Somatostatin and somatostatin analogues: diagnostic and therapeutic uses

Somatostatin and its octapeptide analogues exert their effects through interaction with somatostatin receptor (sst) subtypes 1 through 5 (sst(1-5)). Somatostatin binds with high affinity to all sst subtypes, whereas the currently commercially available octapeptide analogues bind only with a high affinity to sst, and sst(5). Pituitary tumors, endocrine pancreatic tumors, and carcinoid tumors express multiple sst subtypes, but sst(2) predominance is found in 90% of carcinoids and 80% of endocrine pancreatic tumors. Sst(2) and sst, predominance is found in growth hormone-secreting pituitary tumors. In patients harboring sst(2)- or sst(5)-positive neuroendocrine tumors, clinical symptomatology can be controlled by the chronic administration of one of the currently commercially available octapeptide somatostatin analogues. Tumors and metastases that bear sst, or sst(5), can be visualized in vivo after injection of radiolabeled octapeptide analogues. Radiolabeled octapeptide analogues can also be used for radiotherapy of sst(2)- and sst(5)-positive advanced or metastatic neuroendocrine tumors. (C) 2002 Lippincott Williams Wilkins, Inc.