In a report published in the July 2010 issue of the American Society for Clinical Oncology（肿瘤学） Post, new recommendations on the use of the drug cetuximab（西妥昔单抗） have been issued after officials halted enrollment¹ in a phase III clinical trial in patients with spread of colon² cancer into regional lymph nodes（淋巴结） whose tumors had been surgically⁴ removed. Based on earlier studies, cetuximab is now indicated for treatment of patients with advanced colorectal cancer（结肠直肠癌） whose tumors do not have a mutation⁵ in the KRAS gene⁶. KRAS is one of a series of genes⁷ along a pathway that can lead tumors cells to grow, divide and evade⁸ signals that shut the cells down causing their death. Based on the results in advanced disease, researchers had hoped to see similar benefits when cetuximab was added to a standard chemotherapy regimen（养生法，政体） in earlier stages of colon cancer. However, ongoing⁹ analysis during the clinical trial found that patients receiving the combination therapy had no significant improvement in survival compared to standard therapy.

Cetuximab is a monoclonal antibody（单克隆抗体） that inhibits¹⁰ epidermal¹¹（表皮的，外皮的） growth factor receptor (EGFR表皮生长因子受体) – a cell signaling pathway that contributes to tumor³ growth. The drug is given by intravenous（静脉内的） infusion¹² for treatment of metastatic colorectal cancer and head and neck cancer. Previously¹³, researchers found that patients with a mutated KRAS gene – about 40 percent of those with metastatic colon cancer – do not respond to the EGFR inhibitors currently in use.

However, the genetic¹⁴ test for KRAS mutation was not standard until this trial was well underway. Patients enrolled¹⁵ before KRAS testing were segmented from those in the rest of the study and analyzed¹⁶ separately, said Richard Goldberg, MD, chief of the division of hematology/oncology at the UNC-Chapel Hill School of Medicine, who presented the results for this group of patients.

"We expected that patients with the genetic mutation would not respond to cetuximab, and that is what we found," said Goldberg, who is also physician-in-chief of the N.C. Cancer Hospital.

"However, even the patients in the study whose tumors did not harbor the KRAS mutation did not benefit significantly from the combination therapy and the standard treatment proved to have the best results. We also found that the combination therapy was more toxic¹⁷（有毒的） and the side effects of treatment – especially in older patients – negatively impacted their ability to complete the standard treatment," he added.

The researchers issued a recommendation that cetuximab should not be used in patients with stage III colon cancer. It remains¹⁸ a valuable tool in treating patients with advanced colorectal cancers whose tumors do not harbor a KRAS mutation and can either be administered as a single agent or with chemotherapy（化学疗法） .