Quality of Life of Patients With Desmoid-type Fibromatosis

Each question will be scored: not at all (1), a little (2), quite a bit (3), very much (4). The scores of the EORTC-QLQ30 will be calculated using a Likert scale from 1-4. The scoring manual of the EORTC will be followed. After linear transformation, all scales and single item measures range in score from 0-100. Scores for each scale will be reported as mean (SD), or as median (IQR). A higher score on the functional scales and global quality of life means better functioning and HRQoL, whereas a higher score on the symptom scales means more complaints. The EORTC QLQ-C30 summary score will be calculated using the mean scores of the function scales and the reversed mean scores of the symptom scales and represented as the mean of the combined 13 QLQ-C30 scale scores (financial impact and global health status excluded). A higher summary score represented a better outcome.

The scores for each item of the DTF-QoL will be calculated using a Likert scale from 1-4. The scores of each item will be calculated as mean ± SD, or as median (IQR). These scores (median or mean) will be reported per item.

Measures health-related quality of life on five dimensions of health: mobility, self-care, usual activities, pain-discomfort, and anxiety/depression. Additionally two questions aim to rank a patients' health (scale 0-100, with 100 representing a better health). Each of the five dimensions can be divided into five levels of perceived problems: no problems (level 1), slight problems (level 2), moderate problems (level 3), severe problems (level 4) and extreme problems (level). Health states can be converted into single index values. The outcomes will be reported as frequency (proportion) of reported problems for each level and for each dimension. The Visual Analogue Scale (VAS) data will be presented as a mean value (SD). In case of skewed data, median values and IQR will be used.

See primary outcome 1 for a detailed description of the EORTC QLQ-C30 questionnaire.

The median or mean values for each scale of the EORTC QLQ-C30 from DTF patients will be compared to the median or mean scores per scale of the general population.

Subgroups will be created based on the information of the baseline questionnaire and will encompass: sex (male, female), age groups (categorized based by the median age and/or quartiles), primary treatment type (surgical resection, systemic treatment, radiotherapy, local treatment (e.g. cryoablation), ethnicity, educational level, relationship status, job demands, comorbidities, tumour location, and tumour recurrences.

Outcomes of this questionnaire will be descriptive and are expressed as numbers with corresponding percentages.

Mean or median scores of each scale (EORTC QLQ-C30, version 3.0), items (DTF-QoL, version 1,0) or frequency scores (EQ-5D-5L, version 1,0) will be calculated for each relevant subgroup.

The health care utilization questionnaire contains the following topics: satisfaction with received care, frequency of visits to the general practitioner / specialist, satisfaction with the follow-up schedule, preferences and needs for receiving care in a DTF expert centre, receiving additional care of support from professionals (medical and non-medical). Outcomes will be descriptive and reported in numbers and corresponding frequencies per answer option.

Six questions were designed to obtain information on how patients make medical decisions, what their current role is and what their preferred role, and one question regarding their awareness of their choices, the benefits and risks of certain treatment and whether they received support an advice are designed. Two questions were designed to gain insight into the reasons for choosing an active form of treatment.

Outcomes of this questionnaire will be descriptive and expressed as numbers with corresponding percentages.