Study: Sigmoidoscopies Every Three Years Detect Colorectal Cancers

A new study showed that having a sigmoidoscopy screening test every three years instead of the recommended five may be helpful in fighting colorectal cancer, but researchers are using the results to argue for keeping current medical guidelines unchanged.

Sigmoidoscopy is the insertion of a flexible tube to inspect the lower portion of the colon, where 60 percent of all colorectal cancers occur.

In a study involved 9,317 men and women with an average age of about 66 who had a repeat sigmoidoscopy exam three years after receiving normal results, cancer or precancerous tumors called adenomas were found in 292 people, or 3.1 percent.

"One quarter of the individuals with adenomas had advanced adenomas, and 6 distal colon cancers were detected," the researchers reported in the Journal of the American Medical Association.

The findings are being cited by the researchers not as an argument in favor of a shorter screening interval, but in opposition to suggestions based on other studies that the interval between screenings for colorectal cancer might lengthened to 10 years (see earlier Colorectal Cancer Week story)..

"Our results show that 3 years after a negative flexible sigmoidoscopy, there is a 0.8 percent incidence of advanced adenomas or cancer detectable in the distal colon," the researchers said. "Although the overall percentage with detected abnormalities is modest, these data raise concern about the impact of a prolonged screening interval after a negative examination."

Dr. Robert Fletcher of Harvard Medical School, in an accompanying editorial, agreed that the results do not support changing current guidelines calling for screenings every five years.

Other Sources: Journal of the American Medical Association