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

Abstract Background Since 2022, the “13 en Santé” health mediation program has been implemented in Marseille, France, to reduce social health inequalities, in socioeconomically disadvantage neighbourhoods, with a particular emphasis on promoting participation in population-based organised cancer screening programs. Led by multidisciplinary teams including health mediators, nurses, coordinators, and volunteers, the intervention is structured around three core components: (i) territory exploration to develop knowledge of local communities and resources; (ii) culturally appropriate health education delivered through outreach activities to reach underserved populations; and (iii) individualised navigation support tailored to needs and level of autonomy. 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 knowledge-attitude-practice 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. For each cancer, weighted logistic regression models assessed associations between health mediation exposure and screening uptake and awareness at both individual and population levels. Results 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 association was observed between health mediation and cancer screening uptake or awareness. At the individual level, declared exposure to health mediation was associated with significantly higher uptakes of breast and colorectal cancer screenings (breast: 74% vs. 54%, OR = 2.3 [1.1–4.5]; colorectal: 50% vs. 30%, OR = 2.8 [1.3–5.8]). In addition, colorectal cancer screening awareness was significantly higher among exposed participants (93% vs. 83%, OR = 8.1 [2.1–31]). Conclusions This study provides the first evidence that reported individual exposure to a multicomponent health mediation intervention was significantly associated with an important increase in breast and colorectal cancer screening uptake in disadvantaged European neighbourhoods. Although the limitations of this observational study preclude causal conclusions regarding the intervention’s effectiveness, these findings suggest that health mediation may be a promising strategy for reducing inequalities in cancer prevention and warrant further investigation. It also highlights screening-specific mechanisms of action that should be considered to further optimise intervention effectiveness.