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Reviewed by: HU Medical Review Board | Last reviewed: June 2023

Immunotherapy is a type of systemic treatment that aims to boost a person's own immune system to fight cancer. Systemic treatments work by treating the whole body.1

Normally, the body’s immune system fights disease and infection. The white blood cells recognize and destroy damaged or diseased cells and foreign invaders, like bacteria and viruses. Cancer cells often mutate in a way that avoids detection by the immune system. They then grow out of control. Immunotherapies aim to help the immune system identify and destroy cancerous cells.1,2

There are several types of immunotherapy that are approved or being studied for the treatment of advanced breast cancer, including:3

  • Monoclonal antibodies
  • Adoptive cell transfer

How does immunotherapy work?

Each type of immunotherapy has a different way of working.

Monoclonal antibodies are made in the lab to work like how antibodies produced by the body work. They can target specific areas of cancer cells and/or the pathway that allows cancer cells to avoid immune system detection. Some block the function of specific proteins known as PD-L1 and PD-1. These proteins can help disguise cancer cells from the body’s T-cells and prevent them from attacking the cancer cells. This allows the cancer to continue to grow and survive. Certain monoclonal antibodies that target PD-L1 or PD-1 proteins disrupt this pathway in certain forms of breast cancer.3

Examples of immunotherapy

Monoclonal antibody treatments

Keytruda® (pembrolizumab) may be used for the treatment of locally recurrent unresectable (has returned following prior treatment and cannot be removed by surgery) or metastatic (has spread to other parts of the body) triple-negative breast cancer (TNBC). In this circumstance, Keytruda must be combined with chemotherapy, and the tumor must express the PD-L1 protein.5

Keytruda is also used to treat early stage TNBC that is high risk, and is given with chemotherapy prior to surgery, then continued following surgery as a single drug to help reduce the risk of the cancer coming back.

Adoptive cell transfer technique and research

Adoptive cell transfer is an emerging immunotherapy method that collects and uses a person's own immune cells to attack the cancer.

This method uses tumor-infiltrating lymphocytes (TILs). These are a type of white blood cell. Researchers first identify the specific mutations on the person’s cancer and identify which TILs can recognize them. These cells are removed from the person's body and grown in a lab to create a large number of them. This process can take several weeks. During this time, the person may be given treatments to reduce their immune cells. The TILs are then given back to the person, where they can generate an immune response to fight the cancer cells.1,5

What are the possible side effects from immunotherapy?

Side effects can vary depending on the specific immunotherapy method you are receiving. Common side effects of immunotherapy include:1

  • Pain, redness, or soreness at the injection site
  • Flu-like symptoms, such as fever, chills, nausea, vomiting, and muscle or joint aches
  • Fatigue
  • Diarrhea
  • Heart palpitations
  • Swelling or weight gain

These are not all the possible side effects of immunotherapy. Talk to your doctor about what to expect or if you experience any changes that concern you during treatment with immunotherapy.

Things to know about immunotherapy

Certain people may be able to participate in clinical trials that are testing some of these new therapies. Clinical trials are an important part of the scientific process to find and prove the safety and effectiveness of new treatments. They offer people a chance to receive the latest treatments and be closely monitored by doctors. Talk to your doctor about whether clinical trials are a good option for you.

Before beginning treatment for breast cancer, tell your doctor about all your health conditions and any other drugs, vitamins, or supplements you are taking. This includes over-the-counter drugs.

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