Safety and efficacy of tandem ¹³¹I‐metaiodobenzylguanidine infusions in relapsed/refractory neuroblastoma

<jats:title>Abstract</jats:title><jats:sec><jats:title>Background</jats:title><jats:p>Targeted radiotherapy with <jats:sup>131</jats:sup>I‐Metaiodobenzylguanidine (<jats:sup>131</jats:sup>I‐MIBG) is safe and effective therapy for patients with relapsed neuroblastoma, but anti‐tumor activity is sometimes transient. The goal of this study was to determine the safety and efficacy of early (<100 days) second <jats:sup>131</jats:sup>I‐MIBG treatment following an effective initial treatment.</jats:p></jats:sec><jats:sec><jats:title>Procedures</jats:title><jats:p>After an initial infusion of 18 mCi/kg <jats:sup>131</jats:sup>I‐MIBG, patients with tumor response or stable disease (SD), and available hematopoietic stem cell product, were eligible for additional <jats:sup>131</jats:sup>I‐MIBG therapy. Residual thrombocytopenia did not preclude patients from receiving additional treatment. Subsequent treatment was administered a minimum of 6 weeks and maximum 100 days from initial infusion, and subjects could receive subsequent therapy if the same criteria were met.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>Seventy‐six heavily pretreated patients (median 4 prior chemotherapy regimens, range 1–8) with relapsed neuroblastoma were treated with <jats:sup>131</jats:sup>I‐MIBG. Response rate to the first infusion was 30%, with 49% showing SD. Response rate among the 41 patients receiving a subsequent second infusion was 29%. After two treatments, 39% of patients experienced a reduction in overall disease burden. Four of five complete responses (CRs) to the initial infusion were maintained, despite all five having disease readily apparent on immediate post‐second treatment <jats:sup>131</jats:sup>I‐MIBG scanning. Hematologic toxicity was managed with early PBSC support after the second therapy (median: 15 days).</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p>Early second <jats:sup>131</jats:sup>I‐MIBG safely reduces disease burden in patients with relapsed neuroblastoma. Patients with CR by conventional <jats:sup>123</jats:sup>I‐MIBG scintigraphy may have substantial disease burden apparent on high‐dose <jats:sup>131</jats:sup>I‐MIBG scintigraphy, supporting consolidation with subsequent <jats:sup>131</jats:sup>I‐MIBG therapy in cases of apparent complete remission. Pediatr Blood Cancer 2011; 57: 1124–1129. © 2011 Wiley Periodicals, Inc.</jats:p></jats:sec>