Therefore, the present study aims to compare CEA and CA19-9 in esophageal, gastric, and colon cancers, to evaluate the sensitivities of the two markers individually and in combination by analyzing their ROC curves before starting any treatment, and to determine whether the combined use of these markers could improve the diagnostic sensitivity in esophageal, gastric, and colon cancers. This evidence concerns the gene CEACAM5 and malignant colon neoplasm.