Inclusion Criteria:
* Diagnosis: Relapsed/Refractory neuroblastoma, with an original diagnosis made histologically or from elevated urine catecholamines with abnormal tumor cells in bone marrow OR relapsed/refractory pheochromocytoma.
* Disease status: Progressive disease at any time (defined as any new lesion or an increase in size by \>25% of pre-existing disease), or a failure to respond to standard therapy. Patients must have evidence of MIBG uptake into tumor at ≥ one site within 6 weeks prior to entry on study and subsequent to any intervening therapy
* Prior therapy: A minimum of two weeks since should have elapsed since any chemotherapy causing myelosuppression. It must be a minimum of three months since receiving radiation to any of the following fields: craniospinal, total abdominal, whole lung, total body irradiation. For any other sites of radiation, at least 2 weeks should have elapsed. For patients who received radiation to the only site of MIBG-avid disease within two months of study entry, biopsy confirmation of residual active disease is required, with positive bone marrow being sufficient. At least 7 days should have elapsed since completion of therapy with a biologic agent and at least 3 half-lives should have elapsed since therapy with a monoclonal antibody. No cytokine therapy may be given within 24 hours of receiving 131I-MIBG. Patients may have received prior MIBG therapy, provided they demonstrated a response or stable disease initially, with progressive disease occurring at least 35 days following treatment.
* Organ function: ANC \>500/uL, platelets \>20,000/uL with transfusion allowed. Bilirubin ≤2x ULN, AST/ALT ≤10x ULN.Serum Creatinine ≤2x ULN OR 24-hour creatinine clearance OR GFR ≥60ml/min/1.73m2. Normal lung function demonstrated by no dyspnea, exercise intolerance or oxygen requirement. Oxygen saturation ≥94% on room air. No clinically significant cardiac dysfunction and ejection fraction ≥45% on echocardiogram.
* Stem cells: Patients must have a minimum of 2.0 x106/kg viable CD34+ peripheral blood stem cells for re-infusion following 131I-MIBG. An additional back-up of 2.0x106/kg CD34+ cells is recommended but not required.
* Life expectancy longer than 8 weeks,Karnofsky or Lansky performance status of ≥ 50%
Exclusion Criteria:
* Pregnant or lactating patients
* Disease of any organ system that would compromise the patient's ability to participate in the study, including hemodialysis. Significant organ impairment should be discussed with the Principal Investigator prior to study entry
* Patients with active grade 3-4 infection, as defined by the NCI CTCAE V4.0.
* Patients with known MBIG-avid brain parenchymal disease (leptomeningeal or skull based metastases are eligible).
* In patients with metastatic pheochromocytoma, a urinalysis must be preformed prior to study enrollment. If proteinuria is present, a 24 hour urine must be collected and total protein determined. If the 24-hour urine protein is above the institutional upper limit of normal, the patient is excluded.
