The A allele of rs59086055 is assigned a no function allele by CPIC. There is currently only available evidence regarding the association between the rs59086055 AG heterozygote and fluorouracil toxicity. However, patients with the rs59086055 AA genotype and cancer who are treated with fluorouracil, a fluoropyrimidine-based chemotherapy, may have increased risk of drug toxicity as compared to patient with the GG genotype. Other genetic and clinical factors may also influence risk of drug toxicity.