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Definition
Carcinoembryonic antigen (CEA) is an antigen (protein) present in very small quantities in adult tissue. A greater than normal amount may be suggestive of cancer. Normally, its values range from 0.0 to 2.5 nanograms per milliliter of serum (from blood), in non-smokers. CEA levels are higher, on average, in men, smokers, and older individuals.
Tests for its presence aid in screening, in evaluating recurrent or disseminated disease, and in gauging the success of surgical removal of malignant tumors.
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Description
CEA is a substance normally found in a fetus which, when found at elevated levels in the blood of adults, may indicate the presence of colorectal cancer or other types of cancer. CEA is therefore called a tumor marker.
It has been used to monitor patients for the recurrence of a number of different cancers, including breast, thyroid, lung, ovarian, pancreatic, stomach, and colon/rectal. It is also referred to as an "oncofetal antigen" because of its similarity to fetal tissue.
CEA levels can also be an indication of the effectiveness of treatment.
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Examples
In colorectal cancer, levels of CEA are elevated in 70 percent of patients but are poorly correlated with cancer stage. After complete surgical resection of the cancer, CEA levels should return to normal. Persistently elevated levels portend a poor prognosis. A rise in CEA levels that had returned to normal after surgery is suggestive of cancer recurrence. The cost-effectiveness of CEA screening after colorectal cancer resection has not been proven.
In thyroid cancer (medullary carcinoma), CEA levels are usually elevated. Serum determinations of CEA (and calcitonin) should be obtained before surgery and then periodically in follow-up. Rising levels of CEA or calcitonin are a strong indication of recurrence.
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Questions to Ask Your Doctor
Why are you recommending a CEA test?
If the CEA level is low or normal does it positively rule out a tumor?
What are the chances of a false CEA reading?
If this could possibly indicate the presence of a tumor, what tests need to be done to determine where?
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