development of FL-related toxicities come from both DPWG guidelines 14 and looking at the most recent literature. 1,10 These polymorphisms have been previously observed in patients with low DPD enzymatic activity 20 and in some cases were associated to toxicity Grade 3 in the clinical setting. [21][22][23][24] The first aim of our study is to validate the specificity of three DPYD SNPs recommended by CPIC guidelines (i.e., DPYD-rs3918290, DPYD-rs55886062, and DPYD-rs67376798) in predicting the occurrence of severe toxicity events in a large set of oncological patients treated with FL in different clinical settings.…”

“…These data are consistent with previously published studies. 10,11 In particular, within the group of patients with Grade 3 toxicity, 44/95 (46.3%) developed non-hematological toxicities, 28/95 (29.5%) hematological toxicities and 23/95 (24.2%) both.…”

“…Up to date, 160 single nucleotide polymorphisms (SNPs) that alter the DPD aminoacids sequence have been identified within the gene (DPYD) codifying for this enzyme 5,6 and many clinical studies have been trying to investigate their association with FL-related severe toxicities. 3,[7][8][9][10][11] Recently the discussion in the scientific community about the clinical effectiveness of pharmacogenetics has given rise to the publication of drug dosing guidelines with indications and recommendations about drug-related genetic tests and …”

“…Up to date, 160 single nucleotide polymorphisms (SNPs) that alter the DPD aminoacids sequence have been identified within the gene (DPYD) codifying for this enzyme 5,6 and many clinical studies have been trying to investigate their association with FL-related severe toxicities. 3,[7][8][9][10][11] Recently the discussion in the scientific community about the clinical effectiveness of pharmacogenetics has given rise to the publication of drug dosing guidelines with indications and recommendations about drug-related genetic tests and their integration in the clinical routine. In particular, the Clinical Pharmacogenetics Implementation Consortium (CPIC) 12,13 and the Dutch Pharmacogenetics Working Group of the Royal Dutch Association for the Advancement of Pharmacy (DPWG) 14 have published drug-specific guidelines based on the patient genotype.…”

“…15 Particularly, CPIC guidelines recommend choosing an alternative drug for patients who present two variant alleles (compound heterozygous or homozygous variant genotypes) and a 50% reduction of FL starting dose for patients with only one variant allele (heterozygous genotype) for any of these SNPs (http://www.pharmgkb.org/guideline/PA166122686). 1 Despite a number of studies and meta-analyses assessed the association between the DPYD genotyping test and the occurrence of severe toxicity related to FL, [8][9][10][11][16][17][18] its use is still scarcely widespread among clinicians possibly because the rarity of the considered DPYD SNPs renders the three DPYD-markers test sensitivity rather low. In addition, only scanty information is available about the cost-effectiveness of this analysis.…”