CYP2A6 and cancer: Similarly, studies of Japanese cancer patients showed that individuals with CYP2A6 genotypes consisting of two reduce-of-function variants exhibited lower tegafur clearance relative to individuals with one or zero reduce-of-function variants; however, this did not correspond to a lower exposure of patients to 5-fluorouracil, as the overall 5-fluorouracil area under the concentration-time curve did not correlate with that of tegafur [139,140].