Effectiveness of health mediation to promote organized cancer screening among underserved and under-screened populations in Marseille, France: findings from a repeated cross-sectional survey

Abstract Background Although health mediation is widely studied in the U.S. through community health worker programs, evidence on their effectiveness in promoting cancer screening in Europe is limited. Since 2022, the “ 13 en Santé ” program has implemented a multicomponent health mediation intervention — combining educational activities, outreach strategies, and navigation support — in socioeconomically disadvantaged neighbourhoods of Marseille, France. This study evaluates the effectiveness of this program in promoting breast, colorectal, and cervical cancer screening. Methods A controlled before-after design based on two cross-sectional surveys was conducted in 2022 and 2024 in intervention or control neighbourhoods. Individuals aged 18–74 were randomly selected and interviewed via door-to-door questionnaires. Weighting was applied to account for stratified sampling and to align age and sex distributions with census data. Weighted logistic regression models were fitted for each cancer screening to estimate the intervention’s effects on uptake and awareness at both individual and population levels. Findings Overall, 4,523 individuals were included across the two cross-sectional surveys. The program successfully reached individuals facing cumulative socioeconomic barriers to healthcare access. No significant population-level effect was observed. At the individual level, declared exposure to health mediation was associated with significantly higher uptakes of breast and colorectal cancer screenings (breast: 54% vs. 74%, OR=2.3 [1.1–4.5]; colorectal: 30% vs. 50%, OR=2.8 [1.3–5.8]). In addition, colorectal cancer screening awareness was significantly higher among exposed participants (83% vs. 93%, OR=8.1 [2.1–31]). Interpretation This study provides the first evidence that a multicomponent health mediation intervention could effectively promote breast and colorectal cancer screening in disadvantaged French neighbourhoods. The study highlights screening-specific mechanisms of action that should be considered to further optimize intervention effectiveness. Funding The survey was funded by the Regional Health Agency of Provence–Alpes–Côte d’Azur and Santé publique France.