What are immunotherapy drugs?

Immunotherapy drugs help the body’s immune system attack cancer cells. They are used to treat many cancers including melanoma, lung cancer, bladder cancer and kidney cancer.

Some immunotherapy drugs are helpful in treating certain breast cancers.

There are many types of immunotherapy drugs.

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 tumor 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 cancers (TNBC) at high risk of recurrence.

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 [148-149].

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.

How is pembrolizumab given?

Pembrolizumab is given by vein (through an IV) every 3-6 weeks for up to one year. You may get a smaller dose once every 3 weeks or 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

Some possible side effects of pembrolizumab include fatigue, muscle pain, decreased appetite, itchiness, diarrhea, nausea, rash and constipation [150].

Pembrolizumab can cause colitis (inflammation of the intestines), liver problems and hormone gland problems [150].

In rare cases, pembrolizumab can cause lung inflammation, which can lead to death [150]. Tell your health care provider right away if you have shortness of breath or other breathing problems while taking this drug.

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 early stages of development.

Learn about clinical trials.

Updated 06/28/22