The study: Researchers analyzed tumors from 587 patients with metastatic colorectal cancer (cancer that has spread) for a mutated (changed) KRAS gene to determine which patients will benefit the most from treatment with a combination of chemotherapy and cetuximab (Erbitux). The KRAS gene is involved in the growth of cancer cells. About 30% to 45% of colorectal cancers have a KRAS mutation, which has been shown in previous studies to predict whether patients will benefit from treatment with drugs that block the epidermal growth factor receptor (EGFR), such as cetuximab.

This study is a continuation of the CRYSTAL trial, which was the first study to compare chemotherapy alone with chemotherapy plus cetuximab as the primary treatment for patients with metastatic colorectal cancer.

The results: KRAS mutations were found in the tumor samples of 36% of patients. Of the patients whose tumors did not have a KRAS mutation, 59% of the patients who received cetuximab and chemotherapy had a reduction in tumor size, compared with 43% of patients who received only chemotherapy. Patients with tumors with a mutated KRAS gene did not receive any benefit when cetuximab was added to chemotherapy.

What this means for patients

“This study helps us to identify which patients are most likely to benefit from adding cetuximab to treatment,” said lead author Eric Van Cutsem, MD, PhD, Professor at the University Hospital Gasthuisberg in Leuven, Belgium. “KRAS testing in all people with colorectal cancer immediately after diagnosis could help doctors find the best treatment strategies for the individual patient.”

What to ask your doctor

• Would you explain my pathology report (laboratory tests results) to me?
• What are my treatment options?

For more information

Cancer.Net Guide to Colorectal Cancer

Cancer Advances: News from the 2008 Gastrointestinal Cancers Symposium