Irinotecan in Treating Children With Refractory or Advanced Solid Tumors Who Are Receiving Anticonvulsants

DISEASE CHARACTERISTICS: * Histologically confirmed malignancy refractory to conventional therapy or for which no conventional therapy exists * Histologic confirmation not required for brain stem tumors * Concurrently on anticonvulsants at a steady level for at least 2 weeks PATIENT CHARACTERISTICS: Age: * 1-21 years old Performance status: * Karnofsky 50-100% (over 10 years of age) * Lansky 50-100% (10 years of age or under) Life expectancy: * At least 8 weeks Hematopoietic: * Neutrophil count at least 1,000/mm3 * Platelet count at least 100,000/mm3 (transfusion independent) * Hemoglobin at least 8.0 g/dL (red blood cell transfusions allowed) Hepatic: * Bilirubin no greater than 1.5 times normal for age * SGPT less than 5 times normal for age * Albumin at least 2 g/dL Renal: * Creatinine no greater than 1.5 times normal for age OR * Creatinine clearance or radioisotope glomerular filtration rate at least lower limit of normal for age Other: * Not pregnant or nursing * Negative pregnancy test * Fertile patients must use effective contraception * No uncontrolled infection * No evidence of active graft-vs-host disease * Neurologic deficits for CNS tumors stable for at least 2 weeks prior to study PRIOR CONCURRENT THERAPY: Biologic therapy: * At least 1 week since prior antineoplastic biologic therapy * At least 6 months since prior allogeneic stem cell transplantation * At least 1 week since prior growth factors * No concurrent sargramostim (GM-CSF) * No concurrent prophylactic growth factors during first course of study therapy * Recovered from prior immunotherapy Chemotherapy: * At least 2 weeks since prior myelosuppressive chemotherapy (4 weeks for nitrosourea) and recovered Endocrine therapy: * Concurrent dexamethasone for CNS tumors with increased intracranial pressure allowed if dose stable or decreasing for at least 2 weeks prior to study Radiotherapy: * At least 2 weeks since prior local palliative radiotherapy (small part) * At least 6 months since prior craniospinal radiotherapy * At least 6 months since prior radiotherapy to at least 50% of pelvis * At least 6 weeks since prior substantial bone marrow radiotherapy * Recovered from prior radiotherapy Surgery: * Not specified Other: * No other concurrent investigational agent