MIBG and radiolabeled octreotide in neuroendocrine tumors.

Two newly developed radiopharmaceuticals, [131I]metaiodobenzylguanidine (MIBG) and 111In-pentetreotide, are currently used for the diagnosis and therapy of neural crest tumors. They interact with characteristic features of these tumors, such as the active uptake-1 mechanism at the cell membrane and vesicles or neurosecretory granules in the cytoplasm, as well as the presence of specific receptors at the cell membrane. The role of MIBG and Somatostatin analogues in the management of neural crest tumors is reviewed. Other uses of these radiopharmaceuticals are mentioned. It is concluded that both 111In-pentetreotide and 123I/[131]MIBG are sensitive indicators of neural crest tumors, which have a complementary role. Unlike MIBG, 111In-pentetreotide is not specific for neural crest tumors, as scintigraphy is also positive in many other tumors, granulomas and autoimmune diseases. [131I]MIBG is effectively used for the therapy of several neural crest tumors; the biodistribution of 111In-pentetreotide at present does not allow radionuclide therapy using a beta emitting label. However, as an indicator of somatostatin receptors, 111In-pentetreotide scintigraphy may be a predictor of the response to palliative treatment with unlabelled octreotide. Recommendations for the use of these procedures are given.