It was demonstrated in Table 4 that individuals in the fourth quartile of ratio of AST to ALT had 2.555 times (OR: 2.555, 95% CI: 1.263–5.168) risk of colorectal cancer as much as the first quartile group after adjusting covariables, but no significance was found in lung cancer, which indicated that AST‐to‐ALT ratio as a cancer risk factor has tumor specificity. This evidence concerns the gene GPT and colorectal cancer.