PRIOR CONCURRENT THERAPY: Biologic therapy: At least 2 weeks since prior colony stimulating factor and other cytokines active on bone marrow Chemotherapy: At least 4 weeks since prior chemotherapy (6 weeks since mitomycin or nitrosoureas) No prior or concurrent irinotecan and fluorouracil therapy Endocrine therapy: Not specified Radiotherapy: At least 4 weeks since prior radiotherapy No concurrent radiotherapy Surgery: Recovered from prior major surgery