Erbitux™ (cetuximab) blocks EGFR, a receptor on colorectal cancer cells that promotes the growth of the cell. Some patients who are treated with Erbitux™ will respond to the drug, and their tumors will get smaller. For these patients, survival time is increased. Others show no response and have no improved survival.
French scientists explored some of the genes that are associated with the EGFR (epidermal growth factor receptor) pathway for mutations that might affect response to Erbitux™. Looking at 30 patients with metastatic colorectal cancer, they found that 11 (37%) responded to Erbitux treatment.
One mutated gene — KRAS — was significantly associated with lack of drug response. None of patients who responded had mutated KRAS, while nearly 70% of those who had no objective reductions in their tumors did have KRAS mutations.
In addition to Erbitux™ response, KRAS mutations predicted poorer survival. Patients with mutated KRAS in their tumor had a median overall survival time of 6.9 months compared to those without mutations whose median survival was 16.3 months.
Study results were reported in the April 15, 2006 issue of Cancer Research.
The research team, headed by Astrid Lievre, reported:
In conclusion, in this study, KRAS mutations are a predictor of resistance to cetuximab therapy and are associated with a worse prognosis.
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