title: Population-based surveillance by colonoscopy: effect on the incidence of colorectal cancer. Telemark Polyp Study I.
abstract: BACKGROUND
  Most cases of colorectal cancer (CRC) develop from adenomas. Polypectomy is believed to reduce the incidence of CRC, but this effect has never been explored in prospective controlled studies. The aim of the present study was to evaluate the effect of polypectomy on colorectal cancer incidence in a population-based screening program.
  
  
  METHODS
  In 1983, 400 men and women aged 50-59 years were randomly drawn from the population registry of Telemark, Norway. They were offered a flexible sigmoidoscopy and, if polyps were found, a full colonoscopy with polypectomy and follow-up colonoscopies in 1985 and 1989. A control group of 399 individuals was drawn from the same registry. In 1996 both groups (age, 63-72 years) were invited to have a colonoscopic examination. Hospital files and the files of The Norwegian Cancer Registry were searched to register any cases of CRC in the period 1983-96.
  
  
  RESULTS
  At screening endoscopy 324 (81%) individuals attended in 1983 and 451 (71%) in 1996. From 1983 to 1996, altogether 10 individuals in the control group and 2 in the screening group were registered to have developed CRC (relative risk, 0.2; 95% confidence interval (CI), 0.03-0.95; P = 0.02). A higher overall mortality was observed in the screening group, with 55 (14%) deaths, compared with 35 (9%) in the control group (relative risk, 1.57; 95% CI, 1.03-2.4; P = 0.03).
  
  
  CONCLUSIONS
  Endoscopic screening examination with polypectomy and follow-up was shown to reduce the incidence of CRC in a Norwegian normal population. The possible effect of screening on overall mortality should be addressed in larger studies.
authors.affiliation: Dept. of Medicine, Telemark Central Hospital, Skien, Norway.
authors.forename: E
authors.initials: E
authors.lastname: Thiis-Evensen
authors.forename: G S
authors.initials: GS
authors.lastname: Hoff
authors.forename: J
authors.initials: J
authors.lastname: Sauar
authors.forename: F
authors.initials: F
authors.lastname: Langmark
authors.forename: B M
authors.initials: BM
authors.lastname: Majak
authors.forename: M H
authors.initials: MH
authors.lastname: Vatn
mesh_terms: D000368:Aged; D003111:Colonic Polyps / Q000601:surgery; D003113:Colonoscopy / Q000706:statistics & numerical data*; D015179:Colorectal Neoplasms / Q000453:epidemiology* / Q000517:prevention & control; D005260:Female; D006801:Humans; D015994:Incidence; D008297:Male; D008403:Mass Screening / Q000379:methods* / Q000706:statistics & numerical data; D009664:Norway / Q000453:epidemiology; D011446:Prospective Studies; D012042:Registries / Q000706:statistics & numerical data; D012812:Sigmoidoscopy / Q000706:statistics & numerical data*