Description
1. Carcino Embryonic Antigen (CEA)
CEA is a 200.000 Daltons oncofetal glycoprotein expressed by normal tissues during the first six months of fetal life. Later on the expression of CEA by normal cells becomes largely repressed except in cancer tissues of various cell types, which may secrete large amounts of this oncofetal protein into the circulation. Widely accepted as a useful adjunct for monitoring the course of cancer diseases, CEA should not be regarded as a tumor-specific marker because it is still secreted in small amounts by certain normal tissues during adult life, with small serum level increases in case of benign diseases such as cirrhosis, hepatitis, inflammatory bowel diseases, renal failure and in heavy smokers. Therefore, the measurement of CEA serum concentration for diagnostic purposes must be considered with great care.
2. Clinical applications
Monitoring of cancer diseases
When measured before any therapy, the serum concentration of CEA is one of the best parameters to monitor the evolution of cancer following surgery, chemotherapy, etc. After remission, CEA levels appear often as a good screening test for early detection of tumor recurrence.
Diagnostic adjunct in cancer
Although not specific for cancer when elevated to less than 20 ng/ml, CEA levels above this limit are highly suggestive of malignancy (less than 0.5% false positive).
Prognostic adjunct in cancer
CEA levels in serum provide important prognostic information because a direct relationship has been established between CEA serum concentration and Dukes classification in colon. The same relationship exists probably also in mammary carcinoma and lung carcinoma where very high CEA levels occur almost exclusively in case of disseminated metastasis