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Press Release
Large VA Study Finds Colonoscopy May Be Best Way to Screen for Colon Cancer
For immediate release July 19, 2000
In the July 20 issue of the New England Journal of Medicine, researchers from the U.S. Department of Veterans Affairs report on the largest study ever done on screening the entire colon for cancer in people without symptoms.
Using colonoscopy to examine the entire colon’s lining in 3,121 apparently healthy people aged 50-75, the researchers found that about 10 percent had colon cancer or serious precancerous growths. Further, they found that at least a third of these lesions would have been missed by sigmoidoscopy--a commonly used screening technique that reveals only the lower part of the colon’s lining.
“I think we certainly demonstrated that you can make a case for colonoscopy as a primary screening test in men,” said first author David Lieberman, M.D., Chief of Gastroenterology at the Portland VA Medical Center and Professor of Medicine at Oregon Health Sciences University. Supported by the VA Office of Research and Development’s Cooperative Studies Program, Dr. Lieberman and his colleagues conducted the study at 13 VA medical centers around the country.
Colorectal cancer is the second leading cause of cancer deaths in North America. This particular kind of cancer is marked by a premalignant phase, growths called polyps in the colon lining. Not all polyps are destined to become cancerous, Dr. Lieberman noted, but those that progress to cancer typically develop abnormalities along the way that flag them as dangerous.
“Virtually all patients who develop colon cancer go through that premalignant stage,” Dr. Lieberman emphasized. “This gives us a unique opportunity. If we can find the serious polyps and remove them, we can prevent colon cancer.”
Colonoscopy is the only screening technique that allows physicians to search the entire colon’s lining for polyps, Dr. Lieberman noted. During the procedure, a flexible lighted hollow tube about the width of a finger is inserted through the rectum into the colon. The colonoscope is connected to a video camera that reveals the colon’s lining. Sigmoidoscopy is similar, but uses a much shorter tube that only reaches the lower or “distal” part of the colon.
For people 50 and over, the United States Preventive Services Task Force currently endorses colon cancer screening with a yearly fecal occult blood test, a technique designed to detect small amounts of blood leaking from tumor blood vessels, or sigmoidoscopy. Colonoscopy generally is reserved for patients with positive screening tests or those whose family history or other factors put them at higher than average risk.
The VA study is the first to directly compare exams limited to the distal colon with exams of the entire colon to determine possible additional benefits of colonoscopy screening in an asymptomatic group of patients. Among patients with serious pre-malignant growths or cancer in their colon, 1 percent had invasive cancer, 1.6 percent had polyps that already had changes likely to become cancer and another group had large polyps or polyps with so-called “villous” changes—both indications of potential trouble. The most striking finding was that one-third of all patients with serious lesions would not have been detected with sigmoidoscopy. Colonoscopy also appeared to be reasonably safe, the team found, with few complications such as bleeding or reactions to sedation used to make patients more comfortable during the procedure.
Because the VA patient population is largely male, the VA study participants were 97 percent men. A parallel non-VA trial is looking at colonoscopy in women.
Lieberman’s co-authors of the NEJM report included David G. Weiss, Ph.D., John H. Bond, M.D., Dennis J. Ahnen, M.D., Harinder Garewal, M.D., Ph.D., Gregorio Chejfec, M.D, and other investigators of the VA Cooperative Study #380 Group.
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