PRIOR CONCURRENT THERAPY: Biologic therapy: At least 4 weeks since prior biologic therapy Chemotherapy: See Disease Characteristics At least 4 weeks since prior chemotherapy (6 weeks since prior mitomycin or nitrosoureas) Endocrine therapy: At least 4 weeks since prior glucocorticoids (e.g., prednisone, dexamethasone) Radiotherapy: At least 4 weeks since prior radiotherapy No prior radiotherapy to more than 20% of bone marrow Surgery: At least 4 weeks since prior surgery Other: Recovered from the toxic effects of prior therapy No other concurrent therapy