Sociodemographic factors associated with colorectal cancer screening participation have been extensively analysed although few, if any, studies have focused on regional/geographical factors as determinants of non-participation rates. The purpose of this study was to investigate the effects of individual and geographical determinants on the variable participation rates seen for colorectal cancer screening.

The study population comprised 183,978 individuals in the first round of screening and 175,596 in the second round, all of whom were residents of the city of Marseille in France. The influence of age, gender and regional/geographical characteristics, such as proportion of migrants and property prices per square meter, on participation rates was assessed by multilevel analysis.

The participation rate was lower for men (0.85; 95% CI: 0.83–0.86), and higher for those aged 65–69 years. Univariate analysis showed that participation rates were significantly different across the 16 municipal districts of Marseille (range: 22.8–36.7%; OR: 1.97; 95% CI: 1.86–2.08). On multivariate analysis, having a higher proportion of migrants in the district population was still associated with lower participation (OR: 0.96; 95% CI: 0.95–0.97).

In addition to individual factors, regional/geographical factors appear to be relevant determinants of participation rates in urban colorectal cancer screening programs.