Long-term Effectiveness of Endoscopic Screening on Incidence and Mortality of Colorectal Cancer: A Randomized Trial

Background: Due to few randomized trials, there is uncertainty about the long-time effect of endoscopic screening on colorectal cancer (CRC) incidence and mortality.

Aim: To evaluate the long-term effect of endoscopic screening on CRC incidence and mortality, we performed a population-based randomized controlled trial in Norway.

Materials And Methods: In 1983, 799 Norwegian men and women, age 50-59 years were drawn from the population registry and randomly assigned to flexible sigmoidoscopy screening (400 individuals), or no screening (399 individuals). Colonoscopy surveillance was offered after two and six years for all polyp-bearers in the screening group. In 1996, both groups were offered colonoscopy. Only individuals with advanced adenomas at colonoscopy in 1996 were recommended surveillance. All individuals were followed through Norwegian registries until 2008. Hazard ratios (HR) for CRC incidence, and CRC and overall mortality rates were calculated.

Results: During 26 years of follow up (17,327 person-years), 26 colorectal cancers were observed: seven in the screening group and 19 in the control group (HR in screening group 0.40, 95% CI 0.17-0.95, p = 0.04). Eight individuals died of colorectal cancer; one in the screening group and seven in the control group (HR 0.16, 95% CI 0.02-1.28, p = 0.08).

Conclusions: This first randomized trial on the long-term effect of endoscopic screening shows reduced CRC incidence and mortality if screening is combined with rigorous surveillance for individuals with polyps. Colonoscopy screening without such surveillance may not be effective.