Immunotherapy
- uses the body’s immune system, either directly or indirectly, to fight cancer or to
lessen side effects that may be caused by some cancer treatments.
- treatment of allergy to substances such as pollens, house dust mites, fungi, and
stinging insect venom by giving gradually increasing doses of the substance, or allergen,
to which the person is allergic.
- treatment that uses the body’s natural defenses to fight disease.
Sometimes immunotherapy drugs are called
'Biological Response Modifiers' (BRM's) because they stimulate the body to respond
biologically (or naturally) to cancer.
Immunotherapy can be
- Local or systemic (treating the whole body)
- Non-specific or targeted
Local immunotherapy
Local means treating only one part of the body. The best used example of local
immunotherapy is in the treatment of bladder cancer. The vaccine BCG, used to prevent
tuberculosis, causes inflammation in the bladder that fights cancer cells. When body
tissues become inflamed, the cells of the body's immune system are stimulated to fight any
invading bacteria, viruses or 'foreign' cells. The cancer cells are seen as foreign by the
cells of the immune system. So the inflammation caused by the BCG vaccine fights the
cancer cells.
This treatment is often given after superficial bladder tumours have been removed during
an operation. A catheter (tube) is put into the bladder and the BCG vaccine put in. This
treatment is given weekly for several weeks and has been shown to reduce the chance of the
bladder cancer coming back. There will be more about this treatment in the section of
CancerHelp UK on Bladder Cancer.
Systemic immunotherapy
This means immunotherapy that is given to treat the whole body. It is much more common
than local immunotherapy and can be used to treat a cancer that may have spread. Treatment
with interferon or with Interleukin 2 (IL2) are examples of systemic
immunotherapy. This type of treatment is most often used for melanoma and for kidney
cancer.
Non-specific immunotherapy
All the examples given above are of non-specific immunotherapy. This means that the
treatment is given to boost the immune system generally so that it may become more
effective in fighting cancer cells. These treatments have not generally been found to be
as effective as researchers first hoped. But they are continuing their research to improve
this type of treatment and are now looking at how the treatments work in combination with
each other and with other types of cancer treatment.
Targeted immunotherapy
This means immunotherapy that can be aimed at cancer cells and, if possible, leave
normal cells untouched. You may have read about
- Monoclonal antibody treatment, or 'magic bullets'
- Cancer vaccines
What are monoclonal antibodies?
This is a way of making large amounts of a single antibody in the laboratory. The antibody is
then given to patients to kill cancer cells. There is more about how monoclonal antibodies
work in the section of About Cancer on the Immune System.
Researchers try to find an antibody that targets the cells of a particular type of cancer.
They hope that either
- The antibody can be used to mark the cancer cells so they are killed by the body's
immune system
- They can attach an anti-cancer drug or radioactive substance to the antibody to kill the
cancer cells
Research has been going on into these treatments since the 1970's. But it is difficult
to do because
- Mouse cells are used to make the antibodies in the laboratory and these are removed by
the immune system because it knows they are foreign
- Antibodies may react with antigens found on normal cells as well as cancer cells, so the
treatment may have side effects
The scientists are now changing the 'mouse' antibodies to make them unrecognisable to
the human immune system. This is called 'humanization'. They are also working to
find treatments that do not have damaging side effects. |