Immunotherapy is a new area of cancer treatment. In recent years, this type of treatment has proven successful in increasing survival rates in people with certain types of cancer. This includes metastatic prostate cancer and metastatic lung cancer.

Researchers are now looking at immunotherapy for breast cancer. For some time, they didn’t agree on the role of the immune system in breast cancer. More recent research shows that the immune system has an important role.

Keep reading to learn more about how immunotherapy works and the types of immunotherapy now being studied for treating breast cancer.

Immunotherapy is a type of treatment that uses the body’s own immune system to attack cancer cells. The immune system works by attacking substances in the body that it doesn’t recognize. This includes viruses, bacteria, and cancer cells. Cancer cells present a big challenge because they may not seem very different from normal cells to the immune system. Immunotherapy helps the immune system work better to fight the cancer cells.

Different types of immunotherapy work in different ways. Some types work by boosting your immune system to help it work better. Others give your immune system more tools, such as antibodies, to attack specific cancer cells.

There are four main types of immunotherapy that researchers are studying to treat metastatic breast cancer:

  • cancer vaccines
  • checkpoint inhibitors
  • adoptive T cell therapy
  • monoclonal antibodies

These vaccines work by stimulating a type of immunity that attacks and kills cancer cells. The first cancer vaccine approved by the U.S. Food and Drug Administration (FDA) was a vaccine for people with metastatic prostate cancer. This vaccine has been shown to increase overall survival in people with metastatic prostate cancer.

Many vaccine strategies are now being studied in people with breast cancer. Some researchers believe that the breast cancer vaccines may work best when combined with other therapies.

People who haven’t received much treatment may also benefit from vaccines. Vaccines can take months to cause an immune response, so they may not be appropriate for very late-stage cancers when used alone. They may still play an important role when used with other therapies. Research in this area is ongoing.

The immune system has certain checkpoints that help keep it from attacking normal cells in the body. These checkpoints can also weaken the immune system’s attack on cancer cells. Checkpoint inhibitors are drugs that prevent certain checkpoints from working. This makes the immune response stronger.

The FDA has already approved several drugs in this class for use in melanoma and metastatic lung cancer. Clinical trials on checkpoint inhibitors used alone and in combination with other therapies are also underway for people with metastatic or triple-negative breast cancer.

A T cell is a type of white blood cell that plays an important role in the immune response. Adoptive T cell therapy involves removing your T cells, modifying them to improve their activity, and then giving them back into you through injection. Several early research studies are underway to test this approach in women with metastatic or triple-negative breast cancer.

Monoclonal antibodies can be made in a laboratory. They attack very specific parts of a cancer cell. Monoclonal antibodies can be “naked,” meaning they work alone. They can also be “conjugated,” meaning that they’re joined to a radioactive particle or a chemotherapy drug.

There are already monoclonal antibodies available for the treatment of breast cancer. Trastuzumab (Herceptin), a naked monoclonal antibody, targets the HER2-positive protein. This protein is found on some breast cancer cells. Ado-trastuzumab emtansine (Kadcyla), a conjugated monoclonal antibody, is attached to a chemotherapy drug. It also targets the HER2-positive protein.

A number of other monoclonal antibodies are currently being studied as treatments for advanced breast cancer.

Immunotherapy is generally considered to have fewer side effects than other types of cancer treatment. Some people may still experience side effects, though.

The possible side effects may include:

  • a fever
  • chills
  • fatigue
  • a headache
  • nausea
  • vomiting
  • diarrhea
  • weakness
  • low blood pressure
  • rashes

More serious effects can occur in the lungs, liver, kidneys, and other organs. The vaccines typically only cause mild side effects. You may also experience injection site reactions such as itching or redness. These tend to lessen with time.

Right now, immunotherapy is primarily being studied for advanced metastatic breast cancer, but it also looks promising for use in other stages of breast cancer.

Many clinical trials are underway, and new treatments are expected to become available soon. Their success will depend on finding the correct approach for the specific type and stage of breast cancer. It’s also likely that the therapies will be most helpful when they’re combined with other treatments.

Talk with your doctor about new treatment options that may be available. Learn about new therapies. You can also consider taking part in a clinical research trial. Many of these trials are for people who have metastatic breast cancer and have already had or are currently receiving other types of cancer treatment.