Tumor response and toxicity with multiple infusions of high dose 131I‐MIBG for refractory neuroblastoma

Abstract

Background ¹³¹I Metaiodobenzylguanidine (¹³¹I-MIBG) is an effective targeted radiotherapeutic for neuroblastoma with response rates greater than 30% in refractory disease. Toxicity is mainly limited to myelosuppression. The aim of this study was to determine the response rate and hematologic toxicity of multiple infusions of ¹³¹I-MIBG. Procedure Patients received two to four infusions of ¹³¹I-MIBG at activity levels of 3–19 mCi/kg per infusion. Criteria for subsequent infusions were neutrophil recovery without stem cell support and lack of disease progression after the first infusion. Results Sixty-two infusions were administered to 28 patients, with 24 patients receiving two infusions, two patients receiving three infusions, and two patients receiving four infusions. All patients were heavily pre-treated, including 16 with prior myeloablative therapy. Eleven patients (39%) had overall disease response to multiple therapies, including eight patients with measurable responses to each of two or three infusions, and three with a partial response (PR) after the first infusion and stable disease after the second. The main toxicity was myelosuppression, with 78% and 82% of patients requiring platelet transfusion support after the first and second infusion, respectively, while only 50% had grade 4 neutropenia, usually transient. Thirteen patients did not recover platelet transfusion independence after their final MIBG infusion; stem cell support was given in ten patients. Conclusions Multiple therapies with ¹³¹I-MIBG achieved increasing responses, but hematologic toxicity, especially to platelets, was dose limiting. More effective therapy might be given using consecutive doses in rapid succession with early stem cell support.