Toxicity of upfront ¹³¹I-metaiodobenzylguanidine (¹³¹I-MIBG) therapy in newly diagnosed neuroblastoma patients: a retrospective analysis.

Purpose: In the treatment of patients with high-risk neuroblastoma, different doses of (131)I-metaiodobenzylguanidine ((131)I-MIBG) are administered at different time points during treatment. Toxicity, mainly haematological (thrombocytopenia), from (131)I-MIBG therapy is known to occur in extensively chemotherapy pretreated neuroblastoma patients. Up to now, acute toxicity from (131)I-MIBG as initial treatment has never been studied in a large cohort. The aim of this retrospective study was to document acute toxicity related to upfront (131)I-MIBG.

Methods: All neuroblastoma patients (stages 1-4 and 4S) treated upfront with (131)I-MIBG at the Emma Children's Hospital, Academic Medical Centre (1992 - 2008) were included in this retrospective analysis. The acute toxicity (during therapy) and short-term toxicity (1st month following therapy) of the first two (131)I-MIBG therapies were studied.

Results: Of 66 patients (34 boys, 32 girls; median age 2.2 years, range 0.1 - 9.4 years), 49 had stage 4 disease, 5 stage 4S, 6 stage 3, 1 stage 2 and 5 stage 1. The median first dose was 441 MBq/kg (range 157 - 804 MBq/kg). The median second dose was 328 MBq/kg (range 113 - 727 MBq/kg). The most frequently observed symptoms were nausea and vomiting (21 %, maximum grade II). The main toxicity was grade IV haematological, occurring only in stage 4 patients, after the first and second (131)I-MIBG therapies: anaemia (5 % and 4 %, respectively), leucocytopenia (3 % and 4 %) and thrombocytopenia (2 % and 4 %). No stem cell rescue was needed.

Conclusion: The main acute toxicity observed was haematological followed by nausea and vomiting. One patient developed posterior reversible encephalopathy syndrome during (131)I-MIBG therapy, possibly related to (131)I-MIBG. We consider (131)I-MIBG therapy to be a safe treatment modality.