Biomarker
Cancer biomarkers: PSA, CA-125, CEA, AFP and CA 19-9
Tumour markers are substances — usually proteins — that can rise in the presence of certain cancers. They are far better at monitoring a known cancer than at finding an unknown one, and reading them without that context causes real harm.
What it measures
Each marker is tied to particular tissues: PSA to the prostate, CA-125 to ovarian and peritoneal tissue, CEA to colorectal and several other epithelial cancers, AFP to liver and germ-cell tumours, CA 19-9 to pancreatic and biliary disease. All of them also rise in benign conditions, which is the central problem.
Reported in: ng/mL (PSA, CEA, AFP) or U/mL (CA-125, CA 19-9)
Reference ranges
Typical adult reference values. Laboratory ranges differ — always read your own report's range.
PSA (prostate)
Below 4.0 ng/mL
Also raised by benign prostatic enlargement, prostatitis, recent ejaculation or cycling. Age-specific ranges are common.
CA-125 (ovarian)
Below 35 U/mL
Raised by menstruation, endometriosis, fibroids, pregnancy, liver disease and any peritoneal inflammation.
CEA (colorectal and others)
Below 3.0 ng/mL non-smokers
Up to about 5.0 in smokers. Mainly used to monitor treated colorectal cancer for recurrence.
AFP (liver, germ cell)
Below 10 ng/mL
Used with ultrasound for surveillance in cirrhosis. Raised in pregnancy and in hepatitis.
CA 19-9 (pancreatic, biliary)
Below 37 U/mL
Undetectable in the 5–10% of people who are Lewis antigen negative. Raised by any bile duct obstruction.
Laboratory reference ranges vary between analysers and populations. Always read the range printed on your own report.
What moves the number
- Benign disease in the same organ — the commonest reason for a raised marker
- Inflammation, infection and recent procedures
- Smoking, which raises CEA baseline
- Assay differences between laboratories, which make cross-lab comparison unreliable
- The trend over serial tests, which carries far more information than any single value
How Vitals uses this measurement
Vitals stores PSA, CA-125, CEA, AFP and CA 19-9 as trended values so you can see direction rather than a lone figure, and keeps them separate from the guideline-based screening calendar — which follows USPSTF and ACS recommendations for mammography, cervical, colorectal and lung screening rather than blood markers.
Frequently asked questions
Can I use tumour markers to screen myself for cancer?
No, and this is the most important point on the page. In people without symptoms these markers produce far more false positives than true cancers, leading to unnecessary scans and biopsies. Only PSA has a conditional screening role, after a shared decision-making conversation.
My marker is slightly above the range — what now?
A mildly raised marker most often reflects a benign cause. The correct next step is a clinical assessment and usually a repeat test after an interval, not an immediate scan cascade.
What are these tests actually good for?
Monitoring. In someone with a diagnosed cancer that produces the marker, serial values track response to treatment and can detect recurrence earlier than imaging.
Related biomarkers
Sources
- US Preventive Services Task Force, Prostate Cancer: Screening (2018)
- National Cancer Institute, Tumor Markers in Common Use
- American Cancer Society, Guidelines for the Early Detection of Cancer
Educational information only, not medical advice. Discuss your own results with a qualified healthcare professional.
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