Abstract
BACKGROUND AND PURPOSE: Participation in clinical trials is essential to advancing oncological treatments, yet equitable trial access remains challenging. Diverse patient inclusion strengthens external validity and enhances the generalisability of trial outcomes. However, barriers to trial participation persist, and the factors influencing patient enrolment are not fully understood. This study investigates the patient perspective on participation in the Danish Breast Cancer Group (DBCG) Proton Trial. MATERIALS AND METHODS: Patients eligible for the DBCG Proton Trial were invited to participate in interviews. Patients were selected to ensure geographical and perspective-based diversity, including randomised and non-randomised patients from eight radiotherapy clinics in Denmark. Semi-structured interviews were conducted via telephone, transcribed, and analysed using an inductive approach to identify the patient perspective on trial participation. RESULTS: A total of fifteen patients were interviewed. The analysis identified five themes encompassing patients' motivators and barriers to trial participation: distance to the treatment facility, timing of trial information, decisional support, clinical equipoise and patient needs. These factors were reported by both randomised and non-randomised patients. INTERPRETATION: Participation in the DBCG Proton Trial was determined by both logistical and personal factors. Distance to the proton treatment facility was the most important barrier, while the potential for reduced late effects was the main motivator. The decision was difficult for most patients, often guided by one dominant concern rather than a balanced consideration of multiple factors. These findings suggest that improved trial communication, decisional support, and attention to geographical barriers are essential for promoting equitable participation in clinical trials.