Colonoscopy within previous 10 years associated with 77% reduction in overall colon cancer

Brenner HM. Ann Intern Med. 2011;154:22-30.

Colonoscopy in the preceding 10 years was associated with lower risk for all cancer stages at all ages, except right-sided cancer in patients aged 50 to 59 years, according to results from a population-based case control study.

Researchers recruited 1,688 patients aged 50 years or older and 1,932 healthy controls recruited from January 2003 to December 2007. Interviewers questioned participants in the hospital or at home about colonoscopy in the previous 10 years. Researchers then reviewed participants’ medical records to determine disease status and to validate medical history.

A total of 1,023 participants reported undergoing at least one colonoscopy in the preceding 10 years, with 60% undergoing one exam and 23% undergoing two. Researchers said 41.1% of the control group and 13.6% of the study group had a colonoscopy during the study period.

Researchers said preceding colonoscopy was associated with “strong and statistically significant risk reduction of cancer” at every subsite assessed. However, risk reductions was not as strong for cancers located at subsites from the cecum (OR=0.31) to the descending colon (OR=0.58) compared with sigmoid colon cancer (OR=0.14) and rectal cancer (OR=0.13).

The procedure was associated with an 84% reduction in risk for left-side disease (OR=0.16; 95% CI, 0.12-0.20), an effect that has been shown in previous studies. Brenner et al, however, also found a similar protective effect for right-side or proximal cancer, with a 56% reduced incidence (OR=0.44; 95% CI, 0.35-0.55).

Preceding colonoscopy was associated with risk reduction at all stages with a slight trend toward better risk reduction for more advanced cancer, but researchers said the differences were small.

Writing in an accompanying editorial, David S. Weinberg, MD, MSc, chair of the department of medicine and the director of gastroenterology at Fox Chase Cancer Center in Philadelphia, said the results “vindicate colonoscopy as an effective prevention tool.”

“They found that colonoscopy reduced the incidence of cancer of both the proximal and distal colon. Equally important, this study highlights the role of the endoscopist in the production of the most beneficial results,” Weinberg wrote. “Understanding why colonoscopy is less effective in the proximal colon will take time. However, it would be a mistake to conclude that ‘less effective’ is the same as ‘ineffective.’ Brenner and colleagues’ results offer reassurance that colonoscopy can provide substantial protection against right- and left-sided colorectal cancer.”

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