Use Of Metaiodobenzylguanidine Research Articles

MIBG in Neuroblastoma Diagnostic Imaging and Therapy.

Neuroblastoma is a common malignancy observed in infants and young children. It has a varied prognosis, ranging from spontaneous regression to aggressive metastatic tumors with fatal outcomes despite multimodality therapy. Patients are divided into risk groups on the basis of age, stage, and biologic tumor factors. Multiple clinical and imaging tests are needed for accurate patient assessment. Iodine 123 ((123)I) metaiodobenzylguanidine (MIBG) is the first-line functional imaging agent used in neuroblastoma imaging. MIBG uptake is seen in 90% of neuroblastomas, identifying both the primary tumor and sites of metastatic disease. The addition of single photon emission computed tomography (SPECT) and SPECT/computed tomography to (123)I-MIBG planar images can improve identification and characterization of sites of uptake. During scan interpretation, use of MIBG semiquantitative scoring systems improves description of disease extent and distribution and may be helpful in defining prognosis. Therapeutic use of MIBG labeled with iodine 131 ((131)I) is being investigated as part of research trials, both as a single agent and in conjunction with other therapies. (131)I-MIBG therapy has been studied in patients with newly diagnosed neuroblastoma and those with relapsed disease. Development and implementation of an institutional (131)I-MIBG therapy research program requires extensive preparation with a focus on radiation protection.

The evolution in the use of MIBG scintigraphy in pheochromocytomas and paragangliomas

Radioiodinated metaiodobenzylguanidine (MIBG) was developed in the late 1970's, at the Michigan University Medical Center, for imaging of the adrenal medulla and its diseases. Soon after, MIBG was shown to depict a wide range of tumors of neural crest origin other than pheochromocytomas/paragangliomas (Pheo/PGL) with the result that its use rapidly spread to many countries. After more than 30 years of clinical application, MIBG continues to be the most widespread radiopharmaceutical for the functional imaging of Pheo/PGL in spite of the emergent role of PET agents for detection of these tumors. In this paper we review the evolution in the use of MIBG over more than 30 years of experimental and clinical applications, with particular focus on the uptake mechanisms, pharmacokinetics, biodistribution and drug interaction as well as on clinical studies in Pheo/PGL also in comparison to other gamma-emitters tracers and PET radiopharmaceuticals.

Management of Malignant Phaeochromocytoma: A Retrospective Review of the use of MIBG and Chemotherapy in the West Midlands

Metastatic malignant phaeochromocytoma is a rare disorder, with no randomized and few prospective data to facilitate choice between the two main treatment modalities, chemotherapy and radiolabelled metaiodobenzylguanidine (MIBG). In the last decade the latter modality has been preferred and radiological response rates of 30% have been reported. There are fewer patients described in the literature who have received chemotherapy but one prospective trial of chemotherapy reported radiological response rates of 57%. A recent prospective trial combining the two modalities has been disappointing with only one patient completing the treatment schedule. We present six patients with malignant phaeochromocytoma or paraganglioma who received MIBG therapy. Four patients also received chemotherapy.A retrospective review of the case notes was performed. Radiological and hormonal responses were determined and the time to progression after each modality was calculated. One partial hormonal response was seen with MIBG treatment. One complete and one partial hormonal response and one partial radiological response were seen with chemotherapy. The median time to disease progression from commencement of MIBG was 12 months (range 3–44) and from commencement of chemotherapy used as first or second line treatment was 22.5 months (range 7–25).Chemotherapy may be a more active modality in this disease than previously considered. MIBG uptake may increase after a partial radiological response to chemotherapy, enabling subsequent MIBG therapy. Researchers carrying out future trials on combined therapy should consider administering chemotherapy prior to MIBG for the reasons that we outline in this article.

No-carrier-added 123I-MIBG: An initial clinical study in patients with phaeochromocytoma

Radioiodinated meta-iodobenzylguanidine (MIBG) is used routinely for imaging and targeted radiotherapy of tumours derived from the neural crest. Since active uptake of MIBG by the noradrenaline transporter (NAT) makes a greater contribution to total drug accumulation than passive uptake when MIBG is present at low concentrations, tumour-specific uptake should be enhanced by the administration of lower molar amounts of MIBG. This could be achieved through the use of MIBG with a high specific activity. Commercially available preparations of 123I-MIBG have specific activities of approximately 200 MBq.mg-1. We have synthesized and used no-carrier-added (n.c.a.) 123I-MIBG produced by an iododesilylation reaction (specific activity 0.7 TBq.mg-1). We report here the first clinical studies comparing the commercially available and n.c.a. MIBG diagnostic preparations. Five patients with known phaeochromocytoma were studied. Unlike studies in animal models, no consistent improvement in tumour uptake was observed with the n.c.a. material. A larger patient group is required to determine whether there are significant differences between the two preparations, before proceeding to studies at therapeutic activity levels of n.c.a. 131I-MIBG. Even with no improvement in tumour uptake, n.c.a. MIBG may be the favoured formulation for therapeutic applications to reduce the molar amount of drug injected.

Captação diferenciada de meta-iodobenzilgnanidina em paciente com feocromocitoma bilateral e neoplasm endócrina múltipla tipo 2A

O feocromocitoma que ocorre na síndrome de Neoplasia endócrina múltipla tipo 2A (NEM-2A), também conhecida como síndrome de Sipple, é muitas vezes bilateral e multicêntrico. O uso da cintilografia com meta-iodobenzilguanidina (M-IBG) é um método seguro e eficaz para o diagnóstico de localização do feocromocitoma, particularmente nos casos de sítio extra-adrenal, recorrência pós-operatória ou doença metastática maligna. Apresentamos o caso de uma paciente feminina de 26 anos com NEM-2A e feocromocitoma adrenal bilateral (visualizado na Ressonância Nuclear Magnética e confirmado pelo exame histopatológico), cuja cintilografia com I131 M-IBG revelou marcada diferença de captação entre as adrenais (mínima à direita e mais intensa à esquerda). Relevante no caso, foi o fato do tumor à direita ser muito maior (5,5 cm de diâmetro) do que à esquerda (3,0 cm de diâmetro), funcionalmente iguais (caracterizado por complicações pré-operatórias quando da manipulação cirúrgica) e histopatologicamente similares. Concluímos que nos casos de NEM-2A, a captação negativa ou discreta de M-IBG não exclui a necessidade de exploração cirúrgica bilateral das adrenais.