In 2004, the FDA 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. A third drug, Vectibix, was approved in 2007.

What Are Monoclonal Antibodies?

Antibodies are substances produced by the immune system in response to foreign invaders such as bacteria or viruses. 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 of 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. 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 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 two 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.

What Are the Possible Side Effects of Avastin?

Common side effects of Avastin include:

Fatigue and weakness
High blood pressure
Diarrhea
Headache
Loss of appetite

Serious Avastin side effects include:

Holes in the colon requiring surgical repair
Heart failure
Kidney damage due to increased protein in the urine
Decreased ability of wounds to heal (so it shouldn't be used right after surgery)
Bleeding or blood clotting problems

Erbitux and Vectibix

Erbitux and Vectibix are other new monoclonal antibodies. These drugs slow 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 about 75% of colon cancers.

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