Tumour markers in blood tests help monitor cancer treatment and recurrence. Learn what they are, their uses, limitations, and common types.
Blood tests for tumour markers are often used in cancer diagnosis and management. This article explains what tumour markers are, how they're used, and their limitations.
What Are Tumour Markers?
Tumour markers are substances found at higher-than-normal levels in the blood of some people with cancer. They are either produced by cancer cells or by healthy cells in response to cancer.
What Are the Uses of Tumour Markers?
- To assess whether treatment is working — decreasing levels suggest effectiveness.
- To monitor for cancer recurrence after treatment.
- To aid diagnosis when combined with imaging or biopsy in symptomatic patients.
- Rarely, to screen high-risk individuals.
Does Every Cancer Have a Tumour Marker?
No. While some cancers have specific markers, others don’t produce detectable ones. Also, some markers are linked to multiple cancers, while others are cancer-specific.
Common Tumour Markers
CA-125 (Cancer Antigen 125)
Cancer: Ovarian
Uses: Monitor treatment response and recurrence
Normal Value: < 35 units/mL
PSA (Prostate-Specific Antigen)
Cancer: Prostate
Uses: Screening, diagnosis, monitoring treatment and recurrence
Normal Value: < 4 ng/mL
CEA (Carcinoembryonic Antigen)
Cancer: Colon, rectal
Uses: Monitor treatment and recurrence
Normal Value: < 2.5 ng/mL (non-smokers), < 5 ng/mL (smokers)
CA 19-9 (Cancer Antigen 19-9)
Cancer: Pancreatic
Uses: Diagnosis and monitoring treatment
Normal Value: < 37 U/mL
AFP (Alpha-fetoprotein)
Cancers: Liver, ovarian, testicular
Uses: Diagnose liver cancer and monitor treatment
Normal Value: 0–15 IU/mL
What to Expect During a Tumour Marker Test?
It's a simple blood draw from a vein in your arm. No special preparation is needed. You might feel slight pain or bruising at the site, which resolves quickly.
Limitations of Tumour Marker Tests
- Non-cancer conditions (like inflammation or benign tumors) can elevate marker levels.
- Levels may fluctuate over time.
- Some cancers don’t release markers until late stages.
- Not all patients with a known marker-producing cancer will show elevated levels.
Can Tumour Marker Tests Be Wrong?
Yes. Possible errors include:
- False Negative: Test says no cancer, but cancer is present (or treatment isn’t working).
- False Positive: Suggests cancer or progression when none exists.
That’s why tumour markers are never used alone — they’re always interpreted alongside scans, biopsies, and clinical findings.