Immunotherapy, also called biologic therapy or biotherapy, uses the body’s own defense system to fight cancer. Researchers have long been interested in whether there are ways to spark the immune system to fight cancer like it fights other illnesses. Long-term research studies have looked into medicines that might help the immune system better recognize and destroy cancer cells. But it’s only recently that these immunotherapy medicines have started to show signs of success.
Immunotherapy has been most successful in skin (melanoma), bladder, and lung cancers. But there is a lot of research looking at immunotherapy for breast cancer. While some breast cancers can be treated with immunotherapy because of specific genetic features, most people will have to enroll in a clinical trial to get immunotherapy.
The immune system is a complex group of organs and cells that defend the body against bacteria, viruses, and other infectious organisms. Normally, the immune system can tell when cells are harmful to the body. The immune system attacks harmful cells to prevent you from getting sick.
But cancer cells look so much like healthy cells that the immune system can’t tell them apart from the healthy cells. This is why the immune system, so far, can’t heal your body of cancer on its own.
Immunotherapies can make the immune system stronger and help it focus on the parts of cancer cells that are different from normal, healthy cells. Once the immune system sees those differences, it’s more likely to attack the cancer. Many immunotherapies target certain gene mutations, or changes in cell DNA, that are present in cancer cells but not in healthy cells. Cancers that have the most mutations are the cancers that have the best chance of responding well to immunotherapy.
Compared to other subtypes of breast cancer, triple-negative breast cancers have the most gene mutations, making it the type of breast cancer that could see the most improvement from immunotherapy. But immunotherapies are being tested in other breast cancer subtypes, too.
Right now, the only immunotherapy approved to treat breast cancer is pembrolizumab (Keytruda). Pembrolizumab can be given to people who have a very specific type of metastatic breast cancer, considered microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR). That means the cancer is likely to create errors in cell DNA while they cells are multiplying. These errors result in proteins that the immune system might be able to recognize.
Though there is only one immunotherapy medicine available today for breast cancer, researchers are very interested in learning more about immunotherapy as treatment for breast cancer. You may be able to join an immunotherapy clinical trial to get treatment.
Most of these trials are in metastatic disease, but some are looking at early-stage breast cancer. To find out if you’re eligible for an immunotherapy clinical trial, visit clinicaltrials.gov and talk to your oncologist.
Immunotherapy is usually given every few weeks and may take a few minutes to a few hours. There are many different forms of immunotherapy, including ones that:
- Change a person’s immune cells to help them recognize and attack the tumor
- change the tumor to make it seem more “foreign” which helps the immune cells recognize and attack it
In some cancers, doctors can remove a person’s immune cells and change them genetically, to make them better at fighting the cancer. Then the doctors put the changed immune cells back in the person’s bloodstream as a cancer therapy. Right now this method is only available to treat leukemia, but it’s being tested for breast cancer. Some clinical trials are also testing whether immunotherapies could be injected directly into the tumor, rather than given via the bloodstream.
Immunotherapies help the body attack cancer cells. But sometimes they also cause the body to attack healthy cells. This can result in serious autoimmune diseases and affect the lungs, kidneys, reproductive system, colon, skin, pituitary and adrenal glands, and the thyroid. Be sure to tell your doctor or your clinical trial’s care team if you already have an autoimmune disorder. It’s unlikely you’ll be eligible for immunotherapy trials, or to be treated with immunotherapy, if you have an existing autoimmune condition.
Immunotherapies can also lower your white blood cell count, which raises the risk of infection. While you’re on immunotherapy, your doctors will monitor your white blood cell counts and may give you medicine to prevent levels from getting too low. If your counts do get too low, your doctors will recommend you stop immunotherapy treatment for a short period of time or for good.
Flu-like symptoms, including fatigue, aches and fever, are also common side effects of immunotherapy.