Single Autologous Stem Cell Rescue After Single or Tandem 131 I‐Metaiodobenzylguanidine Therapy, With or Without Subsequent Chemotherapy, for Resistant Neuroblastoma: Feasibility, Toxicity, and Response

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Background Myelosuppression is the principal toxicity of 131 I‐metaiodobenzylguanidine (MIBG) therapy for neuroblastoma and can be mitigated with autologous stem cell rescue (ASCR). We evaluated whether sequential 131 I‐MIBG therapy with chemotherapy could be supported by a single ASCR. Methods This is a retrospective analysis of patients who completed a single‐arm expanded access study (NCT00107289) in which 96 patients were treated with 131 I‐MIBG therapy between 2008 and 2020 at Memorial Sloan Kettering Cancer Center. Patients could receive one or two 131 I‐MIBG treatments, with or without chemotherapy. Myelosuppression was rescued with a single ASCR. Results Fifty‐three patients received single‐MIBG therapy, 43 received tandem MIBG therapy, and 61 received chemotherapy following single ( n = 33) or tandem ( n = 28) MIBG. ASCR was required in 11, 8, and 58 patients after single MIBG therapy, tandem MIBG therapy, and chemotherapy, respectively. Hematologic recovery with a single ASCR was adequate, with neutrophil and platelet engraftment in 100% and 90% of patients. Anti‐neuroblastoma activity was modest, with an overall objective response rate (complete/partial/minor response; ORR) of 15% after the first MIBG treatment. Tandem MIBG therapy did not meaningfully improve response (ORR; 21%), whereas chemotherapy after single MIBG therapy produced modest response improvement (ORR; 35%). Conclusion In selected patients with resistant neuroblastoma, sequential MIBG therapy with chemotherapy can be delivered with a single ASCR, potentially conserving stem cell aliquots. Given the modest responses and the toxicities encountered, novel agents rather than tandem MIBG therapy or chemotherapy should be considered to optimize the role of MIBG therapy.