Targeted radiotherapy with submyeloablative doses of 131I-MIBG is effective for disease palliation in highly refractory neuroblastoma

Purpose: Treatment of refractory neuroblastoma remains a significant clinical problem. Targeted radiotherapy with I-131-MIBG has demonstrated antitumor activity in heavily pretreated neuroblastoma patients with recurrent disease. Response rates may be correlated with total radionuclide dose per kilogram body weight delivered, but higher dose levels are associated with protracted grade 4 hematologic toxicity. The optimal method for using single-agent I-131-MIBG for patients with relapsed high-risk neuroblastoma has not been defined. This study was designed to retrospectively determine the clinical response to I-131-MIBG therapy at submyeloablative doses in patients with refractory neuroblastoma and to describe the toxicities. Patients and Methods: A retrospective chart review of 20 patients with neuroblastoma treated with I-131-MIBG at the Children's Hospital of Philadelphia from 1988 to 2000 was performed. Demographic data, 131 I-MIBG dose delivered, toxicities, and clinical responses were reviewed. Results: A median dose of 9.5 mCi/kg of I-131-MIBG was delivered in 32 courses to 20 patients. Three patients were treated in first complete response, and the remaining 17 patients for residual and/or progressive disease. The objective response rate to the first therapy was 31%, and the remaining patients achieved disease stabilization. In addition, 9 of I I patients with pain at study entry had significant improvement. Disease response was not correlated with I-131-MIBG dose delivered. No unanticipated toxicities were observed. Conclusions: Submyeloablative-dose I-131-MIBG is an effective and relatively nontoxic method for neuroblastoma disease palliation. Most patients show subjective improvement in pain and/or performance status. Increased availability and experience with I-131-MIBG therapy would benefit a large number of children with end-stage neuroblastoma and no realistic hope for cure.