The sensitivity of CEA was determined: in esophageal cancer, sensitivity=28%, negative predictive value (NPV)=61.72%, and AUC=0.742  (SE=0.05), with a significance level of P<0.0001; in gastric cancer, sensitivity=30%, NPV=58.82%, and AUC=0.734 (SE=0.05), with a significance level of P<0.0001; in colon cancer, sensitivity=74%, NPV=79.36%, and AUC=0.856  (SE=0.04), with a significance level of P<0.0001. The gene discussed is CEACAM5; the disease is malignant colon neoplasm.