Inclusion Criteria:

• Histologically confirmed renal cell carcinoma (primary tumour or biopsy/surgery of metastases)
• Radiologically confirmed metastatic disease
• Surgically removed primary tumour so feasible (nephrectomy or nephron-sparing surgery as indicated)
• Karnofsky-Performance Status >70%
• Age 19-75 years
• Life expectancy of at least 3 months
• Adequate bone marrow function (i.e. white blood cell count above 3000/μL, platelet count above 75 000 /μL, hemoglobin above 9 mg/dl)
• Adequate organ function (i.e. serum creatinine, bilirubin and AST below 1.25 x the upper limit of the institutions’ normal range)
• Negative pregnancy test for female patients
• Written informed consent

Exclusion Criteria:

• Age <19 or >75 years
• Karnofsky-Performance Status < 70%
• Untreated or uncontrolled brain metastases
• Second neoplasia
• Primary tumour surgically removable
• Solitary, surgically removable metastases
• Major concomitant diseases of the cardiovascular, respiratory or renal systems, as well as active systemic infections
• Severe renal disease or liver insufficiency or myeloid dysfunction (including patients with a history of a disease that is likely to interfere with the metabolism or excretion of the test medication)
• Other less common diseases as peptic ulcer disease, inflammatory bowel disease, autoimmune disease (severe known psoriasis, idiopathic thrombocytopenic purpura, lupus erythematosus, autoimmune hemolytic anemia, scleroderma, rheumatoid arthritis etc.)
• Drug addiction (including excessive alcohol consumption) within 1 year prior to study start.
• History of other conditions consistent with decompensated liver disease or other evidence of bleeding form esophageal varices.
• History of chronic hepatitis and immunsupressiva
• Known HIV Infection
• Evidence of allergy or hypersensitivity against recombinant Interferon alfa-2a or other components of preparation.
• History of severe psychiatric disease, especially depression. Severe psychiatric disease is defined as treatment with an antidepressant medication or a major tranquilizer at therapeutic doses for major depression or psychosis, respectively, for at least 3 months at any previous time or any history of the following: a suicidal attempt, hospitalization for psychiatric disease, or a period of disability due to a psychiatric disease.
• Seizure disorders and /or compromised central nervous system function.
• History of evidence of severe retinopathy
• Patient unwilling or unable to give informed consent
• Pregnancy or breastfeeding