RESUMO
BACKGROUND: Targeted radiotherapy with (131) I-Metaiodobenzylguanidine ((131) 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 (131) I-MIBG treatment following an effective initial treatment. PROCEDURES: After an initial infusion of 18 mCi/kg (131) I-MIBG, patients with tumor response or stable disease (SD), and available hematopoietic stem cell product, were eligible for additional (131) 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. RESULTS: Seventy-six heavily pretreated patients (median 4 prior chemotherapy regimens, range 1-8) with relapsed neuroblastoma were treated with (131) 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 (131) I-MIBG scanning. Hematologic toxicity was managed with early PBSC support after the second therapy (median: 15 days). CONCLUSIONS: Early second (131) I-MIBG safely reduces disease burden in patients with relapsed neuroblastoma. Patients with CR by conventional (123) I-MIBG scintigraphy may have substantial disease burden apparent on high-dose (131) I-MIBG scintigraphy, supporting consolidation with subsequent (131) I-MIBG therapy in cases of apparent complete remission. Pediatr Blood Cancer 2011; 57: 1124-1129. © 2011 Wiley Periodicals, Inc.