Tumour markers: what they can and cannot tell you
Tumour markers are blood proteins, not cancer tests on their own. A raised result raises a question, not an answer.
What tumour markers are
Tumour markers are proteins that can rise in the blood for many reasons. On their own, they are not a test for cancer.
They are made by normal tissue as well as by tumours. That is why everyday conditions can nudge them up.
They do not replace screening
Mammography, colonoscopy and cervical screening remain the standard tests. A blood marker is an addition, not a substitute.
Those screening tests look directly at the tissue at risk. A blood protein only hints at what might be happening.
What each one reflects
| Marker | What it reflects | A common reason it rises |
|---|---|---|
| CEA | Bowel and general tissue turnover | Smoking, more often than anything serious |
| CA125 | The lining of the abdomen and pelvis | Periods, fibroids and ovarian cysts |
| CA19-9 | The pancreas and bile ducts | Gallstones, and some people never produce it |
CA19-9 is a good example of the limits. Around one in ten people do not make it at all, so a normal result can mislead in them.
Why we do not use them alone
When they are useful
They earn their place following a condition already known. A trend across several tests says more than any single value.
After a cancer diagnosis, they can help track response to treatment, and watch for a return afterwards. That steady, monitored use is where they do their real work.
What a raised result means
Most raised results are not cancer. The usual next step is to repeat the test and to look with a scan.
How high it is, and whether it is rising, both matter. A single borderline value is very different from a steep climb.
Should you order them yourself?
As a standalone screen in a well person, they are rarely helpful. If you are considering them, talk it through first.
Ask what a raised result would change, and what a normal result would rule out. If neither answer changes your plan, the test may not earn its place.
A word on PSA
PSA is the one people ask about most. A raised PSA far more often reflects a benign, enlarged prostate than cancer.
Cycling, a recent examination or an infection can all lift it. It is a conversation to have, not a verdict to fear.
The bottom line
Tumour markers add context, they do not screen for cancer. They are read with your history, symptoms and scans.
Keep your standard screening on schedule regardless. That is what the evidence supports.
What we published, what we read, and the one thing worth changing. Nothing to buy.
Early signals, from one blood draw.
The Core Health Test measures 100+ markers, with a doctor to walk you through what each one means for you.
cancer screening in the Core Health Test