Community-Based Study Shows Colonoscopy Is Effective

Zosia Chustecka

January 03, 2011

January 3, 2011 — A new community-based study from Germany confirms that colonoscopy is an effective tool for preventing colorectal cancer (CRC), according to an editorial accompanying the study published in the January 4 issue of the Annals of Internal Medicine.

In Germany, colonoscopy has been the primary screening method offered to people 55 years and older since 2002, explain the authors, headed by Hermann Brenner, MD, MPH, from the German Cancer Research Center in Heidelberg. The introduction of colonoscopy was accompanied by "major efforts" in training and quality assurance measures, they note.

In this setting of high-quality colonoscopy, they conducted a population-based case–control study comparing 1688 patients and 1932 control subjects.

They found that for individuals who had undergone colonoscopy in the previous 10 years, the overall risk for any colorectal cancer was reduced by 77%.

As has been seen in previous studies, there was a larger reduction in the risk for left-sided colorectal cancer (84%) than in right-sided colorectal cancer (56%). Both of these reductions were "significant," they note.

These results show a greater risk reduction than has been reported recently in other studies, Dr. Brenner and colleagues note. Although the original trial that led to the adoption of colonoscopy — the National Polyp Study, published in 1993 — reported up to a 90% reduction in the risk for CRC, more recent population studies from Germany and Canada have reported reductions of only 30% to 50%.

In addition, this latest study shows a substantial reduction in the risk for right-sided CRC, Dr. Brenner and colleagues point out. This is in contrast to the lack of effect seen in a recent study from Canada (based on administrative claims), which found no protection from deaths from right-sided cancer (JAMA. 2008;299:1027-1035). However, the reduction in right-sided CRC seen in the German study showed an age gradient; in patients aged younger than 60 years, the reduction was modest (26%) and statistically nonsignificant, the authors point out.

The new results "vindicate colonoscopy as an effective prevention tool," writes David Weinberg, MD, MSc, from the Fox Chase Cancer Center in Philadelphia, Pennsylvania, in an accompanying editorial.

They also offer reassurance that colonoscopy can provide substantial protection against both right- and left-sided CRC, he adds. Although it does appear that colonoscopy is "less effective" in the right colon, this is not the same as "ineffective," he points out.

Colonoscopy Most Popular Method in the United States

Colonoscopy has become a standard — and for some the preferred — method of screening for CRC, Dr. Weinberg explains. It is certainly the most popular method in the United States, he adds, where more than 14 million colonoscopies are performed annually.

In contrast, other screening methods, such as flexible sigmoidoscopy and fecal occult blood testing, are performed with decreasing frequency in the United States, despite their lower costs and a stronger evidence base demonstrating their effectiveness, he notes.

Against this backdrop, there has been "recent and unwelcome news that colonoscopy may not protect against CRC as effectively as we would like to think," Dr. Weinberg notes.

These latest results from Germany provide reassurance that colonoscopy is effective, he writes. The study was methodologically rigorous, and the protective effect against CRC was "impressive." The protective effect was seen in both sexes and all ages, and even in patients with a family history of CRC, who are presumably at higher risk.

Nonetheless, there are several questions and issues that remain. Colonoscopy is operator dependent, and there is consistent evidence that gastroenterologists, as opposed to practitioners from other backgrounds, miss fewer lesions, Dr. Weinberg notes. There is also research showing that the ability to detect polyps and other lesions depends on the quality of the laxative preparation, he explains. Preparations that work best should become the standard, although any regimen remains a challenge for older sicker patients, he acknowledges.

Colonoscopy is more expensive and carries a higher risk than other CRC screening methods, so there are appropriate concerns about its "value," he writes.

"It is unrealistic to expect that colonoscopy to prevent all cases of CRC," Dr. Weinberg writes. "Physicians need to inform patients that colonoscopy offers very good, but not perfect, protection," he concludes.

The study was funded by the German Research Council and German Federal Ministry of Education and Research. Dr. Weinberg has disclosed no relevant financial relationships.

Ann Intern Med. 2011:154;22-30, 68-69.


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