title: Results of repeat sigmoidoscopy 3 years after a negative examination.
abstract: BACKGROUND
  The necessary frequency of endoscopic colorectal cancer screening after a negative examination is uncertain.
  
  
  OBJECTIVE
  To examine the yield of adenomas and cancer in the distal colon found by repeat flexible sigmoidoscopy (FSG) 3 years after a negative examination.
  
  
  METHODS
  Participants were drawn from the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial (PLCO), a randomized, controlled community-based study of cancer screening. The mean (SD) age was 65.7 (4.0) years at study entry (1993-1995) and 61.6% were men. Individuals underwent screening FSG at baseline and at 3 years as part of the protocol and were referred to their personal physicians for further evaluation of screen-detected abnormalities. Results from subsequent diagnostic evaluations were tracked in a standardized fashion. Of 11 583 eligible for repeat screening FSG 3 years after an initial negative examination, 9317 (80.4%) returned.
  
  
  METHODS
  Polyp or mass detection in distal colon at year 3 repeat FSG; incidence of adenoma or cancer in distal colon at year 3 examination; determination of reason for detection (increased depth of insertion or improved preparation at the year 3 examination or detection in a previously examined area).
  
  
  RESULTS
  A total of 1292 returning participants (13.9%) had a polyp or mass detected by FSG 3 years after the initial examination. In the distal colon, 3.1% (292/9317) were found to have an adenoma or cancer. The incidence of advanced adenoma (n = 72) or cancer (n = 6) in the distal colon was 78 (0.8%) of 9317. Of individuals with advanced distal adenomas detected at the year 3 examination, 80.6% (58/72) had lesions found in a portion of the colon that had been adequately examined at the initial sigmoidoscopy.
  
  
  CONCLUSIONS
  Repeat FSG 3 years after a negative examination will detect advanced adenomas and distal colon cancer. Although the overall percentage with detected abnormalities is modest, these data raise concern about the impact of a prolonged screening interval after a negative examination.
authors.affiliation: Department of Medicine, University of Pittsburgh Cancer Institute, University of Pittsburgh, Pittsburgh, PA, USA. rschoen@pitt.edu
authors.forename: Robert E
authors.initials: RE
authors.lastname: Schoen
authors.forename: Paul F
authors.initials: PF
authors.lastname: Pinsky
authors.forename: Joel L
authors.initials: JL
authors.lastname: Weissfeld
authors.forename: Robert S
authors.initials: RS
authors.lastname: Bresalier
authors.forename: Timothy
authors.initials: T
authors.lastname: Church
authors.forename: Philip
authors.initials: P
authors.lastname: Prorok
authors.forename: John K
authors.initials: JK
authors.lastname: Gohagan
mesh_terms: D000236:Adenoma / Q000175:diagnosis* / Q000453:epidemiology; D000368:Aged; D003110:Colonic Neoplasms / Q000175:diagnosis* / Q000453:epidemiology; D003111:Colonic Polyps / Q000175:diagnosis; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D016032:Randomized Controlled Trials as Topic; D012812:Sigmoidoscopy; D013997:Time Factors