What Is Immunotherapy?

Approved by the Cancer.Net Editorial Board, 05/2022

Immunotherapy is a type of cancer treatment. It uses substances made by the body or in a laboratory to boost the immune system and help the body find and destroy cancer cells.

Immunotherapy can treat many different types of cancer. It can be used alone or in combination with chemotherapy and/or other cancer treatments.

This article will help you understand the basics of how immunotherapy works to treat cancer. Learn more about the side effects of immunotherapy.

How does the immune system fight cancer?

The immune system consists of a complex process that your body uses to fight cancer. This process involves cells, organs, and proteins. Cancer can commonly get around many of the immune system's natural defenses, allowing cancer cells to continue to grow.

Different types of immunotherapy work in different ways. Some immunotherapy treatments help the immune system stop or slow the growth of cancer cells. Others help the immune system destroy cancer cells or stop the cancer from spreading to other parts of the body.

The different types of immunotherapy include:

The type of immunotherapy, dose, and treatment schedule your doctor recommends will depend on many factors. These can include the type of cancer, size, location, and where it has spread. Your age, general health, body weight, and the possible side effects are also important. Talk with your doctor about why a specific immunotherapy plan is being recommended for you.

What are monoclonal antibodies and immune checkpoint inhibitors?

When the immune system detects something harmful, it makes antibodies. Antibodies are proteins that fight infection by attaching to antigens. Antigens are molecules that start the immune response in your body.

Monoclonal antibodies are made in a laboratory to boost the body's natural antibodies or act as antibodies themselves. Monoclonal antibodies can help fight cancer in different ways. For example, they can be used to block the activity of abnormal proteins in cancer cells. This is also considered a type of targeted therapy, which is a cancer treatment using medication that targets a cancer's specific genes, proteins, or the tissue environment that helps the tumor grow and survive.

Other types of monoclonal antibodies boost your immune system by inhibiting or stopping immune checkpoints. Immune checkpoints are used by the body to naturally stop an immune system response and prevent the immune system from attacking healthy cells. Cancer cells can find ways to hide from the immune system by activating these checkpoints.

Checkpoint inhibitors prevent cancer cells from blocking the immune system. Common checkpoints that these inhibitors affect are the PD-1/PD-L1 and CTLA-4 pathways.

Examples of immune checkpoint inhibitors include:

  • Atezolizumab (Tecentriq)

  • Avelumab (Bavencio)

  • Dostarlizumab (Jemperli)

  • Durvalumab (Imfinzi)

  • Ipilimumab (Yervoy)

  • Nivolumab (Opdivo)

  • Pembrolizumab (Keytruda)

Many checkpoint inhibitors are approved by the U.S. Food and Drug Administration (FDA) for specific cancers. There are also 2 checkpoint inhibitors that are used to treat tumors anywhere in the body if they have specific genetic changes. This kind of approach is called a "tumor-agnostic treatment."

For instance, pembrolizumab (Keytruda) is approved to treat any tumors that have spread to distant parts of the body if they have a specific molecular change called microsatellite instability-high (MSI-H) or DNA mismatch repair deficiency (dMMR). Another example is that dostarlimab (Jemperli) can be used for advanced cancer or cancer that has come back if it has dMMR. Learn more about tumor-agnostic treatments.

The side effects of monoclonal antibody treatment depend on the drug's purpose. For example, the side effects of monoclonal antibodies used for targeted therapy are not like those used for immunotherapy. The side effects of immune checkpoint inhibitors may include side effects similar to an allergic reaction. Learn more about side effects of immune checkpoint inhibitors.

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What are non-specific immunotherapies?

Non-specific immunotherapies, also called non-specific immunomodulating agents, help your immune system destroy cancer cells. There are several kinds of non-specific immunotherapies that work in different ways.

Cytokines. Cytokines are a part of the immune system. They are proteins that send messages between cells to activate the immune system. There are two types of cytokines that are used to treat cancer:

  • Interferons. These proteins are produced by your immune system to alert your body that there is a pathogen, typically a virus, in your body. Interferons can be made in a laboratory to help your immune system fight cancer. They can also slow the growth of cancer cells.

    The most common type of interferon used in cancer treatment is called interferon alpha (Roferon-A [2a], Intron A [2b], Alferon [2a]). Interferon can be used to several many different types of cancer. Side effects of interferon treatment may include flu-like symptoms, an increased risk of infection, skin rashes, and hair thinning.

  • Interleukins. Interleukins are proteins that pass messages between cells. They also start an immune response. For example, the lab-made interleukin-2 (IL-2) or aldesleukin (Proleukin) can treat kidney cancer and melanoma. Common side effects of IL-2 treatment include weight gain and low blood pressure. Some people also experience flu-like symptoms.

Bacillus Calmette-Guerin (BCG). This type of immunotherapy is similar to the bacteria that causes tuberculosis. It is used to treat bladder cancer. BCG is placed directly into the bladder through a catheter. It attaches to the inside lining of the bladder and activates the immune system to destroy tumor cells. BCG can cause flu-like symptoms.

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What is oncolytic virus therapy?

Oncolytic virus therapy, sometimes just called virus therapy, uses viruses that have been changed in a laboratory to destroy cancer cells. A genetically modified version of the virus is injected into the tumor. When the virus enters the cancer cells, it makes a copy of itself. As a result, the cancer cells burst and die. As the cells die, they release proteins that trigger your immune system to target any cancer cells in your body that have the same proteins as the dead cancer cells. The virus does not enter healthy cells.

Currently, one type of oncolytic virus therapy is approved in the United States to treat cancer:

Talimogene laherparepvec (Imlygic) or T-VEC. This oncolytic virus therapy is approved to treat advanced melanoma that cannot be treated with surgery. It is used most often for people who cannot or choose not to receive any other recommended treatments. T-VEC is a modified version of the herpes simplex virus, which causes cold sores. It is injected directly into 1 or more melanoma tumors. Side effects of oncolytic virus therapy include flu-like symptoms and pain at the injection site.

Clinical trials are testing other oncolytic viruses for different cancers. They are also testing how the viruses work with other cancer treatments, such as chemotherapy.

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What is T-cell therapy?

T cells are immune cells that fight infection. In T-cell therapy, the doctor removes T cells from the blood. Then, a laboratory adds specific proteins called receptors to the cells. The receptor allows those T cells to recognize cancer cells. The changed T cells are put back into the body. Once there, they find and destroy cancer cells. This type of therapy is known as chimeric antigen receptor (CAR) T-cell therapy. Side effects include fevers, confusion, low blood pressure, and, in rare occasions, seizures.

CAR T-cell therapy is used to treat certain blood cancers. Researchers are still studying this type of therapy and other ways of changing T cells to treat cancer. Learn more about the basics of CAR T-cell therapy.

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What are cancer vaccines?

A cancer vaccine can also help your body fight disease. A vaccine exposes your immune system to a foreign protein, called an antigen. This triggers the immune system to recognize and destroy that antigen or related substances. There are 2 types of cancer vaccine: prevention vaccines and treatment vaccines.

One example of a cancer prevention vaccine is Gardasil, the vaccine to protect against the human papillomavirus (HPV), a virus that can cause specific types of cancer. An example of a treatment vaccine includes spuleucel-T (Provenge), which treats advanced prostate cancer that does not respond to hormone therapy. T-VEC (see above) is also considered a cancer treatment vaccine. Side effects for both of these cancer vaccines are flu-like symptoms.

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In general, immunotherapy is an important approach as cancer researchers continue to look for new cancer treatments. The examples above do not include every type of immunotherapy treatment. Researchers are studying many new drugs. You can learn more about immunotherapy in each cancer-specific section on Cancer.Net. Look at the "Types of Treatment" and "Latest Research" pages for specific information about immunotherapy for that type of cancer. You can also learn about the latest immunotherapy research on the Cancer.Net Blog.

Questions to ask your health care team

If immunotherapy is a cancer treatment option for you, consider asking your health care team these questions:

  • What type of immunotherapy do you recommend? Why?

  • What are the goals of this treatment?

  • What immunotherapy clinical trials are open to me?

  • Will immunotherapy be my only type of cancer treatment? If not, what other treatments will I need? When?

  • How will I receive immunotherapy treatment?

  • Where will I receive this treatment?

  • How long will each treatment take? How often will I need to get this treatment?

  • What are the possible short-term side effects of immunotherapy? How can these be managed?

  • Who should I talk with about any side effects I experience? How soon?

  • What side effects should I let you know about right away?

  • Whom should I call with questions or problems?

  • How can I reach them during regular business hours? After hours?

  • How will this treatment affect my daily life? Will I be able to work, exercise, and do my usual activities?

  • If I'm very worried or anxious about having this treatment, who can I talk with?

  • If I'm worried about managing the cost of this treatment, who can help me?

  • What are possible long-term side effects of this immunotherapy? How can these be managed?

  • How will we know if this immunotherapy is working?

  • Will I need any tests or scans before, during, or after immunotherapy?

  • Could the dose or duration of my immunotherapy change over time?

Related Resources

ASCO Answers Fact Sheet: Understanding Immunotherapy (PDF)

Side Effects of Immunotherapy

More Information

American Cancer Society: Cancer Immunotherapy

National Cancer Institute: Biologic Therapies

ASCO Answers: Understanding ImmunotherapyDownload a free fact sheet on Understanding Immunotherapy (PDF).  This 1-page (front and back) fact sheet provides an overview of the different types of immunotherapy, possible side effects, terms to know, and questions to ask the health care team. Order printed copies from the ASCO Store