CEACAM5 and cancer: Screening and early diagnosis of cancer are the main approaches for CRC prevention; at present, the common used tests for CRC are colonoscopy, computed tomography (CT) colonography (virtual colonoscopy), multitargeted stool DNA test, detection of serum carcinoembryonic antigens (CEA), detection of carbohydrate antigen 19-9 (CA19-9) and a fecal immunochemical test (FIT) [114,115].