Immunotherapy for Breast Cancer

Immunotherapy is the use of medicines to boost a person’s own immune system to recognize and destroy cancer cells more effectively. Immunotherapy typically works on specific proteins involved in the immune system to enhance the immune response. These drugs have side effects different from those of chemotherapy.

Some immunotherapy drugs, for example, monoclonal antibodies, work in more than one way to control cancer cells and may also be considered targeted therapy because they block a specific protein on the cancer cell to keep it from growing.

Immunotherapy is used to treat some types of breast cancer.

Immune checkpoint inhibitors for breast cancer

An important part of the immune system is its ability to keep itself from attacking normal cells in the body. To do this, it uses proteins (or "checkpoints") on immune cells that need to be turned on (or off) to start an immune response. Breast cancer cells sometimes use these checkpoints to avoid being attacked by the immune system. Drugs that target these checkpoint proteins, help restore the immune response against breast cancer cells.

PD-1 inhibitor

Pembrolizumab (Keytruda) for breast cancer  

Pembrolizumab (Keytruda) is a drug that targets PD-1 (a protein on immune system T cells that normally helps keep them from attacking other cells in the body). By blocking PD-1, these drugs boost the immune response against breast cancer cells. This can often shrink tumors.

It can be used with chemotherapy to treat triple-negative breast cancer:

• Before and after surgery for stage 2 or 3 cancers
• That has come back (recurred) locally but can’t be removed by surgery  
• That has spread to other parts of the body.

This drug is given as an intravenous (IV) infusion, typically every 3 or 6 weeks. In certain situations, your doctor might test your cancer cells for the PD-L1 protein to show that the cancer is more likely to respond to treatment with pembrolizumab. 

Possible side effects of immune checkpoint inhibitors

Side effects of these drugs can include fatigue, cough, nausea, skin rash, poor appetite, constipation, and diarrhea.

Other, more serious side effects occur less often.

Infusion reactions:  Some people might have an infusion reaction while getting these drugs. This is like an allergic reaction, and can include fever, chills, flushing of the face, rash, itchy skin, feeling dizzy, wheezing, and trouble breathing. It’s important to tell your doctor or nurse right away if you have any of these symptoms while getting these drugs.

Autoimmune reactions: These drugs remove one of the protections on the body's immune system. Sometimes the immune system starts attacking other parts of the body, which can cause serious or even life-threatening problems in the lungs, intestines, liver, hormone-making glands, kidneys, or other organs.

It’s very important to report any new side effects to your health care team quickly. If serious side effects do occur, treatment may need to be stopped and you may get high doses of corticosteroids to suppress your immune system.