Background: Cancer patients often suffer from high levels of distress. Mobile health (mHealth) applications might be an innovative way to deliver mindfulness and relaxation interventions for cancer patients. However, data about the implementation of apps in health care are lacking. Adherence to mHealth interventions is an important indicator for a successful implementation and might be needed to maximize treatment effects. However, the decrease in distress might reduce the motivation of patients to engage in such self-care tools in the long run. Therefore, the aim of this analysis was to investigate the association between the course of distress over time and the adherence to a relaxation self-care app in cancer patients. Methods: We developed an app for cancer patients (CanRelax) and 83 patients who participated in the prospective observational study used the app at least once. The evaluation was guided by the RE-AIM framework, and this analysis focused on the implementation of the app. Patients were grouped into five subgroups according to their course of distress over 10 weeks (Distress Thermometer). These subgroups of patients were compared with each other to identify different user groups. Findings: About half of the patients were adherent over 10 weeks. However, a decrease in distress was associated with lower adherence to the app intervention, whereas patients with moderate distress or an increase in distress showed more adherence. Conclusion: Adherence to an app intervention might be also driven by patients' distress level. A decrease in distress might reduce patients' motivation to continue with a self-care intervention. The interplay between adherence and treatment outcomes should be explored in upcoming mHealth trials to get a better understanding for the implementation of such interventions. Encouraging patients to continue self-care interventions is a major challenge in integrative medicine if they are delivered digitally. The Clinical Trial Registration number: DRKS00010481.
Keywords: cancer; cohort study; digital health; distress; implementation; quality of life; relaxation.