A genetic test will enable researchers to predict which colon cancer patients may benefit from treatment with Erbitux.
The data also reveal that Erbitux is ineffective in the 40% of colon cancer patients whose tumors have kras gene mutations, which are also found in as many as 90% of patients with pancreatic cancer, which previous studies have shown don't respond to Erbitux, and about 20% of lung cancer patients. The fact that a genetic test will enable researchers to predict which colon cancer patients may benefit from treatment with Erbitux could lead the Food and Drug Administration (FDA) to restrict usage to the 60% of patients without the mutation.
This could meant that up to 40% of patients who previously might have taken Erbitux will not receive it. As a result, many hospitals, such as Memorial Sloan-Kettering are preparing to do KRAS testing on all their colon cancer patients.
Imclone plans to make up for lost revenue by convincing doctors to use Erbitux sooner in patients most likely to benefit. Currently, the drug is almost exclusively used in patients who have failed other treatments. Imclone Chief Executive John H. Johnson stated that 4% of advanced colon cancer patients now get the drug for initial treatment, and only 14% get the drug as their second treatment.
At the 2008 44th Annual Meeting of the American Society of Clinical Oncology (ASCO) on Sunday, European researchers released new data from an old 1,200-patient study testing Erbitux as initial treatment in combination with chemotherapy. In the original study, Erbitux only delayed the progression of colon cancer by about 15%. When researchers reanalyzed the study looking just at those patients with normal kras, they found that Erbitux delayed the disease progression by 32%; it also increased the percentage of patients whose tumors shrunk to 59% from 43%.
Some observers think that the new data are probably not enough to convince oncologists to start using Erbitux up front in patients with colon cancer because there is no proof that switching the order of drugs will make patients live longer, and Erbitux is associated with several side effects, including severe facial rash.