Interleukin-2, Interferon Alfa, and Fluorouracil Compared With Observation in Treating Patients Who Have Undergone Surgery for Kidney Cancer

DISEASE CHARACTERISTICS: Histologically confirmed primary renal cell carcinoma meeting 1 of the following criteria: Stage T3b, T3c, or T4 tumor Any pT stage and nodal status pN 1 or 2 Any pT stage and microscopic positive margins Presence of any microscopic vascular invasion Underwent surgical resection of primary tumor within the past month Removal of clinical N+ disease required No evidence of metastatic disease No evidence of macroscopic residual disease PATIENT CHARACTERISTICS: Age 75 and under Performance status WHO 0-1 Life expectancy Not specified Hematopoietic WBC at least 3,500/mm^3 Platelet count at least 100,000/mm^3 Hepatic Liver function tests no greater than 1.25 times upper limit of normal (ULN) Renal Creatinine less than 1.5 times ULN Cardiovascular No myocardial infarction within the past 6 months No unstable angina pectoris Other Not pregnant or nursing No prior or other concurrent malignancies that would preclude study therapy or comparisons No other concurrent illness that would preclude study therapy No concurrent active infections requiring antibiotic therapy PRIOR CONCURRENT THERAPY: Biologic therapy No other concurrent immunotherapy Chemotherapy No prior chemotherapy Endocrine therapy No concurrent corticosteroids No concurrent hormonal therapy Radiotherapy No prior radiotherapy Surgery See Disease Characteristics No prior major organ allografts Other No other concurrent investigational drugs, agents, or devices