Somatostatin and somatostatin analogues in medullary thyroid carcinoma

Medullary thyroid carcinoma (MTC) is a neuroendocrine tumour characterized by the production and secretion of calcitonin. MTC tumours may express functional somatostatin receptors (hSSTR). A significant proportion of hSSTR receptor-positive MTC tumours, including metastatic disease, may be visualized in vivo through In-111-pentetreotide scintigraphy. Four patients with recurrent/metastatic disease, who had previously been assessed with In-111-anti-CEA monoclonal antibody fragment [F(ab')(2)] imaging, were evaluated. In-111-pentetreotide scintigraphy localized all known disease sites. Furthermore, mediastinal disease was detected in one patient with negative conventional and In-111-anti-CEA F(ab')(2) imaging studies. The detection of somatostatin within the tumour (2 patients), or negative octreotide challenges (2 patients), did not affect the outcome of In-111-pentetreotide scintigraphy. In conclusion, In-111-pentetreotide scintigraphy appears at least as effective as In-111-anti-CEA F(ab')(2) imaging and should be considered in the diagnostic evaluation of MTC, particularly in the setting of recurrent/metastatic disease not detected by conventional means.