Introduction:
Despite all the existing strategies, such as organized cancer screening, healthcare utilization and participation in screening remain insufficient, particularly among underserved population. This population is more exposed to diseases, less receptive to prevention messages, and have less healthcare utilization. Interventions that promote healthcare utilization by underserved populations must therefore go beyond the question of supply. Health Mediation (HM) is one of the promising interventions that promote healthcare utilization. However, except for some pioneering studies, no study seems to have demonstrated HM’s effectiveness and conditions of effect experimentally. The objective of the ECEMSo study is to identify the HM’s conditions of effect on healthcare utilization and participation in cancer screening.

Methods and analysis:
The ECEMSo study adheres to the theory-driven evaluation framework where the realist evaluation method and contribution analysis are used to explore the effects, mechanisms, and influence of context on the outcome. We will conduct a longitudinal study mobilizing mixed methods with a sequential explanatory multi-case and multicenter design. Knowledge mobilization workshops will be organized to promote collaboration between partners involved in HM and the health care system. The centers involved will be located in several regions of mainland France and support underserved populations who live in informal settlements. Outcomes are the evolution of healthcare utilization and cancer screenings used 6 months for those who have never been screened after the start of ECEMSo. To implement this survey we will use questionnaires, semi-structured interviews, focus groups and observations. The target number of participants are 800 beneficiaries and 33 professionals.

Discussion:
The realist evaluation will allow us to identify contextual associations to the intervention, see how they work, and whether they can be adapted to implement health mediation in other settings if it proves effective. This study will allow recommendations / guidelines’ production.