Radiotherapy in the treatment of aggressive fibromatosis: experience from a single institution

Background: Desmoid-type fibromatosis is a rare, potentially locally aggressive disease. Herein we present our experience in the treatment with radiotherapy.

Methods and materials: In total 40 patients who received 44 treatments from 2009 to 2018 at the Heidelberg University Hospital with photons (N = 28) as well as protons (N = 15) and carbon ions (N = 1) were investigated. The median age at radiotherapy was 41 years [range 8-78]. Familial adenomatous polyposis (FAP) was confirmed for nine patients and 30 had a unifocal desmoid tumor. The localizations were abdominal wall, abdominopelvic cavity, thoracic wall, extremity, head and neck and trunk. The median prescribed dose was 54 Gy/ Gy (RBE) [range 39.6-66, IQR 50-60]. Eleven treatments were performed at the time of first diagnosis; 33 at the time of progression or recurrence. Post-operative radiotherapy was performed in 17 cases. The median planning target volume was 967 ml [84-4364 ml, IQR 447-1988]. Survival analysis was performed by the Kaplan-Meier Method.

Results: The median follow-up time was 32 months [1-153]. At the end of the follow-up interval all patients but one were alive. The estimated local progression free survival of the treated lesion in 3 and 5 years was 76.4% and 63,8%, respectively. The progression-free survival in 3 and 5 years was 72.3 and 58.4% and the overall survival was 97.4 and 97.4%, respectively. In case of macroscopic tumor (N = 31) before radiotherapy a partial remission was observed in 12 cases (38.7%) and a complete remission in 4 cases (12.9%). Progression was observed in 13 (29.5%) cases, predominantly at the margin of the planning target volume (PTV, N = 5, 38,4%) followed by progression within the PTV (N = 4, 30.8%). In univariate analysis multifocal localization was associated with impaired progression-free survival (p = 0.013). One patient developed a grade V gastrointestinal bleeding, otherwise no acute toxicity >°III was observed. Late toxicity was depending on the localization of the desmoid tumor and was especially severe in patients with FAP and abdominopelvine desmoids including gastrointesinal fistula, perforation and abscess.

Conclusion: Radiotherapy in the treatment of desmoids can lead to long term control. Treatment of patients with abdominopelvine desmoids should be avoided, as the risk of higher-grade complications is substantial.