MR-guided focused ultrasound therapy of extra-abdominal desmoid tumors: a multicenter retrospective study of 105 patients

Objective To assess the safety and efficacy of magnetic resonance-guided focused ultrasound (MRgFUS) for the treatment extra-abdominal desmoids. Methods A total of 105 patients with desmoid fibromatosis (79 females, 26 males; 35 ± 14 years) were treated with MRgFUS between 2011 and 2021 in three centers. Total and viable tumors were evaluated per patient at last follow-up after treatment. Response and progression-free survival (PFS) were assessed with (modified) response evaluation criteria in solid tumors (RECIST v.1.1 and mRECIST). Change in Numerical Rating Scale (NRS) pain and 36-item Short Form Health Survey (SF-36) scores were compared. Treatment-related adverse events were recorded. Results The median initial tumor volume was 114 mL (IQR 314 mL). After MRgFUS, median total and viable tumor volume decreased to 51 mL (95% CI: 30–71 mL, n = 101, p < 0.0001) and 29 mL (95% CI: 17–57 mL, n = 88, p < 0.0001), respectively, at last follow-up (median: 15 months, 95% CI: 11–20 months). Based on total tumor measurements (RECIST), 86% (95% CI: 75–93%) had at least stable disease or better at last follow-up, but 50% (95% CI: 38–62%) of remaining viable nodules (mRECIST) progressed within the tumor. Median PFS was reached at 17 and 13 months for total and viable tumors, respectively. NRS decreased from 6 (IQR 3) to 3 (IQR 4) ( p < 0.001). SF-36 scores improved (physical health (41 (IQR 15) to 46 (IQR 12); p = 0.05, and mental health (49 (IQR 17) to 53 (IQR 9); p = 0.02)). Complications occurred in 36%, most commonly 1 st /2 nd degree skin burns. Conclusion MRgFUS reduced tumor volume, reduced pain, and improved quality of life in this series of 105 patients with extra-abdominal desmoid fibromatosis. Clinical relevance statement Imaging-guided ablation is being increasingly used as an alternative to surgery, radiation, and medical therapy for the treatment of desmoid fibromatosis. MR-guided high-intensity focused ultrasound is an incisionless ablation technique that can be used to reduce tumor burden effectively and safely. Key Points • Desmoid fibromatosis was treated with MR-guided high-intensity focused ultrasound in 105 patients. • MR-guided focused ultrasound ablation reduced tumor volume and pain and improved quality of life. • MR-guided focused ultrasound is a treatment option for patients with extra-abdominal desmoid tumors.