title: Screening colonoscopy versus sigmoidoscopy: implications of a negative examination for cancer prevention and racial disparities in average-risk patients.
abstract: BACKGROUND
  Both colonoscopy and flexible sigmoidoscopy are accepted procedures for colorectal cancer (CRC) screening in the United States.
  
  
  OBJECTIVE
  To compare risk of CRC after negative findings on screening colonoscopy versus sigmoidoscopy and to evaluate racial/ethnic disparities in postscreening CRC.
  
  
  METHODS
  Retrospective, comparative cohort study.
  
  
  METHODS
  Integrated community-based health-care system.
  
  
  METHODS
  Average-risk patients 50 to 75 years of age with negative findings on an initial endoscopic screening examination from January 2000 to December 2010.
  
  
  METHODS
  Colonoscopy versus sigmoidoscopy as the initial screening procedure.
  
  
  METHODS
  Incident cases of CRC identified via a prospective internal cancer registry, risk of CRC determined by Cox regression adjusted for age, sex, race/ethnicity, and comorbidity.
  
  
  RESULTS
  The study cohort included 138,297 patients (42,938 patients with negative findings on colonoscopy and 95,359 with negative findings on sigmoidoscopy). The median age was 57.9 years (interquartile range 53.0-64.1 years). Women comprised 51.8% of the cohort with 42.2% non-Hispanic white patients, 24.1% Hispanic patients, 10.7% non-Hispanic black patients, 9.7% Asian patients, and 13.3% other/unknown. A total of 241 cases of CRC was detected during 553,543 person-years of follow-up. The adjusted hazard ratio (HR) of postscreening CRC was 0.42 (95% confidence interval [CI], 0.28-0.64; P < .0001) for colonoscopy versus sigmoidoscopy. Risk reduction was primarily among proximal tumors (adjusted HR 0.30; 95% CI, 0.16-0.57). Non-Hispanic black patients were at higher risk of postscreening CRC compared with non-Hispanic white patients (adjusted HR 1.71; 95% CI, 1.20-2.42); however, this disparity was noted only in the sigmoidoscopy cohort.
  
  
  CONCLUSIONS
  Retrospective study with potential selection bias and residual confounding.
  
  
  CONCLUSIONS
  Negative screening colonoscopy was associated with decreased incidence of subsequent CRC and a decrease in disparities compared with negative sigmoidoscopy findings in this large, community-based setting.
authors.affiliation: Center for Digestive Health Research, Southern California Permanente Medical Group, Los Angeles, California, USA; Division of Gastroenterology, Kaiser Permanente Los Angeles Medical Center, Los Angeles, California, USA.
authors.forename: Bechien U
authors.initials: BU
authors.lastname: Wu
authors.affiliation: Center for Digestive Health Research, Southern California Permanente Medical Group, Los Angeles, California, USA; Division of Gastroenterology, Kaiser Permanente San Diego Medical Center, San Diego, California, USA.
authors.forename: George F
authors.initials: GF
authors.lastname: Longstreth
authors.affiliation: Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, California, USA.
authors.forename: Eunis W
authors.initials: EW
authors.lastname: Ngor
mesh_terms: D001741:Black or African American / Q000706:statistics & numerical data; D000368:Aged; D001213:Asian / Q000706:statistics & numerical data; D015331:Cohort Studies; D003113:Colonoscopy / Q000379:methods; D015179:Colorectal Neoplasms / Q000453:epidemiology / Q000517:prevention & control*; D055088:Early Detection of Cancer / Q000379:methods*; D005006:Ethnicity / Q000706:statistics & numerical data*; D005260:Female; D054624:Health Status Disparities; D006630:Hispanic or Latino / Q000706:statistics & numerical data; D006801:Humans; D015994:Incidence; D008137:Longitudinal Studies; D008297:Male; D008875:Middle Aged; D016016:Proportional Hazards Models; D012189:Retrospective Studies; D012812:Sigmoidoscopy / Q000379:methods; D014481:United States / Q000453:epidemiology; D044465:White People / Q000706:statistics & numerical data