Gene changes and cancer cells
Genes are made up of DNA (deoxyribonucleic acid). Each human cell has about 20,000 genes, and most genes come in pairs, with one copy inherited from each parent. As well as telling the cell what to do and when to grow and divide, genes provide the recipe for cells to make proteins. These proteins carry out specific functions in the body.
When a cell divides, it has to make a copy of itself, including all the genes it contains. Some copying mistakes slip through, causing changes (mutations) in the genes. If these mistakes affect the genes that tell the cell what to do, a cancer can occur.
Most gene changes that cause cancer build up during a person’s lifetime (acquired gene changes). Some people are born with a gene change that increases their risk of cancer (an inherited faulty gene, also known as a hereditary cancer syndrome). Only about 5% of cancers are caused by an inherited faulty gene.
Targeted therapy drugs may act on targets from either acquired or inherited gene changes. See below for examples of both types of gene changes.
Testing for targeted therapy
To find out if the cancer contains a gene change that may respond to a particular targeted therapy drug, your doctor will take a sample from the cancer and send it to a laboratory for testing. It may take from a few days to a few weeks before you receive the results.
The testing will find specific mistakes in that cancer, whether they are acquired gene changes found only in the cancer cells, or inherited changes that are also present in normal cells. The testing may involve a simple test known as staining, or more complex tests known as molecular or genomic testing.
If the cancer contains a faulty gene that may be linked to a hereditary cancer syndrome, or if your personal or family history suggests a hereditary cancer syndrome, your doctor will refer you to a family cancer service or genetic counsellor.
Knowing that you have inherited a faulty gene may help your doctor work out what treatment to recommend. It could also allow you to consider ways to reduce the risk of developing other cancers, and it is important information for your blood relatives.
If you are concerned about your family risk factors, talk to your doctor or ask for a referral to a family cancer clinic. To find out more, call Cancer Council 13 11 20 or visit www.genetics.edu.au to find a public family cancer clinic.
Will I have to pay for these tests?
Medicare rebates are available for some genetic tests. You may need to meet certain eligibility requirements and usually the tests must be ordered by a specialist. For more information about genetic testing, talk to your specialist or family cancer clinic, or call 13 11 20.
Some gene changes linked to cancer
Acquired gene change
Linked to these cancers
|ALK mutations||lung, neuroblastoma|
|BRAF mutations||melanoma, bowel, lung, thyroid|
|BRCA1 or BRCA2 mutations (acquired)||ovarian|
|IDH mutations||brain, bile duct|
|KRAS mutations||bowel, lung, pancreatic|
|NRAS mutations||bowel, lung, pancreatic|
|HER2 mutations||breast, stomach|
|KIT mutations||gastrointestinal stromal tumours, melanoma|
Inherited gene change
Increases the risk of these cancers
|BRCA1 or BRCA2 mutations (inherited)||breast, ovarian, pancreatic, prostate|
|Cowden syndrome||breast, thyroid, uterine|
|familial adenomatous polyposis (FAP)||bowel, stomach, thyroid|
|Li-Fraumeni syndrome||breast, primary bone, adrenal|
|Lynch syndrome||bowel, uterine, ovarian, stomach|
Podcast: Immunotherapy and Targeted Therapy
This information was reviewed by: A/Prof Brett Hughes, Senior Staff Specialist, Medical Oncology, Royal Brisbane and Women’s Hospital and The Prince Charles Hospital, and The University of Queensland, QLD; Natalie Dubs, Consumer; Hazel Everett, Clinical Nurse Consultant, Cancer Services, St John of God Subiaco Hospital, WA; Karen Hall, 13 11 20 Consultant, Cancer Council SA; Dr Hilda High, Genetic Oncologist, Sydney Cancer Genetics, NSW; Ingrid Kivikoski, Consumer; Anne McGregor, Consumer; Donna Milne, Nurse Consultant, Melanoma and Skin Service, Peter MacCallum Cancer Centre, VIC; Prof Nick Pavlakis, Board Chair, Thoracic Oncology Group of Australasia (TOGA), and Senior Staff Specialist, Department of Medical Oncology, Royal North Shore Hospital, NSW; Gay Refeld, Clinical Nurse Consultant, Breast Care, St John of God Subiaco Hospital, WA.
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