The impact of diabetes on cancer detection during the prevalence round of a national screening program for colorectal cancer

Abstract

Aims: Diabetes is associated with a higher risk of colorectal cancer (CRC) and inferior survival after CRC. Screening may enable the early detection of CRC. We aimed to assess the impact of diabetes on cancer detection and disease stage during the prevalence round of a national CRC screening program. Methods: We performed a register-based cohort study based on the randomized procedure for inviting Danish residents aged 50–74 years to the prevalence round of national CRC screening program in 2014–2017. By comparing the random half of the population who had been invited by 1 May 2016 with the not yet invited half, the effect of screening was assessed by the detection of CRC and disease stage among individuals with and without diabetes. Further, the impact of diabetes on the screening participation rate was calculated. Results: By randomisation, 504,673 individuals had been invited to the CRC screening by 1 May 2016, and 549,359 individuals had not yet been invited. The diabetes prevalence was 10% in both groups. When comparing those not yet invited to those invited, the effect of screening on the number of detected cancers per 100,000 individuals was higher in those with diabetes (from 207 to 494 cancers) than in those without diabetes (from 147 to 364 cancers), and screening resulted in overall higher proportions of stage I cancer. Among those invited to screening, the participation rate was 9.1% lower (95% CI: 8.7%–9.5%) in individuals with versus without diabetes. Conclusions: Despite a lower participation rate, the effect of CRC screening was higher in individuals with diabetes.