A new study finds that colonoscopy is strongly associated with fewer deaths from colorectal cancer.
However, the risk reduction appears to be entirely due to a reduction in deaths from left-sided cancers. According to the study, colonoscopy shows almost no mortality prevention benefit for cancer that develops in the right side of the colon. Colorectal cancer is the second-leading cause of cancer death in North America.
The study appears today on the Annals of Internal Medicine Web site (www.annals.org) and will be printed in the January 6, 2009, issue.
"While colonoscopy remains the gold standard for evaluation of the colon, our study sheds light on some of the real-world limitations of this practice for screening and prevention," said Nancy Baxter, MD, PhD, Colorectal Surgeon and a Researcher at St. Michael's Hospital, who is lead author on the study.
Researchers reviewed health records for persons aged 52 to 90 who received a colorectal cancer diagnosis between 1996 and 2001 and died of colorectal cancer by 2003. These patients were compared to a control group who were selected from the population of Ontario and had not died of colorectal cancer.
According to the researchers, complete colonoscopy was strongly associated with fewer deaths from left-sided colorectal cancer. Conversely, the data showed that colonoscopy seemed to have almost no mortality prevention benefit for right-sided colorectal cancer.
"Colonoscopy is an effective intervention," said David F. Ransohoff, MD, author of an accompanying editorial. "The study results, however, should caution physicians about saying that colonoscopy will reduce the risk of dying from colorectal cancer by 90 percent. A 60 to 70 percent risk-reduction rate seems more reasonable."