111In-octreotide scintigraphy in endocrine tumors. Preliminary data

A large number of endocrine tumors express somatostatin receptors, and the use of radiolabeled somatostatin analogs has been recently introduced for their localization. Using in vivo scintigraphy with 111In-pentetreotide, primary tumor localizations were demonstrated in 3/3 carcinoids (2 intestinal carcinoids and 1 lung ACTH-secreting carcinoid; in 2 patients liver metastases larger than 1 cm were visualized), in 1/1 GH-secreting pituitary macroadenoma, and in 1/1 thyroid localization of MTC. Bone and/or lymph node metastases were imaged in 2/4 patients previously treated for MTC, with persistently high CT and CEA levels; in the other 2 patients the other scintigraphic techniques were also negative. Octreotide scintigraphy was negative in 2/2 insulinomas and in 2/2 ACT-producing pituitary adenomas. In 2 patients with carcinoid syndrome and 1 patient with Cushing syndrome due to ectopic ACTH, octreotide therapy induced a significant decrease in tumoral markers. Our preliminary data are in agreement with the results of larger series reported in literature: octreotide scintigraphy is a useful noninvasive tool to detect endocrine tumors expressing somatostatin receptors, particularly for carcinoids. It is of great use in the differential diagnosis of Cushing syndrome due to ectopic ACTH. Moreover, 111In-pentetreotide scintigraphy may be useful in selecting patients who may benefit from octreotide therapy to control hormonal hypersecretion effects.