Liver cancer is sometimes called a “silent killer,” because signs and symptoms usually don’t appear until the disease is in an advanced stage. So it’s important for anyone who is at high risk of developing liver cancer to undergo screening tests at regular intervals. One of those tests involves measuring blood levels of a substance called alpha-fetoprotein.

Liver Cancer Screening: What Is Alpha-Fetoprotein?

Also known as AFP, alpha-fetoprotein is a protein made by the liver and yolk sac of the developing fetus and normally found in fetal blood. Usually its levels fall soon after birth. In healthy adults, AFP is present in extremely low levels. Normal adult values are less than 40 micrograms (mg) per liter. An increase is a signal that something may be wrong.

Liver Cancer Screening: Candidates for the AFP Test

AFP is used as a screening test for liver cancer because “two-thirds of liver cancers produce AFP,” says Myron Tong, MD, PhD, director of hepatology at the University of California, Los Angeles, and associate director of the Dumont-UCLA Liver Cancer Center. “We worry about every elevation in AFP levels,” he adds.

People at high risk for liver cancer are urged to have their AFP level measured every six months. Members of this group include anyone with cirrhosis of the liver and certain people with chronic hepatitis B or hepatitis C infection.

Liver Cancer Screening: When AFP Is Used

However, the utility of AFP measurement is clouded by the fact that rising levels are associated with several conditions other than liver cancer. AFP is also used to:

  • Screen for cancer of the testes, ovaries, stomach, or pancreas — or a rare tumor called malignant teratoma
  • Screen pregnant women for possible birth defects in the fetus, or for multiple fetuses
  • Diagnose non-cancerous disorders of the liver, such as cirrhosis

Doctors also use AFP to monitor a patient’s response to cancer treatment. When the treatment is successful, AFP levels drop back to normal. Another rise suggests that the cancer has returned, Dr. Tong explains.

Liver Cancer Screening: AFP and Ultrasound

When someone is already at high risk of developing liver cancer, an elevated AFP level is a strong indication that something is wrong. But its association with so many other conditions means that, by itself, AFP measurement is not definitive. That’s why doctors recommend that people at high risk of liver cancer also have an ultrasound examination every 6 to 12 months.

For this test, a technician places a small instrument called a transducer on the abdomen, just over the liver. The transducer sends sound waves into the abdominal cavity, where they bounce off the abdominal organs, including the liver, and create echoes. A computer analyzes the echoes to create images of the organs. An abnormality on the organs, such as a tumor, becomes visible on those images.

Interpretation of the AFP and ultrasound findings is fairly straightforward, says Tong. “Elevated AFP with no liver lesion on the ultrasound means the patient probably has inflammation of the liver,” he explains. On the other hand, a liver lesion on ultrasound means that the patient probably has liver cancer, even if the AFP levels are normal.

Liver Cancer Screening: Bottom Line on AFP

Some experts think that AFP is not sensitive enough to detect liver cancer in people in the United States and Europe, where liver cancer is relatively rare. Others point out that the optimal interval between ultrasound exams has not yet been established. Ultimately, patients should consult their doctors about which screening tests and schedules are best for them. If you are at risk, you will want to choose a screening schedule that gives you the best shot at early diagnosis and an optimal treatment outcome.