CEA (Carcinoembryonic Antigen)

CEA (carcinoembryonic antigen) is a protein found in the blood that can be raised in certain cancers, most notably bowel (colorectal) cancer. It is used as a tumour marker, mainly to help monitor known cancers rather than to detect them in the first place.

What it can help assess

• Monitoring known bowel cancer, by tracking how levels change during and after treatment to help assess response and check for recurrence
• Following certain other cancers, including those of the pancreas, stomach, lung, and breast, where CEA may also be raised
• Supporting the wider clinical picture, alongside imaging and other tests

An important note on interpretation

CEA is not a screening or diagnostic test for cancer. Levels can be normal in early disease, so a normal result does not rule cancer out, and it should never be used to detect cancer in someone without a diagnosis. Levels can also be raised by a number of non-cancerous conditions, including smoking, inflammatory bowel disease, and liver and lung conditions. For these reasons the result is always interpreted alongside your full clinical picture rather than on its own.

Why it matters

For people diagnosed with bowel or other cancers, CEA is a useful tool for monitoring the condition over time and assessing how well treatment is working. Any result should be discussed with your GP or specialist, who can interpret it in the context of your individual situation and advise on the appropriate next steps.