CEACAM5 and colorectal carcinoma: CEA, also known as carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5) or CD66e, is the only blood based protein biomarker at present that is clinically approved as a prognostic biomarker for determining the treatment regime and as a surveillance biomarker for monitoring tumour recurrence in post-operative CRC patients3,4.