The data of patients with rectal adenocarcinoma confirmed by endoscopic biopsy or postoperative pathology from September 2015 to May 2020 in hospital A (center 1) and hospital B (center 2) were analyzed retrospectively, including age, sex, carcinoembryonic antigen, carbohydrate antigen 19–9, tumor location, tumor length, image staging and characteristics. The gene discussed is CEACAM5; the disease is rectum adenocarcinoma.