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Monoclonal Antibodies for Treating Colorectal Cancer

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 -- in this case, cancer. 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. The injection is given in vein (intravenously or IV) 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 side effects of Avastin  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 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.

Erbitux and Vectibix are 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 and Vectibix are FDA-approved to treat colorectal cancers that have spread to other parts of the body (metastasized). Erbitux is administered intravenously weekly either alone or with a cancer chemotherapy drug called Camptosar.

Vectibix is also given intravenously but every other week and usually with certain combinations of chemotherapy. Before using these drugs a special genetic mutation test needs to be done on the cancer to see if they will be effective. 

 

What Are the Possible Side Effects of Erbitux and Vectibix?

Side effects Erbitux and Vectibix could include:

  • Skin problems, like acne, rash, and dry skin. Skin reactions may actually mean the drug is working against the cancer
  • Fatigue and weakness
  • Fever
  • Constipation
  • Abdominal pain
  • Difficulty breathing
  • Low blood pressure
  • Reactions while the drug is being given

 

WebMD Medical Reference

Reviewed by Andrew Seibert, MD on February 27, 2012
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