What are immunotherapy drugs?

Immunotherapy drugs help your body’s immune system attack cancer cells. There are many types of immunotherapy drugs.

Certain immunotherapy drugs are helpful in treating some breast cancers.

Learn about immunotherapy and metastatic breast cancer treatment.

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) and early breast cancer

Pembrolizumab (Keytruda) is a checkpoint inhibitor immunotherapy drug. Pembrolizumab is FDA-approved for the treatment of early triple negative breast cancer (TNBC) at high risk of recurrence (a return of breast cancer).

TNBC is:

Pembrolizumab is given before breast surgery (called neoadjuvant therapy), along with chemotherapy. Studies show adding pembrolizumab to neoadjuvant chemotherapy helps shrink TNBC during neoadjuvant therapy and may lower the risk of breast cancer recurrence [155-156].

If you’ve been diagnosed with early TNBC, talk with your health care provider about whether pembrolizumab is an option for you.

Other checkpoint inhibitor immunotherapy drugs are under study for use in early breast cancer treatment.

Learn more about triple negative breast cancer.


For a summary of research studies on pemobrolizumab and early breast cancer treatment, visit the Breast Cancer Research Studies section.

How is pembrolizumab given?

Pembrolizumab is given through an IV into a vein every 3 weeks or every 6 weeks for up to one year. You either get a smaller dose once every 3 weeks, or you get a larger dose once every 6 weeks.

Since pembrolizumab is given over a long period of time, if you have neoadjuvant pembrolizumab, you won’t get all the pembrolizumab before surgery. You’ll get some pembrolizumab before surgery and some after surgery.

Pembrolizumab can be given on the same day as chemotherapy.

Learn more about neoadjuvant therapy.

Side effects of pembrolizumab

Before you begin treatment with pembrolizumab, talk with your health care provider about possible side effects and how to manage them.

Side Effects


Possible side effects include fatigue, muscle pain, decreased appetite, itchiness, diarrhea, nausea, rash and constipation.

Pembrolizumab can cause colitis (inflammation of the intestines), liver problems and hormone gland problems.

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 source [157].

Pembrolizumab and metastatic breast cancer treatment

Pembrolizumab (Keytruda) is a checkpoint inhibitor immunotherapy drug FDA-approved for the treatment of some metastatic breast cancers.

Learn more about pembrolizumab and metastatic breast cancer treatment.

Under study


Vaccines are a type of immunotherapy. Like vaccines that protect against the flu or measles, cancer vaccines are designed to build up the body’s immunity against disease.

Breast cancer vaccines are still in the early stages of development.

Learn about clinical trials.

Treatment guidelines

Although the exact treatment for breast cancer varies from person to person, evidence-based 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.

After you get a recommended treatment plan from your health care team, study your treatment options. Together with your health care team, make thoughtful, informed decisions that are best for you. Each treatment has risks and benefits to consider along with your own values and lifestyle.

Clinical trials

Research is ongoing to improve all areas of treatment for breast cancer.

New therapies are being studied in clinical trials. The results of these studies will decide whether these therapies become part of the standard of care.

After discussing the benefits and risks with your health care provider, we encourage you to consider joining a clinical trial.

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

Se habla español. in collaboration with Komen offers a custom matching service to help find clinical trials that fit your needs.

Learn what Komen is doing to help people find and participate in breast cancer clinical trials, including trials supported by Komen.

Learn more about clinical trials.


Komen Perspectives

Read our perspective on clinical trials.*

Learn More

Financial assistance

Costs related to metastatic breast cancer care can quickly become a financial burden. Dealing with finances and insurance can be overwhelming.

Many cancer centers have financial counselors who can discuss insurance and cost coverage with you.

Learn more about insurance plans and prescription drug assistance programs.

Learn more about other financial assistance programs.

Komen Financial Assistance Program

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 Breast Care Helpline at 1-877 GO KOMEN (1-877-465-6636) or email

Se habla español.

Susan G. Komen® Support Resources

  • Do you need help? We’re here for you. The Komen Patient Care Center is your trusted, go-to source for timely, accurate breast health and breast cancer information, services and resources. Our navigators offer free, personalized support to patients, caregivers and family members, including education, emotional support, financial assistance, help accessing care and more. Get connected to a Komen navigator by contacting the Breast Care Helpline at 1-877-465-6636 or email to get started. All calls are answered Monday through Thursday, 9 a.m to 7 p.m. ET and Friday, 9 a.m. to 6 p.m. ET. Se habla español.
  • The Komen Breast Cancer and Komen Metastatic (Stage IV) Breast Cancer Facebook groups are places where those with breast cancer and their family and friends can talk with others for friendship and support.
  • Our fact sheets, booklets and other education materials offer additional information.

*Please note, the information provided within Komen Perspectives articles is only current as of the date of posting. Therefore, some information may be out of date.

Updated 04/11/24


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