Definition

CEA is a protein that is present at high levels during fetal development but at very low levels in healthy adults. Its presence in an adult may point to cancer or other conditions.

Purpose

To assess the severity and prognosis of a cancer after diagnosis; to monitor the effectiveness of treatment (falling levels indicate a response); to detect recurrence after treatment (rising levels). Most often used for monitoring colorectal cancer.

Results

  • Before treatment: a low CEA may suggest a smaller, localized tumor; a high CEA may suggest a larger tumor or spread
  • During/after treatment: falling levels suggest effective treatment; rising levels suggest treatment failure or recurrence

Results should be compared over time and evaluated together with other tests.

Normal Values

Laboratory specific.

Risks and Limitations

  • Effect of smoking: smoking artificially raises CEA levels; patients may need to stop smoking before the test.
  • Cannot be used for screening: a normal result does not rule out cancer, and many non-cancer conditions raise CEA: COPD, cirrhosis, diabetes, Crohn's disease, gastritis

Related Tests

Tumor Markers (General Concept)

Substances produced by cancer cells, or by normal cells in response to cancer. They are measured in blood, urine, or a tissue sample.

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CA 19-9

Measures a protein in the blood called CA 19-9 (cancer antigen 19-9). It is a tumor marker, a substance produced by cancer cells or by normal cells responding to cancer.

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CA 125

Measures the amount of a protein called CA-125 (cancer antigen 125) in the blood. This protein is a tumor marker produced by cancer cells or by normal cells responding to cancer.

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AFP (Alpha-Fetoprotein)

AFP is a protein produced by the liver while liver cells grow and divide. Its level is high in the fetus and drops markedly after birth.

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Other related tests not yet in the glossary: cancer-specific genetic tests (BRAF, TP53).