Immunotherapy for Metastatic Breast Cancer
Watch our March 2024 MBC Impact Series, Research Update on Triple Negative Metastatic Breast Cancer.
What are immunotherapy drugs?
Immunotherapy drugs help the body’s immune system attack cancer cells.
There are many types of immunotherapy drugs. Certain immunotherapy drugs may be helpful in treating some metastatic breast cancers.
Researchers are studying how to identify which metastatic breast cancers will respond best to immunotherapy.
Checkpoint inhibitors
Checkpoint inhibitors are the most widely used type of immunotherapy drugs. These drugs “take the brakes off” the natural factors that limit how the immune system can control cancer cells.
Pembrolizumab (Keytruda) is a checkpoint inhibitor immunotherapy antibody drug used to treat some metastatic breast cancers.
Other immunotherapy drugs to treat metastatic breast cancer are under study.
Pembrolizumab (Keytruda) and treatment for triple negative metastatic breast cancer
Triple negative breast cancers are:
Pembrolizumab in combination with chemotherapy is FDA-approved as a first treatment for metastatic triple negative breast cancers that are PD-L1-positive (programmed cell death ligand 1-positive).
To see if pembrolizumab would be helpful as a first treatment, all metastatic triple negative breast cancers are tested to learn if they are PD-L1-positive [4].
Compared to chemotherapy alone, chemotherapy in combination with pembrolizumab may give people with PD-L1-positive metastatic triple negative breast cancer more time before the cancer worsens and may improve survival [73-75].
| For a summary of research studies on pembrolizumab and triple negative metastatic breast cancer treatment, visit the Breast Cancer Research Studies section. |
Learn more about triple negative breast cancer.
Learn more about treatment for metastatic breast cancer.
Learn about emerging areas in treatment for metastatic breast cancer.
Learn about pembrolizumab and treatment for early triple negative breast cancer.
Pembrolizumab and treatment for metastatic breast cancers with a high tumor burden or high microsatellite instability
Pembrolizumab is also FDA-approved for the treatment of metastatic breast cancers that have a high tumor mutational burden or high microsatellite instability.
A high tumor mutational burden means there are a high number of gene mutations in the metastatic breast cancer cells. A high microsatellite instability means there are problems with DNA repair in the cancer cells.
It’s not common for metastatic breast cancers to have a high tumor mutational burden or a high microsatellite instability. However, high tumor burden is more common in triple negative metastatic breast cancers than in estrogen receptor-positive or HER2-positive metastatic breast cancers.
Learn more about triple negative breast cancer.
Learn more about treatment for metastatic breast cancer.
Learn about emerging areas in treatment for metastatic breast cancer.
How is pembrolizumab given?
Pembrolizumab is given by through an IV into a vein.
Talk with your health care provider if you have any questions or concerns about your medications.
Side effects of pembrolizumab
Before you begin treatment with pembrolizumab, talk with your health care team about possible side effects and how to manage them.
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Side Effects |
Pembrolizumab |
Possible side effects include fatigue, muscle pain, decreased appetite, itchiness, diarrhea, nausea, rash and constipation. Pembrolizumab can cause thyroid problems and other hormone problems, which may be permanent and lead to the need for hormone treatment. Pembrolizumab can also cause severe colitis and liver problems that sometimes can lead to hospitalization. In rare cases, pembrolizumab can cause lung inflammation, which can lead to death. Tell your health care provider right away if you have shortness of breath or other breathing problems while taking this drug. |
Adapted from select sources [75]. |
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Learn more about side effects.
Ashley Fernandez, living with metastatic breast cancer
“What keeps me going is my new normal. My life with cancer is completely different, I know I have it and I live with it every single day but it doesn’t take over every single day.”
A note about atezolizumab (Tecentriq)
The checkpoint inhibitor immunotherapy drug atezolizumab was given accelerated FDA approval in 2019. However, the manufacturer withdrew its application for full FDA approval in 2021, so it’s not newly prescribed for people with metastatic breast cancer.
If you’ve been taking atezolizumab for metastatic breast cancer, talk with your health care provider.
Atezolizumab remains FDA-approved for use in other cancers.
Treatment guidelines for metastatic breast cancer
Although the exact treatment for metastatic breast cancer varies from person to person, guidelines help make sure high-quality care is given. These guidelines are based on the latest research and agreement among experts.
The National Comprehensive Cancer Network (NCCN) and the American Society of Clinical Oncology (ASCO) are respected organizations that regularly review and update their guidelines.
In addition, the National Cancer Institute (NCI) has treatment overviews.
Talk with your health care team about which treatment guidelines they follow.
Monitoring metastatic breast cancer
You’ll be monitored (checked) regularly with scans to see if the cancer is responding to treatment. If the treatment is no longer working, or you’re having a lot of side effects, your health care provider will change your treatment or discuss other options.
Learn more about how metastatic breast cancer is monitored.
Clinical trials
Clinical trials offer the chance to try new treatments and possibly benefit from them. They can also study other parts of care, such as ways to manage side effects. We encourage you to talk with your oncologist and consider joining a clinical trial if there’s one right for you.
Some clinical trials are available as the first step in treating metastatic breast cancer. Others are for later in the disease course.
Consider joining a clinical trial when you’re newly diagnosed, when your oncologist is considering changing treatments or when there are limited treatment options.
Read our blogs:
- Four Things to Know About Clinical Trials When You’re Diagnosed with Breast Cancer
- How Do You Thank Someone for Time
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Susan G. Komen® Patient Care Center |
If you or a loved one needs information or resources about clinical trials, the Patient Care Center can help. Contact the Komen Breast Care Helpline at 1-877-465-6636 or email clinicaltrialinfo@komen.org. Se habla español. |
Metastatic Trial Search |
The Metastatic Trial Search is an online clinical trial matching tool that can help you find clinical trials that fit your needs. You can also register to receive Trial Alerts. |
Learn more about clinical trials for people with metastatic breast cancer.
Learn what Komen is doing to help people find and participate in breast cancer clinical trials, including trials supported by Komen.
Learn how Komen-funded research is improving treatment for breast cancer.
Financial assistance
Costs related to metastatic breast cancer care can quickly become a financial burden. Dealing with finances and insurance can be overwhelming. Cancer or its treatments may also keep you or your partner from working as much as you used to, which can affect your income and possibly your insurance coverage.
You may qualify for financial assistance from federal, state or local programs. A financial counselor or social worker at your hospital can help you learn about these programs.
Many hospitals have financial counselors who can discuss insurance and cost coverage with you. They may be able to arrange a payment plan for hospital-related costs.
Learn about insurance and financial assistance programs.
Learn about transportation, lodging, childcare and eldercare assistance programs.
Learn about resources that offer practical support.
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Komen Financial Assistance Program |
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Susan G. Komen® created the Komen Financial Assistance Program to help those struggling with the costs of breast cancer treatment by providing financial assistance to eligible individuals. To learn more about this program and other helpful resources, call the Komen Patient Care Center at 1-877 GO KOMEN (1-877-465-6636) or email helpline@komen.org. Se habla español. Learn about other financial assistance programs. |
SUSAN G. KOMEN® METASTATIC BREAST CANCER SUPPORT RESOURCES |
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Updated 03/14/26
This content is regularly reviewed by an expert panel including researchers, practicing clinicians and patient advocates.
