title: Screening based on risk for colorectal cancer is the most cost-effective approach.
abstract: OBJECTIVE
  Performing single endoscopic examinations or selective screening based on risk might be more practical than recommended screening strategies for colorectal cancer (CRC). We investigated the cost effectiveness of these strategies, under real-life conditions of suboptimal compliance, and the societal cost perspective.
  
  
  METHODS
  We used Markov modeling to analyze data from 787,000 individuals in Singapore, aged 50 to 75 years, with an age-standardized rate of CRC of 30 to 40/100,000 in 2009. Potential outcomes, incremental cost-effectiveness ratio, and net health benefit were compared between single sigmoidoscopy or colonoscopy and current recommended screening strategies, and also with a strategy of selective screening based on risk of CRC.
  
  
  RESULTS
  Performing single sigmoidoscopies on individuals when they are 60 years old was the cheapest screening strategy; it would reduce CRC incidence by 19% and mortality by 16%, compared with no screening. A single colonoscopy is less cost effective than a single sigmoidoscopy, unless the proportion of right-sided lesions exceeds 65%. The fecal occult blood test (iFOBT) had the lowest incremental cost-effectiveness ratio when all strategies were compared with no screening; iFOBT and colonoscopic examinations every 10 years each had extended dominance over other strategies. Screening subjects 50 to 60 years old by iFOBT and subjects 60 to 72 years old with colonoscopies every 10 years was the most cost-effective strategy (US$25,000/quality-adjusted life-years). Risk for CRC, adherence, and cost of colonoscopy were the main determinants of cost effectiveness, based on sensitivity analysis.
  
  
  CONCLUSIONS
  Markov modeling analysis indicates that selectively screening individuals for CRC based on risk is the most cost-effective approach; it limits the cost and number of colonoscopies needed and significantly reduces CRC mortality.
authors.affiliation: Department of Medicine, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: Yock Young
authors.initials: YY
authors.lastname: Dan
authors.forename: Benjamin Y S
authors.initials: BY
authors.lastname: Chuah
authors.forename: Dean C S
authors.initials: DC
authors.lastname: Koh
authors.forename: Khay Guan
authors.initials: KG
authors.lastname: Yeoh
mesh_terms: D000328:Adult; D000368:Aged; D001774:Blood Chemical Analysis; D003113:Colonoscopy / Q000191:economics / Q000379:methods; D015179:Colorectal Neoplasms / Q000175:diagnosis*; D003362:Cost-Benefit Analysis; D055088:Early Detection of Cancer / Q000191:economics* / Q000379:methods*; D005243:Feces / Q000737:chemistry; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015233:Models, Statistical; D012846:Singapore