Milea Timbergen

236 group, other factors may play a role, which are beyond the individual patient level of these focus groups participants. An international desmoid population-based questionnaire study could ideally give more detailed information. Such a study could also examine which patients are particularly at risk for poor disease related outcomes on their quality of life. Our focus group study has several limitations. First; the recruitment of participants for focus group sessions might have led to selection bias. Patients who are introvert, or who have minor symptoms, or received successful treatment might have been less likely to agree to participate in a focus group session and vice versa. A frequently heard response, when being approached for participation, was the worry about being influenced by negative experiences of other patients. However, in that case, most patients were willing to do a private face-to-face interview with the author to share their experiences. This suggests that not all patients feel comfortable to join a group session. The second limitation involves the small number of DTF patients. Due to the rarity of DTF larger sample sizes are difficult to obtain in a single centre study. Nevertheless the small sample size gave all participants enough time to share their experiences 46 . The third limitation comprises the heterogeneity of the focus group participants, since we did not select participants based on their stage of disease or their treatment. Only one out of fifteen participants received previous systemic treatment, which might be an underestimation of the total percentage of patients in the DTF population receiving medication. We do acknowledge that every treatment modality (e.g., surgery, radiotherapy, chemotherapy) could impact HRQoL on the short- and the long-term. However, regardless of previous treatments, patients, included in the focus groups, shared a wide variety of experiences coinciding with the chronic nature of the disease. This resulted in the report of various HRQoL-issues, which we believe do represent the entire spectrum of HRQoL-issues experienced by the DTF population. To our knowledge this is one of the few studies that explored currently used HRQoL-tools and the experience of HRQoL-issues in the setting of sporadic DTF. The strength of our study is the approach according to the EORTC guidelines for developing questionnaire modules 49 . By conducting the systematic literature review we revealed the necessity for measuring HRQoL-outcomes in clinical practice and exposed a deficit in suitable HRQoL- tools for this patient group. The focus group approach elicits patients to explore and to clarify individual and shared perspectives. This resulted in the identification of key issues experienced by DTF patients and ensures the achievement of high content validity. 8