Download Carcinoembryonic Antigen (CEA)

Carcinoembryonic Antigen (CEA)
CEA is a large family of 36 different, but related, glycoproteins, which are part of the
immunoglobulin superfamily. CEA is present in the gastrointestinal tract during fetal
life and occurs at low concentrations in adults. CEA was first reported to be quite
specific for tumors of the GI tract, but further investigations demonstrated elevations
in several other malignant and benign diseases. Elevated CEA levels are suggestive,
but not diagnostic of cancer, since elevated levels also occur in a variety of benign
conditions:
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The median level of CEA is 3.4 ng/mL in men and 2.5 ug/mL in women.
Healthy persons seldom have levels above 10 ng/mL.
CEA concentrations are twice as high in smokers; female smokers have a
median CEA level of 4.9 ng/mL and male smokers have a median level of 6.2
ng/mL.
CEA levels are not elevated in maternal serum during pregnancy, since CEA
does not cross the placenta.
The liver is the primary site for metabolism of CEA. Benign diseases that
impair liver function reduce CEA clearance, resulting in increased serum
levels. Elevated levels are also frequently seen in other gastrointestinal
diseases including peptic ulcer, pancreatitis, diverticulitis, and inflammatory
bowel disease. Benign diseases rarely produce CEA serum levels >10ng/mL.
CEA levels are slightly elevated in patients with chronic renal failure
undergoing dialysis.
Serum CEA is ordered most often for patients with colorectal cancer. Numerous
studies have demonstrated that:
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Serum concentrations of CEA tend to be higher in patients with welldifferentiated colon cancer compared with poorly differentiated cancer.
Patients with tumours in the left side of the colon generally have a higher
incidence of increased CEA concentrations than those with tumours on the
right side.
Bowel obstruction results in higher CEA concentrations in patients with
colorectal cancer. Decompression alone reduces serum CEA levels.
Serum CEA is not sensitive enough to be used as a screening test for
colorectal cancer.
CEA levels cannot distinguish locally invasive premalignant colonic polyps
from benign polyps.
The majority of studies suggest that preoperative CEA levels can provide prognostic
data in patients with stage II colorectal cancer. High levels are associated with more
aggressive disease.
The circulatory half-life of CEA is ~7 days. After successful surgical resection of
colorectal cancer, an increased CEA concentration should return to normal within 4 to
6 weeks. Failure of an increased preoperative level to decrease in to the normal
range within 6 weeks of surgery frequently is associated with recurrent disease.
Serial CEA determinations are most useful in detecting liver metastasis.
Hepatic resection for isolated liver metastases achieves long-term survival in 20 to
50% of patients and may be the only curative therapy for metastatic colorectal
cancer. Because of this success, the American Society of Clinical Oncology (ASCO)
recommends CEA monitoring only in those patients with stage II and III (Duke's C)
disease who are willing and able to undergo a hepatic resection for metastatic
disease. For this subset, CEA monitoring is recommended every 2 to 3 months for at
least 2 years after diagnosis.
Though CEA has a much lower sensitivity and specificity for detection of local
recurrence after successful primary therapy CEA does appear to be superior to
endoscopy, computerized tomograpy and ultrasound in diagnosing local recurrences.
Because CEA is increased in >80% of patients with distant metastases, it is a
potential marker for monitoring response to chemotherapy.
ASCO recommends obtaining a baseline CEA value before treatment and serial
monitoring every 2 to 3 months during treatment. Two values above the baseline are
adequate to document progressive disease and discontinuation of therapy, even in
the absence of corroborating radiological evidence. However, in spite of this
recommendation, it is important to realize that chemotherapy can cause transient
increases in CEA concentration due to hepatic toxicity in the absence of disease
progression.
Reference range is 0 - 5 ng/mL. A difference of >20% between two CEA
measurements is considered medically significant.
Specimen Type Serum
Container/Tube: Plain, red top or serum gel
Specimen Volume: 0.6 mL
Reject Due To
Specimens other than
Hemolysis
Lipemia
Serum
Mild OK; Gross reject
Mild OK; Gross OK
Transport Temperature
Refrig\Frozen OK\Ambient NO