Table 1 Summary of the OnVaCT intervention [33, 35]

The OnVaCT intervention was systematically developed following the Medical Research Council (MRC) framework for complex interventions, in co-creation with the end-users (i.e. patients and oncologists).

The preparatory OnVaCT for patients was developed by a professional company, specialized in designing and developing interactive, playful, digital ‘learning’ tools such as serious games and interactive experience tools. The OnVaCT was built upon five characters or avatars – all hypothetical patients facing the decision whether to participate in early phase clinical trials – who each consisted of three short narratives in which different (combinations of) patient values were addressed. The narratives and values were derived from a previous systematic review and interview study, and aligned well with the initial codebook for this study (Table 1). In the OnVaCT, patients were supported to actively reflect on their personal values in light of the upcoming consultation by means of questions (e.g. “how do you feel about that?”).

The communication training for oncologists was developed with and led by an experienced psychologist who is an expert in providing communication skills training to medical students and medical specialists. The training consisted of three parts: (1) a web lecture (approx. 15 minutes) regarding SDM during consultations about potential participation in early phase clinical trials; (2) an individual feedback session during which oncologists received personalized feedback on one of their pre-intervention recordings, which they were asked to watch and assess using the SDM steps beforehand (approx. 30 minutes and 1 hour preparation); and (3) a concluding group training, that focused on making the (results from using the) OnVaCT and patient values discussable with the patients by using SDM steps (approx. 2 hours).