Effects of Attendance to an Organized Fecal Immunochemical Test Screening Program on the Risk of Colorectal Cancer: An Observational Cohort Study.

Background & Aims: This cohort study compared colorectal cancer (CRC) incidence and mortality between people who participated in an Italian regional biennial fecal immunochemical test (FIT) screening program and people who did not.

Methods: The program started in 2005. The target population included over 1,000,000 people aged 50 to 69 years. The FIT was a one-sample OC-Sensor (Eiken Chemical Co, Tokyo, Japan) (cutoff, ≥20 μg hemoglobin/g feces). The average annual response rate to invitation was 51.4%. The records of people invited up to June 2016 were extracted from the screening data warehouse. Attenders were subjects who responded to the first 2 invitations or to the single invitation sent them before they became ineligible. Non-attenders were subjects who did not respond to any of these invitations. The records were linked with the regional CRC registry. People registered up to December 2016 were identified. Self-selection-adjusted incidence rate ratios (IRRs) and incidence-based CRC mortality rate ratios (MRRs) for attenders to non-attenders, with 95% confidence intervals (CIs), were calculated.

Results: The cohort generated 2,622,131 man-years and 2,887,845 woman-years at risk with 4490 and 3309 CRC cases, respectively. The cohort of attenders was associated with an IRR of 0.65 (95% CI, 0.61-0.69) for men, 0.75 (95% CI, 0.70-0.80) for women and 0.69 (95% CI, 0.66-0.72) for both sexes combined. The self-selection-adjusted IRR was 0.67 (95% CI, 0.62-0.72) for men and 0.79 (95% CI, 0.72-0.88) for women. The IRR for stage I, II, III, and IV CRC was 1.35 (95% CI, 1.20-1.50), 0.61 (95% CI, 0.53-0.69), 0.60 (95% CI, 0.53-0.68) and 0.28 (95% CI, 0.24-0.32) for men and 1.64 (95% CI, 1.43-1.89), 0.60 (95% CI, 0.52-0.69), 0.73 (95% CI, 0.63-0.85) and 0.35 (95% CI, 0.30-0.42) for women. The overall incidence-based CRC MRR was 0.32 (95% CI, 0.28-0.37) for men, 0.40 (95% CI, 0.34-0.47) for women and 0.35 (95% CI, 0.31-0.39) for both sexes combined. The adjusted MRR was 0.35 (95% CI, 0.29-0.41) for men and 0.46 (95% CI, 0.37-0.58) for women.

Conclusions: Attendance to a FIT screening program is associated with a CRC incidence reduction of 33% among men and 21% among women, and a CRC mortality reduction of 65% and 54%, respectively.