Testing metastatic colorectal cancer patients for their KRAS status is quickly catching on. The percentage of patients who had their tumors tested jumped from 2.5 percent in 2008 to 42 percent in early 2009, according to a survey of international physicians published at the American Society of Clinical Oncology's annual meeting.The significance of KRAS became clear at ASCO's 2008 meeting, when data showed patients with metastatic colorectal cancer that expressed the normal (wild-type) KRAS gene responded better to the targeted drug Erbitux (cetuximab) than patients with mutated KRAS. (Check out CURE's KRAS coverage from the 2008 meeting.)It's estimated that 30 to 50 percent of tumors have mutated KRAS, and these patients are unlikely to benefit from treatment with Erbitux.The survey released at this year's meeting looked at awareness and use of KRAS testing among 1,254 physicians in Europe, Asia, and Latin America. Of the patients with normal KRAS, 44 percent were prescribed Erbitux.In the U.S., the significance of KRAS status led the Food and Drug Administration to approve a label change last July for Erbitux (and another drug called Vectibix, which is in the same class as Erbitux). The label now states that patients with mutated KRAS shouldn't get the drug. In addition, both ASCO and the National Comprehensive Cancer Network now recommend that patients with metastatic colorectal cancer receive KRAS testing before starting treatment.Read more about KRAS and colorectal cancer in "" target="_blank">Bittersweet Gene" from CURE's Winter 2008 issue.Melissa Weber is the former managing editor of CURE and is covering the annual meeting of the American Society of Clinical Oncology.