title: Colonoscopy is associated with a reduced risk for colon cancer and mortality in patients with inflammatory bowel diseases.
abstract: OBJECTIVE
  Crohn's disease and ulcerative colitis are associated with an increased risk of colorectal cancer (CRC). Surveillance colonoscopy is recommended at 2- to 3-year intervals beginning 8 years after diagnosis of inflammatory bowel disease (IBD). However, there have been no reports of whether colonoscopy examination reduces the risk for CRC in patients with IBD.
  
  
  METHODS
  In a retrospective study, we analyzed data from 6823 patients with IBD (2764 with a recent colonoscopy, 4059 without a recent colonoscopy) seen and followed up for at least 3 years at 2 tertiary referral hospitals in Boston, Massachusetts. The primary outcome was diagnosis of CRC. We examined the proportion of patients undergoing a colonoscopy within 36 months before a diagnosis of CRC or at the end of the follow-up period, excluding colonoscopies performed within 6 months before a diagnosis of CRC, to avoid inclusion of prevalent cancers. Multivariate logistic regression was performed, adjusting for plausible confounders.
  
  
  RESULTS
  A total of 154 patients developed CRC. The incidence of CRC among patients without a recent colonoscopy (2.7%) was significantly higher than among patients with a recent colonoscopy (1.6%) (odds ratio [OR], 0.56; 95% confidence interval [CI], 0.39-0.80). This difference persisted in multivariate analysis (OR, 0.65; 95% CI, 0.45-0.93) and was robust when adjusted for a range of assumptions in sensitivity analyses. Among patients with CRC, a colonoscopy within 6 to 36 months before diagnosis was associated with a reduced mortality rate (OR, 0.34; 95% CI, 0.12-0.95).
  
  
  CONCLUSIONS
  Recent colonoscopy (within 36 months) is associated with a reduced incidence of CRC in patients with IBD, and lower mortality rates in those diagnosed with CRC.
authors.affiliation: Division of Gastroenterology, Massachusetts General Hospital, Boston, Massachusetts; Harvard Medical School, Boston, Massachusetts; Department of Medicine, Massachusetts General Hospital, Boston, Massachusetts. Electronic address: aananthakrishnan@mgh.harvard.edu.
authors.forename: Ashwin N
authors.initials: AN
authors.lastname: Ananthakrishnan
authors.affiliation: Research IS and Computing, Partners HealthCare, Charlestown, Massachusetts.
authors.forename: Andrew
authors.initials: A
authors.lastname: Cagan
authors.affiliation: Department of Biostatistics, Harvard School of Public Health, Boston, Massachusetts.
authors.forename: Tianxi
authors.initials: T
authors.lastname: Cai
authors.affiliation: Research IS and Computing, Partners HealthCare, Charlestown, Massachusetts.
authors.forename: Vivian S
authors.initials: VS
authors.lastname: Gainer
authors.affiliation: Harvard Medical School, Boston, Massachusetts; Department of Medicine, Massachusetts General Hospital, Boston, Massachusetts; Center for Systems Biology, Massachusetts General Hospital, Boston, Massachusetts.
authors.forename: Stanley Y
authors.initials: SY
authors.lastname: Shaw
authors.affiliation: i2b2 National Center for Biomedical Computing, Brigham and Women's Hospital, Boston, Massachusetts.
authors.forename: Susanne
authors.initials: S
authors.lastname: Churchill
authors.affiliation: Harvard Medical School, Boston, Massachusetts; Division of Rheumatology, Allergy and Immunology, Brigham and Women's Hospital, Boston, Massachusetts.
authors.forename: Elizabeth W
authors.initials: EW
authors.lastname: Karlson
authors.affiliation: Harvard Medical School, Boston, Massachusetts; Department of Medicine, Massachusetts General Hospital, Boston, Massachusetts; i2b2 National Center for Biomedical Computing, Brigham and Women's Hospital, Boston, Massachusetts; Department of Neurology, Massachusetts General Hospital, Boston, Massachusetts.
authors.forename: Shawn N
authors.initials: SN
authors.lastname: Murphy
authors.affiliation: Harvard Medical School, Boston, Massachusetts; i2b2 National Center for Biomedical Computing, Brigham and Women's Hospital, Boston, Massachusetts; Children's Hospital Boston, Boston, Massachusetts.
authors.forename: Isaac
authors.initials: I
authors.lastname: Kohane
authors.affiliation: Harvard Medical School, Boston, Massachusetts; Division of Rheumatology, Allergy and Immunology, Brigham and Women's Hospital, Boston, Massachusetts.
authors.forename: Katherine P
authors.initials: KP
authors.lastname: Liao
mesh_terms: D000328:Adult; D001900:Boston; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000517:prevention & control*; D005260:Female; D006801:Humans; D015994:Incidence; D015212:Inflammatory Bowel Diseases / Q000150:complications*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D018570:Risk Assessment
keywords: CD; Colon Cancer; Early Detection; Risk Factor; Screening; UC