New Treatments for Colorectal Cancer

Colorectal cancer--cancer of the colon or rectum--is the second leading cause of cancer-related deaths, behind lung cancer, in the United States.

In February 2004, the Food and Drug Administration approved Avastin (bevacizumab) and Erbitux (cetuximab) to treat colorectal cancer that has spread to other parts of the body. Both drugs are genetically engineered versions of antibodies, which are proteins produced by the immune system to fight foreign substances. The antibodies can be produced in a laboratory to target a very specific portion of foreign substances. Because of its precision, treatment with the antibodies can be more effective with fewer side effects.

Avastin is the first FDA-approved treatment for colorectal cancer that is thought to work by preventing the formation of new blood vessels needed by malignant tumors to grow. In a clinical trial of more than 800 people with colorectal cancer, roughly half of them received Avastin intravenously as a combination treatment with the "Salz regimen," also known as IFL, which is a standard chemotherapy for colon cancer. The other half received only IFL. IFL treatment includes irinotecan, 5-fluorouracil (5-FU), and leucovorin.

Overall, those given Avastin in combination with IFL survived about five months longer. Also, the average time before tumors started regrowing or new tumors appeared was four months longer than in those receiving IFL alone.

Serious but uncommon side effects of Avastin include a condition marked by the formation of holes in the colon called gastrointestinal perforation. The condition generally requires surgery and sometimes leads to abdominal infections.

Two distinct patterns of bleeding have been seen in people treated with Avastin. Minor hemorrhages, particularly nose-bleeds, have been commonly seen. More serious bleeding from the lungs has also occurred in people with lung cancer who received the drug. Avastin is not approved as a treatment for lung cancer.

Other severe and life-threatening side effects that occurred in more people receiving Avastin alone, compared with those receiving chemotherapy alone, include abdominal pain, high blood pressure, tiredness, blood clots, fainting, diarrhea, constipation, and a decreased number of white blood cells. Headache, appetite loss, mouth sores, hemorrhoidal bleeding, and shortness of breath also occurred more commonly in people receiving Avastin plus chemotherapy when compared to those receiving chemotherapy alone.

Avastin is manufactured by Genentech Inc. of South San Francisco, Calif.

The FDA approved Erbitux as a combination treatment to be given intravenously with irinotecan, another drug approved to treat colorectal cancer. Erbitux can also be used alone for people who cannot tolerate irinotecan.

Erbitux was approved under the FDA's accelerated approval program, which allows the agency to approve products for cancer and other serious or life-threatening diseases based on early evidence of effectiveness. Though treatment with Erbitux has not been shown to extend people's lives, it was shown to shrink tumors in some people and delay tumor growth, especially when used as a combination treatment.

Erbitux was studied in a controlled trial with 329 people and also in combination with irinotecan in 138 people. It was further evaluated as a single agent in a clinical trial with 57 people, and safety data from an additional 111 patients treated only with Erbitux were also evaluated.

The manufacturer of Erbitux, ImClone Systems Inc. of Branchburg, N.J., submitted its original request for approval in several sections between June and October 2001. The FDA determined at that time that the application could not be reviewed because about half of the patients studied had not failed treatment with irinotecan-a condition of the study. Also, important information about the safety and effectiveness of Erbitux in a portion of the remaining patients was missing.

In a new request for approval in August 2003, ImClone submitted results of a well-run trial that included 329 patients, as well as revisions to the original results from the earlier studies.

Two studies involving about 2,000 people are currently underway to assess the ability of Erbitux to stop the progression of colorectal cancer and to extend the amount of time patients survive with the disease.

Erbitux can cause serious side effects, usually during the administration of the first treatment. Side effects may include difficulty breathing and low blood pressure. Other more common side effects of Erbitux include acne-like rash, dry skin, tiredness or weakness, fever, constipation, and abdominal pain.

Erbitux is distributed and marketed by Bristol-Myers Squibb Co. of Princeton, N.J.

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