Recent advances in radiological and radionuclide imaging and therapy of neuroendocrine tumours.

Neuroendocrine tumours (NETs) constitute a heterogeneous group of tumours that are able to express cell membrane neuroamine uptake mechanisms and/or specific receptors, such as somatostatin receptors, which can be of great value in the localization and treatment of these tumours. Scintigraphy with (111)In-pentetreotide has become one of the most important imaging investigations in the initial identification and staging of gastro-enteropancreatic (GEP) tumours, whereas helical computed tomography (CT), magnetic resonance imaging (MRI), endoscopic and/or peri-operative ultrasonography are used for the precise localization of GEPs and in monitoring their response to treatment. Scintigraphy with (123)I-MIBG (meta-iodobenzylguanidine) is sensitive in the identification of chromaffin cell tumours, although scintigraphy with (111)In-pentetreotide may also have a role in the localization of malignant chromaffin cell tumours and medullary thyroid carcinoma; for further localization and monitoring of the response to treatment both CT and MRI are used with high diagnostic accuracy. More recently, positron emission tomography (PET) scanning is being increasingly used for the localization of NETs, particularly when other imaging modalities have failed, although its precise role and utility remain to be defined. Surgery is still the usual initial therapeutic, and only curative, modality of choice; however, the majority of NETs will require further treatment with somatostatin analogues and/or interferon; chemotherapy may be used for progressive and highly aggressive NETs, but its role has not been clearly defined. For those NETs that demonstrate uptake to a diagnostic scan with (123)I-MIBG or (111)In-octreotide, therapy with radionuclides such as (131)I-MIBG or (111)In/(90)Y-octreotide or other isotopes, presents a further evolving therapeutic modality.