Abstract
Sporadic desmoid-type fibromatosis (DTF) is a rare, non-metastasising soft-tissue tumour. Patients can experience a variety of disease-specific issues related to the unpredictable clinical course and aggressiveness of DTF, which negatively impacts health-related quality of life (HRQoL). These DTF-specific issues are not captured by generic HRQoL tools. A 102-item provisional DTF-specific HRQoL tool, the DTF-QoL, was previously developed. The aim of this study was to pre-test the psychometric properties of the DTF-QoL by administering it together with the EORTC Quality of Life Questionnaire Core 30 (EORTC QLQ-C30) to 236 DTF patients from the United Kingdom and the Netherlands. Construct validity and reliability were determined based on factor analysis, multi-trait scaling analysis, Cronbach's alpha, and correlations with the EORTC QLQ-C30 scales. Ninety-six items were selected, conceptualised into three symptom scales, eleven disease-impact scales and six single items, together forming the final DTF-QoL. Scaling assumptions were fully or moderately met for ten out of fourteen scales. Cronbach's alpha ranged from 0.551-0.908. Most scales of the DTF-QoL were weakly or moderately correlated with the EORTC QLQ-C30. The DTF-QoL is a promising tool capturing the whole spectrum of DTF-specific issues. Implementation of the DTF-QoL in research and clinical practice will help to personalise HRQoL measurement and clinical care for DTF patients.