Abstract: Purpose/Objective: Aggressive fibromatosis (desmoid tumors) are rare non-malignant conditions deriving from the connective tissue. They have a strong tendency for local infiltration and a high relapse rate after surgery alone. Despite some clinical evidence for radiotherapy (RT) to be effective in treating aggressive fibromatosis, the exact role of RT has not yet been fully determined, because of the low incidence, the low sample size in clinical studies and the retrospective data analysis in most studies. Using both own clinical data and a systematic review of the literature, the role of postoperative and primary RT for desmoids is evaluated and compared with other treatment strategies such as surgery alone. Materials/Methods: >From 1980 to 2002, 42 patients (16 men, 26 women) with a median age of 36 (range, 19-56) years and histologically proven aggressive fibromatosis were referred for radiotherapy to the cooperating 4 institutions. As of March 2003, the median follow-up period for all patients was 42 (8-147) months. In 23 cases desmoid tumors were localized in the extremities, in 15 at the chest or shoulder girdle and in 4 at the abdominal wall. The indication for the use of RT were as follows: local inoperability (12 patients), incomplete R2-resection (17 pats.), and R1-resection (15 pats.). Postoperative RT was applied with 50-55 Gy and definitive RT with 60-65 Gy total dose using 2 Gy per day fractions. In addition, a systematic literature research in international electronic databases (Medline, Cancerlit, Embase, Current Contents, and Science Citation Index) was performed for the period from 1966 to 2002. A total of 76 reports with over 1,300 patients were evaluated with levels of evidence ranging from IIb to V. Results: 10 (24%) patients developed a local relapse, i.e. the long-term local control rate was 76%. No patient deceased during follow-up from the disease. The actuarial 5-year local recurrence-free survival rate analyzed by Kaplan-Meier method was 81 %. So far, no acute toxicities or late radiation sequelae > grade 2 (RTOG, LENT-SOMA) were observed. The literature review yielded an average local tumor control rate of 89 % (range, 66-100 %) for postoperative RT, of 77 % (range, 66-93 %) for definitive RT, and of 44 % (range, 18-73 %) for surgery alone (Table 1). Conclusions: Postoperative or primary RT in patients with residual tumor (R 1/2-resection), locally inoperable desmoids or narrow margins in the case of repeatedly operated lesions can achieve markedly improved local contral rates as compared with surgery alone. Mutilizing resections should be avoided. Currently a patterns of care study on radiotherapy on aggressive fibromatosis is conducted by the German Cooperative Group on Radiotherapy for Benign Diseases (GCG-BD). It is suggested to initiate an (inter)national data base for this disorder.