Tumor Marker:- Part 8 – Alpha-Fetoprotein (AFP)

Sample

1. The patient serum is needed.
2. Can take a random sample, and no fasting needed.

Indications

1. For the diagnosis of liver cell carcinoma.
2. Patients with chronic active hepatitis.
3. Patients with cirrhosis and positive serology (HBV and HCV) should be tested with AFP and ultrasound abdomen.
4. AFP is a tumor marker for yolk sac tumors.
5. AFP raised in hepatoid gastric carcinoma.

Alpha-Fetoprotein

1. This is a glycoprotein. This consists of a single polypeptide chain and has a 4% carbohydrate.
   1. The yolk sac produces this in small amounts and the liver with the abundant amount in the fetus.
2. It is normal after about 18 months of birth.

3. It is close to albumin, genetically and structurally.
   1. Gene coding for both is chromosome 4q.
   2. Its concentration is 10% that of the albumin.

The function of the AFP:

1. AFP has increased in pregnancy, usually not >100 ng/mL.
2. Its main role is to bind and transport substances that are not water-soluble, like steroids hormones, lipids, vitamins, and bilirubin.
3. Maternal serum AFP is lower than expected in Down’s syndrome.
4. Maternal serum AFP is raised or higher level in the neural tube defect.
5. Level > 1000 µg/L indicate malignancy.
   1. At this level, 50% of liver cell carcinomas are diagnosed.
   2. It is ideal for diagnosing a liver tumor below the size of 5 cms.
   3. To find these small tumors cut-off value has to be set at a lower level between 200 to 1000 µg/L.
6. In healthy individuals is 10 µg/L.

This is a tumor marker for:

1. Liver cell carcinoma.
   1. AFP is raised in 80% of liver cell carcinoma.
   2. >500 ng/mL is diagnostic of liver cell carcinoma.
   3. AFP may be raised for 18 months before the S/S appears.
   4. AFP is a sensitive indicator of recurrence.
   5. AFP >1000 ng/mL in 50% of the cases indicates tumor size >3 cms in diameter.
      

      AFP in Liver cell carcinoma (Hepatoma)

   6. In 90% of the cases AFP >200 ng/mL, and 70% have concentration of AFP >400 ng/mL.
   7. In benign diseases, AFP >400 ng/mL is extremely rare.
   8. This is more likely raised in immature carcinoma than the mature type of carcinoma.
   9. Initial high level indicates a poor prognosis.
   10. Failure to come to normal indicates a problem with surgery where there is incomplete resection or metastasis.
   11. The postoperative decrease followed by an increase in the AFP indicates recurrence.
   12. If there is a short doubling in the AFP value, suggest metastasis at the time of surgery.
2. AFP is a tumor marker of the Germ cell tumor (nonseminomatous tumor).
   1. Yolk sac tumors lead to an increase in  AFP, which correlates with the tumor prognosis, e.g.,>1000 ng/mL associated with poor prognosis.
   2. Embryonal cell carcinoma in 27% of the cases.
   3. Malignant teratoma in 60% of the cases.
   4. Testicular teratocarcinoma is seen in 75% of the cases.
   5. Choriocarcinoma element is seen in seminoma, yolk sac, teratoma, and embryonal cell carcinoma.
3. Pancreatic carcinoma AFP is positive in 23% of the cases.
4. Gastric carcinoma AFP 18% positive.
5. Bronchogenic carcinoma 7% positive.
6. Colon carcinoma 5% positive.
7. AFP is useful for liver cell carcinoma:
   1. Diagnosing.
   2. Prognosis.
   3. Monitor therapy.
8. Normal
   1. Adult = <40 ng/mL  (<40 µg/L)
   2. Child <1 year = <30 ng/mL

• Note: In some books on the same page, the values are given in ng/mL and ng/dL. For me difficult to decide which one I can follow.