A One-time sigmoidoscopy screening significantly reduces long-term incidence of colorectal cancer (CRC), according to a new pooled analysis of four randomized trials published in Annals of Internal Medicine.
Although endoscopic screening provides a way to detect and remove premalignant polyps early, data to quantify the long-term effects of sigmoidoscopy screening are lacking, said corresponding author Frederik E.Juul, MD.
«Sigmoidoscopy screening has been proven to reduce the incidence and mortality of colorectal cancer, but it was not known how long-lasting the effects are and whether there are differences in gender or age,» Dr. Juul said.
«For the first time, we were able to merge data from all four randomized sigmoidoscopy screening trials and include data from recent updates from two of the studies (U.S. and Italy), meaning we were able to answer these questions better than ever before,» he said.
Researchers from Norway, the United States, Italy and the United Kingdom evaluated data from four studies with a follow-up period of at least 15 years. The analysis included 137,493 people randomized to at least one sigmoidoscopy and 137,459 people assigned to usual care.
The primary endpoints were CRC incidence and mortality following sigmoidoscopy screening compared to usual care in adults at average risk of CRC aged 55 to 64 years.Secondary outcomes included CRC incidence and mortality related to distal vs. proximal involvement, sex, and younger vs. older people (55-59 and 60-64 years, respectively, at study entry).
After a follow-up of 15 years, the pooled cumulative CRC incidence was 1.84 cases/100 people in the screening group versus 2.35 cases/100 people in the usual care group, representing a 21% reduction in incidence in those who participated in screening.
Pooled cumulative CRC mortality was 0.51 deaths/100 people in the screening group vs. 0.65 deaths/100 people in the usual care group, representing a 20% reduction in CRC mortality in the screening group, the researchers said. All-cause mortality was 2% lower in the screening group than in the usual treatment group; pooled cumulative all-cause mortality was 14.3 deaths/100 people in the screening group vs. 14.6 deaths/100 people in the usual treatment group.
As for secondary endpoints, significant reductions in CRC incidence and mortality were confined to the distal colon, while no significant differences were observed in the proximal colon, the researchers said.The reasons for this difference are unclear. Previous research on 3 of the 4 studies showed a small reduction in colorectal cancer in the proximal colon, but this may be related to the longer follow-up time in the analysis of the 4 studies.
CRC incidence varied by gender, with the incidence reduced by 25% in men and 16% in women. The reasons for this difference have yet to be determined, but could lie in varying degrees of bowel preparation, greater technical challenges in screening women, and higher incidence and higher proportions of proximal CRC versus distal CRC in women, the researchers said.
«The long-term benefits of a single procedure probably surprised us the most,» Dr. Juul said in an interview. «Not only were the cumulative incidence and mortality lower in the subjects studied 15 years after screening, but the annual incidence was consistently lower than usual care, even at the end of the follow-up period.»
The main finding of the study is that sigmoidoscopy screening with examination of the distal colon protects against colorectal cancer for at least 15 years; «this could affect how often average-risk individuals need to be screened,» Dr. Juul said.He added: «Our study investigating sigmoidoscopy screening has a longer follow-up period, and it will be interesting to see whether primary colonoscopy screening is as effective or more effective than sigmoidoscopy after 15 years of follow-up.»
«More research is needed to directly compare different colorectal cancer screening methods, such as sigmoidoscopy and colonoscopy,» he said.
A version of this article first appeared on MDedge.com, part of the Medscape Professional Network.
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