Targeted therapy is a drug treatment that targets specific features of cancer cells to stop the cancer growing and spreading. The drugs circulate through the body, but work in a more focused way than chemotherapy and often have fewer side effects. Targeted therapy does not work for everyone affected by cancer, even if they have the same cancer type.
How it works
The body constantly makes new cells to help us grow, replace worn-out tissue and heal injuries. Healthy cells multiply and die in an orderly way. Cancer cells are different – they multiply faster and keep growing when they aren’t supposed to, due to changes in the genes of the cells.
These gene changes help the cancer cells grow and survive, but they also create features within or on the surface of the cancer cells that can be targeted. Each targeted therapy drug acts on a particular feature, which is known as the molecular target. The drug will only be given if the cancer cells have the target.
Targeted therapy may kill the cancer cells or slow their growth, causing the signs and symptoms of cancer to reduce or disappear. The drugs often have to be taken long term, but many people continue their usual activities and enjoy a good quality of life.
Gene changes and cancer cells
Genes are made up of DNA (deoxyribonucleic acid). Each human cell has about 20,000 genes, and most 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, which 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). 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.
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. Medicare rebates are available for some genetic tests.
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. Visit the Health Centre for Genetics Education for more information and to find a public family cancer clinic.
How targeted therapy differs from chemotherapy
Chemotherapy drugs affect all cells that multiply quickly. This means the drugs can kill cancer cells and also damage other cells that multiply quickly, such as healthy cells in the mouth, stomach, bone marrow or hair. This is why chemotherapy side effects often include mouth ulcers, nausea, low numbers of blood cells (leading to infections or anaemia) and hair loss.
Targeted therapy drugs work in a different way. They focus on the cancer cells, while limiting damage to healthy cells. Many people experience fewer side effects with targeted therapy, but it can still cause various side effects that can be serious.
When it is given
Targeted therapy may be used:
- before surgery to reduce the size of a cancer (neoadjuvant therapy)
- after surgery to destroy any remaining cancer cells (adjuvant therapy)
- to treat cancer if it has come back or hasn’t responded to other treatments (second-line therapy or palliative treatment)
- as long-term treatment to try to prevent the cancer coming back or control its growth (maintenance treatment).
Using targeted therapy has improved survival rates for several types of cancer, and many people respond well. However, targeted therapy is not an option for everyone with cancer. Different people with the same cancer type may receive different treatments based on their test results.
Will it work?
The cancer must contain the particular target or the drug won’t work. The response to targeted therapy varies widely. In some cancers, four out of five people assessed as suitable for a particular targeted therapy drug will respond, while for other cancers, the rate of success is much lower. This is due to a range of factors, including how many of the cancer cells carry the target.
Cancer cells can eventually stop responding to a targeted therapy drug even if it works at first. If this happens, another targeted therapy drug or treatment may be offered. Less commonly, a targeted therapy drug may cause serious side effects and the treatment plan will need to be adjusted.
In Australia, targeted therapy drugs are now available for a range of cancers, however for most, it is available only when the cancer is advanced. For some types, it is also available for early-stage cancer.
Targeted therapy drugs can interact with many common medicines and cause harmful side effects. It is also a good idea to talk with your cancer specialist before having any vaccinations. Many targeted therapy drugs are not safe to use during pregnancy or while breastfeeding. Ask your doctor for advice about contraception.
Knowing if it is working
You will have regular check-ups with your doctor, blood tests and scans to see whether the cancer has responded to treatment. A good response from targeted therapy will make a cancer that can be seen on a scan shrink or even disappear completely. In some cases, the cancer remains stable, which means it doesn’t grow in size on scans, but also does not shrink or disappear. People with stable disease can live for many years and have a good quality of life.
Access and cost
Ask your cancer specialist if there is a suitable targeted therapy for you. This will depend on the type and stage of the cancer. Your specialist will also need to test the cancer to see if one of the currently available drugs is an option. Many more targeted therapy drugs are being studied in clinical trials.
The Pharmaceutical Benefits Scheme (PBS) covers most of the cost of many prescription medicines, including some targeted therapy drugs. Medicines not on the PBS are usually expensive, but you may be able to have them as part of a clinical trial or at a reduced cost through a compassionate access program.
It is important to ask your specialist questions, especially if you feel confused or uncertain about your treatment. You may want to include some of the questions below in your list.
- Is targeted therapy available as part of my treatment plan? If not, why not?
- Which targeted therapy drug are you recommending as part of my treatment plan? Does this drug have different names?
- How often have you prescribed this targeted therapy? Has it worked well for your other patients?
- What do you expect the targeted therapy drug to do to the cancer?
- Will it be my only treatment or will I also have other treatments?
- How much will targeted therapy cost? Is there any way to reduce the cost if I can’t afford it?
- Are there any clinical trials that would give me access to new types of targeted therapy?
- How often will I have targeted therapy?
- How long will I receive targeted therapy?
- Where will I have targeted therapy? Will I need to come to the hospital or treatment centre for an IV infusion or injection, or will I just need to take tablets or capsules at home?
- If I am taking the treatment at home, can I get the script filled at any pharmacy?
- What side effects should I watch out for or report?
- Will the drugs affect my immune system?
- Should I still have vaccinations?
- Who do I contact if I get side effects?
- How can side effects be managed?
- How will I know if the treatment is working?
How it is given
Targeted therapy is usually prescribed by a medical oncologist or haematologist. It may be given on its own or combined with chemotherapy. Some targeted therapy drugs are given in repeating cycles, with rest periods. Others are taken every day without any breaks.
Most cancers have treatment protocols that set out which drugs to have, how much and how often. Your specialist may need to adjust the protocols to your individual situation. Targeted therapy may be given in different ways:
- as tablets or capsules that you can swallow
- as an intravenous (IV) infusion into a vein, either through a drip in your arm or into a port (a small device inserted under the skin of the chest or arm)
- as an injection under the skin.
When targeted therapy is given as an infusion, some people react to the process during or several hours afterwards. You will be monitored and may be given medicine to help prevent this. Reactions are more common with the first infusion, so it may be given more slowly than later treatments.
How long you have targeted therapy depends on the aim of the treatment, how the cancer responds and any side effects you have. In many cases, targeted therapy tablets or capsules need to be taken daily for many months or even years.
Possible side effects
Although targeted therapy limits damage to healthy cells, it can still have side effects. Some people don’t have any side effects, while others have several.
Skin problems are a common side effect of targeted therapy. Different drugs may cause:
- sensitivity to sunlight, skin redness, swelling and dry, flaky skin
- a rash that looks like acne or pimples on the face, scalp or upper body (acneiform rash)
- a skin reaction on the palms and soles causing tenderness and blisters (hand–foot syndrome).
Other side effects may include fever, tiredness, joint aches, nausea, headaches, itchy eyes with or without blurred vision, diarrhoea, bleeding and bruising, and high blood pressure.
Less commonly, some targeted therapy drugs can affect the way the heart, thyroid, liver or lungs work, or increase the risk of getting an infection. If left untreated, some side effects can become serious.
Managing side effects
Targeted therapy side effects can sometimes begin within days of starting treatment, but more often they occur weeks or even months later. Most are temporary, lasting from a few weeks to a few months, and will gradually improve over time or once you stop taking the drug. However, some side effects may be permanent.
Your treatment team can help you manage any side effects of targeted therapy, which often need a different approach to side effects from other cancer treatments. In some cases, your treatment team will reduce the dose of the targeted therapy drug to see if that helps ease the side effects.
Reporting side effects
While you are having targeted therapy, you will be carefully monitored with regular check-ups and blood tests. This is because some rare side effects, such as heart and lung problems, can become serious and even life-threatening if not treated.
It is important to tell your treatment team about any new or worsening side effects. Ask the doctor or nurse which side effects to watch out for or report, and who to contact after hours. Some people worry about telling their doctor about side effects because they don’t want to stop the treatment, but side effects can be better managed when they are reported early. Your doctor may be able to prescribe medicine to prevent or reduce side effects.
In some cases, you may need to take a break from treatment to prevent side effects becoming serious and causing long-term damage. Once the side effects have gone away, you may be able to restart the targeted therapy on an adjusted dose, or try a different drug.
Types of targeted therapy drugs
There are many different types of targeted therapy drugs. They are put into groups based on how they work. The two main groups are:
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. Types include:
- angiogenesis inhibitors – reduce the blood supply to a tumour to slow or stop it growing.
- HER2-targeted agents – target the protein HER2, which cause cancer cells to grow uncontrollably.
- anti-CD20 monoclonal antibodies – target the protein CD20 found on some B-cell leukaemias and non-Hodgkin lymphomas.
Small molecule inhibitors
These drugs are small enough to get inside cancer cells and block certain proteins that tell cancer cells to grow. Types include:
- TKIs – block proteins called tyrosine kinases from sending signals that tell cancer cells to grow, multiply and spread.
- mTOR inhibitors – block mammalian target of rapamycin (mTOR), a protein that tells cancer cells to grow and spread.
- PARP inhibitors – block poly (ADP-ribose) polymerase (PARP), a protein that repairs damaged DNA in cancer cells.
- CDK inhibitors – block cyclin-dependent kinase (CDK) from sending signals that tell cancer cells to grow, multiply and spread.
Understanding Targeted Therapy
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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.
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The information on this webpage was adapted from Understanding Targeted Therapy - A guide for people affected by cancer (2021 edition). This webpage was last updated in September 2021.