Milea Timbergen

221 Introduction Desmoid-type fibromatosis (DTF) is a soft tissue tumour that arises frommusculoaponeurotic structures. It is incapable of metastasizing and is often described as a benign tumour in clinical practice. However, due to its local aggressive behaviour and its known tendency of local recurrence after initial surgical resection, it is categorized as a borderline tumour 1 . Desmoid-type fibromatosis is rare, with a reported incidence of 5.4 new cases per million persons per year in the Dutch population 2 . Symptoms vary, depending on tumour location and size, and can be very severe. Roughly two types can be distinguished: sporadic DTF with extra-abdominal or abdominal wall tumour formation and familial adenomatous polyposis (FAP) related DTF with intra-abdominal tumour formation 3, 4 . The aetiology of sporadic DTF remains doubtful although a history of trauma has been reported, as well as specific hormonal status (such as pregnancy) and genetic predisposition 5-8 . With local recurrence rates up to 50%, potential treatment benefits and adverse effects of treatment should be considered carefully 9-11 . Nowadays, active surveillance is recommended in asymptomatic patients, while treatment options for symptomatic patients include surgical resection, radiation therapy, and systemic therapy 12-16 . Determination of treatment effectiveness is currently mainly evaluated by tumour size or recurrence free survival 11, 17, 18 . Although such end-points can be appropriate in malignant diseases, the unpredictable growth behaviour including spontaneous regression and the low mortality rate of sporadic DTF renders such outcomes less appropriate for this borderline disease 16 . Consequently, the question rises whether health related quality of life (HRQoL) assessment could be a more appropriate outcome measure in DTF 10, 14, 19, 20 . The definition of HRQoL is ‘a patients’ evaluation of the impact of a health condition and its treatment on all relevant aspects of life’. Patient-reported outcome measures (PROMS) can be used to measure HRQoL with various purposes: as screening tools, as a method for identifying patient preferences, to guide clinicians for informed decision making, to improve patient-provider communication, and to assess the efficacy of treatments in the context of clinical trials 21 . In DTF, few researchers have sought to understand patient’s perceptions on the disease, and HRQoL is not (yet) widely accepted as an appropriate outcome measure. The aim of this mixed-method study is to explore currently used HRQoL-tools and identify HRQoL-issues of DTF patients. 8