Population-based surveillance by colonoscopy: Effect on the incidence of colorectal cancer - Telemark Polyp Study I

Background: Most cases of colorectal cancer (CRC) develop from adenomas, Po lypectomy is believed to reduce the incidence of CRC, but this effect has n ever been explored in prospective controlled studies. The aim of the presen t study was to evaluate the effect of polypectomy on colorectal cancer inci dence in a population-based screening program. Methods: In 1983, 400 men an d women aged 50-59 years were randomly drawn from the population registry o f Telemark, Norway. They were offered ii flexible sigmoidoscopy and, if pol yps were found, a full colonoscopy with polypectomy and follow-up colonosco pies in 1985 and 1989. A control group of 399 individuals was drawn from th e same registry. in 1996 both groups (age, 63-72 years) were invited to hav e a colonoscopic examination. Hospital files and the files of The Norwegian Cancer Registry were searched to register any cases of CRC in the period 1 983-96, Results: At screening endoscopy 324 (81%) individuals attended in 1 983 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 deve loped 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, wit h 55 (14%) deaths, compared with 35 (9%) in the control group (relative ris k, 1.57; 95% CI, 1.03-2.4; P=0.03). Conclusion: Endoscopic screening examin ation with polypectomy and follow-up was shown to reduce the incidence of C RC in a Norwegian normal population. The possible effect of screening on ov erall mortality should be addressed in larger studies.