IN-111 OCTREOTIDE SCINTIGRAPHY IN ONCOLOGY

Various tumors of neuroendocrine origin that have amine precursor and decarboxylation (APUD) characteristics can be visualized in vivo after intravenous injection of the somatostatin analogue [I-123-Tyr3]-octre otide. However, the relatively short effective half-life of this compo und and the high background of radioactivity in the abdomen are drawba cks in its application. Therefore, an In-111-coupled somatostatin anal ogue ([In-111-DTPA-D-Phe1]-octreotide) was developed. This analogue is excreted mainly via the kidneys, 90% of the dose being present in the urine 24 h after injection. Using In-111-octreotide scintigraphy, 7 o ut of 7 gastrinomas, 4 out of 7 insulinomas, 1 out of 1 glucagonoma, 3 out of 3 unclassified apudomas, but none out of 18 exocrine pancreati c carcinomas were visualized, Also, 19 out of 19 carcinoids, 15 out of 15 glomus tumors, 8 out of 12 medullary thyroid carcinomas, 6 out of 6 small cell lung carcinomas, 4 out of 4 growth hormone-producing and 6 out of 9 clinically nonfunctioning pituitary adenomas were visualize d. Apart from APUD-cell-derived tumors, In-111-octreotide scintigraphy was also succesfully applied to visualize breast cancer, lymphomas an d granulomas. In 39 out of 50 patients with breast carcinoma, 10 out o f 11 patients with non-Hodgkin lymphomas, 3 out of 3 patients with Hod gkin's disease, and 8 out of 8 patients with sarcoidosis, tumor sites accumulated radioactivity during octreotide scintigraphy. In a conside rable number of patients with carcinoids and glomus tumors, but also i n patients with granulomas and lymphomas, In-111-octreotide scintigrap hy revealed more tumor sites than did conventional imaging techniques. The results of imaging in vivo correlated with the somatostatin recep tor status on the tumor in vitro. In conclusion, In-111-octreotide sci ntigraphy is a simple and sensitive technique to demonstrate tumor loc alization in the majority of patients with APUD cell tumors, and also in patients with lymphomas or granulomas. Apart from its merit in tumo r localization, in vivo somatostatin receptor imaging, in consequence of its ability to demonstrate somatostatin receptor positive tumors, c ould be used to select those patients with APUD cell tumors who are li kely to respond favorably to octreotide treatment.