Contributions of early detection and cancer prevention to colorectal cancer mortality reduction by screening colonoscopy: a validated modelling study

Abstract

Background and aimsScreening colonoscopy, recommended every ten years, reduces mortality from colorectal cancer (CRC) by early detection of prevalent but undiagnosed CRC, as well as by prevention of CRC by removal of precursor lesions. The aim of this study was to assess the relative contribution of both components to total CRC mortality reduction over time. MethodsUsing a validated multistate Markov model, we simulated hypothetical cohorts of 100,000 individuals aged 55-64 with and without use of screening at baseline. Main outcomes included proportions of prevented CRC deaths arising from (asymptomatic) CRC already prevalent at baseline and from newly developed CRC during 15-years of follow-up, and mortality rate ratios of screened versus unscreened groups over time. ResultsEarly detection of prevalent cases accounted for 52%, 30% and 18% of deaths prevented by screening colonoscopy within 5, 10 and 15 years, respectively. Relative reduction of mortality was estimated to be much larger for mortality from incident cancers than for mortality from cancers that were already present and early detected at screening endoscopy and for total CRC mortality (i.e., 88% versus 67% and 79% within 10 years from screening). ConclusionsReduction of CRC mortality mainly arises from early detection of prevalent cancers during the early years after screening colonoscopy, but prevention of incident cases accounts for the majority of prevented deaths in the longer run. Prevention of incident cases leads to sustained strong reduction of colorectal cancer mortality, possibly warranting an extension of screening intervals.