At our hospital, we get a lot of questions about immunotherapy treatments for breast cancer. Immunotherapy is one of latest, most promising lines of research in breast cancer, part of a growing breed of biologic therapies. Immunotherapy is often mentioned in the same context as the coveted “breast cancer vaccine.” Although immunotherapy and cancer vaccines are still in the research phase, many believe immunotherapy alone, or in combination with existing drugs, is where the cure for cancer will come from.
What Is Immunotherapy?
Humans, and most biological organisms for that matter, have an incredible variety of natural disease-, virus-, bacteria- and pathogen-fighting processes. Our bodies can detect invaders and automatically organize responses to fight off sickness and disease. This collection of detection abilities and responses is called our “immune system.”
Immunotherapy is a type of treatment that works with this natural immune system, enhancing it, activating it or even suppressing it, to help treat disease. Immunotherapy suppression drugs, for instance, have been used to prevent the body from rejecting organ transplants, to treat allergies, and to treat autoimmune disorders where patients’ own immune systems attack their bodies.
In the realm of cancer treatment, however, it is the passive enhancement and the active immunotherapy treatments that are the most promising.
Types of Passive & Active Immunotherapy Drugs
Passive immunotherapy enhances our natural immune system to help fight cancer better. Active immunotherapy treatments work by hyper-activating and stimulating our immune systems.
Vaccine Therapy
This type of passive therapy introduces tumors into the body, which prompts the body’s normal immune system to fight cancer cells. A number of cancer vaccines are currently in research. Some use cancer cells from the patient’s own body; some use a variety of substances, called antigens, created by tumors. Provenge® is a FDA-approved vaccine for prostate cancer, but breast cancer vaccines have not yet been approved.
Adoptive T Cell Transfer (Immune Cell) Therapy
A T cell is a type of white blood cell and is a key part of our immune system, either attacking infected cells or directing and regulating immune responses. In this type of passive therapy, some of the patient’s own T cells are removed from their body, enhanced through chemical treatment or genetic modification to make them better cancer fighters, and then reintroduced to the body. Another approach to immune cell therapy is using the patient’s own cancer-attacking T cells. Some tumors may have been already attacked by a patient’s T cells, and if this is the case, those special T cells, called tumor-infiltrating lymphocytes (or TILs), are removed, duplicated, and then re-infused back into the blood.
Oncolytic Virus Therapy
Oncolytic viruses are viruses that kill cancer cells. In this type of passive therapy, these viruses are introduced into a patient’s body. The virus seeks out tumor cells and replicates itself inside the tumor cell until the tumor cell bursts and is destroyed. Oncolytic viruses were first researched for their ability to directly destroy cancer cells, but some researchers believe that the viruses work by alerting our immune system to the tumors. T-VEC, or Imlygic® are types of oncolytic virus drugs that are FDA-approved for melanoma, but to date, nothing has been approved for breast cancer treatment.
Immune Checkpoint Inhibitor Therapy
This type of active therapy takes the brakes off our immune systems, disabling key checkpoints, or “off buttons”, in our immune systems, revving them up and putting them on overdrive. The two most studied checkpoints are PD-1 and CTLA-4. Our T cells naturally do not attack cells that exhibit PD-1 and CTLA-4 proteins. However, some types of cancer show high levels of these proteins and evade detection by our bodies because of this. Drugs in this therapy tell our T cells to ignore their natural “off” impulse when they encounter a cell exhibiting PD-1 or CTLA-4 proteins and tell it to attack instead. PD-1 drugs are very popular treatments for other types of cancer but none have been approved yet for breast cancer.
Immunotherapy Treatment Process
Not everyone is a good candidate for immunotherapy. Some cancers are more immunogenic, meaning they respond better to immunotherapy. Triple negative breast cancer responds well to immunotherapy and we especially recommend it for Stage IV patients. Patients with Lynch syndrome or Microsatellite Instability (MSI) are also good candidates for immunotherapy. Immunotherapy is very promising for the patients it works well for, but a very small amount of people are good candidates.
Immunotherapy can also be effective as an adjuvant, or add-on, therapy, along with chemotherapy, radiation or other DNA-damaging drugs. This combination of therapies works by allowing our immune systems to better locate tumors. We describe a tumor as “cold” if it doesn’t respond to the immune system. Chemotherapy and radiation are used to make the tumor “hot” so that the immune system responds and immunotherapy treatments work better.
While there are several FDA-approved immunotherapy cancer drugs on the market now, unfortunately none are approved for treating breast cancer. Because of this, starting an immunotherapy treatment plan is an individualized process that is often dependent on insurance coverage, other treatment options available to you, and your cancer’s unique biomarkers.
Immunotherapy research is incredibly prolific right now and for those who are truly dedicated to pursuing cutting-edge treatment, I wholeheartedly recommend looking into one of the many clinical trials available.
