You may have heard about the latest development in treating cancer using the immune system. But how does this work and what is immunotherapy and can it work for everyone?
What is immunotherapy?
Immunotherapy is a cancer treatment that uses stimulation of the body's immune system to fight cancer cells.
This has been a dream of cancer doctors and patients for many years. If the immune system could fight cancer, it could do it as effectively as the immune system fights an infection, targeting the cancer specifically.
Also, the immune system can keep fighting, even after the treatment stops, because the immune system remembers its targets. Think of how a measles vaccination protects you from measles for many years, maybe your entire life. That is because of the memory in the immune system.
How did the idea of immunotherapy originate?
Immunotherapy developed along two routes.
First, in the cancer treatment world, there has been interest in using immunotherapy to treat cancer for more than 100 years: Since surgeons noted that some patients who had severe infections after lung cancer seemed to eliminate the cancer, and a surgeon named William Coley treated some cancers by injection of bacterial toxins into cancer. Over the years, there have been patients who seem to develop and immune reaction to their cancers, like patients with melanoma who developed depigmentation of the skin and eliminated their melanomas at the same time. This happened rarely, but more often for melanoma than other cancers. For the past 30 years, researchers have attempted to trigger those immune reactions by stimulation of the immune system, with interferon, interleukin 2 and vaccines.
One of the problems is that there are many treatments that can affect the immune system, but it is difficult to find any that consistently impact cancer. For example, vitamins can affect aspects of the immune system, but have not been shown to improve the treatment or prevention of cancer.
So, medical treatments using the immune system to treat cancer have not predictably worked. With each new treatment, researchers learned something about the immune system and with each new advance in understanding of the basic biology of the immune system, new treatments were suggested.
The modern age of immunotherapy dates back to studies of the mouse immune system done at the University of California, Berkeley by Dr. Jim Allison 30 years ago. He found that there were certain proteins on the surface of immune cells that blocked the immune response from developing, and which caused immune tolerance.
Over the years, treatments were developed that blocked this immune tolerance, and these are now used to treat cancers. These are the treatments which are most promising. They are called immune checkpoint inhibitors.
Is immunotherapy used to treat all forms of cancer?
The simple answer is no. The immune checkpoint inhibitors are currently approved for use in certain types of melanoma, lung cancer, colon cancer, cancer of the mouth and throat, kidney cancer, Hodgkin Lymphoma, stomach cancer and bladder cancer.
Recently, a new version of immunotherapy called CAR T-cell therapy was approved to fight aggressive non-Hodgkin lymphoma. There are some other cancers for which immunotherapy seems to work, and clinical trials are underway to see how well they work and whether they are safe and effective. These generally work best in cancers which have many mutations, since those cells look different to the immune system, compared with normal cells.
Are certain patients better candidates for immunotherapy?
Yes. First, the patient must have a cancer where it is likely the immunotherapy would work. That may include some cancers in which the treatment is still under study.
Second, the patient can't have diseases in which the immune system is already attacking the body. This is a very important point. The immune system can attack the body. That is the cause of diseases like rheumatoid arthritis, psoriasis, some other skin diseases, some kinds of liver disease and ulcerative colitis.
The main danger of immune therapy with immune checkpoint inhibitors is that the immune system can be stimulated to attack normal cells, not just the cancer, and that can make people sick. These immune side effects can be treated with prednisone or cortisone, but they can develop quickly and be hard to detect. So doctors always use these with caution, particularly in people who already have some type of immune disease.
Could this change the way we fight cancer?
Immunotherapy has already changed the fight against cancer. In particular, in melanoma, it has dramatically improved the remission rate in advanced melanoma. Patients who had advanced melanoma have had complete disappearance of disease and have stayed free of disease for many years, 7-10 years and counting. This type of response was very rare before these treatments.
Should cancer patients be asking for this type of treatment?
If you have been diagnosed with cancer, speak with your oncologist or cancer doctor. There are many cancers where this type of treatment can help, but not for all cancers. For some cancers, there are clinical trials using these new agents which may be valuable in your fight against cancer.