Long-term effect of faecal occult blood screening on incidence and mortality from colorectal cancer.

Background: Several randomized trials have shown a reduction of colorectal cancer mortality by screening using guaiac-based faecal occult blood tests. However, little is known on the long-term effect of screening at the population level in everyday practice.

Methods: Small-sized geographic areas including a total of 91,199 individuals were allocated to either biennal screening using the Hemoccult-II test or no screening. The expected mortality and incidence in the cohort invited to screening was determined using mortality and incidence in the non-screened population.

Results: Colorectal cancer mortality was significantly lower in the population invited to screening than in the non-screened population after 11 screening rounds (standardized mortality ratio: 0.87; 0.80-0.94). The standardized mortality ratio remained significant whatever the duration of follow-up. This reduction in colorectal cancer mortality was more pronounced in those who participated in the first screening campaign, who were regular participants in screening rounds (standardized mortality ratio: 0.67; 0.59-0.76). In contrast, colorectal cancer incidence was not different between the screened and non-screened populations (standardized incidence ratio: 1.01; 0.96-1.06).

Conclusion: Our findings confirm, in the long term, that screening with Hemoccult can reduce colorectal cancer mortality. The data also highlight the benefit of regular participation in screening and the absence of effect of screening on colorectal cancer incidence.