THURSDAY, Oct. 2 (HealthDay News) -- Older patients with a negative complete colonoscopy have a significantly reduced long-term incidence of developing overall or distal colorectal cancer. But their reduced risk of developing proximal colorectal cancer is usually only significant after seven years of follow-up, according to a report published in the October issue of Clinical Gastroenterology and Hepatology.
Josh Lakoff, of the University of Toronto in Ontario, Canada, and colleagues identified 110,402 Ontario residents aged 50 to 80 with no prior history of colorectal cancer, inflammatory bowel disease or recent colonic resection who had a negative complete colonoscopy between January 1992 and December 1997.
After a 14-year follow-up, the researchers found that the subjects had a significantly reduced risk of overall and distal colorectal cancer compared to the general population (relative risk 0.21 for distal colorectal cancer at year 14). However, they found that the reduced risk of incident proximal colorectal cancer was less consistent and occurred in only about half of the follow-up years, most often after seven years of follow-up.
"Future research should be directed at disentangling the relative contributions of colonoscopy quality and tumor biology in explaining these results," the authors conclude. "Regardless of their explanation, these results highlight an important limitation of colonoscopy in usual clinical practice."
Abstract
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