While the European Medicines Agency, based in London, has approved the use of Erbitux, produced by Merck KGaA, as a first line treatment against colorectal cancer that has spread in the patient’s body, new data has prompted revision of a large study comparing it with Avastin.

New data released Saturday at the annual meeting of the American Society of Clinical Oncology in Chicago shows that even though Erbitux works best with patients that have a Kras non-mutated, or wild-type, tumor, combining it with Avastin shortened the time until disease progression in patients who do have the mutation.

The findings prompted calls for changing the study in such a way that it excludes patients with the mutation. The changes in the landmark study will delay the results but are common sense, the experts said in Chicago. The drug was already approved to treat colon cancer in 2004 as well as head and neck tumors in April 2004.

The German company, which distributes the medicine in Europe and has licensed it from ImClone Systems Inc, has stated that Erbitux works best with patients that have a Kras non-mutated, or wild-type, tumor. The medicine blocks a protein called epidermal growth factor that is supposed to be one of the reasons for which cancer cells multiply. The Kras gene controls the way the epidermal growth factor works. If Kras is non-mutated, then Erbitux can work at its highest potential, if not, the treatment could prove less efficient.

Erbitux faces fierce competition from Genentech Inc and Roche Holding AG’s Avastin, which blocks blood supply to the tumor and is currently the only targeted therapy approved for lung cancer.