Furthermore, chemoprevention using daily low-dose aspirin to reduce the risk of colorectal tumor recurrence tended to be inversely dependent on the predicted enzymatic activities of the CYP2A6 phenotype [based on the genotypes: CYP2A6*1/*1,*7,*9 (normal) and CYP2A6*4,*7,*9/*4,*7,*9 and *1/*4 (impaired)] among a Japanese cohort without familial adenomatous polyposis (Fig. 1e, f). Here, CYP2A6 is linked to colorectal neoplasm.