Types of immunotherapy
Immunotherapy can trigger the immune system to fight cancer in different ways.
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The drugs known as checkpoint inhibitors are the most widely used form of immunotherapy for cancer. They work by helping the immune system to recognise and attack the cancer.
T-cells and checkpoint inhibitors
|What T-cells usually do|
|The immune system’s T-cells circulate throughout the body looking for abnormal cells to destroy. The T-cells carry proteins known as “checkpoints”.|
|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, the cancer cells use these checkpoints to stop T-cells recognising 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 recognise and destroy the cancer. This is like taking the brakes off the immune system.|
There are other types of immunotherapy. A few are available now as approved treatment for cancer, but most are still being tested in clinical trials and may be more widely available in future.
Some treatments are used to stimulate the immune system to attack the cancer. These are known as immune stimulants.
In non-muscle-invasive bladder cancer, the vaccine Bacillus Calmette-Guérin (BCG) may be used as an immune stimulant. It is given into the bladder through a catheter. The BCG stimulates the immune system to stop or delay bladder cancer coming back or becoming invasive.
In some types of skin cancers, a cream called imiquimod is applied directly to the affected area to stimulate a local immune response.
Adoptive cell transfer
This experimental type of immunotherapy is used to boost the ability of T-cells to fight cancer. Chimeric antigen receptor (CAR) T-cell therapy is a type of adoptive cell transfer that is being tested in Australian clinical trials. It is showing good results for some types of leukaemia and lymphoma.
In CAR T-cell therapy, the T-cells are removed from the blood, and a new gene is introduced into the T-cells to enable them to recognise cancer cells. The T-cells are then returned to the blood by an intravenous drip (infusion). The altered T-cells multiply and trigger a number of immune responses that attack the cancer cells.
These viruses directly infect tumour cells and cause an immune response against the infected cells. An oncolytic virus therapy known as talimogene laherparepvec or T-VEC (brand name Imlygic) is sometimes used for melanoma. It is injected directly into the melanoma both to kill the melanoma cells and to stimulate the immune system to attack melanoma cells.
Oncolytic virus therapies for brain cancer and some other types of cancer are being tested in clinical trials, but the research is still in its early stages.
How vaccines help prevent cancer
Vaccines help train the immune system to prevent some types of cancer. The human papillomavirus (HPV) vaccine is used to prevent cervical cancer, and it is hoped it will also prevent anal and penile cancers and some cancers of the head and neck. Vaccines against hepatitis B and hepatitis C viruses help prevent liver cancer.
A/Prof Brett Hughes, Senior Staff Specialist, Medical Oncology, Royal Brisbane and Women’s Hospital and The Prince Charles Hospital, and Associate Professor, The University of Queensland, QLD; Dawn Bedwell, 13 11 20 Consultant, Cancer Council Queensland, QLD; Tamara Dawson, Consumer; A/Prof Craig Gedye, Senior Staff Specialist, Medical Oncology, Calvary Mater Newcastle, and Conjoint Associate Professor, School of Medicine and Public Health, University of Newcastle, NSW; A/Prof Alexander Menzies, Medical Oncologist, Associate Professor of Melanoma Medical Oncology, and Faculty Member, Melanoma Institute Australia, The University of Sydney, Royal North Shore Hospital and Mater Hospital, NSW; Dr Donna Milne, Nurse Consultant Melanoma and Skin Service, Peter MacCallum Cancer Centre, VIC; Dr Geoffrey Peters, Staff Specialist, Medical Oncology, Canberra Hospital and Health Services, and Clinical Lecturer, Australian National University, ACT.
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