The relative effectiveness of fecal immunochemical test-based colorectal cancer screening to detect adenomas and cancer in different demographic and socioeconomic groups. A nationwide cohort study.

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 [RR women = 6.41 (95% confidence interval [CI]: 5.08-8.09), RR men = 7.74 (95% CI: 6.16-9.73), P < 0.01] and among Danes compared with immigrants [RR Danes = 4.71 (95% CI: 3.73-5.93), RR Western = 4.76 (95% CI: 3.39-6.69), RR non-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 (RR women = 1.75 (95% CI: 1.10-2.76), RR men = 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.