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]-octreotide. However, the relatively short effective half-life of this compound and the high background of radioactivity in the abdomen are drawbacks in its application. Therefore, an In-111-coupled somatostatin analogue ([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 out 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 pancreatic 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 visualized. Apart from APUD-cell-derived tumors, In-111-octreotide scintigraphy was also succesfully applied to visualize breast cancer, lymphomas and granulomas. In 39 out of 50 patients with breast carcinoma, 10 out of 11 patients with non-Hodgkin lymphomas, 3 out of 3 patients with Hodgkin's disease, and 8 out of 8 patients with sarcoidosis, tumor sites accumulated radioactivity during octreotide scintigraphy. In a considerable number of patients with carcinoids and glomus tumors, but also in patients with granulomas and lymphomas, In-111-octreotide scintigraphy revealed more tumor sites than did conventional imaging techniques. The results of imaging in vivo correlated with the somatostatin receptor status on the tumor in vitro. In conclusion, In-111-octreotide scintigraphy is a simple and sensitive technique to demonstrate tumor localization in the majority of patients with APUD cell tumors, and also in patients with lymphomas or granulomas. Apart from its merit in tumor localization, in vivo somatostatin receptor imaging, in consequence of its ability to demonstrate somatostatin receptor positive tumors, could be used to select those patients with APUD cell tumors who are likely to respond favorably to octreotide treatment.