Colonoscopy May Cut Advanced Cancer Risk by 70%
If simpler tests are effective, why are patients encouraged to undergo a colonoscopy? "Let me just say there are other factors beyond the evidence that are driving the use of colonoscopy in the U.S.," said Doubeni. "No other country uses colonoscopy for screening purposes as much as the United States, although Germany comes close," he noted.
The U.S. Preventive Services Task Force recommends that people 50 to 75 years old be screened for colon cancer in one of three ways: a home fecal occult blood test every year; a sigmoidoscopy every five years combined with a home fecal occult blood test every three years; or a colonoscopy every 10 years.
A colonoscopy examines the inside of the large intestine with a camera-tipped tube. The test enables the physician to remove any precancerous growths -- adenomatous polyps -- which sometimes develop into cancer. Colorectal tumors are a major cause of death from cancer in the United States, with about 137,000 new cases and 52,000 deaths every year, according to the U.S. Centers for Disease Control and Prevention.
For the study, published in the March 5 issue of the Annals of Internal Medicine, the authors reviewed health records of more than 1,000 average-risk adults between the ages of 55 and 85 who were members in four health management organizations (HMOs).
The researchers identified 474 people with late-stage colon cancer and then looked back 10 years to see if they had been screened for the disease with colonoscopy or sigmoidoscopy. They compared them to 538 "control" patients and used additional information from state or local tumor registries to see whether there was an association between having had a colonoscopy or sigmoidoscopy and developing cancer.
Dr. David Bernstein, a gastroenterologist at North Shore University Hospital in Manhasset, N.Y., said the study had a critical design flaw. "Making assumptions that any cancers that were found would have been seen 10 years prior doesn't make sense," he said. "It doesn't prove that these cancers didn't occur two years ago."
A key part of effective colon screening is getting the tests at the recommended interval, experts say. To better understand what might be effective in prodding people to get screening, another study published this month in the same journal found that people who were mailed a letter, a pamphlet and a fecal occult blood test kit completed recommended screening twice as often and for less cost than those who were not reminded or got automated and other reminders by nurse coaches.