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). AFP levels are normally elevated when a baby is born and then decline rapidly. Outside of pregnancy and birth, liver damage and certain cancers can increase AFP levels significantly. This test measures the level of AFP in your 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 the most common type of liver cancer called hepatocellular carcinoma and in a rare type of liver cancer that most commonly occurs in infants called hepatoblastoma. They are also found in some people with cancers of the testicles or ovaries.
AFP exists in several different forms. The standard AFP test is for a total AFP, one that measures all of the AFP forms together. This is the primary AFP test used in the United States.
One of the AFP forms is called L3. 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 people with low total AFP, AFP-L3 can be higher in those with hepatocellular carcinoma than in people 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 the test 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 you have been diagnosed with hepatocellular carcinoma or another form of AFP-producing cancer, an AFP test may be used to help monitor your response to therapy and to monitor for cancer recurrence.
An AFP-L3% is sometimes also ordered to compare the amount of the AFP form 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 if you have chronic liver disease, and also to evaluate the response of your hepatocellular carcinoma to treatment.
When is it ordered?
A healthcare practitioner may order an AFP blood test:
- When it is suspected that you have 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 you have been diagnosed with and treated for a cancer of the liver, testicles, or ovaries and are being monitored for the effectiveness of treatment
- When you are being monitored for cancer recurrence
- To follow up when you have chronic hepatitis or liver cirrhosis
An AFP-L3% is sometimes ordered to help evaluate the risk of hepatocellular carcinoma when you have 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 AFP levels 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 your AFP levels 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 your AFP levels are not elevated prior to treatment, then the test will not generally be useful to monitor the effectiveness of your treatment or to monitor for recurrence.
When you have chronic liver disease and your AFP levels go from normal or moderately elevated to greatly elevated, your risk of developing liver cancer increases. When total AFP and AFP-L3% are significantly elevated, then you have 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, when you have 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 your 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 you could still have cancer even when the AFP is normal. For these reasons, the AFP test is not 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 liver cancer?
This cancer usually occurs when you 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 and monitor liver cancer.
Can an AFP test be performed at home or in my healthcare practitioner's office?