CEA is also called carcinoembryonic antigen. Mild elevation of carcinoembryonic antigen can be seen in inflammation of the gastrointestinal tract, but if CEA is significantly elevated, if it is 3 times or more than the upper limit of normal value, it is recommended to perform cancer screening, such as gastroscopy, breast ultrasound, gynecological ultrasound, and chest CT to initially rule out cancer diagnosis. If CEA is significantly increased after treatment, it indicates possible recurrence.