Table 3:

Main Categories, Subcategories, and Translated Quotations of the Semi-Structured Interviews

Patients/caregiver
Usability	Main statement	Example quotations
Handling	The app is user-friendly.	[Usability of the app is good] „ because its use is self-explanatory. Because it is easy to move from one question to the next question” (Pat. No. 01, line 28-30)
Design	Clear structured, simple design	„The design is simple and straight-forward, easy to use for everyone.” (Pat. No. 03, line 30-31)
Content	Questions sometimes are challenging/more time-consuming	“Some questions are more difficult to answer, one needs to think longer about them. For example questions that require a “yes” or “no” response but which you cannot answer by a clear/definite “yes” or “no.”” (Pat. No. 01, lines 83–85)
Difficulties	Mainly no difficulties	“Well, sometimes it took some time for the app to load. The questions were not displayed correctly, one could only see the “TRACE” symbol. Only when trying it again after 2–3 days, did it work again. Maybe it’s due to my mobile phone.” (Pat. No. 09, lines 91–95)
Feasibility	Main statement	Example quotations
Answering in the presence of others	Rare problems with completing the questionnaires in the presence of others	“No big deal. Because I think this should be talked about more in the public, anyways. It’s still a taboo issue. Because the topic [cancer] is frequently taboo, still.” (Pat. No. 01, lines 68–70)
App vs. paper	Questionnaires via app are preferable, more modern, and timesaving	“It is easier. You don’t need direct contact [with the clinic] and you don’t have to go into the clinic to fill out the questionnaires.” (Pat. No. 12, lines 23–24)”
Integration into everyday life	Good integration into the daily routine	“You can just pick up your phone and operate the app. It wasn’t a big effort, and it was quick.” (Pat. No 01, lines 57–59)
Effects of answering the questions	No burden due to filling out the questionnaires	“Yes, I had a better overview of my health status and quality of life.” (Pat. No. 03, lines 74)
Health care professionals
Usability	Main statement	Example quotations
Handling	Simple layout of the app and self-explanatory questionnaires	“I experienced it as very self-explanatory. But that could also be due to my generation because such apps are easier and more intuitive for ‘digital natives’.” (HCP No. 1, lines 38–39)
Design	Mainly satisfied with the design of the app. Easy handling for the patients	“Well, the questionnaires are easy to find. But I think it would be good for patients to know the progress status (when which questionnaire has to be answered).” (HCP No. 3, lines 32–33)
Satisfaction	Strong satisfaction, as the app has made a lot of things easier for the staff. But less patient contact.	“I think the app fulfills its purpose. It also worked well on both operating systems, Android and IOS.” (HCP No. 1, lines 43–45)
Feasibility	Main statement	Example quotations
App vs. paper	Innovation in the field of digitalization of medicine. Easier for patients, questionnaires can be completed at any time.	“Most people have a smartphone. We save paper and the patients can do it from home and don’t have to come to the clinic.” (HCP No. 4, lines 25–30)
Implementation	Introducing the app into everyday life can occur without any problems.	“Without any problems. The only difficulty probably was the sometimes-instable internet connection.” (HCP No. 1, lines 29–30)
Data collection	Easy data collection, by use of mandatory fields, all items are completed and there is fewer missing data.	[the app is] “Feasible not only in oncology. Dependent on compliance and willingness of the patient. Dependent on the cooperation of other departments and disciplines.” (HCP No. 2, lines 57–59)
Integration into everyday life	Less effort for patients, the same amount of effort for staff.	”Another advantage is that you can do it at home while drinking coffee or reading the newspaper. I think it can be integrated well.” (HCP No. 4 lines 76–94)

HCP = health care professional.