The short answer: none. No tumor marker is suitable for checking for cancer in a healthy person. Early-stage cancer is detected through other screening tests, and these depend on age, sex, and family history.
Why tumor markers do not detect cancer
Tumor markers are proteins that increase in some types of cancer. The problem is that they are not reliable.
A marker can be elevated without cancer. CA-125 can increase with endometriosis, fibroids, inflammation, and even during menstruation. CEA is elevated in smokers. CA 19-9 can increase with gallstones.
A marker can be normal even when cancer is present. For example, CA 19-9 is not produced at all in approximately 5–10% of people: in these people, it will remain normal even if a large tumor is present.
The result of such testing is usually one of two things:
- unnecessary fear, followed by a CT scan, biopsy, weeks of waiting, and unnecessary radiation exposure;
- false reassurance: “the markers are normal, so everything is fine,” even though this proves nothing.
Therefore, large studies have shown that testing healthy people with tumor markers does not reduce cancer mortality. Ovarian cancer screening with CA-125 and ultrasound has been studied in hundreds of thousands of women. It did not save lives, but it did lead to a large number of unnecessary surgeries.
Where tumor markers are actually useful: in some cases in people who have already been diagnosed with cancer. They are used to assess how well treatment is working and to monitor whether the disease has returned.
Which screening tests are actually needed?
Cervical cancer
For women from 21 to 65 years of age.
- From 21 to 29 years — a cervical smear (Pap test) every 3 years.
- From 30 to 65 years — an HPV test or an HPV test together with a cervical smear every 5 years.
Some guidelines recommend another option: starting with an HPV test as early as age 25 and repeating it every 5 years. Both approaches are considered effective.
Breast cancer
For women from age 40 — mammography once a year. Some guidelines allow an interval of once every 2 years.
Colorectal cancer
For everyone from 45 to 75 years of age. There are two options:
- colonoscopy every 10 years;
- a stool test for occult blood once a year. If the result is positive, a colonoscopy is mandatory.
Lung cancer
Only for people with a significant smoking history: 20 pack-years or more*, aged 50–80 years, if they currently smoke or quit no more than 15 years ago. They should have a low-dose CT scan once a year. A standard chest X-ray is not suitable for this purpose.
What is a pack-year?* It means smoking one pack of cigarettes per day for one year. For example, one pack a day for 20 years equals 20 pack-years. Two packs a day for 10 years also equals 20 pack-years.
Prostate cancer
There is no option to “test PSA for everyone”: this screening has both benefits and disadvantages, so the decision is made together with a doctor. Read more about this in a separate article by our urologist: [link].
Important. If close relatives have had cancer, especially if it was diagnosed at a young age, these screening timelines do not apply to you. A doctor will assess your risk and develop an individual plan: screening may start earlier, be performed more frequently, and sometimes include additional tests and genetic testing.
What else can reduce the risk of cancer?
- do not smoke;
- get vaccinated against HPV;
- get vaccinated against hepatitis B;
- drink less alcohol;
- maintain a healthy weight and exercise regularly;
- testing for Helicobacter pylori and treating it: this reduces the risk of stomach cancer;
- keep an eye on moles: if a mole changes in size, color, or shape, show it to a dermatologist.