Colonoscopy associated with lower risk of advanced cancer

People who have undergone a colonoscopy in the last decade are less likely to be diagnosed with advanced colon cancer than those who haven't been screened recently, according to a study published in the Annals of Internal Medicine.

Researchers led by Chyke Doubeni, M.D., of the University of Pennsylvania's Perelman School of Medicine, analyzed the records of more than 1,000 patients between the ages of 55 and 85. They identified 474 who had advanced colon cancer, and went back 10 years to determine whether they had been screened for cancer with either a colonoscopy or sigmoidoscopy. They did the same for 538 patients who were cancer free.

They determined that 3 percent of the people with advanced cancer had undergone a colonoscopy in the past 10 years, compared to 9 percent of the cancer-free group. About 20 percent of those with advanced cancer had undergone a sigmoidoscopy, compared to 34 percent of those without cancer.

The researchers' conclusion that colonoscopy is associated with less risk of developing advanced colon cancer held for cancers in both the left and right colon for colonoscopy. But, they found that sigmoidoscopy was only associated with preventing advanced cancer on the left side of the colon, which is easier to reach with a scope.

"There's a variety of screening tests for us to choose from," Doubeni told in Reuters Health. "This study doesn't show that colonoscopy is the only test, but it does show that colonoscopy has the advantage in being able to see the right side [of the colon] … unlike sigmoidoscopy and fecal occult blood testing."

Study co-author Robert Fletcher, M.D., a professor emeritus at Harvard Medical School said in an accompanying announcement that the study's results reinforce the importance of screening colonoscopies for men over 50. "As we wait to learn more about the effectiveness of screening colonoscopy through clinical trials, this case-control study provides credible answers that support current screening practices and recommendations," he said.

To learn more:
- see the study abstract
- check out the article in Reuters Health
- read the announcement