CEACAM5 and colorectal carcinoma: Carcinoembryonic antigen (CEA) is a plasma protein biomarker used in disease progression for metastatic CRC5; however, the detection of CEA has not proven to be sufficiently sensitive for detecting primary early stage CRC.6 cfDNA is detected in almost all patients with solid tumors including CRC,7 with levels paralleling that of CEA.