Immunotherapy is a type of systemic treatment (treating the whole body) that aims to boost the individual’s own immune system to fight cancer. Immunotherapies are a type of biologic therapy, as they are made from substances produced from organisms that are alive.1
Normally, the body’s immune system fights disease and infection. The white blood cells recognize and destroy damaged or diseased cells and foreign invaders, like bacteria and viruses. Cancer cells can often mutate in such a way to avoid detection by the immune system, and they grow out of control. Immunotherapies aim to help the immune system identify and destroy cancerous cells.1,2
Several types of immunotherapy are currently being studied for the treatment of advanced breast cancer, including:3
Adoptive cell transfer
How immunotherapy works
Each type of immunotherapy has a different way of working. Monoclonal antibodies are made in the lab to work similarly to how antibodies produced by the body, work. They can target specific areas of cancer cells and/or the pathway that allows cancer cells to avoid immune system detection, such as blocking the function of specific proteins known as PD-L1 and PD-1. The PD-1 and PD-L1 proteins can help disguise cancer cells from the body’s T-cells (a type of white blood cell) and prevent the T-cells from attacking the cancer cells, allowing the cancer to continue to grow and survive. Monoclonal antibodies that target PD-L1 or PD-1 proteins disrupt this pathway and are being studied as a therapy for advanced breast cancer.3
Adoptive cell transfer is an emerging immunotherapy technique that collects and uses the patient’s own immune cells to attack the cancer. In one ongoing Phase II clinical trial, researchers are using tumor-infiltrating lymphocytes (TILs), a type of white blood cell. Researchers first identify the specific mutations on the person’s cancer and identify which TILs can recognize them. These cells are removed from the patient’s body and grown in a laboratory to create a large number of them, which can take several weeks. During this time, the patient may be given treatments to reduce their immune cells. The TILs are then given back to the patient, where they can generate an immune response to fight the cancer cells.1,4
The current trial includes people with several different types of cancer. One patient with metastatic breast cancer has experienced her cancer disappearing from her body. Before participating in the trial, her metastatic breast cancer did not respond to multiple treatments, such as chemotherapy or hormone treatments. With this new immunotherapy, combined with a checkpoint inhibitor called pembrolizumab, all of her cancer has disappeared and has not recurred for at least 22 months. However, not everyone in the trial experienced the same results, and research is ongoing to determine which individuals are best suited for this therapy.4
Possible side effects from immunotherapy
Like all treatments, immunotherapy may cause side effects, although each individual responds differently and may not experience the same side effects as another. Common side effects experienced with immunotherapy include1:
Although there are not currently any immunotherapies approved to treat advanced or metastatic breast cancer, certain patients may be able to participate in clinical trials that are testing these new therapies. Clinical trials are an important part of the scientific process to find and prove the safety and effectiveness of new treatments, and they offer patients a chance to receive the latest treatments and be closely monitored by healthcare professionals. Talk to your doctor about whether clinical trials are a good option for you.
Immunotherapy to treat cancer. National Cancer Institute. Available at https://www.cancer.gov/about-cancer/treatment/types/immunotherapy. Accessed 10/5/18.
Immunotherapy. Cancer Treatment Centers of America. Available at https://www.cancercenter.com/treatments/immunotherapy/. Accessed 10/5/18.
Vonderheide RH, Domchek SM, Clark AS. Immunotherapy for breast cancer: what are we missing? Clinical cancer research: an official journal of the American Association for Cancer Research. 2017;23(11):2640-2646. doi:10.1158/1078-0432.CCR-16-2569.
New approach to immunotherapy leads to complete response in breast cancer patient unresponsive to other treatments. National Cancer Institute. Available at https://www.cancer.gov/news-events/press-releases/2018/immunotherapy-targets-breast-cancer-case-report. Accessed 10/5/18.