Development of a Patient Decision Aid for the DAHANCA 35 Proton Radiotherapy Trial: An Iterative Development Process with User-Centered Design Elements

Background. Deciding whether to participate in a radiotherapy trial is complex for patients with head and neck cancer. Standard patient information leaflets meet ethical requirements but do not provide balanced comparisons, value clarification, or structured decision support. Few patient decision aids (PtDAs) have been developed for clinical trial participation. Objective. To develop a PtDA to support decisions about participation in a randomized trial comparing proton versus photon radiotherapy (DAHANCA 35). Methods. Following the Medical Research Council framework for complex interventions, an iterative development process incorporating elements of user-centered design was undertaken, informed by the Ottawa Decision Support Framework (ODSF), International Patient Decision Aid Standards (IPDAS), and Measure of User- and Human-Centred Design for Personal Health Tools (UCD-11). Five steps were conducted: 1) scoping informed by 3 preceding studies and a workshop with clinicians, 2) drafting of an initial prototype, 3) iterative refinement in a multidisciplinary development group, 4) alpha testing using think-aloud interviews with patients ( n = 5) and clinicians ( n = 8), and 5) finalization. Data from workshops, written feedback, group discussions, and interviews informed revisions. Results. The final iteration of the PtDA provides balanced, plain-language information; value clarification; and decision support regarding participation in DAHANCA 35, including an explicit presentation of the decision between standard photon radiotherapy and the trial option. Visual elements, a comparison table, a decision tree, and tools from the Ottawa Personal Decision Guide were integrated to support comprehension and deliberation. Alpha testing confirmed usability and informed refinements that improved clarity and navigation. Conclusions. This iterative development process, incorporating elements of user-centered design, resulted in a PtDA that addressed decision-making needs within the trial context. Future research will assess the feasibility and implementation of this approach. The development approach may serve as a foundation for adapting PtDAs to other radiotherapy clinical trials. Highlights A patient decision aid (PtDA) was developed to support individuals with head and neck cancer in deciding whether to participate in a proton radiotherapy trial. The PtDA was developed through an iterative, theory-informed, and user-centered process with input from clinicians and trial-eligible patients. The PtDA provides structured, balanced information and explicit comparisons between standard photon radiotherapy and the trial option. This development approach may be adapted to support decision making in other radiotherapy trials and clinical trial contexts.