Colorectal cancer screening in Flanders : impact, challenges, and recommendations

Abstract: The Flemish population-based colorectal cancer (CRC) screening programme, initiated in October 2013, offers a free biennial faecal immunochemical test (FIT) to eligible individuals aged 50-74 years. This PhD research aimed to 1) Assess the programme\u2019s impact on CRC incidence, mortality, and survival; 2) Investigate suboptimal response rates by exploring screening with outside tests, reasons for inconsistent participation, and population preferences for CRC screening; 3) Identify FIT interval cancer characteristics and explore strategies to optimize FIT cut-off and screening interval to reduce FIT interval cancers. Results indicate that the programme has effectively reduced CRC incidence, mortality and improved survival, with a more pronounced impact in men. Screening with outside tests has limited impact on response rates inside the programme but presents challenges such as cost, inadequate result registration and follow-up, and insufficient quality control. Encouraging a shift to organised screening is important. Persistent challenges to increasing uptake include language barriers for individuals with a migrant background, postponed screening due to time constraints and competing priorities, and the misconception that CRC screening is only necessary when symptoms are present. GPs play a vital role in promoting CRC screening and addressing barriers and misconceptions among their patients. Factors associated with a higher risk of having FIT interval cancer versus a screen-detected CRC include female gender, older age, right side and rectum locations, advanced stage, and high grade. The chosen FIT cut-off and screening interval in Flanders are considered optimal with regard to FIT interval cancer, as lowering FIT cut-off or shortening screening interval would have minimal impact on the occurrence of FIT interval cancers. The current evidence does not support expanding the CRC screening programme by reducing the starting age for screening, lowering the FIT cut-off, or shortening the screening interval. Instead, the focus should be on optimizing the existing screening strategy, along with regular monitoring and evaluation for continuous improvement. Introducing pre-invitations and additional reminders can be effective in addressing procrastination in CRC screening participation. Strengthening the involvement of GPs, local authorities, and health insurance organisations seems beneficial in reaching underserved populations. To enhance screening effectiveness, the programme may consider incorporating risk stratification based on previous FIT results to tailor screening invitations. Emerging tests can be explored to be used as an alternative for FIT as the primary screening test or triaging individuals after a positive FIT to reduce unnecessary colonoscopies and associated adverse events