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What is immunotherapy?

Immunotherapy is a treatment that uses the body’s own immune system to fight cancer. There are several types of immunotherapy, and each works differently. Checkpoint inhibitors remove barriers that stop the immune system from finding and attacking cancer. Other types stimulate the immune system to help it work better against cancer.

In this section, the term “immunotherapy” means the use of checkpoint inhibitors. Examples of checkpoint inhibitors include pembrolizumab, nivolumab, ipilimumab, atezolizumab, durvalumab and avelumab.

Immunotherapy may be used on its own or with other cancer treatments. It is most often given when cancer has not responded to or has come back after initial treatment. In some cases, it may be available as part of the first treatment plan.

The immune system is a network of cells, chemicals, tissues and organs. It includes the lymph nodes, spleen, thymus, tonsils and bone marrow, as well as white blood cells known as lymphocytes. Together, this network tries to protect the body from infections and from abnormal cells such as cancer cells.


To keep you healthy, the immune system needs to be carefully balanced. If it is too weak, you will be prone to infection and disease. If it is too active, it can start to attack normal cells and lead to autoimmune diseases such as rheumatoid arthritis and lupus.

Tipping the balance – Cancers find ways to disrupt the balance of the immune system so that it does not see cancer cells as abnormal. Immunotherapy manipulates the immune system to restore the balance and allow it to attack the cancer.

Immune side effects – If immunotherapy makes the immune system overactive, you can get side effects anywhere in the body.

After treatment – Because the immune system has a “memory”, immunotherapy sometimes keeps working long after treatment finishes. This means side effects can also appear months or even years after treatment.

Cancer starts when abnormal cells begin growing out of control. The immune system usually stops new cancers from developing because it  recognises abnormal cells and destroys them. In some cases, the body’s immune response is not able to kill all abnormal cells and they develop into cancer.

Cancer cells find ways to stop the immune system from destroying them – for example, by setting up barriers (“checkpoints”) so the immune system can’t recognise them, or by changing over time (mutating) to avoid being found by the immune system. This is why treating cancer isn’t as simple as boosting the immune system. Modern immunotherapy drugs try to help the immune system in very specific ways.

Some people with cancer wonder if they should try special diets or supplements to boost the immune system so it can fight the cancer. While having a healthy diet is always important, extreme diets are not proven to be effective and can be harmful. Talk to your doctors before starting any special diets or supplements during cancer treatment.

Because each cancer is unique, people may have different treatment plans, even if their cancer type is the same. The three main cancer treatments are:

  • surgery
  • chemotherapy
  • radiation therapy (also called radiotherapy).

Other treatments used for some types of cancer in some people include:

  • immunotherapy
  • targeted therapy
  • hormone therapy.

Chemotherapy, targeted therapy, immunotherapy and hormone therapy are all drug therapies. They are known as systemic treatment because the drugs circulate throughout the body.

Cancer treatments may be used on their own or in combination. For example, you may have surgery to remove a tumour, followed by immunotherapy to stop the cancer returning. Doctors will recommend the best treatment for you based on the type and stage of cancer, its genetic make-up, your age and your general health.

See ‘Cancer treatments’ for more information

The white blood cells known as lymphocytes are an important part of the immune system. There are two main types of lymphocytes – T-cells and B-cells. They travel throughout the body looking for germs and abnormal cells and work together to destroy them.

Checkpoint inhibitors help T-cells to recognise and attack cancer. A simplified explanation of this process is below.

T-cells and checkpoint inhibitors

What T-cells usually do – Your immune system’s T-cells circulate throughout the body looking for abnormal cells to destroy. The T-cells carry “checkpoints”, special proteins with names such as PD-1, PD-L1 and CTLA-4.

What checkpoints usually do – Checkpoints act as natural brakes to stop T-cells destroying healthy cells.

How some cancer cells use checkpoints – In some people, cancer cells use checkpoints to stop T-cells from seeing the cancer cells as abnormal.

What checkpoint inhibitors do – Checkpoint inhibitors are drugs that block these checkpoints so that the T-cells can once again find and attack the cancer. This is like taking the brakes off the immune system.

Featured resource

Understanding Immunotherapy

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This information is reviewed by

This information was last reviewed July 2021 by the following expert content reviewers: Dr Jenny Lee, Medical Oncologist, Chris O’Brien Lifehouse, NSW; Prof Michael Boyer, Medical Oncologist and Chief Clinical Officer, Lung and Thoracic Cancer, Chris O’Brien Lifehouse, and Central Clinical School, The University of Sydney, NSW; A/Prof Christine Carrington, Senior Consultant Pharmacist Cancer Services, Princess Alexandra Hospital, QLD; Dr Inês Pires da Silva, Medical Oncology Fellow, Melanoma Institute Australia and Westmead and Blacktown hospitals, NSW; Sandra Donaldson, 13 11 20 Consultant, Cancer Council WA; Sherry Gilbert, Consumer; Marilyn Nelson, Consumer; Julie Teraci, Skin and Melanoma Cancer Nurse Coordinator, WA Cancer and Palliative Care Network, North Metropolitan Health Service, WA; Helen Westman, Lung Cancer Nurse Coordinator, Cancer and Palliative Care Network, Royal North Shore Hospital, NSW.