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 were published online May 21, 2012, 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 O. Davidson, MD, director of the Division of Gastroenterology at Washington University School of Medicine.
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 pre-cancerous polyps are detected, their removal reduces colorectal cancer risk.
“These findings provide further evidence that regular, scheduled screening is effective in decreasing the incidence of colorectal cancer and mortality from this disease,” says Davidson, who sees patients at the Alvin J. Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine. “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 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 aged 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, M.D., director of 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 the School of Medicine, the PLCO trial is led by Gerald Andriole, MD, the Robert K. Royce Distinguished Professor and chief of urologic surgery at the Alvin J. Siteman Cancer Center at Barnes-Jewish Hospital and Washington University School of Medicine.
Washington University School of Medicine’s 2,100 employed and volunteer faculty physicians also are the medical staff of Barnes-Jewish and St. Louis Children’s
hospitals. The School of Medicine is one of the leading medical research, teaching and patient care institutions in the nation, currently ranked fourth in the nation by U.S. News & World Report
. Through its affiliations with Barnes-Jewish and St. Louis Children’s hospitals, the School of Medicine is linked to BJC HealthCare.
The Alvin J. Siteman Cancer Center is the only NCI-designated Comprehensive Cancer Center within a 240-mile radius of St. Louis. Siteman Cancer Center is composed of the combined cancer research and treatment programs of Barnes-Jewish Hospital and Washington University School of Medicine.