The A allele of this variant, when measured on plus chromosomal strand, is assigned decreased function by CPIC. Patients with the TT genotype and cancer who are treated with fluorouracil, a fluoropyrimidine-based chemotherapy, may have decreased, but not absent, risk and reduced severity of drug toxicity as compared to patients with the AA or AT genotypes. However, conflicting evidence has been reported. Other genetic and clinical factors may also influence risk of drug toxicity.