Immunotherapy, or biologic therapy, is a type of treatment that uses your own immune system to fight cancer.

The immune system is made up of cells and organs that protect the body from threats such as infections, toxins and abnormal cell growth. The immune system recognises when a foreign organism, such as a germ, enters the body and attacks it to stop it from harming the body.

There are many different kinds of immunotherapy which work by slowing the growth and spread of cancer cells, and by helping the immune system destroy existing cancer cells.

• Cancer vaccines are medicines that trigger the body’s immune system to detect cancer cells and either prevent cancer cells from developing or prompt the immune system to fight existing cancer cells.
• Non-specific immunotherapies refer to the use of proteins produced by white blood cells to control immune responses that help the body’s immune system destroy cancer cells. They are often given with other cancer treatments, such as chemotherapy or radiation therapy.
• Monoclonal antibodies, also known as therapeutic antibodies, are immune system proteins designed to attach to specific targets found on cancer cells so that they will be better seen and destroyed by the immune system.
• Checkpoint inhibitors are medicines that help the immune system respond more strongly to a tumour by releasing “brakes” that keep T cells (a type of white blood cell and part of the immune system) from killing cancer cells.
• CAR T-cell therapy is an emerging type of treatment in which a patient’s T cells (a type of immune system cell) are changed in the laboratory so they will attack cancer cells.

Immunotherapy can be given in a clinic, a doctor’s office or at a hospital. How often the treatment is given will depend on the type of immunotherapy, the type of cancer, how advanced the cancer is, how the cancer responds to treatment or the side affects you experience. Different forms of immunotherapy may be given in different ways, including orally, directly into a vein through an intravenous injection or infusion (IV), by applying a cream, directly into the bladder, or injected into a tumour.

Some immunotherapies are given in cycles. A cycle is a period of treatment followed by a period of rest. The rest period gives your body a chance to recover, respond to the immunotherapy and build new healthy cells.

Cancer cells learn to survive and grow in a hostile environment due to their ability to hide from the immune system and avoid detection by the body’s own self defences. Once the immune system is alerted and activated, other healthy cells may be recognised as different and vulnerable to attack by the body’s own defence systems. This is what causes some of the side effects of immunotherapy.

Immunotherapy side effects can affect people in different ways and will depend on how healthy you are before treatment, your type of cancer, how advanced it is, the type of therapy you are getting, and the dose.

The most common side effects are skin reactions at the needle site, which can include pain, swelling, soreness, redness, itchiness and a rash.

You may have flu-like symptoms, such as:

• Fever
• Chills
• Weakness
• Dizziness
• Nausea or vomiting
• Muscle or joint aches
• Fatigue
• Headache
• Trouble breathing
• Low or high blood pressure

Other side effects might include:

• Swelling and weight gain from fluid retention
• Heart palpitations
• Sinus congestion
• Diarrhoea
• Risk of infection

Immunotherapies may, on very rare occasions, also cause severe or even fatal allergic reactions.

For more information about immunotherapy and its side effects, you should talk to your doctor.