Erbitux Works Well for Two-Thirds of Colon Cancer Patients

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Results were even clearer in the current set of findings, culled from tumor samples from 587 patients. Those with normal KRAS genes had a 32 percent reduced risk of developing a recurrence during the study period, compared with a 15 percent reduction for all patients.

"At one year, progression-free survival was 25 percent for those [taking chemotherapy alone] and 43 percent in the combination group," van Cutsem said. "In KRAS-mutant patients, there was no difference."

Also, 59.3 percent of normal gene patients responded to the combination treatment (tumors shrank by more than half), while only 43.2 percent of those on chemo alone responded. There were no differences in response rates among those with the mutation.

The study looked only at first-line treatment in patients with colorectal cancer which had already spread to other parts of their body. Side effects were "manageable," van Cutsem said.

"This is an exciting area of targeted agents," said Dr. Julie Gralow, moderator of the news conference at which the findings were presented and director of breast oncology at the University of Washington and Fred Hutchinson Cancer Center in Seattle. "The question is, how are we going to able to afford these drugs in these patients? It's exciting that KRAS seems to predict who will benefit. The wild-type is two-thirds of patients who will benefit. We don't need to give this drug to the other third now."

More information

The American Cancer Society has more on colon and rectum cancer.