Co-developing a theory of change for a personalised multimodal cancer prehabilitation programme in South Wales

Evidence suggests that prehabilitation interventions, which optimise physical and mental health prior to treatment, can improve outcomes for surgical cancer patients and save costs to the health system through faster recovery and fewer complications. However, robust, theory-based evaluations of these programmes are needed. Using a theory of change (ToC) approach can guide evaluation plans by describing how and why a programme is expected to work. Theories of Change have not been developed for cancer prehabilitation programmes in the literature to date. This paper aims to provide an overview of the methodological steps we used to retrospectively construct a ToC for Prehab2Rehab (P2R), a cancer prehabilitation programme being implemented by the Cardiff and Vale University Health Board.

We used an iterative, participatory approach to develop the ToC. Following a literature review and document analysis, we facilitated a workshop with fourteen stakeholders from across the programme using a 'backwards mapping' approach. After the workshop, stakeholders had three additional opportunities to refine and validate a final working version of the ToC.

Our process resulted in the effective and timely development of a ToC. The ToC captures how P2R's interventions or activities are expected to bring about short, medium and long-term outcomes that, collectively, should result in the overarching desired impacts of the programme, which were improved patient flow and reduced costs to the health system. The process of developing a ToC also enabled us to have a better understanding of the programme and build rapport with key stakeholders.

The ToC has guided the design of an evaluation that covers the complexity of P2R and will generate lessons for policy and clinical practice on supporting surgical cancer patients in Wales and beyond. We recommend that evaluators apply a ToC development process at the outset of evaluations to bring together stakeholders and enhance the utilisation of the findings. This paper details a pragmatic, efficient and replicable process that evaluators could adopt to develop a ToC. Theory-informed evaluations may provide better evidence to develop and refine cancer prehabilitation interventions and other complex public health interventions.