Understanding Targeted Therapy
Common questions about targeted therapy
What is targeted therapy? Targeted therapy is a type of drug treatment that attacks specific features of cancer cells, known as molecular targets, to stop the cancer growing and spreading. Other names for targeted therapy include biological therapies and molecular targeted therapy.
Answers to some common questions about targeted therapy are below.
Targeted therapy drugs circulate throughout the body. Each drug acts on a specific molecular target within or on the surface of cancer cells (for example, a gene or protein). These molecular targets are involved in the growth and survival of cancer cells. Blocking them can kill cancer cells or slow their growth, while minimising damage to healthy cells.
Targeted therapy drugs work in a different way to chemotherapy drugs. Chemotherapy drugs also circulate throughout the body, but they particularly affect cells that divide rapidly. They kill cancer cells, but can also damage other rapidly dividing cells, such as the healthy cells in a person’s mouth, stomach, skin or hair.
Targeted therapy drugs are used to control cancer growth. They often cause the signs and symptoms of cancer to reduce or disappear. This means many people can return to their usual activities. The drugs may need to be taken long-term, and you will need to have regular tests to monitor the cancer.
Your doctors will test the cancer to see if the cells contain a particular molecular target that is helping the cancer grow. Different people with the same cancer type may receive different treatments based on their test results.
Cancer is caused by abnormal changes in a person’s genes that can cause cancer cells to multiply and grow. These gene abnormalities are known as molecular targets. They may be acquired or inherited.
What are genes?
Genes are made up of DNA (deoxyribonucleic acid). They are found in every cell of the body and are inherited from both parents. Each human cell has about 20,000 genes. Genes tell the cell what to do, and when to grow and divide. Cells use this information to make proteins that carry out specific functions in the body.
Acquired gene changes
Most cancers are not caused by inherited genetic changes but by mistakes that build up over time in the body’s cells (known as acquired changes). These gene faults are in the structure of the cancerous cell, not in normal cells. Researchers have found several gene abnormalities that play a key role in a number of cancers. For example:
- epidermal growth factor receptor (EGFR) mutations in lung cancer
- BRAF mutations in melanoma, bowel and thyroid cancers
- anaplastic lymphoma kinase (ALK) mutations in lung cancer and neuroblastoma
- KRAS mutations in bowel cancer
- NRAS mutations in melanoma, leukaemia and bowel cancer
- high levels of human epidermal growth factor receptor 2 (HER2) in breast and stomach cancers
- KIT mutations in gastrointestinal stromal tumours and melanoma.
To find out if the cancer contains a change in a gene or related protein that may respond to a particular targeted therapy drug, your doctor will take a tissue sample from the cancer and send it to a laboratory for molecular testing. It may take from a few days to a few weeks before you receive the results.
Inherited faulty genes
Some genetic abnormalities are linked to a faulty gene (mutation) we inherit from our parents. Inherited faulty genes may increase a person’s risk of developing cancer. However, not all people who inherit a faulty gene develop cancer.
About 5% of cancers are caused by an inherited faulty gene. Inherited genetic conditions associated with cancer continue to be discovered, for example:
- an inherited mutation in one of the BRCA genes is linked to breast, ovarian and prostate cancers
- Lynch syndrome increases the risk of developing bowel, uterine, ovarian and stomach cancers
- Li-Fraumeni syndrome increases the risk of developing breast, primary bone and adrenal cancers
- Cowden syndrome increases the risk of developing breast, thyroid and uterine cancers
- familial adenomatous polyposis (FAP) is a risk factor for bowel, stomach and thyroid cancers.
If your doctor suspects that the cancer is linked to an inherited gene fault, they will refer you to a family cancer service or genetic counsellor. A pathologist can run special tests on a blood or tissue sample to look for possible inherited gene changes. This is known as a genetic test.
Knowing whether you have a particular faulty gene may help determine suitable treatment options. Doctors may be able to recommend a targeted therapy drug that has been shown to work on cancers caused by that faulty gene.
If you are concerned about your family risk factors, talk to your doctor about having regular check-ups or ask for a referral to a family cancer clinic. To find out more, call Cancer Council 13 11 20.
Medicare rebates are available for genetic tests for some people with specific cancers. You may need to meet certain eligibility requirements to have a Medicare-funded test. For more information about genetic testing, talk to your specialist or family cancer clinic, or call 13 11 20. Visit genetics.edu.au to find a family cancer clinic near you.
Targeted therapy drugs have been approved for use in Australia for bowel, breast, cervical, kidney, lung, ovarian, stomach and thyroid cancers, as well as melanoma and some forms of leukaemia, lymphoma and myeloma.
The development of targeted therapy drugs has led to improved survival rates for several types of cancer and some people have had very encouraging outcomes. These drugs are becoming an increasingly important part of cancer treatment.
Targeted therapy drugs may be used:
- after surgery to destroy any remaining cancer cells
- to treat advanced cancer that hasn’t responded to other treatment, or cancer that has come back
- as maintenance treatment for advanced cancer to try to prevent the cancer coming back.
Less commonly, targeted therapy drugs are used as the first treatment for primary cancer or in combination with radiation therapy.
Many targeted therapy drugs are not safe to use during pregnancy or while breastfeeding. Ask your doctor for advice about contraception. If you become pregnant, let your medical team know immediately.
While many people respond well, targeted therapy is suitable for only a small number of cancers.
Will it work? – The cancer must contain the particular molecular target or the drug won’t work. However, even if the cancer is shown to contain the target, there is no guarantee the drug will kill the cancer cells. The response to targeted therapy varies widely depending on the cancer type and molecular target. In some cancers, four out of five people assessed as suitable for a particular targeted therapy drug will respond.
Some cancer cells can become resistant to the targeted therapy even if it works at first. If this happens, another type of targeted therapy or another treatment may be offered.
How much will it cost? – The Pharmaceutical Benefits Scheme (PBS) subsidises the cost of many prescription medicines, including some targeted therapy drugs. The PBS has approved a number of targeted therapy drugs for use in Australia, under specific circumstances and for certain cancers. Medicines or treatments that are not on the PBS are usually very expensive, however, you may be able to access them as part of a clinical trial.
Ask your oncologist or haematologist if there is a suitable targeted therapy drug for you. Targeted therapy drugs are becoming more available on the Pharmaceutical Benefits Scheme (PBS) for specific cancers including melanoma, bowel cancer, stomach cancer, ovarian cancer, non-Hodgkin lymphoma, thyroid cancer, breast cancer and lung cancer. You will need a test to see if you are suitable for one of these drugs.
Many more targeted therapy drugs are being studied in clinical trials. Talk with your doctor about the latest developments and whether you are a suitable candidate.
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This information is reviewed by
This information was last reviewed June 2018 by the following expert content reviewers: Dr Fiona Day, Medical Oncologist, Calvary Mater Newcastle, and Conjoint Senior Lecturer, University of Newcastle, NSW; Dawn Bedwell, 13 11 20 Consultant, Cancer Council Queensland; Jennifer Cardwell, Consumer; Christine Henneker, Nurse Practitioner Cancer Services, WA Country Health Service, WA; Dr Rohit Joshi, Medical Oncology Consultant, Calvary Central Districts Hospital, and Clinical Lecturer, University of Adelaide, SA; Prof Ross McKinnon, Director, Flinders Centre for Innovation in Cancer, SA; Prof Miles Prince, Haematologist, Director of Molecular Oncology and Cancer Immunology, Epworth HealthCare, VIC; Prof Ben Solomon, Medical Oncologist, and Group Leader, Molecular Therapeutics and Biomarkers Laboratory, Peter MacCallum Cancer Centre, VIC; Dr Subotheni Thavaneswaran, Medical Oncologist, The Kinghorn Cancer Centre and St Vincent’s Hospital, and Translational Research Fellow, Garvan Institute of Medical Research, NSW; A/Prof Kathy Tucker, Clinical Cancer Geneticist, Nelune Comprehensive Cancer Centre, NSW.