Breast Cancer: Biomarker Testing
Biomarker Testing for People with Breast Cancer
This section covers the following topics:
testing for treatment selection
Biomarker tests look at samples of blood, tumor or other tissue for changes or abnormalities caused by cancer. These tests can give doctors clues about the cancer, including:
- how fast the cancer is growing
- which treatments are most likely to work
- whether or not the cancer is responding to treatment or growing
- whether or not the cancer has come back after remission
Biomarker tests may be used to select treatments, and help patients avoid side effects from treatments that will not work for them. Biomarker tests used to select a specific treatment are sometimes called "companion diagnostic tests." These tests may be done on tumor tissue or (in many cases) on blood. See our Biomarker Testing section for more information.
After breast cancer tissue is removed by surgery or biopsy, all breast cancers are tested for three common biomarkers: receptors, progesteron receptors and a protein known as .
Hormone receptors: estrogen (ER) and progesterone (PR)
Testing is done to look for two separate hormone receptors, estrogen receptors (ER) and progesterone receptors (PR).
- Cancers that test positive for estrogen and progesterone receptors are known as . They may also be called . These cancers are often treated with hormone therapies.
- Cancers that test negative for estrogen and progesterone receptors are known as or HR-negative. These cancers are not usually treated with hormone therapy.
HER2 testing
HER2 is a protein that is found on all breast cancer cells. Doctors use a test to measure the amount of a protein called HER2 on cancer cells. HER2 test results range from 0 to 3+. cancers contain a large amount of HER2 protein. These cancers are usually treated with targeted therapies known as "anti-HER2 therapy." Common anti-HER2 treatments include Herceptin (trastuzumab) and Perjeta (pertuzumab). See our section on targeted therapies for more information.
- A HER2 score of 3+ is considered HER2-positive. These cancers are often treated with anti-HER2 therapy.
- A HER2 score between 1-2 is considered HER2-low: In the past, these were considered . Some people with advanced HER2-low breast cancer may benefit from an anti-HER2 therapy known as Enhertu (trastuzumab deruxtecan).
- A HER2 score between 0-1 is considered HER2-ultralow: In the past, these were considered HER2-negative. Some people with advanced HER2-ultra-low breast cancer may benefit from an anti-HER2 therapy known as Enhertu (trastuzumab deruxtecan).
- HER2-negative: A tumor with a HER2 score of 0 is considered HER2-negative.
Possible HER2 scores
HER2 Test Score |
HER2 Status |
Score is 0 |
HER2-negative |
Score is more than 0 and less than 1 |
HER2-ultralow |
Score is 1+ or 2+ |
HER2-low |
Score is 3+ |
HER2-positive |
Possible HER2 test results and meaning |
|
()
Breast cancers that are negative for the biomarkers ER, PR and HER2 are known as triple-negative breast cancers. These cancers do not usually respond to hormonal therapies or anti-HER2 targeted therapies. For this reason, TNBC is often treated with chemotherapy. New approaches to treating TNBC include and targeted therapies. Additional biomarker testing can help people learn if they qualify for other treatments.
Other biomarkers used for breast cancer treatment selection
Additional biomarker testing may be done to study the genes and proteins within the cancer to help doctors choose the best treatment. Some treatments will work best for people whose cancer cells have specific changes. These treatments are sometimes called targeted therapies. The for a specific is sometimes called a . Some tests look for only one biomarker at a time, while others may test for all many biomarkers at the same time. Panel tests look for multiple markers, including FDA-approved treatments as well as those that have not yet been proven effective in breast cancer. Examples of multiple biomarker tumor tests for breast cancer include:
- FoundationOne
- MSK-IMPACT
- Tempus xT
Examples of biomarkers used to guide breast cancer treatment include:
- ESR1 mutation testing in HR-positive advanced breast cancer for treatment with the drug Oserdu (olacestrant).
- PIK3CA mutation testing in ER-positive, Her2-negative advanced breast cancer for treatment with the drug PIQRAY (alpelisib).
- , PIK3 or AKT1 mutation testing in HR-positive, HER2-negative advanced breast cancer for treatment with the targeted therapy Truqap (capivasertib).
- PD-L1: Testing for the protein can help find people with advanced triple-negative breast cancer (TNBC) who are most likely to respond to the immunotherapy drug Keytruda (pembrolizumab).
- Additional tumor biomarker testing may help people learn if they are eligible for certain clinical trials.
Biomarker tests for prognosis in breast cancer
These tests are used for people with early-stage ER/PR-positive cancers to predict:
- if the cancer is likely to come back
- the benefit of adding chemotherapy to the treatment plan
- how long hormonal therapy should be used
Some examples of the most commonly used prognostic tests for breast cancer are listed below:
- Oncotype Dx
- Breast Cancer Index
- MammaPrint
- Prosigna
Genetic tests for inherited mutations for treatment selection
Genetic testing for an may be used to guide treatment selection for people diagnosed with breast cancer.
- People with advanced breast cancer who test positive for an inherited or mutation may benefit from treatments known as PARP inhibitors. Two PARP inhibitors—Lynparza and —are approved as targeted therapy for treating advanced breast cancer in people with a BRCA1 or BRCA2 mutation.
- Lynparza may be used to as therapy after treatment for people with an inherited BRCA1 or BRCA2 mutation who have early-stage breast cancer this is high risk for recurrence.
- People who test positive for other inherited gene mutations may qualify for clinical trials looking at targeted therapies to treat hereditary breast cancer.
Visit our section on genetic testing for people diagnosed with breast cancer.
Related Videos
The Role of HER2 Low in Breast Cancer
Biomarkers and Liquid Biopsies
Participate in Research
Study of a New InvestigationaI Inhibitor to Treat People with Advanced Solid Tumors
Clinicaltrials.gov identifier: NCT05932862
