131I-MIBG in Neuroblastoma, is Not Simply the Uptake in the Primary Mass

Neuroblastoma is the third most common malignancy of childhood. Nowadays. MlBG has become a central procedure for staging and defining extent and location of neuroblastoma tumors. The recommendations of the International Neuroblastoma Staging System (INSS) indicate that MlBG scintigraphy must be performed in patients with neuroblastoma at the time of initial staging and as a followup tool during therapy. Purpose: Of this study is to identify the role of 131IMlBG scintigraphy in neuroblastoma patients and to correlate it with other diagnostic modalities for staging and follow up of neuroblastoma. Methods: The study was conducted on 26 patients provisionally diagnosed to have neuroblastoma. On histopathologic verification 5 of these 26 patients were re diagnosed as non-neuroblastoma. Since the study aims at assessing the diagnostic power of 131IMIBG scan, these 5 cases were not excluded. The 21 histopathologically diagnosed as neuroblastoma were 11 patients in stage IV, 7 in stage III and 1 patient in each of stages I, 11 and IVS. Each. patient underwent a standard comprehensive diagnostic work up, Radiological imaging by conventional X-ray. ultrasound. CT and/or MRI was carried out. In all patients I3IIMIBG scintigraphy was performed, among them 15 patients underwent additional 99mTc-MDP bone scan as well. The 21 neuroblastoma patients were studied according to the results obtained from CT, MRI and 131IMlBG scanning. The outcome demonstrated that CT and MR1 were able to detect lesions in 19 out of 2] patients; while in 2 patients no lesions were detected. 131IMIBG scan showed actively functioning lesions in ] 6 out of the above] 9 patients. while in 3 patients MIBG scan was negative. There was no false positive result by 131IMIBG scan. Accordingly. 1311MIBG is able to detect neuroblastoma lesions with an overall sensitivity of 84.2%. specificity of 100% and an accuracy of 85.7%. Detection of primary lesions by 131IMlBG was significantly better than 99mTc-MDP bone scanning (92.31 % vs 61.54% respectively) (ρ< 0.01). For skeletal metastases, 131I-MIBG scan has a higher ability to detect more lesions than 99mTc-MDP bone scan (17 0.023). Conclusions: 131IMIBG has excellent ability to discriminate between neuroblastoma and other small round cell pediatric tumors. 131IMIBG was found to be significantly superior to conventional bone scanning in revealing both primary and metastatic osseous lesions. It is recommended to perform 131IMIBG scanning at initial presentation to confirm the histopathologic diagnosis and to monitor subsequent response to therapy