Understanding Immunotherapy

Approved by the Cancer.Net Editorial Board, 05/2015

Immunotherapy, also called biologic therapy, is a type of cancer treatment designed to boost the body's natural defenses to fight the cancer. It uses materials either made by the body or in a laboratory to improve, target, or restore immune system function. It is not entirely clear how immunotherapy treats cancer. However, it may work in the following ways:

  • Stopping or slowing the growth of cancer cells
  • Stopping cancer from spreading to other parts of the body
  • Helping the immune system work better at destroying cancer cells.

There are several types of immunotherapy, including monoclonal antibodies, non-specific immunotherapies, and cancer vaccines.

Monoclonal antibodies

When the body’s immune system detects antigens, it produces antibodies. Antigens are harmful substances, such as bacteria, viruses, fungi, or parasites. Antibodies are proteins that fight infection. Monoclonal antibodies are made in a laboratory. When they are given to patients, they act like the antibodies the body produces naturally. A monoclonal antibody is directed against a specific protein in the cancer cells, and it does not affect the cells that do not have that protein. When a monoclonal antibody attaches to a cancer cell, they may accomplish the following goals:

  • Allow the immune system to destroy the cancer cell. The immune system doesn't always recognize cancer cells as being harmful. A monoclonal antibody can mark cancer cells by attaching to specific parts of cancer cells not found on healthy cells. This makes it easier for the immune system to find and destroy these cells. The monoclonal antibodies that target the PD-1 protein are a good example. PD-1 keeps the immune system from recognizing that a cell is cancerous, so drugs that block PD-1 allow the immune system to identify and eliminate the cancer.

  • Prevent cancer cells from growing rapidly. Chemicals in the body tell cells to grow by attaching to receptors on the surface of cells. These chemicals are called growth factors. The receptor they attach to is called a growth factor receptor. Some cancer cells make extra copies of the growth factor receptor. This makes the cancer cells grow faster than normal cells. Monoclonal antibodies can block these receptors and prevent the growth signal from getting through.

  • Deliver radiation directly to cancer cells. This treatment, called radioimmunotherapy, uses monoclonal antibodies to deliver radiation directly to cancer cells. By attaching radioactive molecules to monoclonal antibodies in a laboratory, they can deliver low doses of radiation specifically to the tumor while leaving healthy cells alone. Examples of these radioactive molecules include ibritumomab tiuxetan (Zevalin) and tositumomab (Bexxar). 

  • Diagnose cancer. Monoclonal antibodies carrying radioactive particles may also help diagnose certain cancers, such as colorectal, ovarian, and prostate cancers. Special cameras identify the cancer by showing where the radioactive particles build up in the body. In addition, a pathologist may use monoclonal antibodies to determine the type of cancer a person may have by analyzing the sample of tissue removed during a biopsy. A pathologist is a doctor who specializes in interpreting laboratory tests and evaluating cells, tissues, and organs to diagnose disease.

  • Carry drugs directly to cancer cells. Some monoclonal antibodies carry other cancer drugs directly to cancer cells. Once the monoclonal antibody attaches to the cancer cell, the treatment it is carrying enters the cell. This causes the cancer cell to die without damaging other healthy cells. One example is Brentuximab vedotin (Adcetris), a treatment for certain types of Hodgkin and non-Hodgkin lymphoma. Another example is trastuzumab emtansine or TDM-1 (Kadcyla), which is a treatment for HER2-positive breast cancer.

Other monoclonal antibodies approved by the U.S. Food and Drug Administration (FDA) to treat cancer include:

  • Alemtuzumab (Campath)
  • Bevacizumab (Avastin)
  • Cetuximab (Erbitux)
  • Ipilimumab (Yervoy)
  • Nivolumab (Opdivo)
  • Ofatumumab (Arzerra)
  • Panitumumab (Vectibix)
  • Pembrolizumab (Keytruda)
  • Rituximab (Rituxan)
  • Trastuzumab (Herceptin)

Clinical trials of monoclonal antibodies are ongoing for several types of cancers. Learn more about clinical trials.  

Side effects of monoclonal antibody treatment are usually mild and are often similar to an allergic reaction. Possible side effects include rashes, low blood pressure, and flu-like symptoms, such as fever, chills, headache, weakness, extreme tiredness, loss of appetite, upset stomach, or vomiting.

Although monoclonal antibodies are considered a type of immunotherapy, they are also classified as a type of targeted therapy. Targeted therapy is a treatment that targets the cancer’s specific genes, proteins, or the tissue environment that contributes to cancer growth and survival. Learn more about targeted treatments.

Non-specific immunotherapies

Like monoclonal antibodies, non-specific immunotherapies also help the immune system destroy cancer cells. Most non-specific immunotherapies are given after or at the same time as another cancer treatment, such as chemotherapy or radiation therapy. However, some non-specific immunotherapies are given as the main cancer treatment.

Two common non-specific immunotherapies are:

  • Interferons. Interferons help the immune system fight cancer and may slow the growth of cancer cells. An interferon made in a laboratory, called interferon alpha (Roferon-A [2a], Intron A [2b], Alferon [2a]), is the most common type of interferon used in cancer treatment. Side effects of interferon treatment may include flu-like symptoms, an increased risk of infection, rashes, and thinning hair.

  • Interleukins. Interleukins help the immune system produce cells that destroy cancer. An interleukin made in a laboratory, called interleukin-2, IL-2, or aldesleukin (Proleukin), is used to treat kidney cancer and skin cancer, including melanoma. Common side effects of IL-2 treatment include weight gain and low blood pressure, which can be treated with other medications. Some people may also experience flu-like symptoms.

Cancer vaccines

A vaccine is another method used to help the body fight disease. A vaccine exposes the immune system to an antigen. This triggers the immune system to recognize and destroy that protein or related materials. There are two types of cancer vaccines: prevention vaccines and treatment vaccines.

  • Prevention vaccine. A prevention vaccine is given to a person with no symptoms of cancer. It is used to keep a person from developing a specific type of cancer or another cancer-related disease. For example, Gardasil and Cervarix are vaccines that prevent a person from being infected with the human papillomavirus (HPV). HPV is a virus known to cause cervical cancer and some other types of cancer. Learn more about HPV and cancer. In addition, the U.S. Centers for Disease Control and Prevention recommends that all children should receive a vaccine that prevents infection with the hepatitis B virus. A hepatitis B infection may cause liver cancer. Learn more about hepatitis B screening.

  • Treatment vaccine. A treatment vaccine helps the body's immune system fight cancer by training it to recognize and destroy cancer cells. It may prevent cancer from coming back, eliminate any remaining cancer cells after other types of treatment, or stop cancer cell growth. A treatment vaccine is designed to be specific, which means it should target the cancerous cells without affecting healthy cells. At this time, sipuleucel-T (Provenge) is the only treatment vaccine approved in the United States. It is designed for treating metastatic prostate cancer. Additional cancer treatment vaccines are still in development and only available through clinical trials.

Learn more about cancer vaccines.

Questions to ask the doctor

Talk with your doctor about whether immunotherapy may be part of your treatment plan. If so, consider asking the following questions: 

  • What type of immunotherapy do you recommend? Why?
  • What are the goals of this treatment?  
  • Will immunotherapy be my only treatment? If not, what other treatments will be a part of my treatment plan?
  • How will I receive immunotherapy treatment and how often?
  • What are the possible side effects of immunotherapy, both in the short term and the long term?
  • How will this treatment affect my daily life? Will I be able to work, exercise, and perform my usual activities?
  • What clinical trials of immunotherapies are open to me?
  • Whom should I call for questions or problems?

More Information

How Cancer is Treated

Research Summaries

Side Effects

Additional Resources

American Cancer Society: Cancer Immunotherapy

National Cancer Institute: Cancer Vaccines