CEACAM5 and gastric cancer: The patient was assessed according to the Japanese gastric cancer treatment guideline, which was comprised of routine physical examinations, measurements of serum tumor markers such as CEA and CA 19-9 (every three months during the 5 years after the surgery), thoracoabdominal computed tomography (every 6 months during the first 3 years after the surgery and once every 12 months from the fourth year onward), and upper endoscopy (1, 3, and 5 years after the surgery).