Tumor Markers: Can They Screen for Cancer? What a High Result Means

A patient once walked in looking worried, holding a checkup report with a CEA level slightly above normal. He hadn't slept for several nights. In the end, further tests found no cancer; the cause was probably his smoking. This happens very often, so in this article I want to explain clearly what tumor markers can do and what they can't.

What are tumor markers?

Tumor markers are substances made by cancer cells, or by the body in response to cancer, that can be measured in blood, urine or other body fluids. The problem is that normal cells can make these substances too, and many early-stage cancers don't raise the levels at all.

What tumor markers are genuinely useful for

1. Monitoring treatment in patients already diagnosed with cancer, to see whether treatment is working
2. Watching for recurrence after surgery or completed treatment
3. Supporting a diagnosis once there are symptoms or a lump, such as an ovarian mass or a liver lump
4. Assessing prognosis in some cancers, such as testicular cancer

Why they aren't recommended for screening people without symptoms

Large studies, such as PLCO, which used CA-125 with ultrasound to screen for ovarian cancer, and UKCTOCS, which followed more than 200,000 women, did not find a reduction in deaths from ovarian cancer, but did lead to unnecessary surgery in women who didn't have cancer. Major organizations such as the USPSTF and the American Cancer Society therefore don't recommend CEA, CA 19-9 or CA-125 to screen the general population.

CEA

Colon

• Smoking
• Bowel, liver, lung inflammation; kidney failure

CA 19-9

Pancreas, bile ducts

• Gallstones, bile duct blockage
• Pancreatitis, poorly controlled diabetes

CA-125

Ovary

• Periods, pregnancy
• Endometriosis

AFP

Liver, testis

• Chronic hepatitis, cirrhosis
• Pregnancy

PSA

Prostate

• Enlarged or inflamed prostate
• Ejaculation or cycling before the test

USPSTF and the American Cancer Society do not recommend CEA, CA 19-9 or CA-125 to screen the general public.

Exceptions you should know

• PSA can be used to screen for prostate cancer in men aged 55–69, but the decision should be shared with a doctor, because it reduces deaths slightly at the cost of overdiagnosis and overtreatment in some men. Men taking finasteride or dutasteride have PSA levels about half of what they would otherwise be, so tell your doctor. Men on TRT have PSA monitored according to plan.
• AFP with ultrasound is used to watch for liver cancer every 6 months in people with cirrhosis or some hepatitis B carriers.
• People with high-risk genetics, such as BRCA genes, should have a specific plan from their doctor.

So what cancer screening actually works?

• Cervical cancer: HPV DNA test or Pap smear
• Colorectal cancer: fecal immunochemical test (FIT) or colonoscopy, from age 45–50
• Breast cancer: mammogram
• Lung cancer: low-dose CT in heavy smokers aged 50–80
• Anal cancer in certain high-risk groups; see Anal cancer screening

See the full table in Health checkups for working-age adults: what to test, and remember that the HPV vaccine and hepatitis B vaccine genuinely prevent cancer.

If your tumor marker result comes back high, what should you do?

1. Don't panic. Most slightly high values are not cancer.
2. Bring the result to a doctor with your history, such as smoking, liver disease, periods and medicines you take.
3. Have an examination and discuss your symptoms, such as weight loss, changed bowel habits, abdominal pain or jaundice.
4. You may retest after 4–8 weeks to see the trend.
5. Do further tests as appropriate, such as ultrasound, endoscopy or CT when there is a reason, rather than everything at once.

1. 1Don't panicMildly high values are mostly not cancer
2. 2Doctor reviews with historySmoking, liver disease, periods, medicines
3. 3Examination, symptomsWeight loss, bowel change, abdominal pain, jaundice
4. 4Repeat in 4–8 weeksLook at the trend, not one value
5. 5Further tests if warrantedUltrasound, endoscopy or CT as assessed by your doctor

When to see a doctor promptly

Whatever your tumor marker result, see a doctor if you have any of these: unexplained weight loss, blood in your stool or bowel habits that have changed for several weeks, a lump you can feel, coughing up blood, yellowing of the skin or eyes, chronic abdominal pain, or abnormal vaginal bleeding.

At Dr. Kris Clinic I can interpret the results you've received, explain which values are concerning and which aren't, and plan cancer screening that suits your age and risk, with referral to a specialist when needed. English-speaking consultations are available.