Tumor markers, the extended review: CA 15-3, CA 19-9, HE4 and CEA beyond the basic trio

CA 15-3: breast cancer monitoring

CA 15-3 is a marker associated with breast cancer: its main use is watching an advanced process and assessing response to treatment once the diagnosis is established. At early stages it rises rarely, so it is unsuitable for finding disease: a normal value excludes nothing.

Non-cancer causes of elevation are liver diseases and benign breast conditions. Like all tumor markers, CA 15-3 is valuable in dynamics for a given patient: a rise or a fall says more than a single figure.

CA 19-9: pancreas and bile ducts

CA 19-9 is the main marker in pancreatic and biliary tract cancer, where it is used to assess spread and monitor therapy. The test has two important caveats. First: people with a Lewis-negative blood group (several per cent of the population) do not produce this antigen at all — the marker is always low in them, even in disease. Second: any bile stasis and bile duct inflammation raises CA 19-9 without any oncology.

An isolated CA 19-9 rise with jaundice or cholecystitis is therefore not read as an alarm by itself: it is revisited after the bile stasis resolves and together with imaging.

HE4: the complement to CA-125

HE4 — human epididymis protein 4 — is a marker that rises in ovarian cancer less often from benign processes than CA-125: endometriosis and inflammation raise CA-125 but barely touch HE4. The pair is therefore used together — in risk indices for an adnexal mass: the combination of two markers with age and ultrasound separates high and low risk.

An important caveat: HE4 rises with age and with reduced kidney function — creatinine in the report helps read the result correctly. Like CA-125, HE4 is not a screening test for healthy women.

CEA: colorectal cancer monitoring

Carcinoembryonic antigen is the classic marker of colorectal cancer: its main role is assessing stage, prognosis and post-treatment observation. Smokers have a higher baseline, and benign causes of elevation — liver disease, inflammatory bowel disease, pancreatitis — are common.

In practice this means a simple thing: CEA is not used to search for colon cancer — screening programmes with a different logic exist for that. The marker works where the diagnosis is already known and a laboratory reflector of process activity is needed.

The common principle: why screening does not work

All tumor markers share one limitation: insufficient specificity for a healthy person. Elevations occur in benign diseases, and a normal value does not exclude an early tumour. Mass marker testing 'for a check-up' therefore yields false alarm and false reassurance, but not early diagnosis.

The right niches: risk assessment in a defined situation (for instance, an adnexal mass), monitoring an established diagnosis, tracking treatment response and watching remission. Within these frames markers are the oncologist's working tool; outside them, a source of noise.

Where tumor markers actually work

Markers covered in this article

Frequently asked questions

Sources

Keep reading