Tumor markers are substances produced by cancer cells (or by normal cells in response to cancer) that can be measured in blood. The tumor markers commonly tested include CEA, CA-125, CA 19-9, AFP, PSA, hCG, and others. They’re useful for monitoring known cancers but have significant limitations as screening tests. This guide covers major tumor markers and their clinical use.
Why tumor markers aren’t good screening tests
Most tumor markers have:
- Low sensitivity (miss many cancers)
- Low specificity (false positives common from benign conditions)
- Variable correlation with disease activity
This means tumor markers don’t reliably detect early cancer in asymptomatic populations. Most experts don’t recommend routine tumor marker screening for healthy people.
Common tumor markers and uses
CEA (carcinoembryonic antigen):
- Most useful for monitoring colorectal cancer recurrence
- Also elevated in lung, breast, pancreatic cancers
- Elevated in smokers and chronic conditions
- Not used for screening
CA-125:
- Ovarian cancer monitoring
- Elevated in many benign conditions (endometriosis, PID, pregnancy)
- Limited screening value
CA 19-9:
- Pancreatic cancer monitoring
- Cholangiocarcinoma
- Limited screening value
AFP (alpha-fetoprotein):
- Hepatocellular carcinoma monitoring
- Germ cell tumors (testicular, ovarian)
- Pregnancy screening (different use)
PSA: See our PSA test guide for prostate cancer testing.
hCG:
- Germ cell tumors (testicular cancer particularly)
- Gestational trophoblastic disease
- Pregnancy testing (very different use)
Appropriate uses of tumor markers
- Monitoring known cancer for treatment response
- Detecting recurrence after treatment
- Specific high-risk populations (e.g., AFP for hepatitis-related HCC surveillance)
- Diagnostic adjunct in specific clinical situations
- Research applications
Why patients shouldn’t request “screening”
Patients sometimes request tumor markers for cancer screening. The problems:
- False positives cause unnecessary workups, biopsies, anxiety
- False negatives provide false reassurance
- Most cancers don’t reliably elevate any specific marker
- Cost-benefit of routine screening is poor
Established cancer screening tests (mammography, colonoscopy, low-dose CT for lung cancer in smokers, etc.) are evidence-based for screening. Tumor markers generally aren’t.
Frequently Asked Questions
Should I get tumor markers checked annually?
No, not recommended for routine screening of healthy individuals.
What if my tumor marker is elevated?
Many causes including benign conditions. Workup depends on which marker, severity, and clinical context.
Are tumor markers useful for cancer monitoring?
Yes for many specific cancers. Monitoring CEA after colorectal cancer treatment, CA-125 in ovarian cancer follow-up, AFP after liver cancer treatment.
Can lifestyle affect tumor markers?
Smoking elevates CEA. Inflammation, infections, and other conditions affect various markers.
Should I trust direct-to-consumer tumor marker panels?
Be cautious. False positives are common and can cause significant anxiety and unnecessary testing.
The bottom line on tumor markers
Tumor markers are useful for monitoring known cancers and specific clinical situations but not for routine screening of healthy people. Stick with established evidence-based cancer screening (mammography, colonoscopy, low-dose CT for lung cancer in smokers). Discuss tumor marker testing with your healthcare provider in appropriate clinical contexts.