April 1 (HealthDay News) -- People with advanced colorectal cancer were modestly helped by the drug Erbitux, as long as they didn't have a particular gene mutation, a new study reports.
The study involved more than 1,100 people who had metastatic colorectal cancer that could not be surgically removed. Half were given a standard chemotherapy regimen -- irinotecan, fluorouracil and leucovorin, known as FOLFIRI. The others were given a combination of cetuximab, which is marketed under the brand name Erbitux, along with the standard regimen.
In those who had what's called a "wild type," or normal, form of the KRAS gene, Erbitux kept colorectal cancers from spreading 15 percent longer than did the FOLFIRI drugs alone, the study found. Results are published in the April 2 issue of the New England Journal of Medicine.
That translated to 1.2 additional months without the cancer progressing, although the overall length of survival in the group taking the Erbitux was not increased.
"The authors are correct in saying if you add Erbitux to the regimen, it delays the progression of disease," said Dr. Len Lichtenfeld, deputy chief medical officer for the American Cancer Society. "But the impact, in my opinion, is not overwhelming."
About 36 percent of the participants in the study had the gene mutation, which renders Erbitux ineffective, while the rest had the normal form of the gene. That's about the same as in the general population, the researchers noted.
Colorectal cancer is the third most common cancer worldwide. In about 25 percent of people with this type of cancer, the disease has spread by the time it's discovered, according to the study.
Lichtenfeld said that though an additional month of having a tumor not progress may not seem dramatic, progress in treating colorectal cancer has been incremental. Before chemotherapy, the expected survival for metastatic colorectal cancer was 6 months. It's now 21 to 24 months.
A drug that can keep a tumor at bay for an additional month is a welcome addition to an oncologists' arsenal, he said.
In the study, it took 9.9 months for the cancer to progress in people with the normal gene who took Erbitux, compared with 8.7 months for those on FOLFIRI alone.
Cetuximab was approved by the U.S. Food and Drug Administration in 2006 for use in squamous cell carcinoma of the head and neck. Since then, it's been increasingly used by doctors to treat colorectal cancer that has spread or recurred after other chemotherapy.
Clinical trials are ongoing to test Erbitux in people whose cancer has not yet metastasized, said Dr. Carmen Allegra, chief of hematology/oncology at the University of Florida Shands Cancer Center in Gainesville.
Erbitux, which is administered through an intravenously, can cause side effects. About 20 percent of those in the study who were given the drug experienced an acne-like rash, nearly 16 percent had diarrhea and 2.5 percent had IV-related allergic reactions.
To avoid toxicity and unnecessary cost, both doctors agreed that people should be tested for the KRAS mutation before undergoing Erbitux treatment.
Previous research, including two studies reported last year, also showed the significance of the KRAS mutation in the effectiveness of Erbitux. Since then, oncologists have been increasingly ordering genetic tests to detect the mutation in tumor cells before beginning Erbitux, and the test is becoming more widely available
"It's pretty clear if you have the mutation you didn't derive benefit," Allegra said. "That is an important piece of information that has changed how we are managing patients with colorectal cancer."
The American Cancer Society has more on colorectal cancer.
SOURCES: Len Lichtenfeld, M.D., deputy chief medical officer, American Cancer Society; Carmen Allegra, M.D., professor and chief, division of hematology/oncology, Department of Medicine, Shands Cancer Center, University of Florida, Gainesville, Fla.; April 4, 2009, New England Journal of Medicine