NEW YORK (Reuters Health), Dec 31 - Colonoscopy is more protective against advanced neoplasms in the left colon and rectum than in the right colon, results of a German study indicate.
The finding that the protective effect of colonoscopy varies by anatomical site is reported by Dr. Hermann Brenner, from the German Cancer Research Center, Heidelberg, and his colleagues in the January 20 Journal of the National Cancer Institute.
In a cross-sectional community-based study, the researchers compared 586 individuals who had undergone colonoscopy in the previous 10 years (but not in the previous year) with no evidence of colorectal disease, with 2701 who had not.
Screening colonoscopy detected advanced neoplasia in 6.1% of subjects with a previous colonoscopy compared with 11.4% of those undergoing the procedure for the first time (adjusted prevalence ratio 0.52).
The authors also found, however, that while previous colonoscopy was strongly and inversely associated with the prevalence of advanced neoplasia in the left colon and rectum, there was no such association with advanced neoplasia in the right colon.
They estimate that adjusted prevalence ratios were 0.33 for the left-sided colon and rectum but 1.05 for the right-sided colon.
These patterns are consistent with previous observations that "a greater proportion of colorectal cancer is right sided among those who have had a previous colonoscopy than among the general population," the authors add.
They point out that adenomas in the right colon are more likely to be sessile or flat, and therefore easier to miss with colonoscopy. Other explanations for missing right-sided neoplasms include incomplete colonoscopy or poorer bowel preparation in the right colon.
If their findings are verified, "then the relative merits of sigmoidoscopy and colonoscopy in the early detection and prevention of colorectal cancer would need to be reevaluated," the researchers conclude.
Editorialists Dr. Nancy N. Baxter and Dr. Linda Rabeneck from the University of Toronto agree. Furthermore, they say, "the rate of serious adverse complications ... associated with colonoscopy, although low, is unprecedented for a screening maneuver recommended for use in the general population."
The lifetime colorectal cancer risk for an individual is "quite low" at 5%, they say, which leads them to ask whether any "incremental benefit of colonoscopy over flexible sigmoidoscopy" is large enough "to justify the additional risks and costs of colonoscopy for screening in the population."
J Natl Cancer Inst 2010;102:1-7,70-71.
Last Updated: 2009-12-30 18:53:27 -0400 (Reuters Health)
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