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How Does Immunotherapy Work?

Immunotherapy is a type of cancer treatment that uses the body’s natural defenses (the immune system) to identify, attack, and kill cancer cells.

The immune system’s purpose is to attack any cell that it sees as unhealthy or abnormal. Cancer cells can hide from these defenses or even stop an attack. New knowledge about the complex interactions between the immune system and cancer is leading to new treatments. Although there are promising results, immunotherapy does not work for every cancer type or every patient. There is still a lot that researchers don’t know.

Types of Immunotherapy

Most immunotherapies today are biologic therapies— made by living organisms. They help fight cancer by:

  • Boosting the immune system. A "revved up" immune system can fight cancer better.
  • "Marking" cancer cells so that your immune system can find and destroy them. This keeps the cancer from being able to hide.
  • Helping the immune system find cancer cells and deliver treatment (like chemotherapy, radiation, or even T cells) directly to the cancer cells.

There are many kinds of immunotherapy treatment in development. They fall into two main categories:

  • Agents that boost the immune response. A “revved up” immune response will be better at fighting cancer cells.
  • Agents that help the immune system target cancer cells. "Marking" cancer cells to help your immune system find and destroy cancer. This prevents the cells from being able to hide. It can also help the immune system find cancer cells and deliver treatment (like chemotherapy, radiation, or even T cells) directly to cancer cells.

Enabling the Immune Response

Checkpoint Inhibitors

The immune system has safeguards to prevent it from attacking healthy cells. These safeguards are called checkpoints. They slow down or stop an immune system attack when healthy tissue is threatened. Some cancers have learned how to activate these checkpoints to avoid being attacked. New drugs, called checkpoint inhibitors, are designed to turn off these checkpoints and help the body find and fight cancer.

Most patients who receive immunotherapy today are on one of two kinds of checkpoint inhibitors: PD-1 and PD-L1 Inhibitors or CTLA-4 Inhibitors. So far, these drugs have only worked for up to one third of patients who try them. More research is underway. Some clinical trials are testing checkpoint inhibitors with other therapies, such as chemotherapy or other immunotherapy drugs.

Other Monoclonal Antibodies

Checkpoint inhibitors are one type of monoclonal antibody (mAb). Not all mAbs are immunotherapies. Some types let the immune system find and destroy cancer cells using targets. Other types take chemotherapy or radiation therapy directly to cancer cells. Each mAb is made to find and attach to a specific protein that occurs in cancer cells. Most mAb treatments (that aren’t checkpoint inhibitors) are used in blood cancers.

To learn more, see our Immunotherapy and Blood Cancers page.

Adoptive (or CAR) T Cell therapies

In adoptive T cell therapy, T cells are removed from a person with cancer, taken to a lab, and modified. Once returned to the person, these modified T cells can find and destroy cancer cells. This approach is being tested in several types of cancers. One type of adoptive cell therapy, CAR T cell therapy, is approved to treat certain leukemias and lymphomas. CAR T cell therapy is only available in a few major cancer centers. These centers have the technical
ability to provide this treatment to patients.

See our CAR T Immunotherapy booklet for more information.

Boosting the Immune System

Bacillus Calmette-Guerin (BCG)

BGG therapy is injected directly into the bladder to cause an immune response against bladder cancer. It prevents cancer from returning in about 70 percent of patients with early stage bladder cancer.

Cytokines

Cytokines work by speeding up the growth of T cells and activating other immune cells. Interleukins and interferon are examples of cytokines that have shown some success. High dose interleukin 2 (IL2) has greatly helped a small percent of people with advanced melanomas and kidney cancers.

Treatment Vaccines

Cancer Vaccines are designed to “teach” T cells to respond to specific cancer antigens. Currently, there is only one approved cancer vaccine, sipuleucel-T (Provenge®). It is used to treat advanced prostate cancer. Provenge® is made from the patient’s own white blood cells. These cells are sent to a lab where their ability to attack prostate cancer cells is boosted. They are then re-infused into the patient.

Researchers are studying possible vaccines for other cancers, such as blood and breast cancers.

Radioimmunotherapy

This treatment uses an antibody with a radioactive substance to direct radiation to cancer cells. Ibritumomab tiuxetan (Zevalin®) is the only radioimmunotherapy approved by the FDA in the U.S. This type of therapy lets doctors target cancer cells with higher doses of radiation, safely. It is used to treat certain types of lymphomas.

Oncolytic Virus Therapy

Oncolytic virus therapy is an experimental form of immunotherapy. Oncolytic viruses infect both cancer and normal cells, but they have little effect on normal cells. They multiply inside cancer cells and cause them to die. Several viruses are currently being tested in clinical trials. The only oncolytic virus therapy approved in the U.S. is talimogene laherparepvec (Imlygic®). It is used to treat very specific types of melanoma.

There is broad interest and excitement about the potential for immunotherapy to treat many kinds of cancer. As researchers learn more about how the immune system interacts with cancer, they will be able to apply that knowledge to more cancer types

Current Immunotherapies by Cancer Type