title: Systematic review and meta-analysis of the evidence for flexible sigmoidoscopy as a screening method for the prevention of colorectal cancer.
abstract: BACKGROUND
  Colorectal cancer is a significant cause of death. Removal of precancerous adenomas, and early detection and treatment of cancer, has been shown to reduce the risk of death. The aim of this review and meta-analysis was to determine whether flexible sigmoidoscopy (FS) is an effective population screening method for reducing mortality from colorectal cancer.
  
  
  METHODS
  MEDLINE (1946 to December 2012) and Embase (1980-2012, week 15) were searched for randomized clinical trials in which FS was used to screen non-symptomatic adults from a general population, and FS was compared with either no screening or any other alternative screening methods. Meta-analysis was carried out using a random-effects Mantel-Haenzsel model.
  
  
  RESULTS
  Twenty-four papers met the inclusion criteria, reporting results from 14 trials. Uptake of FS was usually lower than that for stool-based tests, although FS was more effective at detecting advanced adenoma and carcinoma. FS reduced the incidence of colorectal cancer after screening, and long-term mortality from colorectal cancer, compared with no screening in a selected population. Compared with stool-based tests in a general population, FS was associated with fewer interval cancers.
  
  
  CONCLUSIONS
  FS is efficacious at reducing colorectal cancer mortality compared with no screening. It is more effective at detecting advanced adenoma and carcinoma than stool-based tests. FS may be compromised by poorer uptake. Introduction of FS as a screening method should be done on a pilot basis in populations in which it is not currently used, and close attention should be paid to maximizing uptake. The relative risk of adverse events with FS compared with stool-based tests should be quantified, and its real-world effectiveness evaluated against the most effective stool-based tests.
authors.affiliation: NHS Grampian, Institute of Applied Health Sciences, University of Aberdeen, School of Medicine and Dentistry, Foresterhill, Aberdeen, UK. chris.littlejohn@nhs.net
authors.forename: C
authors.initials: C
authors.lastname: Littlejohn
authors.forename: S
authors.initials: S
authors.lastname: Hilton
authors.forename: G J
authors.initials: GJ
authors.lastname: Macfarlane
authors.forename: P
authors.initials: P
authors.lastname: Phull
mesh_terms: D000236:Adenoma / Q000517:prevention & control; D015179:Colorectal Neoplasms / Q000517:prevention & control*; D055088:Early Detection of Cancer / Q000295:instrumentation / Q000379:methods / Q000706:statistics & numerical data; D006801:Humans; D007159:Immunologic Tests; D009780:Occult Blood; D010342:Patient Acceptance of Health Care / Q000706:statistics & numerical data; D016032:Randomized Controlled Trials as Topic; D012812:Sigmoidoscopy / Q000295:instrumentation / Q000379:methods*