Hematologic toxicity of high-dose iodine-131-metaiodobenzylguanidine therapy for advanced neuroblastoma

Purpose Iodine-131-metaiodobenzylguanidine (I-131-MIBG) has been shown to be active against refractory neuroblastoma. The primary toxicity of I-131-MIBG is myelosuppression, which might necessitate autologous hematopoietic stem-cell transplantation (AHSCT). The goal of this study was to determine risk factors for myelosuppression and the need for AHSCT after I-131-MIBG treatment. Patients and Methods Fifty-three patients with refractory or relapsed neuroblastoma were treated with 18 mCi/kg I-131-MIBG on a phase I/II protocol. The median whole-body radiation dose was 2.92 Gy. Results Almost all patients required at least one platelet (96%) or red cell (91%) transfusion and most patients (79%) developed neutropenia (< 0.5 x 10(3)/muL). Patients reached platelet nadir earlier than neutrophil nadir (P < .0001). Earlier platelet nadir correlated with bone marrow tumor, more extensive bone involvement, higher whole-body radiation dose, and longer time from diagnosis to I-131-MIBG therapy (P less than or equal to .04). In patients who did not require AHSCT, bone marrow disease predicted longer periods of neutropenia and platelet transfusion dependence (P less than or equal to .03). Nineteen patients (36%) received AHSCT for prolonged myelosuppression. Of patients who received AHSCT, 100% recovered neutrophils, 73% recovered red cells, and 60% recovered platelets. Failure to recover red cells or platelets correlated with higher whole-body radiation dose (P less than or equal to .04). Conclusion These results demonstrate the substantial hematotoxicity associated with high-dose I-131-MIBG therapy, with severe thrombocytopenia an early and nearly universal finding. Bone marrow tumor at time of treatment was the most useful predictor of hematotoxicity, whereas whole-body radiation dose was the most useful predictor of failure to recover platelets after AHSCT. (C) 2004 by American Society of Clinical Oncology.