The information on this page was reviewed and approved by
Maurie Markman, MD, President, Medicine & Science at CTCA.

This page was updated on April 1, 2021.


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.

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.

Are you a candidate for immunotherapy?

At Cancer Treatment Centers of America® (CTCA), our doctors and clinicians form multidisciplinary teams and work together to come up with treatment options that meet your cancer care needs. Immunotherapy treatment may be an option for you if you have certain forms of cancer. The treatment may work better for some types of cancer, so your doctor would monitor your progress closely and may pair immunotherapy with other treatments.

The different cancer vaccines help to prevent cervical cancer or treat prostate cancer or bladder cancer.

Cancer patients and their caregivers are the ones who ultimately decide which treatment they want to pursue. Our clinicians are sensitive to your concerns and work to design treatment options that are appropriate for your needs and goals. We will provide you with the information you need to make an informed decision about immunotherapy for your specific cancer.