What is Immunotherapy?
Chemotherapy drugs work by attacking all fast-growing cells in the
body. This approach is effective against cancer cells, but unfortunately
it also damages some of the rapidly multiplying normal cells. By contrast,
immunotherapy (also called biological response modifier therapy, or
biotherapy) is a relatively new approach to cancer treatment that
targets cancer cells specifically.
The action of immunotherapy centers around the body's own built-in
defense system—the immune system. This system includes various
white blood cells (B cells, T cells, Natural Killer cells and monocytes),
that circulate through the blood, each with its own specific way of
attacking foreign particles, defective cells, and cancer cells. Think
of the immune system as an army that relies on tanks, planes and foot
soldiers, each group with its own responsibilities.
Immunotherapy works in a variety of ways:
• It can boost the immune system's natural cancer-fighting
• It can coat the surface of cancer cells, cutting off the
oxygen and nutrients they need to grow.
• It can make cancer cells more recognizable, and therefore
more susceptible to destruction.
• It can boost the killing power of your immune system cells,
such as T cells, NK cells, and macrophages.
For a long time, scientists have been looking for new drugs that could
tell the difference between normal and cancerous cells. The search
is beginning to bear results.
The first immunotherapy compound to gain acceptance in breast cancer
treatment is called Herceptin. Herceptin is a monoclonal antibody.
An antibody is a protein naturally produced by the body to fight off
all foreign particles. A monoclonal antibody is a protein bioengineered
in a laboratory and designed to target certain cancer cells.
About 25% to 30% of breast cancer patients have cells that suffer
from an excess of a protein called HER-2/neu. This causes the cells
to grow faster, and make tumors that are more aggressive.
Herceptin finds and attaches itself to the HER-2/neu protein on
the surface of these cells, slowing their growth. There is little
if any effect on normal cells, which do not have an excess of HER-2/neu.
Herceptin also works by attracting the body's own immune cells to
help them find and destroy the cancer cells.
Side Effects of Immunotherapy
Even though immunotherapy is more focused on abnormal cells than either
chemotherapy or hormone therapy, it still causes some unwanted side
effects. One example is flu-like symptoms after the first injections.
In addition, Herceptin may interfere with the effective pumping of
the heart, so the oncologist may order periodic MUGA scans of the
heart to assess its function.
Even so, the side effects of immunotherapy are far less severe than
the ones caused by chemotherapy.
Do You Need
After the biopsy, your tumor will be tested for a variety of items,
including the protein HER-2/neu. The tumor can be tested at a later
date, if the biopsy sample was saved by the hospital. If the cells
show an excess of HER-2/neu, chances are you will benefit from treatment
with Herceptin. A new test, using serum rather than tissue, can monitor
the patient's response to treatment, in real time.
Currently Herceptin is FDA-approved for use in select women whose
advanced breast cancer has spread to other parts of the body, but
scientists are investigating its effectiveness in early breast cancer
Many experts believe that Herceptin represents the future direction
of breast cancer drugs, because it targets a particular protein on
the cancer cell, rather than attacking all cells at random. As research
progresses, scientists hope to make all anti-cancer drugs as specific
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