Understanding Targeted Therapy
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Understanding Targeted Therapy
Types of targeted therapy
There are many different types of targeted therapy drugs. They are put into groups based on how they work. The two main groups of targeted therapy drugs are monoclonal antibodies and small molecule inhibitors. New drugs become available every year, so talk to your cancer specialist for the latest information.
Monoclonal antibodies
The body’s immune system makes proteins called antibodies to help fight infections. Monoclonal antibodies are manufactured (synthetic) versions of these natural antibodies. They lock onto a protein on the surface of cells or surrounding tissues to affect how cancer cells grow and survive. Monoclonal antibodies can be classified as targeted therapy or immunotherapy, depending on the type of monoclonal antibody. Types of targeted therapy monoclonal antibodies include:
| angiogenesis inhibitors | These drugs reduce the blood supply to a tumour to slow or stop it growing. They target various proteins linked with the growth of new blood vessels and stop them from working. An example is bevacizumab. |
|---|---|
| HER2-targeted agents | High levels of the protein HER2 cause cancer cells to grow uncontrollably. Some targeted therapy drugs destroy the HER2 positive cancer cells, or reduce their ability to divide and grow. Examples include trastuzumab and pertuzumab. |
| anti-CD20 monoclonal antibodies | These drugs target a protein called CD20 found on some B-cell leukaemias and non-Hodgkin lymphomas. Examples include rituximab and obinutuzumab. |
Small molecule inhibitors
These drugs can get inside cancer cells and block certain proteins that tell cancer cells to grow. Types of small molecule inhibitors include:
| TKIs | Tyrosine kinase inhibitors (TKIs) block proteins called tyrosine kinases from sending signals that tell cancer cells to grow, multiply and spread. Without this signal, the cancer cells may die. Examples include erlotinib, sunitinib, imatinib and dasatinib. |
|---|---|
| mTOR inhibitors | These drugs block mammalian target of rapamycin (mTOR), a protein that tells cancer cells to grow and spread. An example is everolimus. |
| PARP inhibitors | These drugs block poly (ADP-ribose) polymerase (PARP), a protein that repairs damaged DNA in cancer cells. An example is olaparib. |
| CDK inhibitors | These drugs block cyclin-dependent kinase (CDK) from sending signals that tell cancer cells to grow, multiply and spread. Without this signal, the cancer cells may die. Examples include palbociclib, ribociclib and abemaciclib. |
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.
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.
Family 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.
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 Cancer Council 13 11 20.
Some acquired gene changes are linked to the cancers below.
| ALK mutations | lung, neuroblastoma |
|---|---|
| BRAF mutations | melanoma, bowel, lung, thyroid |
| BRCA1 or BRCA2 mutations (acquired) | ovarian |
| EGFR mutations | lung |
| 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 |
| ROS1 mutations | lung |
Some inherited gene changes are linked to the cancers below.
| 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 |
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This information is reviewed by
This information was last reviewed June 2021 by the following expert content reviewers: 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.