Colorectal cancer mortality after randomized implementation of FIT-based screening - a nationwide cohort study.

Objective: Evidence of reduction in colorectal cancer (CRC) mortality following CRC screening based on the faecal immunochemical test (FIT) is insufficient. This study aimed to analyse if CRC mortality was reduced after implementing FIT-based screening.

Setting: The Danish national CRC screening programme.

Methods: This nationwide cohort study included residents aged 50-71 years invited to the prevalence round of the screening programme. Invitation order was decided by randomising on birth month; the first two birth months to be invited were classified as invited and the five last were classified as not-yet-invited and given a pseudo invitation data. Follow-up was from (pseudo)invitation date until 31 December 2017, emigration or death. Relative risk (RR) of CRC death was calculated with 95% confidence intervals (CIs).

Results: A total of 897,812 residents were included (29% invited and 71% not-yet-invited). The median follow-up was 3.3 years. The RR of CRC death at end of follow-up was 0.83 (95% CI 0.66; 1.03) among those invited to screening compared with those not yet invited. For men aged 60-71 years, this RR was 0.68 (95% CI 0.49; 0.94). For those participating in screening compared with a similar group of not-yet-invited residents, the RR was 0.71 (95% CI 0.46-1.08). For male participants aged 60-71 years, this RR was 0.49 (95% CI 0.27-0.89). For women and men aged 50-59 years, RRs were small and statistically non-significant.

Conclusion: This nationwide study showed that even within a median follow-up of only 3.3 years, implementing FIT-based CRC screening reduced CRC mortality among older men.