For the second time in a year, researchers have found that a drug that has proved useful in treating advanced colon cancer provides no benefit in the early stages of the disease. Last year, researchers found that the widely used cancer drug Avastin does not work well in the early stages of the disease. Sunday, researchers reported at a Chicago meeting of the American Society of Clinical Oncology that the drug Erbitux produced the same results. The findings have left onocologists puzzled and scratching their heads. Cancer drugs are typically tested first in the most advanced cases for ethical reasons, but the assumption has always been that a drug that works for advanced disease should work even better when the tumor is of a smaller, more manageable size. The new findings turn that assumption on its head.
Dr. Steven Alberts of the Mayo Clinic in Rochester, Minn., and his colleagues studied 1,864 patients with an intermediate stage of colon cancer in which the disease had spread to nearby lymph nodes but not throughout the rest of the body. Half received conventional chemotherapy for the disease and half the same chemotherapy plus Erbitux. Three years after the beginning of treatment, 75% of the patients receiving conventional chemotherapy were still alive without a recurrence of the disease, compared with 72% of those also receiving Erbitux.
Doctors already knew that, in advanced colon cancer, Erbitux works in only the roughly 60% of patients who have a healthy copy of a gene called KRAS. In those with a mutated form of the gene, the drug provides no benefit. The Mayo team screened all the patients in the trial to ensure that they had a normal KRAS gene.
The study "says what we learn in metastatic disease does not always apply to the adjuvant setting," Alberts said at a news conference. "It also indicates that disease in early stage may be different than in later stage. Clearly, it is important to understand why the drug didn't work."
-- Thomas H. Maugh II