Resource center · Early cancer diagnostics
Cancer biomarkers: what they are and how they are used
Cancer biomarkers are measurable characteristics, such as proteins or gene changes, that give information about a cancer. This guide covers the main types, how laboratories measure them and why most cannot be used on their own to find cancer.
- Educational guide
- Reviewed October 2026
What cancer biomarkers are
Cancer biomarkers are measurable characteristics of a person or a tumor that give information about a cancer. The BEST glossary, maintained jointly by the U.S. Food and Drug Administration and the National Institutes of Health, defines a biomarker as “a defined characteristic that is measured as an indicator of normal biological processes, pathogenic processes, or biological responses to an exposure or intervention.”
In oncology the terms biomarker and tumor marker are often used for the same thing. The U.S. National Cancer Institute (NCI) describes a tumor marker as anything present in or produced by cancer cells, or by other cells of the body in response to cancer or certain benign conditions, that provides information about a cancer. Traditionally these were proteins; many are now genomic, such as gene mutations or patterns of gene expression.
Types of cancer biomarkers by clinical purpose
A biomarker is classified by the question it answers, not by the kind of molecule. The BEST glossary lists several categories. Those met most often in cancer care are:
- Susceptibility or risk: indicates the potential to develop a disease in someone who does not currently have it.
- Diagnostic: helps detect or confirm a disease, or identify its subtype.
- Prognostic: indicates the likely course of the disease.
- Predictive: identifies people more likely to respond to a particular treatment.
- Monitoring: measured repeatedly to follow disease status or the effect of treatment.
A marker validated for one purpose is not automatically valid for another. A protein that is useful for following treatment may be of little use for finding cancer in people without symptoms.
Examples of tumor markers in common use
Six markers from the NCI list, with the specimen analyzed and the use NCI gives for each.
| Marker | Cancer types | What is analyzed | How it is used |
|---|---|---|---|
| Alpha-fetoprotein (AFP) | Liver cancer and germ cell tumors | Blood | Helps diagnose; follows response to treatment; assesses stage and prognosis |
| Carcinoembryonic antigen (CEA) | Colorectal cancer and some other cancers | Blood | Checks how well treatment is working and whether cancer has returned |
| Prostate-specific antigen (PSA) | Prostate cancer | Blood | Helps in diagnosis; assesses response to treatment; looks for recurrence |
| CA-125 | Ovarian cancer | Blood | Helps in diagnosis; assesses response to treatment; evaluates recurrence |
| HER2 | Breast, stomach and several other cancers | Tumor tissue | Helps determine treatment |
| PD-L1 | Lung and several other cancers | Tumor tissue | Helps determine treatment |
Source: National Cancer Institute, Tumor Marker Tests in Common Use (reviewed December 2023). Wording condensed.
Where biomarkers are measured and how
Circulating markers are measured in blood, urine, stool or other body fluids. Tissue markers are measured in a sample of the tumor itself. Tumors can also shed cells or fragments of genetic material into the blood, and tests that measure these are called liquid biopsies.
The method depends on the molecule. Protein markers are usually measured by immunoassay, which uses antibodies to capture and label the target. Formats range from automated laboratory analyzers to lateral flow tests read within minutes. DNA and RNA markers need molecular methods such as PCR or sequencing, and proteins in tissue sections are assessed by immunohistochemistry. Protein markers are covered in more detail in tumor antigen detection.
What a biomarker result can and cannot show
NCI is direct about the limits. An elevated tumor marker level does not mean that a person has cancer, because noncancerous conditions can raise the level too. PSA, for example, is made by normal as well as malignant prostate cells, and it rises in benign prostatic hyperplasia and prostatitis. The reverse also holds: not everyone with a given cancer has a raised level of the marker associated with it.
For these reasons NCI states that circulating tumor markers have generally not worked well for screening. They miss some people who have the disease and flag some who do not. CA-125 is an example: NCI’s evidence summary notes that a raised level is not specific to ovarian cancer, and that screening with CA-125 and transvaginal ultrasound did not reduce deaths from ovarian cancer.
In practice a marker result is one input among several. It is interpreted with the clinical history, imaging and, where cancer is suspected, examination of tissue by a pathologist. The case for and against testing people without symptoms is set out in why early detection matters.
From candidate marker to routine test
Many candidate markers are reported in research and few reach routine use. A marker has to be measurable reliably (analytical validity), has to separate the groups it claims to separate (clinical validity), and has to lead to better decisions or outcomes when used (clinical utility).
Laboratories also need to allow for differences between methods. Results for the same marker can differ from one assay to another, so serial measurements are normally made with the same method and read against the reference range or cut-off stated for that method.
Where First Diagnostic fits
First Diagnostic™ Corporation distributes rapid tests for professional in vitro diagnostic use, including qualitative PSA, CEA and AFP tests listed with its tumor-marker and general health rapid tests. These tests are aids used alongside other clinical and laboratory findings; they are not cancer screening or diagnostic tools. Wider rapid cancer-marker testing is a longer-term interest for the company, and nothing beyond the current catalog is available yet. For documentation, contact the sales team.
Frequently asked questions
What is the difference between a biomarker and a tumor marker?
A biomarker is any measured characteristic that indicates a biological process or a response to an intervention. A tumor marker is a biomarker that gives information about a cancer. In cancer care the two terms are often used interchangeably.
Can a biomarker test diagnose cancer on its own?
Generally not. Marker levels can be raised by noncancerous conditions and can be normal in people who have cancer. A result is interpreted with the clinical picture and imaging, and a diagnosis is normally confirmed by pathology.
Which specimens are used for cancer biomarker testing?
Blood is the most common specimen for circulating markers; urine, stool and other body fluids are used for some. Markers that guide treatment, such as HER2 and PD-L1, are usually measured in tumor tissue.
Are there rapid tests for cancer biomarkers?
Qualitative lateral flow tests exist for some protein markers, including PSA, CEA and AFP. They report whether the marker is above the cut-off defined in the product insert, as an aid for professional use. They do not replace quantitative laboratory measurement, imaging or pathology.
Keep reading
- Tumor antigen detection — Antigen classes, immunoassay methods and the limits of protein tumor markers.
- Why early detection matters — Early diagnosis versus screening, and what the evidence supports.
- Liquid biopsy explained — Measuring tumor-derived material in blood.
- How lateral flow assays work — Strip components, sandwich and competitive formats, and reading results.
- Lateral flow tests explained — The pillar guide: what lateral flow tests are, where they are used and how to choose them.
References
- U.S. Food and Drug Administration–National Institutes of Health Biomarker Working Group. BEST (Biomarkers, EndpointS, and other Tools) Resource: glossary entry “biomarker”. NCBI Bookshelf. ncbi.nlm.nih.gov
- National Cancer Institute. Tumor Markers. Reviewed December 7, 2023. cancer.gov
- National Cancer Institute. Tumor Marker Tests in Common Use. Reviewed December 7, 2023. cancer.gov
- National Cancer Institute. Prostate-Specific Antigen (PSA) Test. Reviewed January 31, 2025. cancer.gov
- National Cancer Institute. Ovarian, Fallopian Tube, and Primary Peritoneal Cancers Screening (PDQ®)–Health Professional Version. Updated April 9, 2025. cancer.gov
Regulatory status: Products shown on this website are for professional in vitro diagnostic use. They are not cleared, approved or authorized by the U.S. Food and Drug Administration and are not offered for sale in the United States. Product availability and regulatory status vary by country; contact us for the status in your market.