Immunotherapy is a treatment option for some types of breast cancer. It uses medications to stimulate the immune system to destroy cancer cells.

Immunotherapy drugs work with an individual’s immune system to help it recognize and attack breast cancer cells. Doctors may use immunotherapy by itself or in combination with chemotherapy, radiation therapy, or other treatments.

This article looks at the currently available immunotherapy treatments in more detail, including how they work and which types of breast cancer they may treat.

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Immunotherapy is a treatment method for some types of breast cancer. It uses drugs that stimulate the immune system to identify and destroy cancer cells. These medications include immunomodulators and targeted antibodies.

Cells in the body contain proteins called immune checkpoints. These immune system regulators signal that cells are healthy.

Immune checkpoints allow the immune system to fight infected or diseased cells while preventing it from attacking healthy tissues.

The immune system is complex and involves different types of cells, including T cells, which circulate the body checking for disease or infection. These specialized cells examine other cells to identify immune checkpoints.

If the immune system does not recognize proteins within cells, it attacks them. This process is essential in allowing the body to fight diseases and infections.

Sometimes, the immune system does not fight off breast cancer cells effectively. There are two main reasons for this.

Firstly, precancerous or early cancerous cells are similar to healthy cells. The immune system may not recognize them as harmful until breast cancer develops further. Secondly, as cancerous cells develop, they can change genetically to prevent the immune system from detecting them and identifying them as harmful. Cancer cells can also grow and multiply quickly, which can overwhelm the immune system.

Immunotherapy drugs can help support the immune system to destroy cancer cells. Doctors may prescribe various options, depending on the type of breast cancer.


Cancer cells can contain immune checkpoints that prevent the immune system from attacking them.

PD-1 and PD-L1 are two types of immune checkpoint proteins. T cells contain PD-1, and healthy cells contain PD-L1. These proteins bind, which prevents T cells from destroying healthy cells.

Cancer cells can contain PD-L1, which prevents T cells from destroying them. Immune checkpoint inhibitors stop PD-1 from binding to PD-L1, which allows T cells to kill cancer cells.

Immune checkpoint inhibitors are drugs that block immune checkpoints on cancerous cells or the T cells that see them as healthy. The immune system can then identify the cells as harmful and attack them.

Targeted antibodies

Immune targeted therapies, or targeted antibodies, recognize specific markers on cancer cells and stop these cells from growing.

Other targeted therapies work in the same way as the body’s natural antibodies and help the immune system recognize cancer cells as harmful.

People may also use immunotherapy in combination with other treatments, such as chemotherapy, to target cancer cells.


Although the Food and Drug Administration (FDA) has not yet approved any vaccines for breast cancer treatment, research is ongoing.

The type and stage of breast cancer will determine what type of immunotherapy a person receives.


There are currently two FDA-approved immune checkpoint inhibitors: Tecentriq (atezolizumab) and Keytruda (pembrolizumab).


Tecentriq inhibits PD-L1 proteins, and doctors may use it to treat:

  • metastatic triple-negative breast cancer (TNBC)
  • PD-L1-positive breast cancer
  • locally advanced breast cancer where surgery is not effective

Doctors may use Tecentriq alongside a chemotherapy drug called Abraxane (albumin-bound or nab-paclitaxel) to target advanced triple-negative breast cancer.


Keytruda inhibits PD-1 proteins. Doctors may use Keytruda alongside chemotherapy to target triple-negative breast cancer that has spread to other areas of the body or has returned locally and is not treatable with surgery.

Targeted antibodies

Targeted antibodies include:

  • Perjeta (pertuzumab): For HER2-positive breast cancer.
  • Trodelvy (sacituzumab govitecan): For triple-negative breast cancer.
  • Herceptin (trastuzumab): For HER2-positive breast cancer.
  • Enhertu (trastuzumab deruxtecan): For advanced HER2-positive breast cancer.
  • Kadcyla (trastuzumab emtansine): For HER2-positive breast cancer.

The American Cancer Society states that people taking Tecentriq will need to receive it intravenously every 2 weeks. Those on Keytruda will receive it intravenously every 3–6 weeks.

Currently, there is no clear time frame for how long immunotherapy may take to work. More research is necessary to confirm the ideal duration of treatment.

Doctors may give targeted antibodies as a single injection or as a course of injections spanning several months. In some cases, they may use this treatment alongside chemotherapy.

According to the Cancer Research Institute (CRI), HER2-directed immunotherapy treatment is highly effective. However, only about 20% of people who have high levels of HER2 expression respond to this type of treatment.

Even with treatment, HER2-positive breast cancer can progress or recur, creating the need for other treatment methods.

Researchers are testing immunotherapy with chemotherapy. In a 2018 study, researchers trialed adding Tecentriq to nab-paclitaxel in people with metastatic TNBC who had not previously received treatment for this cancer. They found that some of the participants did benefit from this combination, but others had to discontinue the treatment due to side effects. In March 2019, the FDA approved this treatment combination.

Experts believe that a combination of immunotherapy treatments, such as using a vaccine alongside monoclonal antibodies or chemotherapy, may be more effective in stimulating an immune response.

Immunotherapy drugs may cause side effects, which can include:

In some cases, more serious side effects can occur, although these are less common.

Some people may have an infusion reaction when taking drugs intravenously. The symptoms are similar to those of an allergic reaction and can include:

  • fever
  • chills
  • facial flushing
  • a rash
  • itching
  • dizziness
  • wheezing
  • difficulty breathing

Immunotherapy removes some of the protection against healthy cells. Without this protection, the individual may experience an autoimmune reaction, meaning that the immune system mistakenly attacks healthy tissues. Corticosteroids can help suppress the immune system and reduce potential autoimmune reactions.

If people experience any side effects from immunotherapy drugs, they should let their healthcare team know immediately. If the side effects are severe, a person may have to stop the treatment.

Immunotherapy drugs are relatively new treatments, and research is ongoing to confirm how best to use them. If people want to learn about immunotherapy treatment for breast cancer, they can talk with their healthcare team about local clinical trial options.

The CRI states that current FDA-approved immunotherapy treatments are unlikely to cure advanced breast cancer. However, researchers are currently studying new immunotherapy treatments, many of which are producing promising results. People with advanced breast cancer may, therefore, wish to consider taking part in clinical trials exploring newer treatment options.

The CRI has a database where people can search for clinical trials that are currently enrolling participants.

Immunotherapy is a relatively new treatment method for cancer that stimulates the immune system to attack cancer cells. It can effectively treat some types of breast cancer.

Whether immunotherapy is successful for an individual depends on doctors finding the best approach for the type and stage of cancer. Immunotherapy may work better if doctors combine it with other treatments.

These therapies are relatively new, and research into their use is ongoing. If people want to find out about current clinical trials using immunotherapy for breast cancer treatment, they can discuss the options with their healthcare team or directly search for trials using the National Library of Medicine’s clinical trials database.