Targeted therapies are medicines that block the growth and spread of cancer by interfering with specific molecules. Targeted therapies differ from standard chemotherapy because they are designed to act on specific molecular targets and attack cancer cells without harming healthy cells. This is done by targeting some key differences between cancer cells and other cells. These targets may be genes, so the treatment aims to ‘switch off’ genes that tell cancer cells to grow or to ‘switch on’ genes that tell cancer cells to die. Other targeted therapies deliver substances directly to proteins in the cancer cell to destroy them or prevent growth.
Targeted therapies need to be matched to your genes or particular cancer type. For some types of cancer, most patients have a target for targeted therapy. For some other cancer types, the tumour tissue must be tested to see if an appropriate target is present. Some patients will be offered targeted therapy if some other specific criteria are met, such as not responding to other treatment or if the cancer has spread.
Most targeted treatments are given orally as a pill or capsule, or intravenously (directly into a vein). Oral treatments can usually be taken at home. You will need to go to a clinic or hospital for intravenous (IV) treatment. Like other cancer treatments, targeted therapies may be given in cycles. This is a period of treatment followed by a period of rest.
Types of targeted therapy
The 2 main types of targeted therapy are treatment using monoclonal antibodies (also called immunotherapy) and small molecule therapy.
Monoclonal antibodies deliver molecules to the target on cancer cells to stop the cells from growing and multiplying. Examples include trastuzumab and cetuximab. These treatments have a specific target on the cancer cells. Other monoclonal antibodies act like immunotherapy to allow the immune system to find and attack cancer cells.
Small molecule therapies are medicines that block processes in the body that make cancer cells grow, survive or spread. These therapies are small enough to enter the cells and are used for targets inside the cancer cells. Examples of small molecule therapies include tyrosine kinase inhibitors such as imatinib and Osimertinib.
Angiogenesis inhibitors, such as bevacizumab, can be used as another type of targeted therapy. This treatment targets the tissue around a tumour to limit its blood supply and slow or prevent its growth.
Targeted therapies have several limitations. If you do not have the target gene or protein, the therapy cannot work, but even if you have the target gene or protein, there is no guarantee that the treatment will work. In addition, the cancer may become resistant to the treatment, which means that targeted therapy may work at first but then stop working.
Side effects of targeted therapy
The side effects and how severe they are will depend on the type of targeted treatment you receive. These may include:
- changes to your skin, hair and nails
- damage to organs such as the thyroid gland, liver or kidneys
- mouth sores
- eye problems
- high blood pressure
- problems with bleeding or blood clotting
- problems with wound healing
- heart damage
- autoimmune reactions.
For more information about targeted therapy and its side effects, talk to your doctor or a member of your treating team.