Many prostate cancer survivors (PCS) suffer from long-term side effects well beyond treatment, such as urinary incontinence, erectile dysfunction, fatigue, depression, and anxiety. Supportive care interventions are needed to reduce the chronic effects of cancer and its treatment during the transition into survivorship. Physical activity (PA) has a positive impact on many clinical outcomes, including improved quality of life (QoL), cancer-specific mortality, and reducing treatment-related toxicities among PCS. Despite this, few PCS achieve current PA guidelines and there is a significant decrease in PA during and following treatment. PCS spend most of their day sedentary (i.e., 69% of waking hours) or engaged in light-intensity PA (LPA; 30% of waking hours), therefore focusing on reducing sedentary behaviour (SB) among PCS may be a more feasible intervention approach than supervised exercise. SB is defined as any waking behaviour characterized by a low energy expenditure (i.e., ≤1.5 resting metabolic equivalents) while in a sitting, reclining, or lying down posture. Despite the growing evidence that reducing SB can result in better health outcomes for cancer survivors, there are no known effective strategies aimed at reducing SB and replacing it with PA among PCS.

It is important that behavioural interventions are informed by theory, as theory-driven approaches are crucial for facilitating the adoption and maintenance of behaviour change. The Multi-Process Action Control (M-PAC) framework, a theoretical framework developed from PA behaviour change research specifically, suggests a layered, progressive approach to behaviour change where an individual moves from intention formation to adoption of action control and onto maintenance of action control. Intention formation is predicated on initiating reflective processes (i.e., instrumental attitude and perceived capability). Reflective processes are hypothesized to influence intention formation and initiate regulatory processes to enact this intention (i.e., affective attitude and perceived opportunity). The translation of intention into PA (i.e., action control) is determined partially by regulatory processes (e.g., action planning, coping planning, self-monitoring, social support) during the initial adoption of the behaviour. Continuation of PA action control is thought to include the addition of reflexive processes (e.g., habit) for long-term PA maintenance. This is a useful approach for PA and SB behaviour change interventions as it highlights processes for several stages of change including adoption and maintenance.

Previously supervised interventions have demonstrated success in increasing PA behaviours among cancer survivors but, distance-based interventions make an attractive alternative as they have extended reach due to potentially easier access and lower cost. Wearable activity monitors (e.g., FitBit) have been a successful SB and PA self-management intervention tool for cancer survivors. A previous pilot study conducted by our research group examined the feasibility of an unguided mhealth application (RiseTx) for reducing SB and increasing MVPA among PCS undergoing androgen deprivation therapy (ADT). PCS were given an activity tracker, access to the RiseTx mhealth web application which deployed a range of behaviour change support tools to reduce SB, and a goal of increasing step counts by 3,000 daily steps above baseline levels over 12-weeks. The RiseTx mhealth application was successful in reducing device-measured SB by 455 minutes/week and increasing MVPA by 44 minutes/week, as well as increasing steps by 1535 between baseline and post-intervention. Building upon this successful pilot study, the current RCT will harness the many lessons learned during the implementation of the RiseTx mhealth application. As an extension of this prior work, this updated iSTRIDE intervention will provide additional synchronous behavioural support aligned with processes in the M-PAC framework through videoconferencing, to reduce SB.

The multi-site, two-arm RCT will test the efficacy of this updated intervention on changing SB and PA in PCS. The primary objective is to determine the effects of the 12-week intervention (i.e., FitBit + behavioural counselling) compared to a control condition (FitBit + public resources) in reducing sitting time in PCS. It is hypothesized that that the intervention group will decrease their SB compared to the FitBit-only control condition at post-intervention (12 weeks) and 6-month follow-up. Secondary objectives of this trial are to determine the effects of the intervention on secondary outcomes including changes in MVPA, LPA, motivational outcomes from the M-PAC framework, sleep quality, social support, physical function and patient reported outcomes (i.e., QoL, fatigue, disability and mental health) compared to the FitBit-only control condition.