What Is the AFP Tumor Marker?
AFP stands for alpha-fetoprotein, a protein produced mainly by the developing liver during pregnancy.
After birth, AFP levels fall considerably and usually remain low throughout adult life.
In adults, increased AFP levels may occur in certain liver diseases, including liver cancer. AFP can also be elevated in some cancers arising outside the liver, particularly certain testicular and ovarian germ cell tumors.
AFP is not specific to cancer. Its concentration may increase when liver cells are damaged or regenerating.
Why Do Doctors Measure AFP?
AFP is most commonly associated with hepatocellular carcinoma, the main type of primary liver cancer.
Doctors may use AFP together with liver imaging when assessing patients who have an increased risk of developing this cancer.
AFP can also help monitor selected patients with diagnosed liver cancer. Changes in its concentration may provide additional information about treatment response or possible recurrence.
However, not every liver cancer produces elevated AFP.
A normal AFP result therefore cannot exclude liver cancer.
What Can Cause Elevated AFP Levels?
AFP may increase in several conditions, including:
- Hepatocellular carcinoma.
- Chronic hepatitis B or hepatitis C.
- Liver cirrhosis.
- Active liver inflammation or regeneration.
- Certain germ cell tumors.
AFP also rises naturally during pregnancy.
The degree of elevation matters, but there is no single AFP value that reliably distinguishes cancer from noncancerous liver disease.
Doctors consider AFP results alongside liver function tests, imaging findings, and the patient’s medical history.
What Is a Normal AFP Level?
Many laboratories use an upper reference limit of approximately 10 nanograms per millilitre for nonpregnant adults, although some laboratories use different thresholds.
A mildly elevated result may be associated with chronic liver disease rather than cancer.
Conversely, early liver cancer can develop while AFP remains within the normal range.
For patients undergoing surveillance, changes over time may be more informative than a single measurement.
Can AFP Help Detect Liver Cancer Early?
AFP has an established role in surveillance strategies for certain people at increased risk of liver cancer.
These include many patients with liver cirrhosis and selected individuals with chronic hepatitis B, even when cirrhosis is absent.
Current liver cancer guidelines recommend ultrasound surveillance approximately every six months for eligible patients. AFP may be measured alongside ultrasound to improve detection.
AFP alone is not sufficiently reliable for liver cancer screening.
When ultrasound or AFP results raise concern, doctors may recommend further assessment using contrast-enhanced computed tomography (CT) or magnetic resonance imaging (MRI).
What Does AFP Mean for Proactive Liver Health?
Liver cancer prevention begins with identifying and managing the conditions that increase long-term risk.
Important measures include hepatitis B vaccination, testing and treatment for viral hepatitis when indicated, limiting alcohol consumption, and addressing obesity and metabolic liver disease.
For people with known liver disease, an individualized surveillance plan can help detect complications before symptoms develop.
AFP may contribute to this assessment when clinically appropriate, but it does not replace liver imaging or evaluation of the underlying liver condition.
