In Switzerland, colorectal cancer (CRC) is the third most common cause of death from cancer with 1600 persons dying from CRC each year. CRC screening can prevent most of these deaths. If screening begins at age 50, with either colonoscopy or faecal immunological test (FIT), the absolute risk of dying from CRC at age 80 can be cut in half. The choice between CRC screening methods can be seen as preference-sensitive condition. FIT can detect CRC at a similar rate as colonoscopy, but cannot detect as many polyps and advanced polyps as colonoscopies. Colonoscopy would seem the best choice for patients who want to reduce their risk of developing CRC or dying from CRC, but colonoscopy is an invasive procedure with rare but serious adverse effects. Patients who choose FIT do not need to prepare their bowels, or take a day off, but instead sample their own stool at home and mail the test to the laboratory. Offering the choice of test might also increase overall screening rates. Guidelines from the US Services Task Force (USPSTF) suggest shared decision making as a method for increasing adherence to screening and elicit patients' preferences for screening options.

Family physicians are recognized as the most trusted professional to discuss CRC screening in Switzerland. However, many primary care physicians (PCPs) appear to prefer colonoscopy over FIT, and the preferred method seems to vary widely between regions. Physician preferences and local medical culture likely determine these choices more than patient preference. It may be possible to reduce the number of PCPs who prescribe only one screening method by encouraging them to diagnose their patient's preferences for screening method. In Switzerland, training PCPs with educational support and decision aids increased the number who intend to prescribe both screening modalities in equal proportions (prescription of both colonoscopy and FIT in equal proportions).

To implement the intervention and determine how and if it changes PCP practice over time, the study will be conducted in quality circles (QCs) of PCPs. QCs are usually groups of 6 to 12 PCPs who meet regularly to reflect on their practice. QCs are a multifaceted, step-based intervention for quality improvement that has gained international traction because they can foster long-lasting behaviour change. In Switzerland, 80% of all PCPs attend QC regularly. Through QCs following the principles of Plan-Do-Check-Act (PDCA) quality improvement cycles, PCPs can find ways to lower structural barriers to screening, assess their screening practices, and give each other feedback.

The study hypothesizes that providing PCPs with evidence summaries on CRC screening, decision aids for patients, and sample FIT tests will increase the number of patients screened for CRC, better balance the selection of screening methods (colonoscopy vs. FIT), increase the proportion of patients with whom PCPs discuss CRC testing, and increase the number of patients who make decision for or against CRC screening.

The outcomes in PCPs of QCs allocated to the intervention group will be compared to those in the control group. The outcomes will be measured through anonymous structured patient data collected on 40 consecutive patients by PCPs and questionnaires filled by PCPs.

To ensure that relevant outcomes important for future implementation and dissemination works are collected, the Reach, Effectiveness, Adoption, Implementation and Maintenance (RE-AIM) framework will be followed for structuring the data collection. The RE-AIM framework helps structure the collection of data on the characteristics of the participants invited who finally participate in the study (Reach), on the integration of the planned intervention in their work (Adoption), on the consistency of implementation of the planned intervention by study participants (Implementation), on the maintenance of the intervention effects over time (Maintenance), and finally, on the effectiveness of the intervention on the planned outcomes (Effectiveness). The RE-AIM criteria are useful for identifying the translatability and public health impact of this intervention, and for making clear to future stakeholders the internal and external validity of study results.

This study will test the benefits of a multilevel training program in participatory medicine designed to help PCPs in Switzerland to better diagnose patient preferences for screening and method of screening method (colonoscopy or FIT) through. If the program is successful it will increase the proportion of patients who can decide to undergo testing or not and with which method. This should increase in number of patients who are screened or intend to be screened for CRC, and thus reduce CRC deaths in the longer term.

Inclusion Criteria:

• Physician-level: PCPs of different regions in Switzerland participating in Quality Circles comprising 4 to 19 PCPs and willing to participate in the study
• Patient-level: Three Repeated measures over three years on 40 consecutive patients aged 50 to 75 years old seen in PCP offices over a 2 weeks to 2 months period. Patients will be included if there is a face-to-face consultation billed for at least 5 minutes at the practice.

Exclusion Criteria:

• None except criteria which do not respect inclusion criteria.