This page was reviewed under our medical and editorial policy by

Maurie Markman, MD, President, Medicine & Science.

This page was updated on July 20, 2022.

Immunotherapy is a broad category of cancer therapies that triggers the body's immune system to fight cancer cells. Cancer cells are different from normal cells, in that they do not die normally. They rapidly divide like an out-of-control copy machine that won't stop creating images.

These abnormal cells frequently change, or mutate, helping them evade the immune system, which protects the body from disease and infections. Cancer immunotherapy drugs are designed to alert the immune system about these mutated cells so it can locate and destroy them.

To help answer your questions about immunotherapy and when it may be used as part of a cancer treatment regimen, this guide will cover:

How does the immune system work?

A key function of the immune system is to distinguish normal cells in the body from foreign cells.

The immune system is always on patrol, like a police force charged with ridding the body of foreign invaders, such as viruses, bacteria or fungi. Lymph nodes, which make up most of the immune system, serve as police stations throughout the body. White blood cells, including lymphocytes such as “T cells,” fight infection and cancer. They are the police officers. When a foreign invader is detected, the entire immune system is alerted through chemical signals, just as a police station would radio police officers to alert them about a problem.

The immune system relies on receptor proteins on certain immune cells to detect the invaders. At certain checkpoints, when activated or deactivated, these receptors allow it to distinguish between healthy and invading cells. The checkpoints are needed to keep the immune system from attacking healthy cells.

Cancer cells don't trigger an immune response because they are the body’s own cells that have mutated—so those once-healthy cells no longer behave like normal cells. Because the immune system doesn’t recognize the distinction, these dangerous cells can continue to grow, divide and spread throughout the body.

How does immunotherapy spark the immune system to help fight cancer?

Immunotherapies use different methods to attack tumor cells. Immunotherapy types fall into three general categories:

  • Checkpoint inhibitors, where cancer cell signals that trick the immune system into thinking they’re healthy cells are disrupted, exposing them to attack by the immune system

  • Cytokines, where protein molecules called cytokines—those that help regulate and direct the immune system—are synthesized in a laboratory and then injected into the body in much larger doses than are produced naturally

  • Cancer vaccines, which may reduce the risk of cancer by attacking viruses that cause cancer, or may treat cancer by stimulating the immune system to attack cancer cells in a specific part of the body

Immunotherapy may be used alone or in combination with other cancer treatments, such as surgery, chemotherapy, radiation therapy and targeted therapy.

What are some of the drugs used in immunotherapy?

Current checkpoint inhibitor drugs target the PD-1 and the CTLA-4 receptors. Common checkpoint inhibitors include:

  • Ipilimumab (Yervoy®)
  • Pembrolizumab (Keytruda®)
  • Nivolumab (Opdivo®)
  • Atezolizumab (Tecentriq®)

Common cytokines used in cancer therapy include:

  • Interleukin-2 (IL-2)
  • Interferons-alpha (IFN-alpha)

New immunotherapy drugs continue to be developed.

Tumor-agnostic therapies

The FDA has also approved immunotherapy to treat cancers with specific genetic features, regardless of where in the body they originate. These treatments, called tumor-agnostic therapies, may be used to treat the these malignancies:

Solid tumors with microsatellite instability-high (MSI-h) or mismatch repair deficiency (dMMR): These tumors may have unstable strands of DNA or are unable to repair DNA damage.

Solid tumors with high tumor mutation burden (TMB-h): These tumors have cells with a high number of different gene mutations, which may make them more likely to respond to immunotherapy.

What are immunotherapy side effects?

Immunotherapy may cause a variety of side effects—many are flu-like symptoms—including:

  • Fatigue
  • Nausea or vomiting
  • Mouth sores
  • Diarrhea
  • High blood pressure
  • Fluid buildup, usually in the legs
  • Fever or chills
  • Pain or weakness
  • Headaches
  • Rashes or itching

The side effects of immunotherapy generally become less severe after the first treatment.

Throughout your treatment, your care team will provide integrative care services, including nutritional support, naturopathic support, pain management, oncology rehabilitation, behavioral health and spiritual support. These therapies may help reduce side effects and improve your overall quality of life during immunotherapy.

Types of immunotherapy

The goal of immunotherapy is to try to reset the body’s immune system to once again be able to find and attack cancer cells. The many types of immunotherapies work differently and have their own risks and benefits. Which of these treatments your care team recommends depends on the type of cancer and its stage.

Monoclonal or therapeutic antibodies are grown in a lab and injected into the body. Some mark cancer cells so the immune system is able to recognize and destroy them. Others are more direct in their approach, stopping the growth of cancer cells or causing their self-destruction.

CAR T-cell therapy goes by many names—including adoptive cell therapy, adoptive immunotherapy or immune cell therapy. Essentially, your care team harvests white blood cells from inside your tumor and grows them in a lab, making changes to strengthen their natural ability to fight cancer. These cells are grown in large batches and injected back into the body to fight the cancer.

Immune checkpoint inhibitors are a type of drug that removes natural blockades within the body that keep your immune system in check. Without these natural blockades, it may overreact—like in autoimmune diseases. But cancers will often use these blockades, or proteins, to hide from the immune system. With these blockades deactivated through checkpoint inhibitors, the door is opened, and your body is able to respond more strongly to the cancer cells.

Cancer vaccines, sometimes called immunotherapeutic or treatment vaccines, boost the immune system response when you already have cancer. They aren’t preventative vaccines like those for viruses, such as the flu. By providing immune cells with a target found on cancer cells, they prime the body to create antibodies to attack cancer cells. Vaccines usually contain an immune-stimulating agent to rally the white blood cell troops specifically against that protein target.

Cytokines are proteins created by your body during natural infections that play an important role in stimulating your immune system cells. By supplementing your body’s natural cytokines, these treatments help ramp up immune cells and move them toward their target: the tumor.

Immune system modulators, sometimes called immunomodulators, are drugs that ramp up the body’s immune reaction. Different immunomodulators act in different ways—some focus specifically on certain parts of the immune system, while others act across the whole body.

Immunotherapy may be given as an IV medication into your vein, an oral medication in pills or capsules, or even a topical medication on your skin.

What’s the difference between immunotherapy and chemotherapy?

Both immunotherapy and chemotherapy are commonly used cancer treatments that use drugs to stop or slow the growth of cancerous cells. However, while chemotherapy drugs are used to attack rapidly producing cells throughout the body, immunotherapy triggers the immune system’s ability to identify and attack cancer cells.

The side effects can be very different between chemotherapy and immunotherapy, too. Because chemotherapy can’t differentiate between the cells it’s targeting, it affects both fast-growing cancerous and fast-growing normal cells, like those responsible for hair and skin growth and those lining the digestive tract and forming bone marrow. That why side effects like hair loss, nausea and vomiting, and skin and nail changes are more common and sometimes more severe with chemotherapy.

Benefits of immunotherapy

Overall, immunotherapies are still less common than surgery or chemotherapy to treat cancer. But for some types of cancer, these therapies are now an important treatment option. Many other immunotherapies are still in clinical trials.

Immunotherapies have the potential to be more comprehensive and less toxic than other types of treatments for cancer, because they harness the power of the body itself to attack the tumor instead of introducing chemicals into the body.

Immunotherapies are a very active area of research in cancer therapy, and new treatments continue to be approved.

Risks of immunotherapy

Risks vary by the type of immunotherapy, the type of cancer, the stage, a patient’s general health and current treatment regimen. Every treatment has different side effects, and patients may respond differently to the same treatment.

Generally, there are side effects when you ramp up the immune system to function on “high.” Like when you get a vaccine, you may experience flu-like symptoms—including fever, chills, weakness, dizziness, nausea, muscle aches, fatigue or headache—because the immune system is doing its job.

These treatments may cause high levels of inflammation in healthy cells and tissues and side effects from that response, such as a skin rash. Steroids may treat the side effects from that inflammation—but steroids also have some side effects of their own.

Some people develop resistance to immunotherapy. Rarely, doctors have observed severe or even fatal allergic and inflammatory reactions to some types of immunotherapy.

Your body may or may not respond to immunotherapy. Only some people receiving these treatments respond to them. Researchers are working on better understanding the common link between people who do respond and why.

Ask your care team about the risks and benefits of immunotherapy for your type and stage of cancer.

Are you a candidate for immunotherapy?

Our doctors and clinicians work together on multidisciplinary teams to develop treatment options tailored to each patient’s individual cancer care needs. Immunotherapy treatment may be an option for you if you have certain types of cancer. The treatment may work better for some types of cancer than others, so your oncologist would closely monitor your progress and may recommend immunotherapy be used in combination with other treatments.

Once your care team develops a recommended treatment plan, they’ll spend the time necessary with you and your caregiver to explain each option, its potential risks and benefits, side effects and other essentials. Then you’ll work together as a team to decide which immunotherapy or other treatment options are right for you, helping you make informed decisions about your care.

Many patients come to CTCA to get a better understanding of their cancer diagnosis or treatment plan. Our cancer experts have access to a wide range of diagnostic tools and comprehensive treatment options, including genomic testing, immunotherapy, targeted therapy and clinical trials. We also offer a personalized approach to cancer care and a team of multidisciplinary experts to help you prevent or manage the side effects of your cancer treatment.

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