CEA (Carcinoembryonic Antigen)

A broad tumour marker used mainly for colorectal cancer monitoring.

What it is

CEA is a glycoprotein expressed during foetal development and typically at very low levels in adults. It is elevated in many cancers, most notably colorectal, lung, breast, and stomach cancers. It is also mildly elevated in smokers.

Why it matters

CEA is primarily useful for monitoring known disease — trending it over time gives information about treatment response or recurrence rather than as a primary diagnostic tool. A rising CEA in a patient with known cancer warrants investigation. CEA alone has poor sensitivity and specificity for screening.

How to test

Blood test.

This information is for educational purposes only. Always discuss testing and interpretation of results with your care team.

Optimal range

Below 2.5 ng/mL (non-smoker)

normal

Above 5 ng/mL

elevated — monitor trend

How often

At baseline and each oncology review cycle if indicated.