The short answer
Tumor markers are proteins that cancer cells and healthy tissue both make. Levels shift with benign conditions, inflammation, medicines and lab methods, so a trend tells you more than one number.
No tumor marker is made only by cancer — healthy organs produce these same proteins, which is why benign conditions raise them.
PSA can rise with an enlarged prostate, infection, a recent biopsy, vigorous exercise such as cycling, or ejaculation. CEA can rise with smoking and some liver and other noncancer conditions.
Ask whether your results came from the same lab and test as your last one, since a change in method could change the number.
If tumor marker levels go down during treatment, it usually means the treatment is helping. Your care team looks at the trend over time.
On this page
Watch: Tumor markers, explained
2 min 34 sec · Captioned · PSA, CA-125, CEA — what tumor marker blood tests can and cannot tell you.
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Educational only — this video explains general report language and is not medical advice. Only your care team can say what a result means for you.
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This page is for people watching tumor marker numbers on their blood tests. It explains why markers go up or down, and why the trend matters more than any single result.
What a tumor marker actually is
A tumor marker is a substance, usually a protein, that can be measured in blood, urine or tissue. Levels of it may be higher when cancer is present. Here are the ones you are most likely to see on a results portal:
- CA-125 (ovarian cancer)
- CEA (colorectal and some other cancers)
- PSA (prostate cancer)
- CA 19-9 (pancreatic, gallbladder, bile duct and stomach cancers)
- AFP (liver cancer, ovarian cancer and germ cell tumors)
- Beta-hCG (choriocarcinoma and germ cell tumors)
- LDH (germ cell tumors, lymphoma, leukemia, melanoma and neuroblastoma)
One fact explains most of what follows. Some conditions that are not cancer can also raise these markers, so a marker is not a direct count of cancer cells.
Why a level rises
More cancer, or more active cancer. This is the first thing people think of, and it is a real possibility. Doctors use markers to follow how well treatment is working.
Benign conditions in the same organ. Benign means not cancer. PSA can rise with an enlarged prostate, prostatitis (an inflamed prostate) or an infection of the prostate. A recent prostate biopsy can raise it for a month or two. Vigorous exercise such as cycling and ejaculation can raise it for a short time. Other markers can also be raised by noncancer conditions. Ask your care team what could affect your marker.
Inflammation and organ stress elsewhere. MedlinePlus says smoking increases CEA levels. It also lists liver conditions such as cirrhosis, gallstones and steatotic liver disease, as well as other conditions such as COPD, diverticulitis and Crohn's disease, as noncancer causes of a higher CEA.
Other reasons. A change of laboratory or test kit may also change a number. Ask your care team whether your results came from the same lab. Your team can tell you whether anything about your treatment could affect the result.
Why a level falls
MedlinePlus says that if tumor marker levels go down, it usually means your treatment is helping. But levels also fall when a benign cause clears up. An infection settles. A bile duct is unblocked. A period ends. Some medicines lower markers directly. NCI says finasteride and dutasteride, taken for an enlarged prostate, lower the PSA level.
Why the trend matters more than any single number
A marker taken once is a snapshot with no context. A marker taken several times over weeks or months shows a trend. Your care team looks at that trend together with your other tests.
Your care team decides what size of change matters for your marker and your cancer. Ask what change they would consider meaningful.
What markers cannot tell you
A marker is not a diagnosis. It is not a stage. It is not a score of how serious your cancer is. A high number does not translate into a prognosis, the likely course of the illness. Two people with the same CA-125 can be in completely different situations. Markers also cannot stand alone. The picture is built from imaging, examination, symptoms and pathology, with the marker as one input.
What usually happens next
When a marker moves in an unexpected direction, the usual response is to repeat the test after a gap. Your team compares it against your own earlier values. They check whether anything else could explain it. They add imaging if the trend continues. Treatment is rarely changed on the strength of one result.
Sources
Common questions
My marker went up by a few points. Is that a real change?
Maybe not. Some conditions that are not cancer can raise tumor marker levels. Your care team may repeat the test and compare it with your earlier results before drawing a conclusion. Ask what size of change they consider meaningful.
Why did my result change when nothing about my treatment changed?
Some conditions that are not cancer, such as infection or inflammation, can raise tumor markers. A different laboratory or test kit may also be a reason. Your team may ask about these before ordering more tests.
Does a falling marker always mean the treatment is working?
MedlinePlus says that if levels go down, it usually means treatment is helping, but a marker is not proof on its own. NCI says some medicines, such as finasteride and dutasteride, lower PSA. Your team also uses other tests to see how treatment is working.
Should I keep my own chart of my results?
Many people find it helpful, and it makes patterns easier to discuss. Record the value, the date and the laboratory name so you can share them with your team. Try to hold the chart lightly between appointments — a graph of two points can look alarming and mean very little.
Questions to ask your doctor
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Written by: Cancer ExplainedSources last checked: 2026-07-30 what this meansLast updated: 2026-10-16Next planned review: 2027-07-30
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Cancer Explained does not originate medical claims. Every page restates guidance already published by the National Cancer Institute, the CDC, the USPSTF and the FDA, in plain language, with the source cited so you can check the original yourself. AI does the translating and organizing; automated checks test claims, citations, clarity and safety before anything publishes, and this is translation and navigation, not clinical judgment. Nothing here is personal medical advice, and no page can account for your particular situation.
Editorial status: Source checked — This page was written with AI assistance and then compared with the sources listed on it, looking for statements those sources do not back up. That check is not a sentence-by-sentence record and can miss errors. It is not a medical review, and it does not confirm the page is complete or right for your situation.
Human medical review: not completed. Pages here are not signed off by a clinician before they publish. That is not an oversight we are quietly working around: we restate published guidance and cite it, so the authority belongs to the source rather than to us, and every page names where its claims come from — you can verify us instead of trusting us. Where a volunteer clinician has reviewed a page, their name and credentials appear on it; where no name appears, no clinician has checked it. We are glad to have reviewers and are recruiting them, and we do not hold pages back waiting for one. Use this site to understand your situation and to ask better questions of the people treating you.
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