Targeted therapies are drugs or other substances 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 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.
Small molecule therapies are medicines that block processes in the body that make cancer cells grow, survive or spread.
Angiogenesis inhibitors 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
- eye problems
- high blood pressure
- problems with bleeding or blood clotting
- problems with wound healing
- heart damage
- autoimmune reactions.
For targeted therapies using monoclonal antibodies, see side effects of immunotherapy.