Milea Timbergen

13 several patients received adjuvant therapy after surgery, distorting the true prognostic value of the CTNNB1 mutation. In Chapter 7 , we investigated the association of the different CTNNB1 mutations with the risk of recurrence, in a large international cohort of primary DTF patients treated with surgery solely. Studies were included based on an extensive literature search and individual patient data was used to create a large homogenous cohort of DTF patients. Part III - Health-related Quality of Life The rarity, the high morbidity, and the increasing use of active surveillance as a first line management are reasons to better study the patients’ perspective. In Chapter 8 , we performed a systematic literature search to investigate which HRQoL-tools are being used for DTF in clinical practice and in research setting. Additionally, we organized focus groups to gain insight into the HRQoL-problems experienced by DTF patients. In Chapter 9 , we presented the retrieved HRQoL-issues to a new, international cohort of DTF patient and to healthcare professionals involved in the care of DTF patients, to identify the most important HRQoL-issues. In Chapter 10 , we describe the study protocol of the QUALIFIED study (The evaluation of health-related quality of life issues experienced by patients with desmoid- type fibromatosis): an international, multicentre, cross-sectional, observational cohort study which evaluates HRQoL-problems in the adult DTF population. Part IV - General Discussion and Future Perspectives This thesis describes the many faces of DTF. We provide insights into the molecular biology contributing to DTF pathogenesis, we incorporate new techniques such as radiomics to change the diagnostic pathway, we assess the role of the CTNNB1 mutation in risk of recurrence, and we evaluate how DTF impacts a patients’ life. In Chapter 11 , the results from the previous chapters are discussed. Chapter 12 outlines future perspectives for DTF research. 1