• Immunotherapy is a newer type of treatment that modifies your immune system to better fight breast cancer.
• Immunotherapy can be added to chemotherapy before or after surgery.
• Currently, immunotherapy is mainly used to treat triple negative breast cancer.

Immunotherapy is a type of cancer treatment that harnesses your own immune system to better fight cancer. People with breast cancer may use immunotherapy as part of their treatment plan to help their bodies kill cancer cells.

Currently immunotherapy is mostly used to treat triple negative breast cancer (TNBC). It may be used along with chemotherapy either before or after surgery. If immunotherapy will be part of your treatment plan, you may feel more confident and prepared if you understand how it works and what to expect.

What Is Immunotherapy?

Immunotherapy modifies aspects of your immune system to better find and destroy cancer cells. Immunotherapies are based on immune proteins either made by your own body or synthesized in a laboratory.

Overcoming Cancer Cells’ Defenses

The immune system is made up of a group of organs, specialized cells, and substances that protect you from disease and infections by getting rid of anything in the body that shouldn’t be there. When your immune system is working properly, it keeps track of what belongs in your body so that it can recognize when something doesn’t belong.

Cancer cells may escape the body’s immune defenses to grow out of control. Some cancer cells may not be different enough from normal cells for the immune system to recognize that they shouldn’t be there. Additionally, the immune system may not be strong enough to kill cancer cells. In some cases, cancer cells can suppress the immune system to avoid being attacked. Immunotherapy can help the immune system overcome these defenses.

Immunotherapy can use substances made in the laboratory, such as monoclonal antibodies, to boost a person’s own immune system to better recognize and destroy cancer cells. Some monoclonal antibodies are also referred to as targeted therapy because they have a specific target on a cancer cell. When a monoclonal antibody works to affect the immune system, it is considered immunotherapy.

How Is Immunotherapy Different From Chemotherapy?

Chemotherapy drugs usually target any cells in the body that grow quickly. Cancer cells are typically fast-growing cells, which makes them good targets for chemotherapy drugs. However, chemotherapy drugs can’t tell the difference between fast-growing healthy cells (such as skin cells) and cancer cells. This means that normal, healthy cells will also be damaged by chemotherapy.

Unlike chemotherapy, immunotherapy doesn’t target fast-growing cells. Instead, it changes how a person’s own immune system works. These changes can help the immune system work harder to find cancer cells and either kill them or stop them from growing.

How Does Immunotherapy Work To Treat Breast Cancer?

Immunotherapy for breast cancer helps the body overcome the cancer cells’ defenses against the immune system.

To continue growing, cancer cells have to avoid being recognized by the immune system. Some breast cancer cells do this by using proteins known as checkpoints on immune cells called T cells. Checkpoints need to be turned on or off to start an immune response.

Types of Immunotherapy for Breast Cancer

Immunotherapy drug development for breast cancer has focused on blocking the checkpoints that breast cancer cells use to avoid being recognized by the immune system. These drugs are also known as immune checkpoint inhibitors.

Currently, the U.S. Food and Drug Administration (FDA) has approved one class of immunotherapy to treat breast cancer called PD-1 inhibitors. Immunotherapy is a new type of cancer treatment, and there are currently several clinical trials (research studies) to find other types of immunotherapies to treat breast cancer.

PD-1 Inhibitors

PD-1 is a protein on T cells that can prevent them from attacking other cells of the body. Some cancer cells have a protein called PD-L1 that binds to PD-1 on T cells and tells the T cells not to attack. When cancer cells have lots of PD-L1, they can hide from T cells. However, when PD-1 is blocked by a PD-1 inhibitor, the T cells aren’t prevented from attacking cancer cells. This can result in tumors getting smaller.

These medications are more likely to work if your cancer has a lot of the PD-L1 protein. Before you start taking a PD-1 inhibitor, your doctor may order tests to see if your cancer cells have PD-L1.

Pembrolizumab (Keytruda) is a PD-1 inhibitor that is FDA-approved to treat triple-negative breast cancer.

Immunotherapies Under Study

Immunotherapy for cancer is a relatively new area of study for breast cancer treatment. Scientists are investigating new treatments that involve immune checkpoints, such as other PD-1 inhibitors and PD-L1 inhibitors, in clinical trials.

Vaccines are also a type of immunotherapy. We usually think of vaccines as preventing disease, but a cancer vaccine could help people who already have cancer. Scientists are working on developing a vaccine that can activate T cells to attack breast cancer tumors.

Talk to your doctor if you’re interested in participating in a clinical study for breast cancer treatment. They can help you find a trial focused on your type of breast cancer in which you may be qualified to participate.

When Is Immunotherapy for Breast Cancer Used?

Pembrolizumab can be used along with chemotherapy to treat triple-negative breast cancer.

TNBC cells test negative for three proteins. They don’t have estrogen or progesterone receptors, and they don’t make much of the protein HER2. TNBC usually spreads faster and has fewer treatment options.

Pembrolizumab can be added to chemotherapy before or after surgery for people with recurrent TNBC that cannot be removed by surgery and in people with metastatic TNBC. Metastatic TNBC means that the cancer has spread to other parts of the body.

Pembrolizumab is given as an IV infusion every three to six weeks for up to two years. You may go to a cancer treatment center to receive your dose. Each person is different, so your doctor may recommend a different schedule based on your specific needs.

Studies show that compared to chemotherapy alone, pembrolizumab along with chemotherapy can give some people with triple-negative breast cancer more time before their cancer spreads.

Immunotherapy Side Effects

Immunotherapy treatment can cause side effects. Your side effects can depend on the type of treatment you are taking and the dose. The same treatment can affect two people differently. Talk to your health care team about ways to prevent or relieve the side effects caused by immunotherapy.

The most common side effects of pembrolizumab include:

• Tiredness
• Cough
• Nausea
• Rash
• Itchiness
• Decreased appetite
• Muscle pain
• Constipation
• Diarrhea

In some cases, more serious side effects such as infusion reactions and autoimmune reactions can occur.

Infusion reactions might feel like an allergic reaction and can include:

• High fever
• Chills
• Facial flushing
• Rash
• Itchiness
• Dizziness
• Breathing difficulties

You could experience autoimmune reactions if the immunotherapy causes your immune system to attack healthy cells in your body. This can cause serious or life-threatening problems in many organs, such as the lungs, kidneys, liver, intestines, or hormone-making glands.

Talk With Others Who Understand

MyBCTeam is the social network for people with breast cancer and their loved ones. On MyBCTeam, more than 59,000 members come together to ask questions, give advice, and share their stories with others who understand life with breast cancer.

Have you taken immunotherapy for breast cancer? Share your experiences in the comments below, or start a conversation by posting on your Activities page.