title: Time to benefit for colorectal cancer screening: survival meta-analysis of flexible sigmoidoscopy trials.
abstract: OBJECTIVE
  To determine the time to benefit of using flexible sigmoidoscopy for colorectal cancer screening.
  
  
  METHODS
  Survival meta-analysis.
  
  
  METHODS
  A Cochrane Collaboration systematic review published in 2013, Medline, and Cochrane Library databases.
  
  
  METHODS
  Randomized controlled trials comparing screening flexible sigmoidoscopy with no screening. Trials with fewer than 100 flexible sigmoidoscopy screenings were excluded.
  
  
  RESULTS
  Four studies were eligible (total n = 459,814). They were similar for patients' age (50-74 years), length of follow-up (11.2-11.9 years), and relative risk for colorectal cancer related mortality (0.69-0.78 with flexible sigmoidoscopy screening). For every 1000 people screened at five and 10 years, 0.3 and 1.2 colorectal cancer related deaths, respectively, were prevented. It took 4.3 years (95% confidence interval 2.8 to 5.8) to observe an absolute risk reduction of 0.0002 (one colorectal cancer related death prevented for every 5000 flexible sigmoidoscopy screenings). It took 9.4 years (7.6 to 11.3) to observe an absolute risk reduction of 0.001 (one colorectal cancer related death prevented for every 1000 flexible sigmoidoscopy screenings).
  
  
  CONCLUSIONS
  Our findings suggest that screening flexible sigmoidoscopy is most appropriate for older adults with a life expectancy greater than approximately 10 years.
authors.affiliation: San Francisco VA Medical Center, San Francisco, CA 94121, USA Victoria.Tang@ucsf.edu.
authors.forename: Victoria
authors.initials: V
authors.lastname: Tang
authors.affiliation: San Francisco VA Medical Center, San Francisco, CA 94121, USA Division of Geriatrics, University of California San Francisco CA, USA.
authors.forename: W John
authors.initials: WJ
authors.lastname: Boscardin
authors.affiliation: San Francisco VA Medical Center, San Francisco, CA 94121, USA Division of Geriatrics, University of California San Francisco CA, USA.
authors.forename: Irena
authors.initials: I
authors.lastname: Stijacic-Cenzer
authors.affiliation: San Francisco VA Medical Center, San Francisco, CA 94121, USA Division of Geriatrics, University of California San Francisco CA, USA.
authors.forename: Sei J
authors.initials: SJ
authors.lastname: Lee
mesh_terms: D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000401:mortality; D055088:Early Detection of Cancer / Q000379:methods*; D006801:Humans; D015233:Models, Statistical; D009010:Monte Carlo Method; D016032:Randomized Controlled Trials as Topic; D012812:Sigmoidoscopy / Q000379:methods; D016019:Survival Analysis