CEACAM5 and cancer: Thus, the use of liquid biopsy-based, noninvasive cancer biomarkers has become increasingly desirable, and several promising molecular biomarkers have been identified in blood, urine, and gastric juice.3,4,5 Despite these advances, serum levels of carcinoembryonic antigen (CEA) and cancer antigen 19-9 (CA19-9) are the only markers currently available for clinical use.