Targeted therapies for cancer are a relatively recent treatment type. The first targeted therapies resulted from experiments in the 1970s and 80s that investigated monoclonal antibodies as a treatment for malignant (i.e. cancerous) tumours in the laboratory. Unlike chemotherapy, which targets all cells in the body that are reproducing rapidly, targeted therapy involves using specific drugs to 'target' particular genes or proteins. As cancer is often caused by changes (mutations) in genes, targeted therapies are able to affect malignant cells with these mutations more than they affect healthy cells.
Targeted therapy drugs can work via a number of methods, including:
- Killing the cancerous cells.
- Stopping cells from living longer than normal.
- Blocking signals that cancerous cells send to other cells to get them to divide.
Forms of targeted therapy
There are two common types of targeted therapy:
These are antibodies that are identical (i.e. 'clones') of a parent cell. They work by either blocking a specific protein on a cancer cell or in tissue around the cancer cells. They also assist other therapies such as chemotherapy and radiotherapy when used in conjunction with these. Drugs whose names end in '-mab' are monoclonal antibodies. Monoclonal antibody treatment is generally via IV (intravenous) infusions.
Small molecule drugs (inhibitors)
Like antibodies, these drugs work by stopping cancerous cells from dividing and spreading. Tumours need to form new blood vessels to grow - the process of forming new blood vessels is called 'angiogenesis' and one type of inhibitor - angiogenesis inhibitors - prevent the formation of new blood vessels around the cancerous cells. Small molecule drugs have names ending in '-ib' for 'inhibitor'. Small molecule treatment is generally taken in the form of oral tablets or capsules.
Before starting any targeted therapy treatment, it is important for the medical team to establish that it will work. A number of factors will determine the likely success of a treatment, and tests normally have to be carried out to determine whether the genes and proteins present would be affected by a particular targeted drug. Examples of targeted therapies currently approved in Australia include BRAF inhibitors for melanoma where there is a BRAF mutations, and PARP inhibitors for ovarian cancer where there is a BRCA mutation.
Although targeted therapies do not target normal cells, there can still be side effects with treatment. Also, targeted therapies are not available for many types of cancer. Many targeted therapies are being assessed in clinical trials, and there may be one or more clinical trials that you could join for your type and stage of cancer. Your oncologist will be able to advise you on the availability of appropriate targeted drugs, or the possibility of suitable clinical trials.