Sigmoidoscopy, Colonoscopy and Colorectal Cancer Incidence
Objectives To review, summarise, and compare the evidence for effectiveness of screening sigmoidoscopy and screening colonoscopy in the prevention of colorectal cancer occurrence and deaths.
Design Systematic review and meta-analysis of randomised controlled trials and observational studies.
Data sources PubMed, Embase, and Web of Science. Two investigators independently extracted characteristics and results of identified studies and performed standardised quality ratings.
Eligibility criteria Randomised controlled trials and observational studies in English on the impact of screening sigmoidoscopy and screening colonoscopy on colorectal cancer incidence and mortality in the general population at average risk.
Results For screening sigmoidoscopy, four randomised controlled trials and 10 observational studies were identified that consistently found a major reduction in distal but not proximal colorectal cancer incidence and mortality. Summary estimates of reduction in distal colorectal cancer incidence and mortality were 31% (95% confidence intervals 26% to 37%) and 46% (33% to 57%) in intention to screen analysis, 42% (29% to 53%) and 61% (27% to 79%) in per protocol analysis of randomised controlled trials, and 64% (50% to 74%) and 66% (38% to 81%) in observational studies. For screening colonoscopy, evidence was restricted to six observational studies, the results of which suggest tentatively an even stronger reduction in distal colorectal cancer incidence and mortality, along with a significant reduction in mortality from cancer of the proximal colon. Indirect comparisons of results of observational studies on screening sigmoidoscopy and colonoscopy suggest a 40% to 60% lower risk of incident colorectal cancer and death from colorectal cancer after screening colonoscopy even though this incremental risk reduction was statistically significant for deaths from cancer of the proximal colon only.
Conclusions Compelling and consistent evidence from randomised controlled trials and observational studies suggests that screening sigmoidoscopy and screening colonoscopy prevent most deaths from distal colorectal cancer. Observational studies suggest that colonoscopy compared with flexible sigmoidoscopy decreases mortality from cancer of the proximal colon. This added value should be examined in further research and weighed against the higher costs, discomfort, complication rates, capacities needed, and possible differences in compliance.
Since 1992, several observational studies have suggested a major protective effect of lower gastrointestinal endoscopy (in particular sigmoidoscopy and colonoscopy) against colorectal cancer through detection and removal of precancerous lesions. As a result, and supported by further improvements in technology, use of sigmoidoscopy and colonoscopy for diagnostic and screening purposes has substantially increased in many countries. Both procedures have been recommended as screening options for colorectal cancer by expert committees and offered as primary screening in several European countries (including Germany, Italy, Poland, and Austria) long before the availability of results from randomised controlled trials. Recent studies of trends in incidence and mortality from colorectal cancer suggest that increased use of lower gastrointestinal endoscopy has already led to major reductions in the incidence of and deaths from colorectal cancer in the United States.
Emerging evidence on the protective effects of endoscopy from detection and removal of adenomas also prompted the initiation of several randomised controlled trials to prove the efficacy of endoscopy based screening for reducing colorectal cancer incidence and mortality. In the 1990s four large scale randomised controlled trials began to investigate the effects of screening by flexible sigmoidoscopy, and the first results were published in 2009, 2010, 2011, and 2012. Screening colonoscopy has the potential to prevent colorectal cancer of the entire large bowel but is associated with higher costs, discomfort, complication rates, and capacities needed. Given that colonoscopy is recommended and offered for primary screening in an increasing number of countries, it is important to know its relative effectiveness compared with sigmoidoscopy. The only randomised controlled trial to assess the impact of screening colonoscopy (compared with no screening) on colorectal cancer incidence and mortality started recruitment in 2009, and the first results on reduction of colorectal cancer incidence and mortality are not expected before the mid-2020s.
We reviewed, summarised, and compared the evidence from published randomised controlled trials and observational studies investigating the effect of screening sigmoidoscopy and screening colonoscopy on colorectal cancer incidence and mortality in the population at average risk for colorectal cancer available to date.
Abstract and Introduction
Abstract
Objectives To review, summarise, and compare the evidence for effectiveness of screening sigmoidoscopy and screening colonoscopy in the prevention of colorectal cancer occurrence and deaths.
Design Systematic review and meta-analysis of randomised controlled trials and observational studies.
Data sources PubMed, Embase, and Web of Science. Two investigators independently extracted characteristics and results of identified studies and performed standardised quality ratings.
Eligibility criteria Randomised controlled trials and observational studies in English on the impact of screening sigmoidoscopy and screening colonoscopy on colorectal cancer incidence and mortality in the general population at average risk.
Results For screening sigmoidoscopy, four randomised controlled trials and 10 observational studies were identified that consistently found a major reduction in distal but not proximal colorectal cancer incidence and mortality. Summary estimates of reduction in distal colorectal cancer incidence and mortality were 31% (95% confidence intervals 26% to 37%) and 46% (33% to 57%) in intention to screen analysis, 42% (29% to 53%) and 61% (27% to 79%) in per protocol analysis of randomised controlled trials, and 64% (50% to 74%) and 66% (38% to 81%) in observational studies. For screening colonoscopy, evidence was restricted to six observational studies, the results of which suggest tentatively an even stronger reduction in distal colorectal cancer incidence and mortality, along with a significant reduction in mortality from cancer of the proximal colon. Indirect comparisons of results of observational studies on screening sigmoidoscopy and colonoscopy suggest a 40% to 60% lower risk of incident colorectal cancer and death from colorectal cancer after screening colonoscopy even though this incremental risk reduction was statistically significant for deaths from cancer of the proximal colon only.
Conclusions Compelling and consistent evidence from randomised controlled trials and observational studies suggests that screening sigmoidoscopy and screening colonoscopy prevent most deaths from distal colorectal cancer. Observational studies suggest that colonoscopy compared with flexible sigmoidoscopy decreases mortality from cancer of the proximal colon. This added value should be examined in further research and weighed against the higher costs, discomfort, complication rates, capacities needed, and possible differences in compliance.
Introduction
Since 1992, several observational studies have suggested a major protective effect of lower gastrointestinal endoscopy (in particular sigmoidoscopy and colonoscopy) against colorectal cancer through detection and removal of precancerous lesions. As a result, and supported by further improvements in technology, use of sigmoidoscopy and colonoscopy for diagnostic and screening purposes has substantially increased in many countries. Both procedures have been recommended as screening options for colorectal cancer by expert committees and offered as primary screening in several European countries (including Germany, Italy, Poland, and Austria) long before the availability of results from randomised controlled trials. Recent studies of trends in incidence and mortality from colorectal cancer suggest that increased use of lower gastrointestinal endoscopy has already led to major reductions in the incidence of and deaths from colorectal cancer in the United States.
Emerging evidence on the protective effects of endoscopy from detection and removal of adenomas also prompted the initiation of several randomised controlled trials to prove the efficacy of endoscopy based screening for reducing colorectal cancer incidence and mortality. In the 1990s four large scale randomised controlled trials began to investigate the effects of screening by flexible sigmoidoscopy, and the first results were published in 2009, 2010, 2011, and 2012. Screening colonoscopy has the potential to prevent colorectal cancer of the entire large bowel but is associated with higher costs, discomfort, complication rates, and capacities needed. Given that colonoscopy is recommended and offered for primary screening in an increasing number of countries, it is important to know its relative effectiveness compared with sigmoidoscopy. The only randomised controlled trial to assess the impact of screening colonoscopy (compared with no screening) on colorectal cancer incidence and mortality started recruitment in 2009, and the first results on reduction of colorectal cancer incidence and mortality are not expected before the mid-2020s.
We reviewed, summarised, and compared the evidence from published randomised controlled trials and observational studies investigating the effect of screening sigmoidoscopy and screening colonoscopy on colorectal cancer incidence and mortality in the population at average risk for colorectal cancer available to date.
SHARE
