Colorectal cancer is a major health burden. Screening is recommended in many countries.
Dr Řyvind Holme and colleagues estimated the effectiveness of flexible sigmoidoscopy screening on colorectal cancer incidence and mortality in a population-based trial.
The team performed a randomized clinical trial of 100,210 individuals aged 50 to 64 years, identified from the population of Oslo city and Telemark County, Norway.
Screening was performed in 1999-2000, and in 2001, with follow-up ending 2011.
Of those selected, 1415 were excluded due to prior colorectal cancer, emigration, or death, and 3 could not be traced in the population registry.
|Adherence with screening was 63%|
|Journal of the American Medical Association|
The research team invited participants randomized to the screening group to undergo screening.
Within the screening group, participants were randomized 1:1 to receive once-only flexible sigmoidoscopy or combination of once-only flexible sigmoidoscopy, and fecal occult blood testing (FOBT).
The team offered participants with positive screening test results colonoscopy.
The control group received no intervention.
The team's main outcomes included colorectal cancer incidence and mortality.
A total of 98,792 participants were included in the intention-to-screen analyses, of whom 78,220 comprized the control group, and 20,572 comprized the screening group.
The researchers noted that adherence with screening was 63%.
After a median of 11 years, 71 participants died of colorectal cancer in the screening group vs 330 in the control group.
The team diagnosed colorectal cancer in 253 participants in the screening group vs 1086 in the control group.
Colorectal cancer incidence was reduced in both the 50- to 54-year age group, and the 55- to 64-year age group.
The researchers observed no difference between the flexible sigmoidoscopy only vs the flexible sigmoidoscopy and FOBT screening groups.
Dr Holme's team concludes, "In Norway, once-only flexible sigmoidoscopy screening or flexible sigmoidoscopy and FOBT reduced colorectal cancer incidence and mortality on a population level compared with no screening."
"Screening was effective both in the 50- to 54-year and the 55- to 64-year age groups."