Cancer diagnostics
CEA, the most well known tumour marker in the routine clinical laboratoryIn the lab CEA, or carcinoembryonic antigen, was one of the first tumour markers to be described and exploited clinically. It belongs to the group of tumour antigens, more specifically, the oncofoetal antigens. These substances, present in the embryo or foetus, diminish to low levels in adults but reappear in some tumours. CEA is tested in blood. The normal range is <2.5 ng/mL in an adult non-smoker to <5.0 ng/mL in a smoker. CEA is a complex glycoprotein, which is associated with the plasma membrane of tumour cells, from where it may be released into the blood. Elevated CEA levels are found in malignancy in general, but they are also detected in benign conditions including cirrhosis, inflammatory bowel disease, chronic lung disease and pancreatitis. CEA was found to be elevated in 19% of smokers and in 3% of a healthy control population.
Despite these findings, CEA is widely used as a prognostic value in many cancers. In colon cancer for instance, preoperative CEA values have been positively correlated with stage and negatively with disease-free survival. CEA is also used to monitor recurrence. Data suggest that CEA precedes clinical relapse by several months. Subsequently, serial CEA monitoring is used as an indicator for second look surgery so that relapse can be detected at a time when surgical resection for cure is still possible. Criteria for a new operation include a significant rise of CEA above a base line level on serial determinations, which should be carried out frequently, at least once every three months. |
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