LAUSR

Introduction This study aimed at analyzing the relative effectiveness in removal of adenomas and detection of cancer of implementing colorectal cancer (CRC) screening in different demographic and socioeconomic groups. Methods This register-based retrospective cohort study included residents aged 50–72 years. Those randomly selected to be invited for CRC screening from 1 March 2014 to 30 June 2015 were classified as invited; those invited from 1 January 2016 to 31 December 2017 were classified as not yet invited. Strata-specific relative risks (RRs) of having adenomas removed and CRC detected were estimated. Results A total of 1 343 090 individuals were included. The RR of having adenomas removed were higher among men compared with women [RRwomen = 6.41 (95% confidence interval [CI]: 5.08–8.09), RRmen = 7.74 (95% CI: 6.16–9.73), P < 0.01] and among Danes compared with immigrants [RRDanes = 4.71 (95% CI: 3.73–5.93), RRWestern = 4.76 (95% CI: 3.39–6.69), RRnon-Western = 3.35 (95% CI: 2.39–4.69), P = 0.03]. Regarding detection of CRC, the effectiveness increased with increasing age ranging from RR = 1.53 (95% CI: 0.93– 2.51) to RR = 1.97 (95% CI: 1.22–3.17) (P = 0.04) and was higher among men compared with women (RRwomen = 1.75 (95% CI: 1.10–2.76), RRmen = 2.07 (95% CI: 1.32–3.26), P = 0.02. Conclusion Attention must be paid to the potential differences in screening effectiveness among diverse subpopulations; first, by securing equal opportunities for participation across subpopulations and second, by considering sex and age-specific screening programs.