α-Fetoprotein (AFP) Tumor Marker, Serum

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Subject: α-Fetoprotein (AFP) Tumor Marker, Serum

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Definition

  • AFP is a glycoprotein that is normally produced during gestation by the fetal liver and yolk sac, the serum concentration of which is often elevated in patients with hepatocellular carcinoma (HCC). It is also found in some patients with cancer of the testes and ovaries.

  • Normal range: 0.6–6.60 ng/mL.

Use

  • Marker for hepatocellular and germ cell (nonseminoma) carcinoma.

  • Follow-up management of patients undergoing cancer therapy, especially for testicular and ovarian tumors and for hepatocellular carcinoma. The measurement of AFP in serum, in conjunction with serum human chorionic gonadotropin, is an established regimen for monitoring patients with nonseminomatous testicular cancer. In addition, monitoring the rate of AFP clearance from serum after treatment is an indicator of the effectiveness of therapy. Conversely, the growth rate of progressive cancer can be monitored by serially measuring serum AFP concentration over time.

  • Serial serum AFP testing is a useful adjunctive test for managing nonseminomatous testicular cancer.

Interpretation

  • AFP is increased in the following disorders:

    • Ataxia telangiectasia

    • Hereditary tyrosinemia

    • Primary hepatocellular carcinoma

    • Teratocarcinoma

    • Gastrointestinal tract cancers with and without liver metastases

    • Benign hepatic conditions such as acute viral hepatitis, chronic active hepatitis, and cirrhosis

Limitations

  • AFP is not recommended as a screening procedure to detect cancer in the general population. This assay is intended only as an adjunct in the diagnosis and monitoring of AFP-producing tumors. The diagnosis should be confirmed by other tests or procedures.

  • Serum levels of AFP do not correlate well with other clinical features of HCC, such as size, stage, or prognosis.

  • A case–control study evaluated the diagnostic characteristics of the serum AFP in screening for HCC in patients with different types of chronic liver disease. The following sensitivities and specificities were observed:

    • AFP cutoff 16 μg/L (sensitivity 62%, specificity 89%)

    • AFP cutoff 20 μg/L (sensitivity 60%, specificity 91%)

    • AFP cutoff 100 μg/L (sensitivity 31%, specificity 99%)

    • AFP cutoff 200 μg/L (sensitivity 22%, specificity 99%)

  • False-positive elevations can occur with tumors of the GI tract or with liver damage (e.g., cirrhosis, hepatitis, or drug or alcohol abuse) and pregnancy.

  • Failure of the AFP value to return to normal by approximately 1 month after surgery suggests the presence of residual tumor.

  • Elevation of AFP after remission suggests tumor recurrence; however, tumors originally producing AFP may recur without an increase in AFP.

  • Fucosylated form of serum AFP that is most closely associated with HCC is recognized by a lectin from the common lentil (AFP-L3). AFP-L3 is most useful in the differential diagnosis of individuals with total serum AFP ≤200 ng/mL.

Suggested Reading

Trevisani  F, D'Intino  PE, Morselli-Labate  AM Serum alpha-fetoprotein for diagnosis of hepatocellular carcinoma in patients with chronic liver disease: influence of HBsAg and anti-HCV status. J Hepatol.  2001;34(4):570–575.
 
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