MIBG for Refractory Neuroblastoma and Pheochromocytoma

Primary Objective is to provide access to therapy with 131I-MIBG for patients with relapsed/refractory neuroblastoma or metastatic pheochromocytoma. Secondary Objective is to assess disease response to 131I-MIBG therapy for patients with relapsed/refractory neuroblastoma or metastatic pheochromocytoma. Tertiary Objectives are to 1) gain more information about the toxicities of 131I-MIBG therapy; 2) assess improvement of symptoms, including pain and fatigue, for patients with relapsed/refractory neuroblastoma or metastatic pheochromocytoma who are receiving 131I-MIBG therapy. * The therapeutic dose of 131I-MIBG will be based on the following: 1. Minimum dose of 10 mCi/kg for patients without a stem cell source whose renal function is above the upper limit of normal but still meets eligibility criteria. 2. Dose of 12 mCi/kg for patients without a stem cell source with normal renal function and meets other eligibility criteria. 3. Dose of \> 12 mCi/kg to 18 mCi/kg maximum at investigator's discretion for patients meeting eligibility criteria with stem cells available. * A urinary catheter and intravenous fluids will be used for bladder protection, and potassium iodide solution for thyroid Protection. * G-CSF is recommended for patients with ANC less than 750 after MIBG infusion. * hematopoietic stem cell infusion is recommended for patients with grade 4 hematologic toxicity following 131I-MIBG therapy that continues to have an ANC \<200 on G-CSF without signs of recovery for \>2 weeks and any patient requiring platelet transfusion more than two times weekly for 4 consecutive weeks. * Follow-up will be done until disease progression, death or other therapies are initiated.