Clinical Significance

   Monitoring colorectal cancer and selected other cancers such as medullary thyroid carcinoma. May be useful in assessing the effectiveness of chemotherapy or radiation treatment.

Specimen

   Serum

Stability

   Refrigerated (preferred) : 7 days

   Frozen : 90 days

Reference Range

   Smoker < 5.5 ng/ml

   Non-smoker < 3.8 ng/ml

Interpretation

   Grossly elevated carcinoembryonic antigen (CEA) concentrations (>20 ng/mL) in a patient with compatible symptoms are strongly suggestive of the presence of cancer and suggest metastasis. Most healthy subjects (97%) have values less than or equal to 3.0 ng/mL.

   After removal of a colorectal tumor, the serum CEA concentration should return to normal by 6 weeks, unless there is residual tumor. Increases in test values over time in a patient with a history of cancer suggest tumor recurrence.

Limitation

   Single values of CEA are less informative than changes assessed over time. Do not interpret serum CEA levels as absolute evidence of the presence or the absence of malignant disease. Use serum CEA in conjunction with information from the clinical evaluation of the patient and other diagnostic procedures.