Stratum 1 Eligibility Criteria

• Must be ≥ 1 and ≤ 21 years of age.
• Must have histologically or cytologically documented diagnosis of solid tumor refractory to conventional therapeutic modalities or for which no effective therapy is known. Patients with brain tumors will be eligible for this study. For patients with brain stem gliomas the requirement for histologic verification may be waived.
• Must have evaluable disease. Evidence of measurable disease on radiographic studies is not required for entry onto the protocol.
• Karnofsky ≥ 50% for patients > 10 years of age and or Lansky ≥ 50% for children ≤ 10 years of age. Patients who are unable to walk because of paralysis, but who are up in a wheelchair will be considered ambulatory for the purpose of assessing the performance score.
• Patients must have a life expectancy of at least 8 weeks.
• Patients must have recovered from the acute toxic effects of all prior therapy.
• Myelosuppressive chemotherapy: Must not have received within 3 weeks of entry onto this study (six weeks if prior nitrosourea)
• XRT: ≥ 6 months must have elapsed if prior craniospinal XRT or if ≥ 50% radiation of pelvis; ≥ 6 wks must have elapsed if other substantial BM radiation
• Autologous BMT without TBI: ≥ 6 mos must have elapsed (if applicable). Does not include prior treatment with high dose chemotherapy followed by stem cell rescue.
• Growth factor(s): Must not have received within 1 week of entry onto this study
• Patients with brain tumors who are receiving dexamethasone must be on a stable or decreasing dose for at least 2 weeks prior to study entry.
• Must have adequate bone marrow function (peripheral ANC ≥ 1,500/mm3, platelet count ≥ 100,000/mm3; hemoglobin ≥ 8.0 g/dl.)
• Must have adequate renal function (normal creatinine for age or GFR ≥ 70 ml/min/1.73m2) and hepatic function (bilirubin < 1.5 mg/dl; SGPT < 5x normal).

Stratum 1 Exclusion Criteria:

• Patients who have previously received irinotecan.
• Patients who are pregnant or lactating. Males or females of reproductive potential may not participate unless they have agreed to use an effective contraceptive method.
• Patients who have an uncontrolled infection.
• Patients who are receiving any other cancer chemotherapy or any other investigational agents.
• Patients who have had a BMT which included TBI or an allogeneic BMT.
• Patients with bone marrow involvement.
• Patients who are receiving anticonvulsants as outlined in stratum 3.

Stratum 2:

• Stratum 1 must be closed. All patients who fulfill the Eligibility Criteria for Stratum 1and the Exclusion Criteria plus the following exclusions:
• Patients who have received more than two prior multi-agent chemotherapy regimens.
• Patients who have had prior central axis radiation.
• Patients who have had bone marrow transplantation (with or without TBI).
• Patients who have had pelvic, and/or total abdominal radiation.

Stratum 3:

• Patients receiving enzyme inducing anticonvulsants ( phenytoin, phenobarbital, carbamazepine, etc.) are eligible for this study if they meet the eligibility and exclusion criteria for the corresponding open stratum (Stratum 1 or 2).
• Patients must be on a stable dose of their anticonvulsant medication for a minimum of two weeks prior to study entry.
• Patients who are taking valproic acid must also be receiving another enzyme inducing anticonvulsant drug in order to be eligible for the study.