What is the immune system?
The immune system is made up of a network of cells and organs and is designed to protect the body from threats such as infections, toxins and abnormal cell development. The immune system recognises when a foreign organism, such as a germ, enters the body and attacks it to stop if from harming the body.
Lymphocytes (white blood cells) are a key part of the immune system. There are two main types:
- B-cells which fight bacteria and viruses.
- T-cells which help control the immune system and help B-cells make antibodies.
The immune system usually prevents cancers from developing because of its ability to detect and eliminate abnormal cell growth. Sometimes the body's natural immune system may not be strong enough to fight the cell growth that causes cancer. Cancer cells may also change over time, which can allow them to escape the immune system.
How does immunotherapy work?
There are different kinds of immunotherapy and they work in different ways. Immunotherapy can boost the immune system to work better against cancer or remove barriers to the immune system attacking the cancer.
Types of immunotherapy
Checkpoint inhibitors
Proteins called ‘checkpoints’ on the surface of T-cells can stop the immune system from attacking cancer cells.
Checkpoint inhibitors are drugs designed to block these proteins to enable the T-cells to recognise and destroy cancer cells. These types of drugs are currently the most widely used form of immunotherapy. Some are subsidised on the Pharmaceutical Benefits Scheme (PBS).
Immune stimulants
Some immunotherapy treatments aim to stimulate the immune system so it reactivates and attacks cancer cells.
CAR T-cell therapy
Chimeric antigen receptor (CAR) T-cell therapy boosts the ability of T-cells to fight cancer. These cells are removed from the blood and altered to better recognise cancer cells before being returned to the blood via intravenous drip.
CAR T-cell therapy is used for some types of leukaemia and lymphoma and clinical trials are testing whether this type of therapy works for other types of cancer.
Oncolytic virus therapy
Oncolytic virus therapy uses viruses that infect cancer cells, causing them to die and stimulating the immune system to attack the cancer. This therapy is sometimes used to treat melanoma and clinical trials are testing oncolytic virus therapies for brain cancer and some other cancers. Research is in its early stages.
When is immunotherapy used?
Surgery, chemotherapy and radiotherapy are still the most widely used cancer treatments but checkpoint immunotherapy is likely to benefit some people with some types of cancer.
In Australia immunotherapy has been predominantly used for the following cancers:
How is immunotherapy treatment given?
How often and how long you receive immunotherapy may depend on:
- the type of immunotherapy
- the type of cancer
- how advanced the cancer is
- how you respond to treatment
- the side effects you may experience.
Checkpoint inhibitors are usually given with an injection into a vein (intravenously).
When immunotherapy is used to treat some melanoma cases, a cream called imiquimod may be applied directly to the affected area.
Sometimes more than one type of immunotherapy drug is prescribed. Immunotherapy drugs appear to keep working for varying periods of time, and in some cases, can keep working long after other treatments are no longer used.
What are the side effects of immunotherapy?
Side effects from immunotherapy can vary depending on the type of treatment you receive and how your body responds. The side effects of checkpoint immunotherapy are different from those of other cancer treatments.
Common side effects include:
- fatigue
- skin rash and itching
- diarrhoea
- abdominal pain
- dry eyes
- changes in weight and body temperature
- joint pain.
Rare side effects include:
- headaches
- changes in vision
- shortness of breath and coughing
- fainting or chest pain
- yellowing of the eyes
- thyroid related issues
- severe abdominal pain and dark urine
- excessive thirst or urination
- reduced urination or blood in the urine
- muscle pain
- confusion or seizures.