A 21-year population-level analysis from Spain’s Basque Country found that an organized fecal immunochemical test (FIT) screening program was associated with a 50.1% reduction in colorectal cancer mortality among adults aged 50–69. The program invited average-risk adults to complete FIT every two years, with tests mailed directly to their homes.
The study, covering 2004–2024, found that overall age-standardized CRC mortality fell by 29.6%, from 32.8 to 23.1 deaths per 100,000 people. More than 70% of screen-detected cancers were diagnosed at stage I or II, while average screening participation reached 70.1% and adherence to colonoscopy after a positive FIT exceeded 91%.
Notably, the largest mortality decline emerged three years after the program began, highlighting the time needed for population-level screening benefits to become evident. The findings provide some of the strongest long-term evidence that organized FIT screening can translate into substantial reductions in CRC deaths.