The A allele of this variant, when measured on plus chromosomal strand, is assigned decreased function by CPIC. Patients with the AT genotype and cancer who are treated with fluorouracil, a fluoropyrimidine-based chemotherapy, may have increased risk and increased severity of drug toxicity as compared to patients with the TT genotype. However, conflicting evidence has been reported. Other genetic and clinical factors may also influence risk of drug toxicity.