Study to Evaluate Imatinib in Desmoid Tumors

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