Flexible Sigmoidoscopy May Miss Colon Cancers in Highest-Risk Group

Martha Kerr

May 23, 2007

May 23, 2007 (Washington) — Analyses of data from the National Cancer Registry, the Surveillance, Epidemiology and End-Results (SEER) database, and colonoscopy record reviews conducted at a number of institutions across the country revealed that flexible sigmoidoscopy is associated with some significant drawbacks, according to a number of reports presented here at Digestive Disease Week 2007.

C. Greg Nesmith, MD, a research fellow with the Department of Digestive Diseases at Emory University School of Medicine in Atlanta, Georgia, presented findings from a retrospective review of all colonoscopies performed at Emory University Hospital and Grady Memorial Hospital between January 2000 and December 2005.

A total of 16,737 procedures were reviewed, 5,597 (33%) of which were conducted to screen patients at average risk for colorectal cancer.

Of those at average risk for colorectal cancer, 8% had advanced neoplasia — including 67.8% with tubular adenomas larger than 10 mm, 21.6% with tubulovillous adenomas, 1.5% with high-grade dysplasias, and 9.1% with cancers.

There were 262 cases of advanced neoplasms confined to the proximal colon. White patients had a 2-fold higher risk for proximal colon cancer than for neoplasms in other regions of the colon; blacks had a 6-fold increase in the risk for proximal tubulovillous adenomas (1.38 to 26.14; = .016) and a more than 10-fold increase in risk for proximal adenocarcinomas (1.37 to 86.42; = .035), compared with lesions elsewhere in the colon.

"African Americans, especially African American men, have the highest risk of cancers in the proximal colon," Dr. Nesmith told meeting attendees. "Flexible sigmoidoscopy would miss these. Colonoscopy would be the preferred method for colon cancer screening."

There has been a trend toward greater use of flexible sigmoidoscopy because of the ease of use and the fact that no general anesthesia is required.

Colonoscopy not only can be used to diagnose colon cancers, but it can be used to remove small lesions," Dr. Nesmith added. "With flexible sigmoidoscopy, you can only visualize lesions. You would have to go ahead to do colonoscopy anyway if you see suspect areas."

Colonoscopy should be the preferred modality, especially in African American men," Dr. Nesmith told Medscape. "There is a trend away from performing flexible sigmoidoscopy."

A large proportion of the population receives no screening at all, moderator Gregory Ginsberg, MD, professor of medicine at the University of Pennsylvania School of Medicine, Gastroenterology Division, in Philadelphia, commented.

Similar findings were announced by Ananya Das, MD, from the Department of Gastroenterology at the Mayo Clinic in Scottsdale, Arizona. His team used SEER data and found that the overall incidence of colon cancer dropped between 1973 and 2003. Proximal colon cancers have declined in white men and women, but have increased in blacks, particularly black men.

"Colonoscopy is a very effective tool for removing polyps," he told Medscape. "The American Society for Gastrointestinal Endoscopy has endorsed the use of colonoscopy for screening, and recently, there has been a movement away from using flexible sigmoidoscopy."

Drs. Nesmith, Ginsberg, and Das report no relevant financial relationships.

DDW 2007: Abstract 431, presented May 21, 2007; abstract 595, presented May 22, 2007.

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