PRIOR CONCURRENT THERAPY: Biologic therapy: Not specified Chemotherapy: No chemotherapy within past 4 weeks (6 weeks for nitrosoureas) unless there is evidence of disease progression in CNS No concurrent chemotherapy Endocrine therapy: Patients receiving corticosteroids must be on stable dose for 10 days prior to entry Radiotherapy: No radiotherapy to disease site within past 3 months unless there is evidence of disease progression in CNS No concurrent radiotherapy Surgery: Not specified