title: Current status of screening for colorectal cancer.
abstract: BACKGROUND
  Colorectal cancer (CRC) is a leading cause of cancer morbidity and mortality. A well-defined precursor lesion (adenoma) and a long preclinical course make CRC a candidate for screening. This paper reviews the current evidence for the most important tests that are widely used or under development for population-based screening.
  
  
  METHODS
  In this narrative review, we scrutinized all papers we have been aware of, and carried out searches in PubMed and Cochrane library for relevant literature.
  
  
  RESULTS
  Two screening methods have been shown to reduce CRC mortality in randomised trials: repetitive faecal occult blood testing (FOBT) reduces CRC mortality by 16%; once-only flexible sigmoidoscopy (FS) by 28%. FS screening also reduces CRC incidence (by 18%), FOBT does not. Colonoscopy screening has a potentially larger effect on CRC incidence and mortality, but randomised trials are lacking. New screening methods are on the horizon but need to be tested in large clinical trials before implementation in population screening.
  
  
  CONCLUSIONS
  FS screening reduces CRC incidence and CRC mortality by removal of adenomas; FOBT reduces CRC mortality by early detection of cancer. Several other tests are available, but none has been evaluated in randomised trials. Screening strategies differ considerably across countries.
authors.affiliation: Department of Medicine, Sørlandet Hospital, Kristiansand, Norway. kjetil.garborg@sshf.no
authors.forename: K
authors.initials: K
authors.lastname: Garborg
authors.forename: Ø
authors.initials: Ø
authors.lastname: Holme
authors.forename: M
authors.initials: M
authors.lastname: Løberg
authors.forename: M
authors.initials: M
authors.lastname: Kalager
authors.forename: H O
authors.initials: HO
authors.lastname: Adami
authors.forename: M
authors.initials: M
authors.lastname: Bretthauer
mesh_terms: D000236:Adenoma / Q000175:diagnosis; D014408:Biomarkers, Tumor / Q000032:analysis / Q000235:genetics; D003113:Colonoscopy; D015179:Colorectal Neoplasms / Q000175:diagnosis* / Q000401:mortality / Q000517:prevention & control*; D055088:Early Detection of Cancer; D006801:Humans; D008403:Mass Screening / Q000379:methods*; D009780:Occult Blood; D010349:Patient Compliance; D012680:Sensitivity and Specificity; D012812:Sigmoidoscopy
chemical_list: D014408:Biomarkers, Tumor
keywords: adenoma; colonoscopy; colorectal cancer; prevention; screening