Colon Cancer Drug Won't Help Those With Certain Gene Mutation

People with changes in K-ras gene won't benefit from cetuximab, study finds

By Serena Gordon
HealthDay Reporter

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WEDNESDAY, Oct. 22 (HealthDay News) -- A new study suggests that people with advanced colon cancer who have a particular gene mutation won't benefit from the medication cetuximab (Erbitux).

While the drug can add months to the lives of people without a mutation in a gene called K-ras, those who have the mutation won't see any benefit from this additional therapy, reports the study, which is published in the Oct. 23 issue of the New England Journal of Medicine.

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"We believe that, in the context of pre-treated advanced bowel cancer, the K-ras mutation status of the cancer should be determined before using cetuximab, and cetuximab should only be given to patients with tumors that do not have the mutation," said study author Dr. Christos S. Karapetis, a senior consultant medical oncologist and director of clinical research in the department of medical oncology at Flinders Medical Centre in Australia.

Karapetis said that about four in 10 people with colon cancer have the K-ras mutation.

Erbitux works by interrupting cell growth and division. It does this by binding to a receptor known as epidermal growth factor receptor (EGFR). A mutation in the K-ras gene is believed to interfere with cetuximab's ability to disrupt EGFR, according to the study.

For the study, 572 people with advanced colorectal cancer were randomly assigned to receive either weekly treatment with cetuximab and supportive care (287 people) or supportive care alone (285 people). All had undergone other treatment options without success.

Almost 400 tumor specimens from the study volunteers were tested for K-ras mutations (198 from the cetuximab group and 196 from the supportive care group). Just over 42 percent of the tumors evaluated were found to have mutations in the K-ras gene.

Even with cetuximab treatment, people with K-ras mutations had no significant changes in overall survival or in progression-free survival. Those without the mutations, on the other hand, appeared to benefit significantly from the therapy.

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