Carcinoembryonic antigen (CEA)
A protein used mainly to monitor bowel (colorectal) cancer after treatment — a rising level can signal recurrence. It is not a screening test, because it is often normal in early cancer and can be mildly raised in benign conditions and in smokers.
What it measures
Carcinoembryonic antigen is a protein present in fetal tissue that is normally low in adults. Its established clinical role is as a tumour marker in colorectal (bowel) cancer: measured before treatment for a baseline, then followed afterwards, where a rising CEA can be the first sign of cancer returning, often before it shows on scans. It can also be raised in some other cancers (stomach, pancreas, lung, breast). Importantly, it is not used to screen healthy people for cancer, for two reasons: it is often normal in early, curable cancer (so a normal result is falsely reassuring), and it is mildly raised by many benign things — smoking (the commonest reason for a mildly high CEA), inflammatory bowel disease, liver disease, and other inflammation. So a modestly raised CEA in a well person, especially a smoker, usually has a benign explanation, and the number matters most as a trend in someone already diagnosed.
What a high value can mean
- Colorectal cancer — the main use; a raised or, more importantly, rising level in monitoring can signal recurrence.
- Other cancers — stomach, pancreas, lung, breast (less specific).
- Smoking — the commonest cause of a mildly raised CEA in a well person.
- Benign conditions — inflammatory bowel disease, liver disease, pancreatitis, other inflammation.
What a low value can mean
- Normal — expected in health, but note a normal CEA does not exclude cancer, which is why it is not a screening test.
- After successful cancer treatment — a fall toward normal indicates a good response.
When to discuss with a doctor
CEA is a monitoring tool, not a screening test. Its greatest value is the trend in someone treated for colorectal cancer: a baseline before treatment and periodic checks afterwards, where a rising level prompts imaging to look for recurrence. It should not be used to 'check for cancer' in a healthy person, because a normal result can be falsely reassuring and a mildly raised one usually has a benign cause, especially smoking. A modestly raised CEA found incidentally is interpreted in context and often simply monitored. Mediora.AI shows CEA alongside the other tumour markers and flags it as a monitoring rather than screening test; the interpretation belongs with your doctor or oncology team.