Additional Value of PET/CT to Other Radionuclide Imaging in Diagnosis in Neuroblastoma

Nuclear Medicine imaging is needed in Neuroblastoma for proper staging of primary tumor identification and metastatic surveillance, and monitoring of patients response. Metaiodobenzylguanidine (MIBG) is an analog of catecholamine precursors which localizes to neuroblastoma in primary sites and in bone, bone marrow, and lymph nodes with high specificity (95-100%). It helps to study of tumor uptake and residence time in order to decide and plan a treatment with high activities of radiolabelled MIBG(1). Also in evaluation of tumor response to therapy by measuring the intensity of MIBG uptake and the number of focal MIBG uptake sites. Also the extent of MIBG uptake might have prognostic significance. In some cases MIBG scintigraphy yields the only evidence of residual disease in a small percentage of patients (33). (Fig.1)
Persistent MIBG positivity during and after induction therapy forebodes a poor outcome. However one of the drawbacks
of MIBG imaging is that a considerable minority of tumors are not MIBG avid (2), the use of MIBG scintigraphy in routine
patient assessment is controversial; as a recent study showed that MIBG results did not alter staging or treatment for any
of the patients studied. Also, recurrent NB may fail to show uptake in some patients with recurrence(3).Common
falsely positive findings: Increased diffuse physiological uptake in hyperplastic adrenal gland after contralateral adrenalectomy increased focal physiological uptakes in the urinary tract or bowel, Urine contamination or any other external contamination (salivary secretion)(4,5). Falsely negative MIBG findings: Lack of tumor-cell MIBG avidity in view of differentiation, necrosis or interfering drugs. Nonvisualization of lesions because of intense radiotracer uptake in normal liver, myocardium, salivary glands, intestines(5, 6).