Shared decision-making for organised breast cancer screening (OBCS) could be improved by fostering interaction and exchanges of information between women and General Practitioners (GPs), for instance by including an assistance tool in the dispatch of the invitation letter for Organised Screening for breast cancer. In 2018 the national cancer Institute funded the development of a decisional aid (DA) on the theme of whether or not to take part in breast cancer screening, specific to the French setting. It is the website Discutons-mammo.fr DEDICACES project 1.

DEDICACES 2 is a population-based trial with a cluster design. It studies humans, without modifying their usual care. The experiment assesses the effect of the discutons-mammo.fr tool on the decision to take part (or not) in OBCS among women who are invited for screening.

Inclusion Criteria :

- General practitioners (GPs):

The following GPs will be included:

1) Practicing in one of the French départements (administrative area) covered by the study.

- Women:

The following women will be included:

1. Invited to participate in OBCS by the National Health Insurance Agency (Caisse Nationale d'Assurance Maladie; CNAM) during the studied month: eligible for OBCS, therefore aged between 50 and 74 at the time of inclusion;
2. On the patient list of a GP who is covered by the study at the time of inclusion;
3. Covered by one of the CPAM (Caisse Primaire d'Assurance Maladie) in the participating departments.

Exclusion Criteria :

- General practitioners (GPs) :

The following GPs will be excluded:

1. Those who do not have any patients invited for OBCS in the studied month;

2. Those whose practice does not correspond to the usual activities of a GP (known as a Mode d'Exercice Particulier), or who have very few patients (who have seen fewer than 100 different patients in the year preceding the experiment);

3. Those who practice within a health centre (as it is impossible to evaluate the activity of an individual practitioner in health insurance databases);

4. Those who explicitly state that they do not want to take part in the study, in response to an initial letter of invitation. This letter will inform them that the study is being run, and will inform them of the option to refuse to participate if they so wish;

5. Those who are participating in the MyPEBS study (the only national study of OBCS at the time the present protocol was drawn up).

   • Women:

The following women will not be included:

1. Participants in the MyPEBS study ( the only national study of OBCS at the time the present protocol was drawn up); or,
2. If their GP refuses to participate in the study; or,
3. women under guardianship.

The following women will be excluded:

• Those who object to the study in accordance with regulatory procedures issued by the Data Protection Officer (DPO),
• Those who do not respond within 1 month after the questionnaire has been sent.

Open Label