CEACAM5 and colorectal carcinoma: Many different methods have been proposed for the follow-up of CRC patients, which can be subdivided into three categories: laboratory tests, as determination of carcinoembryonic antigen (CEA) serum levels, other markers as the carbohydrate antigens (CA), or liver enzymes; image tests, as ultrasound, X-ray or computed tomography; and endoscopies.