CEA (carcinoembryonic antigen) is a protein made by some types of cancer including bowel cancer.
Your CEA level can be measured by a simple blood test. CEA markers can be used by your doctor to monitor the response to chemotherapy, as well as often being used in the follow-up period when treatment ends. However a CEA test cannot be used on its own as a means to diagnose bowel cancer, because not all bowel cancers produce the protein. So, some people who have bowel cancer do not show raised CEA levels at all.
Measuring CEA as part of your follow-up care becomes a useful test if your level was raised before the tumour was removed. In this case, a rising CEA level in the months and years following your operation could be an indicator of the cancer coming back. CEA can be a useful marker for detecting a new CEA-producing tumour, but a one-off raised CEA is not necessarily a sign of the cancer returning. Sometimes the CEA test is repeated to check that it wasn’t just a blip or it might trigger scans in order to find out more. Understandably, any rise in your CEA level can cause a great deal of anxiety for you and everyone close to you.
A normal CEA level for an adult non-smoker is less than 2.5 and for a smoker less than 5. However your CEA level goes up and down over time, just like your blood sugar level, blood pressure and heart rate. So a rise of anything up to 5, 6 or 7 could still be normal.
A CEA level rise from 4 to 5 does not mean that your cancer is returning. On the other hand, an upward trend of, for example, 4 to 10 to 20 at consecutive readings would trigger further investigation.
Several factors can cause your CEA level to rise, including smoking, an infection, inflammatory bowel disease, pancreatitis, liver cirrhosis and other cancers. Chemotherapy and radiotherapy can also cause a temporary rise in CEA levels.