CEA (carcinoembryonic antigen): what it is, what it tells you and when it’s tested

CEA, or carcinoembryonic antigen, is a protein found in small amounts in your blood. Some cancers, mainly of the colon and rectum, make more of it. But it also rises for reasons that have nothing to do with cancer, such as smoking. That is why it is not used to look for cancer in people who feel well: it is mainly used to follow a disease that is already known.

When it’s tested

It is usually ordered by an oncologist, for people who have or have had cancer, mainly of the colon and rectum. It is measured before surgery, as a starting point, then at check-ups in the years after and to see whether a treatment is working.

It is not a screening test. Italian and international guidelines advise against using it to look for cancer in people who feel well: it often rises for other reasons, and in early cancer it is often normal. Bowel cancer screening uses a faecal occult blood test, offered by your region.

That is why Rosa does not test it. The Rosa panel is a general prevention check-up, not a cancer test: it looks at your heart, metabolism, liver, kidneys, thyroid and blood.

What it tells you, and what it does not

A high CEA does not mean cancer. Smoking, alcohol and some liver, lung and kidney conditions can raise it.

A normal CEA does not rule out cancer. Many cancers, especially early on, do not raise it.

What matters most is how it changes over time, in the same person and at the same lab. That is why it is useful for people being followed after treatment.

Your doctor reads it together with other tests:

• Faecal occult blood: It is the bowel cancer screening test
• ALT and AST: Liver conditions can raise CEA
• Gamma GT: It says something about your liver and alcohol
• CA 19-9: Another marker, sometimes measured alongside

Normal CEA levels

The lab decides what is normal. Many lab reports give a CEA below 5 ng/mL. In smokers it is often a little higher, and some labs print a different limit for people who smoke.

Each lab uses its own method, and the same blood can give slightly different numbers at two labs. If your CEA needs to be followed over time, it is best to use the same lab every time.

Why CEA can be high

There are many causes, and often they are not cancer.

• Smoking: It is a common cause of a slightly high CEA. People who smoke often have higher levels than people who do not.
• Drinking a lot: Heavy drinking can raise it.
• Liver conditions: Chronic hepatitis or cirrhosis can raise it.
• Lung conditions: Chronic bronchitis and other long-term lung conditions can raise it.
• Kidneys working less well: Chronic kidney failure can raise it.
• Some cancers: Mainly of the colon and rectum, but others too. That is why, if the value is high, your doctor first tries to understand why.

If you have had bowel cancer

This is where CEA really helps. It is measured before surgery, as a starting point, and then at regular intervals in the first years of check-ups, as your oncologist decides.

A single slightly higher result is usually repeated. If the rise is confirmed, your doctor orders other tests, such as a CT scan, to find out where it comes from.

CEA does not replace check-up visits, colonoscopy and the other follow-up tests. It works alongside them.

If your CEA is above the limit

Try not to worry: it is common, and often harmless. Where to start:

• Show the report to the doctor who ordered it, or to your GP.
• Tell them whether you smoke, how much you drink and whether you have liver, lung or kidney problems.
• Your doctor often has it repeated a few weeks later, at the same lab, to see whether it stays the same or rises.
• Only your doctor decides whether more tests are needed. A high result on its own is not enough for a diagnosis.

If you are of bowel screening age and have not done it yet, this is a good moment to talk to your doctor about it.

When to talk to a doctor

Talk to your doctor if:

• Your CEA is above the limit on your report, even if you feel well.
• You have had cancer and your CEA rises from one check-up to the next.
• You have blood in your stools, a change in your bowel habits that has lasted for weeks, or you are losing weight without trying.
• You have black stools or a lot of blood in your stools, or you vomit blood: call 112 or go to the emergency department.

Frequently asked questions

High CEA: what are the benign causes? The most common are smoking, alcohol and some liver, lung and kidney conditions. That is why a high CEA, on its own, does not mean cancer.

What are normal CEA levels? Many lab reports give a value below 5 ng/mL, sometimes with a different limit for smokers. The range on your own report is what counts.

Is CEA a good test for prevention? No. It is not a test to have as a check-up when you feel well. For the bowel, screening uses a faecal occult blood test or a colonoscopy, as your doctor advises.

Does a normal CEA rule out cancer? No. Many cancers, especially early on, do not raise it. If you have symptoms, talk to your doctor even if your CEA is normal.

Does Rosa test CEA? No. Rosa is a general prevention check-up and does not include tumour markers. If your doctor thinks CEA is useful, they order it separately.

Sources

• AGENAS (Italian National Agency for Regional Health Services), circulating tumour markers in oncology: a guide to appropriate clinical use, summarising guidelines including AIOM, ESMO and ASCO. Quaderno di Monitor, 2016. AGENAS 2016
• Locker and colleagues, ASCO 2006 update of recommendations for the use of tumor markers in gastrointestinal cancer. Journal of Clinical Oncology, 2006. PMID 17060676
• Sturgeon and colleagues, National Academy of Clinical Biochemistry guidelines for use of tumor markers in testicular, prostate, colorectal, breast, and ovarian cancers. Clinical Chemistry, 2008. PMID 19042984