title: Smoking, lower gastrointestinal endoscopy, and risk for colorectal cancer.
abstract: BACKGROUND
  Lower gastrointestinal endoscopy can decrease colorectal cancer risk strongly through detection and removal of adenomas. Thus, we aimed to investigate whether utilization of lower gastrointestinal endoscopy modifies the effect of lifetime smoking exposure on colorectal cancer risk in a population-based case-control study.
  
  
  METHODS
  In this study from Southern Germany including 2,916 patients with colorectal cancer and 3,044 controls, information about lifetime smoking and other risk factors was obtained from standardized interviews. Self-reported endoscopies were validated by medical records. Multivariate logistic regression was performed to investigate associations of smoking with colorectal cancer risk after stratification by utilization of lower gastrointestinal endoscopy in the preceding 10 years.
  
  
  RESULTS
  Median age of patients and controls was 69 and 70 years, respectively. Former regular smoking was associated with increased colorectal cancer risk in the group with no previous endoscopy [adjusted OR, 1.50; 95% confidence interval (CI), 1.28-1.75], whereas no association was found in the group with preceding endoscopy (OR, 1.05; CI, 0.83-1.33; P for interaction <0.01). Lower gastrointestinal endoscopy did not modify the association of smoking and colorectal cancer risk among current smokers and among the more recent quitters.
  
  
  CONCLUSIONS
  Our results suggest that the increased risk of colorectal cancer among former regular smokers is essentially overcome by detection and removal of adenomas at lower gastrointestinal endoscopy. However, risk of colorectal cancer was increased if smoking was continued into higher adult age.
  
  
  CONCLUSIONS
  The strong protective effect of lower gastrointestinal endoscopy may be compromised by continued smoking. Smoking cessation may increase the efficacy of lower gastrointestinal endoscopy.
authors.affiliation: Authors' Affiliations: Division of Clinical Epidemiology and Aging Research; Institute of Medical Biometry and Informatics, University of Heidelberg and; Unit of Genetic Epidemiology, German Cancer Research Center, Heidelberg, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Hoffmeister
authors.forename: Lina
authors.initials: L
authors.lastname: Jansen
authors.forename: Christian
authors.initials: C
authors.lastname: Stock
authors.forename: Jenny
authors.initials: J
authors.lastname: Chang-Claude
authors.forename: Hermann
authors.initials: H
authors.lastname: Brenner
mesh_terms: D000368:Aged; D016022:Case-Control Studies; D015179:Colorectal Neoplasms / Q000175:diagnosis / Q000453:epidemiology*; D016099:Endoscopy, Gastrointestinal / Q000379:methods / Q000706:statistics & numerical data*; D005260:Female; D005858:Germany / Q000453:epidemiology; D006801:Humans; D008297:Male; D012307:Risk Factors; D012907:Smoking / Q000009:adverse effects / Q000453:epidemiology*