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In 2004, the U.S. Food and Drug Administration
approved two new treatments for advanced colon cancer that has spread outside of
the colon (metastasized). These drugs, Avastin and Erbitux are both part of a
new class of drugs called monoclonal antibodies.
What are monoclonal antibodies?
Antibodies are substances produced by the immune system in response to a
foreign invader such as a bacteria or a virus. Antibodies can stick to the
invader and help destroy it. Monoclonal antibodies are a specific type of
antibody, created in a lab to find and destroy a particular target. Because of
their precision, it is hoped that treatment of a tumor with a monoclonal
antibody will be more specific than chemotherapy drugs and therefore have fewer
side effects.
Avastin
Avastin is a first of its kind monoclonal antibody that shuts down a process
called angiogenesis – the process whereby tumors grow new blood vessels to
help them receive the nutrients needed to survive. The class of drugs is called
angiogenesis inhibitors or anti-angiogenic drugs.
Specifically, Avastin stops the action of a substance released by tumors
called vascular endothelial growth factor or VEGF for short. VEGF binds to
certain cells to stimulate new blood vessel formation. Interfering with
tumor blood vessels might slow their growth.
Avastin was approved in February 2004 to treat advanced colon cancer that has
spread to other organs (metastasis).
What is Avastin used to treat?
Avastin is approved by the U.S. FDA to treat patients with cancer of the colon
or rectum that has spread to other parts of the body. The drug is not a cure,
but studies show that the use of the drug along with chemotherapy increased
survival of patients with metastatic colon cancer by five months.
How is Avastin given?
Avastin is an injection that is given along with the chemotherapy for colon
cancer. The injection is given by vein (intravenously) every 2 weeks.
Studies show that the drug enhances the effects of chemotherapy, but does not
appear to be effective when given alone in patients with colorectal cancer.
Common side effects include:
- Fatigue and weakness
- High blood pressure
- Diarrhea
- Headache
- Loss of appetite
Serious side effects include:
- Holes in the colon requiring surgical repair
- Heart failure
- Kidney damage
- Decreased ability of wounds to heal
Erbitux
Erbitux is another new monoclonal antibody. Erbitux slows cancer growth by
targeting a protein found on the surface of some cells called the epidermal
growth factor receptor (EGFR). EGFR plays a role in regulating cell growth
and is present in around 75 percent of colon cancers.
Erbitux is believed to interfere with the growth of cancer cells by binding
to EGFR so that the normal epidermal growth factors cannot bind and stimulate
the cells to grow.
Erbitux was approved in February 2004 to treat colorectal cancers that have
spread to other parts of the body (metastasized). Erbitux is administered
(intravenously, by vein) along with a cancer chemotherapy drug called irinotecan
(Camptosar) or alone in patients who can’t tolerate irinotecan.
What are the possible side effects of Erbitux?
Side effects include:
- Rash (acne, rash, dry skin)
- Fatigue and weakness
- Fever
- Constipation
- Abdominal pain
- Difficulty breathing
- Low blood pressure
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