Less Invasive Alternative to Colonoscopy Reduces Colorectal Cancer Cases, Death
Nicholas Davidson, MD, director of the Division of Gastroenterology at Washington University School of Medicine and a gastroenterologist at the Siteman Cancer Center.
May 21, 2012 – A less invasive screening test for colorectal cancer reduces deaths from the disease but is probably not
as effective as colonoscopy, the gold standard.
Researchers found that screening with sigmoidoscopy reduced overall colorectal cancer deaths by 26 percent and new cases by 21 percent when compared to no screening.
The nearly 20-year study involved 154,900 patients at major centers nationwide, including about 17,000 at Washington University School of Medicine in St. Louis. Results will be published online May 21 in the New England Journal of Medicine.
No studies have compared mortality outcomes between sigmoidoscopy and colonoscopy. But recent research showed that colonoscopy reduced colorectal cancer deaths by 53 percent, making it the preferred screening method, says Nicholas Davidson, MD, director of the Division of Gastroenterology at Washington University School of Medicine and a gastroenterologist at the Siteman Cancer Center.
But sigmoidoscopy is a valid option if its less invasive nature and easier preparation prompt more people to be screened, he adds. No matter how precancerous polyps are detected, their removal reduces colorectal cancer risk.
“These findings provide further evidence that regular scheduled screening is effective, not only in decreasing the incidence of colorectal cancer but also in decreasing mortality from this disease,” Davidson says. “Taken together with findings published earlier this year from the results of screening colonoscopy, the new research strongly suggests that colorectal cancer deaths are preventable through aggressive screening programs.”
Sigmoidoscopy uses a thin, flexible tube-like instrument called a sigmoidoscope to view the anus, rectum and lower colon. People who opt for this screening test don’t need to undergo rigorous bowel preparation, which is required for colonoscopy and is one reason that many people avoid the test. Sigmoidoscopy also poses a lower risk of bowel perforation (an uncommon event that occurs when the scope pokes a hole in the intestine) compared to colonoscopy, in which a similarly flexible but longer tube is used to view the entire colon.
Researchers estimated that if they had used colonoscopy rather than sigmoidoscopy in the study, they would have identified 16 percent more cancers. But they concede that screening with sigmoidoscopy is better than no screening at all.
Colorectal cancer is the second-leading cause of cancer-related death in the U.S. Previous research has shown that colorectal cancer cases and deaths can be reduced with a number of screening methods, including a third one called fecal occult blood testing. However, flexible sigmoidoscopy and colonoscopy are more sensitive than the blood test for detecting polyps that may lead to colorectal cancer.
The National Cancer Institute (NCI) funded the new research, part of the Prostate, Lung, Colorectal and Ovarian (PLCO) Cancer Screening Trial, at 11 sites across the U.S. The study involved men and women ages 55 through 74 who were randomly assigned to receive flexible sigmoidoscopy screening or usual care. People in the usual care group only received screening if they asked for it or if their physician recommended it.
Participants in the flexible sigmoidoscopy group were screened once on entering the study and again three years to five years later. The participants were followed for approximately 12 years to collect data on cancer diagnoses and deaths.
Overall, after an average of nearly 12 years, participants in the screening group had a 21 percent lower incidence of colorectal cancer overall and a 26 percent lower rate of colorectal cancer mortality than participants in the usual care group. This means that, over the course of 10 years, if 1,000 people received two sigmoidoscopy screenings, there would be approximately three fewer new cases and one fewer death from colorectal cancer than in a comparable group not receiving regular screenings.
“This is the second major trial that has shown that sigmoidoscopy is effective in reducing the risk of dying of colorectal cancer,” says Barnett Kramer, MD, director of the NCI’s Division of Cancer Prevention. “Sigmoidoscopy is less invasive than colonoscopy and carries a lower risk of the colon being perforated, which may make it more acceptable as a screening test to some patients. There are several effective screening tests for colorectal cancer, and the most effective screening test is the one that people choose to take.”
At Washington University, the PLCO trial is led by Gerald Andriole, MD, the Robert K. Royce Distinguished Professor and chief of urologic surgery at Siteman.