Immunotherapy for breast cancer

Immunotherapy helps to strengthen or restore the immune system's ability to fight cancer. This works to kill cancer cells and stop cancer cells from growing and spreading.

Immunotherapy is sometimes used to treat triple-negative breast cancer (TNBC). If you have immunotherapy, your healthcare team will use what they know about the cancer and about your health to plan the drugs, doses and schedules.

The immune system normally stops itself from attacking normal cells in the body by using specific proteins called checkpoints, which are made by some immune system cells. PD-1 is an immune checkpoint protein that attaches to a protein on cells called PD-L1. When PD-1 attaches to PD-L1, it turns off the body's immune response so it doesn't destroy healthy cells in our bodies. But it also means that our immune system doesn't recognize cancer cells.

Checkpoint inhibitor drugs may target either PD-1 or PD-L1 proteins. They stop the proteins from attaching to each other, and allow the immune system to recognize and destroy cancer cells. Diagnostic tests are done on breast cancer tumours to see if the cells have too much (overexpress) PD-1 or PD-L1. If the cells don't overexpress these proteins, immune checkpoint inhibitors are not used.

The following PD-1 or PD-L1 checkpoint inhibitors are used to treat TNBC.

Atezolizumab (Tecentriq, Tecentriq SQ) is used in combination with the chemotherapy drug nab-paclitaxel (Abraxane) to treat advanced or metastatic TNBC.

Pembrolizumab (Keytruda) is used:

• in combination with chemotherapy before surgery (called neoadjuvant therapy) for high-risk early-stage TNBC
• after surgery for TNBC by itself, and continued until the cancer stops responding
• in combination with chemotherapy for TNBC that is metastatic or can't be removed with surgery and has not been treated yet

Side effects of immunotherapy will depend mainly on the type of drug or drug combination, the dose, how it's given and your overall health. Tell your healthcare team if you have side effects that you think might be from immunotherapy. The sooner you tell them of any problems, the sooner they can suggest ways to help you deal with them.

These are common side effects of immunotherapy for breast cancer:

• fatigue
• decreased appetite
• nausea and vomiting
• infection
• constipation
• fever
• skin problems
• diarrhea
• low white blood cell count
• cough
• muscle and joint pain
• stomach pain
• low levels of thyroid hormone
• breathing problems
• headache

Immunotherapy drugs work by blocking some of the immune system functions. This can cause a serious side effect where the immune system starts to attack organs in the body like the lungs, liver and intestines.

If you are on immunotherapy drugs, it's important to report any new side effects to your healthcare team right away. You may need to have treatment to stop your immune system from reacting to immunotherapy.

Find out more about immunotherapy. To make the decisions that are right for you, ask your healthcare team questions about immunotherapy.

Details on specific drugs change regularly. Find out more about sources of drug information and where to get details on specific drugs.