Cancer: Using Your Immune System to fight the Disease
Newest Cancer Treatment: Immunotherapy
Some of the most promising advances in cancer research in recent years involve treatments known as immunotherapy. These advances have spurred billions of dollars in investment at leading universities around the world and hundreds of clinical trials. I have written some basic answers to questions about this complex and rapidly evolving field.
What is immunotherapy?
Immunotherapy refers to any treatment that uses the immune system to fight diseases, including cancer. Unlike chemotherapy, which kills cancer cells, immunotherapy acts on the cells of the immune system to help them attack the cancer cells.
What are the types of Immunotherapy?
Drugs called checkpoint inhibitors are the most widely used form of immunotherapy for cancer. They block a mechanism that cancer cells use to shut down the immune system. This frees killer T-cells—a critically important part of the immune system—to attack the tumour. Four checkpoint inhibitors have been approved by the United States Food and Drug Administration, two of them in Canada; have been approved for intravenous injection.
Another form of immunotherapy, called cell therapy, involves removing immune cells from the patient, altering them genetically to help them fight cancer, then multiplying them in the laboratory and dripping them, like a transfusion into the patient. This type of treatment is manufactured individually for each patient and is still experimental.
Bispecific antibodies are an alternative to cell therapy, one that does not require individualized treatment for each patient. These antibodies are proteins that can attach to both a cancer cell and a T-cell, that way bringing them close together so the T-cell can attack the cancer. One drug of this nature has been approved to fight leukemia.
A very new method is the use of the Polio vaccine which is being done at Duke University in North Carolina. Glioblastoma brain tumours are injected with a genetically modified form of the polio virus. Under normal circumstances your body’s immune system will not attack cancer cells because they are simply normal cells that will not die. However, once the tumour is injected with the polio virus, the cells start to attack and destroy the tumour. This is the type of cancer that is killing Gord Downie from the Tragically Hip and hopefully his neurosurgeon will let him try the treatment. So far it has had a huge success rate with a very small group of patients.
The only vaccine approved specifically to treat cancer is Provenge, for prostate cancer. Another vaccine that was used to treat tuberculosis has been used for a long time to treat bladder cancer. The theory is the same. Infect the tumour and the immune system will activate to destroy the cancerous cells.
Which types of cancer are treated with immunotherapy?
Checkpoint inhibitors have been approved to treat advanced melanoma, Hodgkin’s lymphoma and cancers of the lung, kidney and bladder. Of course they are being used experimentally in other forms of cancer but the main ones are leukemia and lymphoma.
Which cancer drugs are checkpoint inhibitors?
The four on the market are: Yervoy (ipilimumab) and Opdivo (nivolumab),Keytruda (pembrolizumab) and Tecentriq (atezolizumab).
How well does immunotherapy work?
Though immunotherapy has been highly successful in some cases, it still works in only a minority of patients. Generally between 20 and 40 per cent of patients are helped by checkpoint inhibitors, although the rate can be higher among those with melanoma. Some patients with advanced disease have had remissions that have lasted for many years. In some cases, combining two checkpoint inhibitors increases effectiveness but the danger is destruction of normal cells. Remember, checkpoint inhibitors disarm all the cells of the body, thus allowing the drug to attack the cancer cells. But just like chemotherapy, many good cells will be destroyed in the process.
Cell therapy can produce complete remissions in 25 to 90 percent of patients with lymphoma or leukemia. In some cases the remission lasts for years but in other cases only for a very short period of time, usually within a year.
What are the side-effects?
Checkpoint inhibitors can cause severe problems that are essentially autoimmune illnesses, in which the immune system attacks healthy tissue as well as cancerous growths. One result is inflammation. In the lungs it can cause breathing problems; in the intestine it can cause diarrhea. Joint and muscle pain, and rheumatoid arthritis can also occur, and the immune system can also attack viral glands like the thyroid and pituitary. These reactions are dangerous but can be controlled with the use of corticosteroids such as prednisone.
Cell therapy can also lead to severe and potentially fatal reactions resulting from the overstimulation of the immune system. Some patients may have to be treated in an intensive care unit.
What does immunotherapy cost? Does insurance cover it?
Checkpoint inhibitors can cost as much as $150,000 a year. Most people will get special consideration, either from their provincial health care plan or from the drug companies themselves. If you have supplementary insurance, you are probably not covered if the drugs are brand new and of course the insurance companies always figure out a way to wiggle out of payment. If you are in a clinical trial you will not have to pay anything.
Where can I get immunotherapy?
Any oncologist can prescribe the four checkpoint inhibitors that are on the market. However, if the patient’s cancer is not on the list of cancers specific to the drug, then the patient may have to pay. Always best to try and get into a free clinical trial.
How can I find out about clinical trials in immunotherapy?
Information is available at the Canadian Cancer Society or the Cancer Research Institute website. Your oncologist will always be aware of any clinical trials that you may be eligible for.