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