Protocol for Fit4Transplant: iterative optimisation of an exercise prehabilitation service for haematological cancer patients using phase II adaptive trials and co-design

Hematopoietic stem cell transplantation is a critical intensive treatment option for many people with haematological cancer but often leads to long-term reductions in physical function. Exercise-based prehabilitation can help to mitigate these effects and improve wellbeing. This study aims to evaluate and iteratively refine co-designed enhancements to an existing exercise-prehabilitation service. Two intervention packages will be evaluated in sequential single-arm Bayesian optimal phase II adaptive trials. Package 1 will include two staff training modules (focused on trauma-informed service delivery and delivering engaging exercise classes online) and a behaviour Change booklet for patients. Package 2 will include refined (if necessary) Package 1 components, as well as an interactive self-management website/mobile application for patients. Outcome assessments will be conducted at baseline and post-intervention. The rate of promising response (a composite efficacy and acceptability outcome) in each trial will be monitored with interim analyses after 30 participants have completed post-intervention assessments. The intervention will be ceased prior to reaching the recruitment target (n = 60) if inadequate promising responses are observed (≥ 11 participants not meeting promising response criteria). A sub-sample of participants will also be invited to participate in an interview regarding stakeholder experiences delivering and receiving the intervention packages. Recruitment will commence in February 2025. This sequential adaptive design allows trialling a simpler intervention while the digital component is finalised, with iterative refinements guided by interim analyses and co-design. The outcomes of this study will help inform future prehabilitation programs involving exercise programs and provide an example of how co-design and adaptive trials can be combined to optimise behavioural health interventions within routine care. Australian NewZealand Clinical Trial Registry ACTRN12624000363583p. Registered 28th March 2024.