USE OF RADIOLABELED SOMATOSTATIN ANALOGS IN THE IDENTIFICATION AND TREATMENT OF SOMATOSTATIN RECEPTOR-BEARING TUMORS

Radiolabeled somatostatin analogs are potentially of considerable valu e in both the localization and treatment of somatostatin receptor-bear ing tumors. Whole body I-123-labeled Tyr3-octreotide scintigraphy is c apable of detecting and localizing primary tumors and metastatic disea se that may not be detectable by other methods. Although it is possibl e that this technique may be applicable to a wide variety of neoplasms , I-123-Tyr3-octreotide scans appear particularly useful for imaging v arious gut neuroendocrine tumors, meningiomas, and paragangliomas. Thi s primarily reflects the level of expression of somatostatin receptors by these lesions. In addition to whole body scintigraphy, intraoperat ive localization by receptor identification utilizing a hand-held gamm a detector probe may prove to be an effective means of identifying spr ead and micrometastasis of somatostatin receptor-bearing tumors. Aside from identification and topographic localization of disease, the dete ction of an I-123-Tyr3-octreotide labeled tumor may be utilized as in vivo assay for the presence of somatostatin receptors. Such observatio ns may prove useful in predicting the susceptibility of an individual tumor to octreotide therapy. Additionally, it may prove possible to de liver a therapeutic dose of radiation to receptor-bearing tumors by th e administration of specific radiolabeled somatostatin analogs.