Feasibility of Technology-Based SSIP in Prostate Cancer Patients

Primary outcome is prostate cancer patients' perceived usability of the WINGS-IP1 Smartphone Application measured by the German version of the 'Intervention Usability Scale' (IUS, [Lyon et al., 2021]). This scale was adapted from the 'System Usability Scale' (SUS, [Brooke, 1996]), a widely used self-reported scale to assess usability of digital systems, mobile applications, devices, and websites (see Kaya et al., 2019; Klug, 2017; Usability.gov, 2013). The SUS is composed of 10 items, assessed on a five-point Likert-scale, ranging from 0 = "strongly disagree" to 4 = "strongly agree" (Brooke, 1996). This scale will be completed by prostate cancer patients and their supporters.

In order to assess change mental burden related to medical condition the investigators will use the German version of the 'Mental Health Component Summary Score' of the 'Short Form-36 Version 1'(SF-36, [Ware, 2000]). The SF-36 is a validated, self-report instrument consisting of 36 items rated on five-choice response scales. The possible score ranges from 0 to 100 points, whereby 0 points represent the greatest possible health restriction and 100 points represent no health restriction at all. This scale will only be completed by prostate cancer patients.

The investigators will use the German version of the 'Patient Health Questionnaire' with 8 items (PHQ-8) to assess the severity of depressive symptoms in prostate cancer patients (Kroenke et al., 2009; Kroenke \& Spitzer, 2002). The last criteria had been excluded as it assesses suicidal or self-injurious thoughts, which investigators will not be able to address adequately within the context of the proposed study. Prostate cancer patients and their supporters will be asked to indicate how often they experienced a depressive symptom in the past two weeks (Kroenke et al., 2009). They rate these symptoms on a four-point Likert-scale ranging from 0 = "not at all," 1 = "several days," 2 = "more than half the days," to 3 = "nearly every day". The PHQ-8 demonstrated acceptable internal consistency with Cronbach's α = 0.82 (Pressler et al., 2011).

The investigators will implement the German version of the seven item 'General Anxiety Disorder Scale' (GAD-7) to assess the presence of generalized anxiety disorder, social phobia, panic disorder, and post-traumatic stress disorder (Spitzer et al., 2006; Staples et al., 2019). Prostate cancer patients and their supporters rate items on a four-point Likert-scale ranging from 0 = "not at all," 1 = "several days," 2 = "more than half the days," to 3 = "nearly every day", based on their symptoms in the last two weeks. The GAD-7 showed acceptable discriminative validity (AUCs between 0.74 and 0.75, ps < 0.001) and good test-retest reliability (r = 0.83) and internal consistency with Cronbach's α = 0.88 (Staples et al., 2019).

In order to measure daily fluctuations of depressive symptoms and anxiety during the eight-week intervention phase, the investigators will implement the 'Patient Health Questionnaire' (PHQ-4) which consists of the PHQ-2 (Kroenke et al., 2003) and the 'General Anxiety Disorder Scale' (GAD-2, [Staples et al., 2019]) as Ecological Momentary Assessment (EMA, [Stone et al., 1999]). Both measures will be adapted in accordance with procedures of Bauer and colleagues (2018) to adjust instructions and Likert-scales to daily assessments. This scale will only be completed by prostate cancer patients.

In the proposed study the investigators will assess prostate cancer patients perceived stigma using the German version of the 'Social Impact Scale' (SIS-D) with 24 items (Fife \& Wright, 2000). The SIS-D has been previously used to measure stigma in cancer patients and covers four dimensions, namely social rejection, internalised shame, social isolation, and financial insecurity. All items are answered on a 4-point Likert scale from 1 ("strongly disagree") to 4 ("strongly agree"). This scale will only be completed by prostate cancer patients.

To assess prostate cancer patients' perceived social support, the investigators will use the German version of the 'Oslo Social Support Scale' (OSSS-3, [Dalgard et al., 2006; Kocalevent et al., 2018]). The OSSS-3 is a very brief, three-item scale. In addition to pre- and post-intervention assessment, the investigators will also measure the OSSS-3 weekly, to assess fluctuations in perceived social support. The sum score ranges from 3 to 14, with high values representing strong levels and low values representing poor levels of social support. This scale will only be completed by prostate cancer patients.

To assess prostate cancer patients' perceived social support, the investigators will use the German version of the 'Oslo Social Support Scale' (OSSS-3, [Dalgard et al., 2006; Kocalevent et al., 2018]). The OSSS-3 is a very brief, three-item scale. In addition to pre- and post-intervention assessment, the investigators will also measure the OSSS-3 weekly, to assess fluctuations in perceived social support. The sum score ranges from 3 to 14, with high values representing strong levels and low values representing poor levels of social support. This scale will only be completed by prostate cancer patients.

The investigators will assess somatic symptom disorder using the 'Somatic Symptom Disorder-B Criteria Scale' (SSD-12) composed of 12 items (Toussaint et al., 2016). These subscales are divided into three psychological subscales including cognitive aspects, affective aspects, and behavioural aspects. All items are answered on a 5-point Likert scale from 1 ("never") to 4 ("very often"). This scale will only be completed by prostate cancer patients.

The investigators will assess symptoms associated with prostate cancer and its treatment with the German version of the 'Expanded Prostate Cancer Index Composite' (EPIC-26, [Wei et al., 2000]). The EPIC-26 is a self-reported measure to assess patient function and distress after prostate cancer treatment. It covers multiple health-related quality of life (HRQOL) domains, namely urinary (incontinence and irritative/obstructive), bowel, sexual, and hormonal functionality. Each of these domains are assessed in terms of their function and bother and summarized into domain summary scores. The higher the EPIC-26 score (maximum 100 points), the better the patient's assessment of functionality in the dimension covered. This scale will only be completed by prostate cancer patients.

In order to assess prostate cancer patients' expectancy and the perceived credibility of the WINGS-IP1 Smartphone Application the investigators will use the 'Credibility Expectancy Questionnaire' (CEQ, [Devilly \& Borkovec, 2000]). A total of six items are rated on a 1-9 or a 0%-100% scale, depending upon the item. Higher scores refer to higher expectancy and higher credibility. This scale will only be completed by prostate cancer patients.

In addition, the 'Expanded Prostate Cancer Index Composite' (EPIC-26, [Wei et al., 2000]) will be assessed in prostate cancer patients six months post-prostatectomy as part of the clinical standard procedures at the University Hospital Basel. Hence, instead of a follow-up assessment 12 weeks after T1, the investigators will retrieve prostate cancer patients' EPIC-26 data from hospital records entered during the standard six months post-prostatectomy follow-up.