The short answer
Tumor markers are substances, often measured in blood, that can be higher in people with certain cancers. They can help guide treatment decisions and monitor how a cancer responds, but they are not usually enough to diagnose cancer on their own.
Tumor markers are substances, often in blood, that can be higher with certain cancers.
They can help guide treatment and monitor how a cancer responds.
Markers are usually not enough to diagnose cancer by themselves.
Some non-cancer conditions can also raise tumor marker levels.
Choose how you want to understand this
The full explanation.
The simple version
Tumor markers are substances — often proteins measured in blood — that can be higher in people with certain cancers. They are a useful tool, but they are only one piece of the picture and usually cannot diagnose cancer by themselves.
How they are used
Tumor markers can help doctors:
- Guide treatment decisions for some cancers
- Check how well a treatment is working, by seeing if the level falls
- Watch for recurrence after treatment, by tracking the level over time
Their limits
Markers are not perfect. Some non-cancer conditions can raise them, and some cancers do not produce them at all. That is why they are used together with imaging, biopsy, and other tests rather than alone.
Tumor markers are one clue among many — rarely enough to diagnose cancer on their own.
Biomarker testing
Newer biomarker tests go further, examining the cancer's genes or proteins to match a person with targeted therapies or immunotherapy. This kind of testing is increasingly part of planning modern cancer treatment.
Words to know
Tap any term to see what it means.
Common questions
▸What is a tumor marker?
A tumor marker is a substance — often a protein — that can be found in higher amounts in the blood, urine, or tissue of some people with cancer. Examples include PSA for prostate and CA-125 for ovarian cancer.
▸Can a tumor marker diagnose cancer?
Usually not on its own. Markers can rise for reasons other than cancer, and some cancers do not raise them. They are used along with other tests, not as a stand-alone diagnosis.
▸How are tumor markers used?
They can help guide treatment choices, check how well treatment is working, and watch for recurrence over time by tracking whether the level goes up or down.
▸What are biomarker tests?
Newer biomarker tests examine the cancer's genes or proteins to help match a person to targeted therapies or immunotherapy. These are increasingly part of planning treatment.
Questions to ask your doctor
Being prepared helps you get the most out of your appointments. Save or print these questions.
Tap a question to save it to your list (kept on this device).
Test your knowledge
0 of 3 answered
This quiz checks understanding of educational content only. It is not medical advice. Open this quiz on its own page.