Jan. 3, 2011 -- It is considered one of the most effective cancer screening and prevention exams, but recent studies have raised concerns that a colonoscopy may not be useful for detecting certain colorectal cancers.
Now a new study from Germany offers strong evidence that the test can prevent colorectal cancers located throughout the colon -- not just those easiest to reach with the fiberoptic imaging scope.
Experts say the findings should reassure patients that a colonoscopy saves lives by detecting and removing precancerous polyps throughout the colon before they can become malignant.
The study appears in the Jan. 4 issue of Annals of Internal Medicine.
“This study tells us that when done well, colonoscopy is effective in both the left and right side of the colon,” Fox Chase Cancer Center director of gastroenterology David S. Weinberg, MD, tells WebMD.
Worldwide, more than a million people are diagnosed with colorectal cancer each year, and about half a million people die of the disease.
Colonoscopy involves a flexible fiberoptic scope with a video camera, which is threaded through the large intestine to search for and remove polyps before they become malignant. Widely performed in the U.S. and Europe, it is considered the most effective screening tool for colorectal cancer.
It is used to visualize the entire large intestine, including the section farthest away from the rectum.
But several recent studies from Canada have raised doubts about the effectiveness of colonoscopy in this area, known as the right side of the colon.
In one study, researchers in Ontario failed to find evidence that colonoscopy screening reduced deaths from right-sided colorectal cancers, although a survival benefit was seen in patients with left-sided cancers.
In another study, researchers from the University of Manitoba found that colorectal cancers occurring on the right side of the colon appeared to be missed during colonoscopy far more often than cancers occurring on the left side.
Reduction in Right-Side Cancers
In the newly published study, investigators from the German Cancer Research Center compared the colonoscopy histories of close to 1,700 colorectal patients living in southwest Germany with 1,900 people without cancer matched for age, sex, and place of residence.
Study participants were asked whether they had had a colonoscopy during the previous 10 years, and patient medical records were analyzed.
After taking into account known colorectal cancer risk factors, colonoscopy screening within the previous decade was associated with a 77% overall reduction in colorectal cancer risk.
The risk reduction was 84% and 56%, respectively, for left-sided and right-sided cancers. In patients younger than age 60, however, screening was associated with a 26% reduction in risk in right-sided cancer, which was not statistically significant.
The reduction in risk was seen for all cancer stages and for both men and women.