The objective of the present study is to evaluate the activity and safety of imatinib in patients with aggressive fibromatosis who, after receiving the standard therapy, show an inoperable recurrent tumor or disease not readily controllable by surgery or radiotherapy.

Inclusion Criteria:

• Patients with histological confirmed aggressive fibromatosis (desmoid tumor)
• Measurable disease according to the RECIST criteria
• Evidence of relapse or disease progression within the last 6 months (based on RECIST criteria) in computed tomography or magnetic resonance imaging
• No possibility of complete surgical resection or cases in which surgical therapy leaving a large tissue defect, functional deficit or disfigurement would be required
• No possibility of curative radiotherapy with acceptable toxicity and/or late morbidity
• Previous treatment of the tumor region by surgical intervention and/or radiotherapy and/or antihormonal therapy possible
• Age > or = 18 years
• WHO PS < or = 1
• Effective contraception during study medication
• Signed informed consent form

Exclusion Criteria:

• Surgical intervention < 4 weeks
• Prior therapy with imatinib
• Pregnancy or lactation
• Severe hepatic dysfunction
• Known allergic reaction to imatinib or one of its components
• The following laboratory values: Absolute neutrophil count < 1.5 x 103/mm3, Platelets < 100,000/mm3, Serum creatinine > or = 2.5 mg/dl, SGOT and/or SGPT > 2.5 x ULN (upper limit of normal), Total bilirubin > 1.5 x ULN
• Participation in another study (four weeks before and during the study)
• Prior malignancy apart from completely resected basal cell carcinoma of the skin or carcinoma in situ of the uterine cervix