MONDAY, March 28, 2005 (HealthDay News) -- No one disputes the value of colonoscopies for screening for colon cancer, but a recent National Cancer Institute report finds that some doctors may be recommending follow-up colonoscopies when the benefits of those extra screenings just aren't there.
And this unneeded vigilance may be preventing some people from getting initial colonoscopies, while requiring others who have had a screening to undergo an unnecessary invasive follow-up procedure, the researchers said.
"Only 40 percent of persons over 50 have had any form of screening for colon cancer, compared to 70 to 80 percent for breast and prostate cancers. We were very interested in why so few were being screened," said Dr. Pauline A. Mysliwiec, an associate professor of gastroenterology at the University of California, Davis School of Medicine, who headed up the study.
"One of the concerns we addressed was, 'Are there too many surveillance procedures, which is limiting the access for screening?'" she added. A surveillance procedure is a subsequent colonoscopy on someone who has been found to have a polyp or polyps in the bowel, while screening refers to a first-time colonoscopy.
Mysliwiec's study, originally published in August 2004 in the Annals of Internal Medicine, found that nearly half of the approximately 600 gastroenterologists and surgeons surveyed went beyond recommended medical guidelines in performing follow-up colonoscopies.
Part of this could be due, she said, to the lack of clear guidelines available at the time of the study, which covered the years 1999 and 2000. In 2003, the American Gastroenterological Association (AGA) updated its screening guidelines to reflect the latest research.
A "better-safe-than-sorry attitude" could also be a contributing factor in unnecessary follow-up procedures, Mysliwiec said.
"Some people and providers are erring on the side of being more aggressive, but you are subjecting yourself to an invasive procedure that is not without risk," she said.
A colonoscopy allows a physician to use a scope to look inside the entire large intestine, from the lowest part -- the rectum -- all the way up through the colon to the lower end of the small intestine. The procedure is used to check for early signs of cancer in the colon and rectum, according to the National Digestive Diseases Information Clearinghouse.
The most common non-cancerous polyps found in colonoscopies are hyperplastic polyps, which most research shows do not become cancerous, and small adenomas, which are considered precancerous. The latest AGA guidelines call for no treatment for hyperplastic polyps, and a follow-up colonoscopy five years after finding a small adenoma in otherwise low-risk patients.
However, Mysliwiec and her colleagues found in their study that 24 percent of gastroenterologists and 54 percent of surgeons surveyed recommended follow-up colonoscopies for hyperplastic polyps. And more than 50 percent of all the doctors recommended follow-up colonoscopies every three years or sooner for small adenomas.
Dr. Vincent Yang is director of the Division of Digestive Diseases at Emory University School of Medicine. He said the National Cancer Institute study does reflect an established pattern that many people tend to have more surveillance than perhaps is needed because of "the very confusing criteria for surveillance." But he doesn't think that's the main reason why there can be a waiting list for an initial colonoscopy.
"First of all there is a shortage of manpower," Yang said. "And secondly, since Medicare starting covering the procedure three or four years ago, there has been an increased demand." To illustrate that point, he said that in his own practice, he is performing twice as many colonoscopies as he did five years ago.
Another reason for low rates of initial screening, he said, is that many people are reluctant to undergo a procedure that requires fasting the day before, and then having a mild anesthesia while a doctor inserts a tube up the intestine to look for polyps.
Colonoscopies are recommended every 10 years for people over the age of 50 at average risk for colon cancer.
Mysliwiec said patients should be aware that most follow-up screening should not be done sooner than three years after the original procedure unless there are special considerations.
"If your physician recommends having another colonoscopy in a time period of less than three years, ask him why," she said.
More information
To learn more about colorectal cancer, visit the American Cancer Society.
