Retrospective analysis of neuroblastoma and pheochromocytoma therapy with I-131 metaiodobenzylguanidine at a reference oncology hospital in Brazil.

Abstract

Background: Metaiodobenzylguanidine (MIBG) is a norepinephrine analogue with high affinity and specificity for the norepinephrine transporter. I-131-labeled MIBG (I-131 MIBG) is a therapeutic radiopharmaceutical used in selected cases of refractory or metastatic neuroblastoma and pheochromocytoma, tumors that overexpress the norepinephrine transporter. While the use of I-131 MIBG in neuroblastoma and pheochromocytoma therapy is well-established, the literature shows significant variability in treatment response, regarding the dose of the radiopharmaceutical, previous therapies administered, and the clinical condition of the patients involved in the studies. To contribute to the current literature, this study analyzed the use of I-131 MIBG at a cancer treatment institution in Brazil.

Methods: Retrospective, observational, single-center study was conducted, with a descriptive and exploratory character, involving patients diagnosed with neuroblastoma and pheochromocytoma treated with I-131 MIBG from 2010 to 2025. Demographic, clinical, and laboratory parameters were collected before and after I-131 MIBG therapy. The outcome was determined through survival analysis.

Results: Thirty-two patients were treated with I-131 MIBG, including 24 patients with neuroblastoma and six patients with pheochromocytoma. Leukocytes and platelets showed a reduction, and aspartate aminotransferase (AST) levels exhibited a significant increase posttherapy in patients with neuroblastoma. Survival rate was 84% in patients with pheochromocytoma and 55% in patients with neuroblastoma in the first year following I-131 MIBG therapy; however, both groups showed a gradual reduction in the cumulative survival rates, reaching 20% after 5 years.

Conclusion: I-131 MIBG was primarily used for the treatment of neuroblastoma in pediatric patients, and pheochromocytomas in adults. Anemia, leukopenia, thrombocytopenia, and increased serum AST were the main adverse events, and cumulative survival rates were 20% after 5 years.