The researchers examined the effect of polypectomy on the long-term prevalence of colorectal adenomas, and reported their findings in the June issue of the American Journal of Gastroenterology.
In 1983, a total of 799 men and women, aged 50-59 years, were drawn from the general population register. Of these, 400 were assigned to a screening group and 399 to a matched control group.
Those in the screening group were invited to undergo a once-only flexible sigmoidoscopy.
Persons with polyps had a baseline colonoscopy with follow-ups in 1985 and 1989.
In 1996, both members of the screening group and the controls were invited to a colonoscopic examination. A total of 451 (71%) individuals attended this.
Screening group 37%
|American Journal of Gastroenterology|
Adenomas were found in 78 (37%) individuals in the screening group and 103 (43%) in the control group (relative risk, 0.9).
The occurrence of high-risk adenomas was also assessed. These were defined as adenomas greater than or equal to 10 mm, with severe dysplasia and villous components. 16 (8%) subjects in the screening group and 32 (13%) in the control group were found to have these (relative risk, 0.6).
Researcher E. Thiis-Evensen, of the Telemark Central Hospital, Skien, said on behalf of the group, "There was no significant difference in adenoma prevalence between the group after the screening program, and the controls after the usual care."
"There was a trend toward more high-risk adenomas in the control group. This suggests a very limited effect of one-time screening sigmoidoscopy, with surveillance colonoscopy, on the prevalence of adenomas.
"However, this screening has a preventive effect on the development of high-risk adenomas consistent with the reported effect on cancer prevention," it was concluded.