Alpha-fetoprotein (AFP) Tumor Marker
A blood sample drawn from a vein in your arm
Alpha-fetoprotein (AFP) is a protein produced primarily by the liver in a developing baby (fetus) and the portion of a developing embryo that is similar to the yolk cavity in bird eggs (yolk sac tissues). AFP levels are typically elevated when a baby is born and then decline rapidly. Liver damage and certain cancers can increase AFP concentrations significantly. This test measures the level of AFP in the blood.
AFP is produced whenever liver cells are regenerating. With chronic liver diseases, such as hepatitis and cirrhosis, AFP may be chronically elevated. Very high concentrations of AFP may be produced by certain tumors. This characteristic makes the AFP test useful as a tumor marker. Increased amounts of AFP are found in many people with a type of liver cancer called hepatocellular carcinoma and in a liver cancer occurring in infants called hepatoblastoma. They are also found in some people with cancers of the testicles or ovaries.
AFP exists in several different variants. The standard AFP test is for a total AFP, one that measures all of the AFP variants together. This is the primary AFP test used in the United States.
One of the AFP variants is called L3 because of its ability, in the laboratory, to bind to a particular protein called Lens culinaris agglutinin. The AFP-L3% test is a relatively new test that compares the amount of AFP-L3 to the total amount of AFP. An increase in the percentage of L3 is associated with increased risk of developing hepatocellular carcinoma in the near future and of having a poorer prognosis, as the L3-related cancers tend to be more aggressive.
Among patients with low total AFP, AFP-L3 can be higher in those with hepatocellular carcinoma than patients with benign liver diseases. Tumor markers including total AFP and AFP-L3 are used in addition to ultrasound for surveillance of hepatocellular carcinoma in Japan. This practice is different from that in the U.S. and Europe, but the two tests are occasionally ordered by healthcare practitioners in the U.S.
How is it used?
Alpha-fetoprotein (AFP) is used as a tumor marker to help detect and diagnose cancers of the liver, testicles, and ovaries. Though the test is often ordered to monitor people with chronic liver diseases such as cirrhosis, chronic hepatitis B or hepatitis C because they have an increased lifetime risk of developing liver cancer, most current guidelines do not recommend this use. A healthcare practitioner may order an AFP test, along with imaging studies, to try to detect liver cancer when it is in its earliest and most treatable stages.
If a person has been diagnosed with hepatocellular carcinoma or another form of AFP-producing cancer, an AFP test may be ordered periodically to help monitor the person's response to therapy and to monitor for cancer recurrence.
An AFP-L3% is sometimes also ordered to compare the amount of the AFP variant called AFP-L3 to the total amount of AFP. The AFP-L3% test is not yet widely used in the U.S. but has gained wider acceptance in other countries such as Japan. The test is used to help evaluate the risk of developing hepatocellular carcinoma, especially in those with chronic liver disease, and also to evaluate response of hepatocellular carcinoma to treatment.
When is it ordered?
A healthcare practitioner may order an AFP blood test:
- When it is suspected that someone has liver cancer or certain cancers of the testicles or ovaries; cancer may be suspected when, for example, lumps are felt in the abdominal area during a physical exam or when imaging tests detect possible tumors.
- When someone who has been diagnosed with and treated for a cancer of the liver, testicles, or ovaries is being monitored for the effectiveness of treatment
- When someone is being monitored for cancer recurrence
- To follow up patients with chronic hepatitis or liver cirrhosis
An AFP-L3% is sometimes ordered to help evaluate the risk of hepatocellular carcinoma when a person has chronic liver disease or to test the effectiveness of treatment of hepatocellular carcinoma or monitor for its recurrence.
What does the test result mean?
Increased AFP levels may indicate the presence of cancer, most commonly liver cancer, cancer of the ovary, or germ cell tumor of the testicles. However, not every liver, ovarian, or testicular cancer will produce significant quantities of AFP.
Elevated levels may sometimes be seen with other cancers such as stomach, colon, lung, breast, and lymphoma, although it is rarely ordered to evaluate these conditions. Other diseases such as cirrhosis and hepatitis can also cause increased levels.
When AFP is used as a monitoring tool, decreasing levels indicate a response to treatment. If concentrations after cancer treatment do not significantly decrease, usually to normal or near normal levels, then some of the tumor tissue may still be present.
If AFP concentrations begin to increase, then it is likely that the cancer is recurring. However, since AFP can be increased in hepatitis or cirrhosis, AFP levels can sometimes be misleading. If AFP levels are not elevated prior to treatment, then the test will not generally be useful to monitor the effectiveness of treatment or to monitor for recurrence.
When the AFP concentrations of people with chronic liver disease go from normal or moderately elevated to greatly elevated, their risk of developing liver cancer increases. When total AFP and AFP-L3% are significantly elevated, then the affected person has an increased risk of having or developing hepatocellular carcinoma in the next year or two. However, both AFP and AFP-L3% concentrations can be elevated, and fluctuate, in people with chronic hepatitis and cirrhosis. In these cases, a sharp increase in AFP is more important than the actual numerical value of the test result.
Is there anything else I should know?
Not every person with increased AFP and AFP-L3% test results has cancer or will develop liver cancer. The AFP and AFP-L3% tests are not diagnostic per se; they are indicators. They must be used in conjunction with information from a medical history and physical examination as well as histopathological examination and imaging studies to look for the development of tumors.
Although these tests can provide useful information, they are not as specific or sensitive as healthcare practitioners would wish. AFP can temporarily increase whenever the liver is injured and regenerating, and moderate elevations can be seen with a variety of conditions. Because of this, AFP testing cannot be used solely to diagnose cancer. In addition, not every cancer will produce AFP, so a person could still have cancer even when the AFP is normal. For these reasons, the AFP test should not be used to screen the general population for cancer.
AFP is not only a tumor marker. Because AFP is produced by the fetus, levels are normally higher in pregnant women and in their newborns. For more information on AFP testing during pregnancy, see the Second Trimester Maternal Serum Screen.
What are the risk factors for hepatocellular carcinoma?
This cancer usually occurs in people who have chronic scarring of the liver, called cirrhosis. Most commonly, this is caused by chronic infection from one of two viruses: hepatitis B or hepatitis C. Alcohol abuse also increases the risk of developing cirrhosis. Some inherited diseases, especially a disorder called hemochromatosis (in which the body absorbs too much iron, which gets deposited in liver among other organs), can cause cirrhosis and, in time, hepatocellular carcinoma, as can non-alcoholic steatohepatitis (NASH), which is fat deposition in the liver, along with inflammation and damage.
If my AFP is abnormal, do I need other tests?
If you have chronic liver infection or damage and your AFP suddenly rises, or if it is very elevated, your healthcare practitioner will usually ask for a study to look at your liver, such as an ultrasound exam, a CT scan, an MRI scan, or a biopsy for histopathological evaluation of tumor tissues. The scans can usually spot liver cancers if they are present. Your healthcare practitioner may also order a blood test for des-gamma carboxy prothrombin (DCP), which is also known as prothrombin induced by vitamin K absence-II (PIVKA-II), to help detect liver cancer and monitor patients with hepatocellular carcinoma.
Can an AFP test be performed at home or in my healthcare practitioner's office?
On This Site
Elsewhere On The Web
MedlinePlus Medical Encyclopedia: Hepatocellular carcinoma
National Cancer Institute: Liver and Bile Duct Cancer
National Cancer Institute: Testicular Cancer
American Cancer Society: Liver Cancer
American Cancer Society: Ovarian Cancer
American Liver Foundation: Liver Cancer
Mayo Clinic: Liver cancer