title: Yield of advanced adenoma and cancer based on polyp size detected at screening flexible sigmoidoscopy.
abstract: OBJECTIVE
  Observational screening of the colon with subsequent referral for colonoscopy raises questions about the threshold of polyp size that necessitates referral. To examine the yield at colonoscopy when a given size lesion is observed, we assessed the yield of advanced adenoma and cancer at colonoscopy based on the size of the abnormality detected at flexible sigmoidoscopy (FSG).
  
  
  METHODS
  We used data from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial, a randomized, controlled, community-based study of FSG.
  
  
  RESULTS
  Subsequent colonoscopy was performed on 10,850 subjects (60.4% male; mean age, 62.9 years) with a polyp visualized on screening FSG. For women with a polyp 0.5-0.9 cm on FSG (n = 1426), the yield in the distal colon on colonoscopy was 0.6% for cancer (number needed to screen [NNS] = 166) and 14.5% for advanced adenoma (NNS = 7). In men (n = 2183), the yield was 0.7% (NNS = 142) for cancer and 15.9% (NNS = 6) for advanced adenoma. Among persons with polyps 0.5-0.9 cm identified on FSG, 5.5% (198/3609) had distal advanced adenomas that measured <1.0 cm but had villous histology or high-grade dysplasia, and 9.9% (357/3609) had adenomas > or =1 cm.
  
  
  CONCLUSIONS
  The yield for a distal advanced adenomatous lesion when a polyp 0.5-0.9 cm is observed at FSG is substantial and is due to the presence of advanced histology in polyps <1 cm and to detection of polyps that measure > or =1.0 cm on colonoscopy. Establishing thresholds for observation versus evaluation will require careful assessment of the overall yield.
authors.affiliation: Department of Medicine, University of Pittsburgh, Pittsburgh, Pennsylvani 15213-2582, USA. rschoen@pitt.edu
authors.forename: Robert E
authors.initials: RE
authors.lastname: Schoen
authors.forename: Joel L
authors.initials: JL
authors.lastname: Weissfeld
authors.forename: Paul F
authors.initials: PF
authors.lastname: Pinsky
authors.forename: Thomas
authors.initials: T
authors.lastname: Riley
mesh_terms: D000236:Adenoma / Q000175:diagnosis* / Q000473:pathology*; D000368:Aged; D003110:Colonic Neoplasms / Q000175:diagnosis* / Q000473:pathology*; D003111:Colonic Polyps / Q000473:pathology*; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D008403:Mass Screening / Q000379:methods; D008875:Middle Aged; D016032:Randomized Controlled Trials as Topic; D012812:Sigmoidoscopy / Q000379:methods*