A single colonoscopy significantly reduced colorectal cancer incidence but did not lower mortality over 13 years, according to updated results from an ongoing randomized controlled trial.
The population-based trial enrolled 84,583 men and women, aged 55 to 64, from Norway, Poland, and Sweden. Participants were assigned to either a colonoscopy screening group or a no-screening group.
After 13 years, colorectal cancer incidence was 1.46% in the screening group versus 1.80% in the no-screening group. The protective effect was more pronounced for distal cancers and in men. Among women, the difference was smaller.
However, colorectal cancer mortality was not significantly different: 0.41% in the screening group and 0.47% in the no-screening group. This is far below the 0.82% mortality rate expected when the trial was designed.
Colonoscopy has long been considered the gold standard for colorectal cancer screening, with observational studies suggesting it cuts incidence and mortality by at least 50%. This study challenges those assumptions.
In an accompanying commentary, Dr. Aasma Shaukat of NYU Grossman School of Medicine said the results compel a recalibration of what colonoscopy can achieve at the population level.