The T allele of rs3918290 is assigned no function by CPIC. Patients with the CC genotype and cancer who are treated with capecitabine, a fluoropyrimidine-based chemotherapy, may have decreased, but not absent, risk and reduced severity of drug toxicity as compared to patients with the TT or CT genotype. However, conflicting evidence has been reported. Other genetic and clinical factors may also influence risk of drug toxicity.