The Alpha-Fetoprotein, or AFP, tumor marker test helps diagnose certain types of cancer in the ovaries, testes and liver. It can also be used by people who have already received a positive diagnosis to monitor the effectiveness of their therapies. This test is effective for monitoring of people who have cirrhosis, chronic hepatitis B or other liver problems, since they have an increased lifetime risk of liver cancer. The AFP test is not effective against all types of cancer, however.

Doctors are most likely to recommend an AFP tumor marker test when they suspect liver, testicle or ovary cancer in its early stages. During these stages, the cancer is the most treatable and offers the greatest chance of recovery. In patients who already have hepatocellular carcinoma or another cancer that produces alpha-fetoprotein, doctors may recommend periodic testing to make sure that the cancer does not come back. This test may sometimes be used in conjunction with an AFP-L3% test, which compares total AFP with one of its variants.

If the test returns low levels of AFP in the bloodstream, the patient is unlikely to have cancer or is responding to treatment. When patients who have had cancer treatment do not show a significant decrease in AFP levels, some of the tumor tissue may have survived. An increasing level of AFP in the blood indicates the growth of new tumors or the spread of old ones. 

Significant elevations in people with liver disease indicate a relatively high risk of developing liver carcinoma within one or two years. Not everyone who shows signs of high AFP levels has or will get liver cancer, however. This test is an indicator and should be used in conjunction with patient medical histories and imaging studies to make sure that cancer is the cause of the high test levels.