title: Screening colonoscopy and risk for incident late-stage colorectal cancer diagnosis in average-risk adults: a nested case-control study.
abstract: BACKGROUND
  The effectiveness of screening colonoscopy in average-risk adults is uncertain, particularly for right colon cancer.
  
  
  OBJECTIVE
  To examine the association between screening colonoscopy and risk for incident late-stage colorectal cancer (CRC).
  
  
  METHODS
  Nested case-control study.
  
  
  METHODS
  Four U.S. health plans.
  
  
  METHODS
  1039 average-risk adults enrolled for at least 5 years in one of the health plans. Case patients were aged 55 to 85 years on their diagnosis date (reference date) of stage IIB or higher (late-stage) CRC during 2006 to 2008. One or 2 control patients were selected for each case patient, matched on birth year, sex, health plan, and prior enrollment duration.
  
  
  METHODS
  Receipt of CRC screening 3 months to 10 years before the reference date, ascertained through medical record audits. Case patients and control patients were compared on receipt of screening colonoscopy or sigmoidoscopy by using conditional logistic regression that accounted for health history, socioeconomic status, and other screening exposures.
  
  
  RESULTS
  In analyses restricted to 471 eligible case patients and their 509 matched control patients, 13 case patients (2.8%) and 46 control patients (9.0%) had undergone screening colonoscopy, which corresponded to an adjusted odds ratio (AOR) of 0.29 (95% CI, 0.15 to 0.58) for any late-stage CRC, 0.36 (CI, 0.16 to 0.80) for right colon cancer, and 0.26 (CI, 0.06 to 1.11; P = 0.069) for left colon/rectum cancer. Ninety-two case patients (19.5%) and 173 control patients (34.0%) had screening sigmoidoscopy, corresponding to an AOR of 0.50 (CI, 0.36 to 0.70) overall, 0.79 (CI, 0.51 to 1.23) for right colon late-stage cancer, and 0.26 (CI, 0.14 to 0.48) for left colon cancer.
  
  
  CONCLUSIONS
  The small number of screening colonoscopies affected the precision of the estimates.
  
  
  CONCLUSIONS
  Screening with colonoscopy in average-risk persons was associated with reduced risk for diagnosis of incident late-stage CRC, including right-sided colon cancer. For sigmoidoscopy, this association was seen for left CRC, but the association for right colon late-stage cancer was not statistically significant.
authors: Department of Family Medicine and Community Health, Perelman School of Medicine, University of Pennsylvania, 3400 Spruce Street, Gates 2, Philadelphia, PA 19104, USA. chyke.doubeni@uphs.upenn.edu
authors: Chyke A
authors: CA
authors: Doubeni
authors: Sheila
authors: S
authors: Weinmann
authors: Kenneth
authors: K
authors: Adams
authors: Aruna
authors: A
authors: Kamineni
authors: Diana S M
authors: DS
authors: Buist
authors: Arlene S
authors: AS
authors: Ash
authors: Carolyn M
authors: CM
authors: Rutter
authors: V Paul
authors: VP
authors: Doria-Rose
authors: Douglas A
authors: DA
authors: Corley
authors: Robert T
authors: RT
authors: Greenlee
authors: Jessica
authors: J
authors: Chubak
authors: Andrew
authors: A
authors: Williams
authors: Aimee R
authors: AR
authors: Kroll-Desrosiers
authors: Eric
authors: E
authors: Johnson
authors: Joseph
authors: J
authors: Webster
authors: Kathryn
authors: K
authors: Richert-Boe
authors: Theodore R
authors: TR
authors: Levin
authors: Robert H
authors: RH
authors: Fletcher
authors: Noel S
authors: NS
authors: Weiss
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D016022:Case-Control Studies; D003113:Colonoscopy / Q000191:economics; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000473:pathology / Q000517:prevention & control; D055088:Early Detection of Cancer / Q000191:economics; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D008403:Mass Screening / Q000191:economics; D008875:Middle Aged; D009367:Neoplasm Staging; D012307:Risk Factors; D012680:Sensitivity and Specificity; D012812:Sigmoidoscopy