Evaluation of a Mobile Mammography Unit. A Randomized Cluster Trial Protocol of a Population Health Intervention Research to Reduce Breast Cancer Screening Disparities in Normandy, France (Mammobile)

Context In most EU member states, breast cancer screening is organised with a mammography screening. However, there are still differences in the way screening programmes are implemented. In France, the organized breast cancer screening (OBCS) has been conducted, nationwide since 2004. A screening mammography is offered every two years to women aged 50 to 74 at average risk for this cancer. They receive from management structures in charge of this screening (SMS), an invitation to visit an accredited radiologist's office. A radiological imaging of the breast with two views plus a clinical breast examination is realized. Two different radiologists assure readings. In the last three year, the national participation rate remains stable around 51%. In addition, studies, using ecological indices of deprivation, highlight social and territorial inequalities: women living in disadvantaged area or far from a radiologist's office less participate. Different strategies can be implemented to increase participation to breast cancer screening, especially in populations with low-income or in rural areas, who have less access to screening. Among these strategies, mobile mammography units (MMU) seem effective. Therefore, in the French context, there is very little evidence on how to intervene to reduce health socio-territorial inequalities in screening, so public health decision-makers are unable to base proposals on evidence.

Intervention The main intervention will be a proposition for an appointment at the MMU in complement to the current OBCS. This complementary mode of screening offers the possibility for women furthest away from the radiologist's office to undergo screening in the MMU. All women eligible for OBCS and living in the zone selected for the intervention will be invited to participate either in a radiologist's office or in the MMU, keeping the choice of their place of screening. The breast screening in the MMU will follow the same protocol as screening at the radiologist's office according to national recommendations, so that the quality level of screening proposed in the MMU will the same as in any radiologist office. The MMU will be equipped with a latest-generation digital scenographer as well as an ultrasound system according to the compliance rules of the specifications published by the National Institute of Cancer. The quality of the mammographic radiographic equipment will also be certified by the Nuclear Safety Agency.

About two weeks before the MMU is parked, local actors, will carry out actions to inform women on the organized breast cancer screening and on the MMU. Women will receive the timetable of these actions with the invitation to participate in screening.

Design This intervention will be conducted during two years in 2022-2024, as a prospective randomized controlled cluster trial in the general population in the departments of Calvados, Manche, Eure and Seine-Maritime (Normandy Region in the north west of France). The cluster of the study is a group of IRIS (Ilots Regroupés pour l'Information Statistique). This geographical unit is the smallest scale for which census data are available and represents an average of 2000 inhabitants.

An algorithm was developed to constitute clusters integrating some constraints in a regional scenario.