Digital Patient Support Program for Self-efficacy and Medication Adherence in Women on Adjuvant Endocrine Treatment for Breast Cancer

Difference in change in total score of the Health Education Impact Questionnaire (heiQ) between the intervention and control groups.

The heiQ has 8 subscales and is composed of in total 42 questions with a Likert scale of 4 options where 1 represents "strongly disagree" to 4 "strongly agree". Scores on the heiQ range from 42 to 168, with a lower score representing a low impact on patient education.

Group difference in self-reported adherence according to MARS-5 questionnaire at 12 weeks The MARS-5 questionnaire consists of five questions measuring adherence ranging from "never" (5 points) to "always" (1 points), therefore the score has a range from 5 - 25 points with higher score indicating high medication adherence.

Group differences in self-efficacy measured by eight scales of Health Education Impact Questionnaire (heiQ) at 24 weeks and 1 year.

Group difference in self-reported adherence according to MARS-5 questionnaire after 24 weeks and 1 year.

Adherence to adjuvant endocrine breast cancer treatment over 1 year based on percentage of days covered (PDC) from data from the Icelandic Medicine Registry.

The proportion of days covered (PDC) is used to estimate medication adherence by looking at the proportion of days in which a person has access to the medication, over a given period of interest, in this case 1 year.

Compare the difference between groups in the proportion of participants still taking antihormonal therapy after 1, 2, 3 and 5 years, based on data from the Icelandic Medicine Registry.

Group difference in Body Mass Index (BMI) calculated from self-reported weight and height at 12, 24 weeks and 1 year.

BMI = weight (kg) ÷ height2 (meters)

Group difference in self-reported physical activity according to IPAQ-SF at 12, 24 weeks and 1 year.

Group difference in total score of Endocrine Therapy Symptoms from Endocrine Symptoms Questionnaire at 12, 24 weeks and 1 year

The questionnaire is composed of 11 questions, where 10 are answered on a Likert scale of 4 options where 1 represents "not at all" to 4 "very much", and 1 question with a 2-option yes or no.

Work status is a categorical variable representing participants' self-reported employment condition at each follow-up time point. This outcome will be used to assess potential group differences over time.

No validation measurement tool is used, only questions regarding participant status.

Work full time Work part-time 50-99% Work part-time, <50% Not on the labor market And reason for not being on labor market or working part time Sick leave Disability Pension Unemployed Other

One PRO that asks users to rate the quality of sleep, energy level, stress level and quality of life.

The longitudinal change of in-app ePRO in the intervention group will be analysed for these parameters:

• quality of sleep
• energy levels
• stress levels
• quality-of-life thermometer

Scores in the mHealth App Usability Questionnaire (MAUQ) of the intervention group.

The MAUQ is an 18-item questionnaire. It is composed of questions with Likert scales of 7 options where 1 represents "strongly disagree" to 7 "strongly agree". Scores on the MAUQ range from 18 to 126, with a higher score representing a higher usability.

Percentage of users that are active in the digital program, finish the program and engage with the content of the Sidekick digital Program