title: Likely effect of adding flexible sigmoidoscopy to the English NHS Bowel Cancer Screening Programme: impact on colorectal cancer cases and deaths.
abstract: BACKGROUND
  From 2013, once-only flexible sigmoidoscopy (FS) at age 55 is being phased into the England National Health Service Bowel Cancer Screening Programme (NHSBCSP), augmenting biennial guaiac faecal occult blood testing (gFOBT) at ages 60-74. Here, we project the impact of this change on colorectal cancer (CRC) cases and deaths prevented in England by mid-2030.
  
  
  METHODS
  We simulated the life-course of English residents reaching age 55 from 2013 onwards. Model inputs included population numbers, invitation rates and CRC incidence and mortality rates. The impact of gFOBT and FS alone on CRC incidence and mortality were derived from published trials, assuming an uptake of 50% for FS and 57% for gFOBT. For FS plus gFOBT, we assumed the gFOBT effect to be 75% of the gFOBT alone impact.
  
  
  RESULTS
  By mid-2030, 8.5 million individuals will have been invited for once-only FS screening. Adding FS to gFOBT screening is estimated to prevent an extra 9627 (-10%) cases and 2207 (-12%) deaths by mid-2030. If FS uptake is 38% or 71%, respectively, an extra 7379 (-8%) or 13 689 (-15%) cases and 1691 (-9%) or 3154 (-17%) deaths will be prevented by mid-2030.
  
  
  CONCLUSIONS
  Adding once-only FS at age 55 to the NHSBCSP will prevent ∼10,000 CRC cases and ∼2000 CRC deaths by mid-2030 if FS uptake is 50%. In 2030, one cancer was estimated to be prevented per 150 FS screening episodes, and one death prevented per 900 FS screening episodes. The actual reductions will depend on the FS invitation schedule and uptake rates.
authors.affiliation: 1] Policy Research Unit in Cancer Awareness, Screening and Early Diagnosis, Centre for Cancer Prevention, Wolfson Institute of Preventive Medicine, Queen Mary University of London, London, UK [2] Radboud university medical center, Radboud Institute for Health Sciences, Nijmegen, The Netherlands.
authors.forename: S M E
authors.initials: SM
authors.lastname: Geurts
authors.affiliation: Policy Research Unit in Cancer Awareness, Screening and Early Diagnosis, Centre for Cancer Prevention, Wolfson Institute of Preventive Medicine, Queen Mary University of London, London, UK.
authors.forename: N J
authors.initials: NJ
authors.lastname: Massat
authors.affiliation: Policy Research Unit in Cancer Awareness, Screening and Early Diagnosis, Centre for Cancer Prevention, Wolfson Institute of Preventive Medicine, Queen Mary University of London, London, UK.
authors.forename: S W
authors.initials: SW
authors.lastname: Duffy
mesh_terms: D015179:Colorectal Neoplasms / Q000175:diagnosis*; D004739:England; D008403:Mass Screening / Q000706:statistics & numerical data*; D012812:Sigmoidoscopy / Q000379:methods*; D006113:United Kingdom