Methotrexate-based Chemo-immunotherapy Followed by Maintenance Therapy for Patients > 65 Years With Central Nervous System (CNS)-Lymphoma

Inclusion Criteria: * first diagnosis of PCNSL, histologically confirmed * age \> 65 years * written signed and dated informed consent of the legal representative and - if possible - of the patient Exclusion Criteria: * manifestations of further lymphoma outside the CNS * sero-positive for HIV * severe pulmonary, cardiac, hepatic, renal impairment * uncontrolled infection * neutrophil count \< 1.500/µl, platelet count \< 100.000/µl * pulmonary disease with IVC \< 55%, DLCO \< 40% * cardiac ejection fraction \< 50%, uncontrolled malign arrhythmia * creatinine \> 1,5 mg% or creatinine-clearance \< 50ml/min * bilirubin \> 2mg/dl * ascites or pleural effusion (\> 500ml) * known hypersensitivity against methotrexate, lomustine, procarbazine, rituximab, leukovorin, or dexamethasone * participation in another clinical trial within the last 30 days prior to the begin or parallel to this study * known or current drug or alcohol abuse