Use of isotope-labeled somatostatin analogs for visualization of islet cell tumors.

The results of visualization of the islet cell tumors of 25 patients after intravenous administration of two isotope-labeled somatostatin analogs (123I-Tyr3-octreotide and 111In-octreotide) are described. The primary tumors, as well as previously often unrecognized distant metastases were visualized in 20 of the 25 patients (80%). Parallel in vitro detection of somatostatin receptors on those tumors that had also been visualized in vivo indicates that the ligand binding to the tumor in vivo indeed represents binding to specific somatostatin receptors. The detection of somatostatin receptors on these tumors in vivo predicted a good suppressive effect of octreotide on hormonal hypersecretion by these tumors. It is an easy, quick, harmless procedure that is valuable for localization of primary endocrine pancreatic tumors and their often radiologically and clinically not yet recognized metastases.