Types of Immunotherapy
Immunotherapy helps the immune system recognize that cancer cells are harmful and must be attacked. Immunotherapy medicines are divided into different types based on how they help the immune system identify cancer cells.
Most immunotherapies for breast cancer are only available in clinical trials. Whether you’re eligible for an immunotherapy clinical trial will depend on your diagnosis and some cancer cell traits. Talk to your oncologist about your eligibility to get an immunotherapy or join a clinical trial exploring one.
In this section, you’ll learn more about the types of immunotherapy and some breast cancer medicines within each class.
The body has ‘checkpoints’ that keep the immune system from attacking cells it thinks are healthy. The checkpoints make it less likely the body will attack itself. But those checkpoints also stop the immune system from using its disease-fighting powers on cancer cells. Cancer cells are so similar to healthy cells that the checkpoints don’t realize they are harmful.
Checkpoint inhibitors are medicines that help the immune system recognize that cancer cells are different from healthy cells. They do this by making the body notice mutations found on some cancer cells, but not on healthy cells, such as mutations on proteins called PD-1 and PDL-1. Once the immune system can “see” those differences, it can attack the cancer cells.
In May 2017, the Food and Drug Administration approved use of a checkpoint inhibitor called pembrolizumab (Keytruda) in some situations. It was approved for people with metastatic tumors (regardless of what body part the cancer is in) that grow in part because of problems that occur when DNA makes copies of itself. The tumors are referred to as microsatellite instability-high (MSI-H) or mismatch repair deficient (dMMR). But it’s unusual for breast cancer tumors to have these features, and they haven’t been studied often in breast cancer alone. If you think you may be eligible for this treatment, talk to your oncologist. Pembrolizumab is also being studied in other types of breast cancer. So are many other checkpoint inhibitors.
Vaccines are most often associated with preventing diseases caused by viruses, like the flu. They work by helping your body recognize and attack the influenza virus. Cancer vaccines work the same way: They can help your body recognize and attack cancer cells.
Vaccines for illnesses like the flu are preventive, meaning they work to keep you from getting the flu. But for most cancers, vaccines are used as part of treatment, after you’ve already been diagnosed.
The goal of breast cancer vaccines is to help the immune system destroy cancer cells that may have spread throughout the body, to prevent the cancer from becoming metastatic. Or, in metastatic disease, vaccines could be used to stop a tumor from continuing to grow.
The vaccines are made from cancer cells that have been removed from your body or from the body of another person with breast cancer. Doctors make the vaccine using parts of the cancer cells that are different from healthy cells. Getting the vaccine could help your immune system notice the differences between breast cancer cells and healthy cells, which could help it fight the cancer.
No cancer vaccines are currently approved for breast cancer, but a few are under study.
T cells, a kind of white blood cell, protect the body from disease. In T-cell therapy, a person’s blood is drawn and their T cells are removed from the blood and multiplied in a lab to make more than the body could make on its own. Scientists also change the T cells’ DNA to make the cells better at recognizing cancer. Then, the T cells are put back inside the body with an infusion.
One type of T-cell therapy focuses on white blood cells called tumor-infiltrating lymphocytes, or TILs, that exist deep inside some tumors. Another involves putting chimeric antigen receptors, or CARs, on T cells. These receptors attach themselves to proteins that appear on some cancer cells, killing the cancer.
Immune stimulants, in the form of viruses or other proteins, attract immune cells to the cancer under false pretenses. Here’s how it works: Viruses can be injected near, or even into, the tumor. The immune system might not have realized the cancer was something to destroy, but the injected virus can within a tumor cell, allowing the immune system to recognize that the infected cancer cells are harmful. Other proteins may work in the same way to attract immune cells to the cancer, so they can find and destroy the tumor.
No immune stimulants are approved to treat breast cancer, but many are being studied.