An Organized Fecal Immunochemical Test-Based Screening Program Affects Colorectal Cancer Early Diagnosis and Survival in the Short Term.

[INTRODUCTION] In 2018, a biennial fecal immunochemical test (FIT) screening program for colorectal cancer (CRC) was introduced in northern Portugal, targeting 1.1 million residents aged 50-74 years. The aim of this study was to evaluate trends in CRC incidence, early diagnosis, and survival before and after the program's implementation.

[METHODS] This was a population-based retrospective cohort study in northern Portugal. Data on CRC cases diagnosed between 2014 and 2020 were retrieved from the Portuguese National Cancer Registry. Early diagnosis was defined as stage I/II tumors. Net survival estimates for 2014-2016 vs 2018-2020 were compared. Data from Portuguese National Cancer Registry were linked to the FIT-based screening program of the Northern Portugal Regional Health Administration for the years 2018-2020 to assess screening outcomes.

[RESULTS] Between 2018 and 2020, the first 3 years of the program, 482,938 invitations for FIT screening were sent, resulting in an adherence rate of 34.4% (165,895). The negative predictive value of FIT was 99.95% (95% CI: 99.94-99.96). Overall, coverage by FIT and/or colonoscopy was 44.9%. The proportion of early cancers was significantly higher among individuals who accepted FIT screening (58.3%) or underwent colonoscopy (62.8%) compared with unscreened individuals (49.2%) ( P < 0.001). Net survival rates at 1 year and 3 years were significantly higher among individuals who accepted FIT screening or underwent colonoscopy compared with those who remained unscreened ( P < 0.001).

[DISCUSSION] Biennial FIT led to an increase in early diagnoses and improved survival, compared with no screening, in the short term after its introduction. A screening program that includes alternatives to FIT may increase population coverage and improve CRC outcomes.