COMPARISON OF RADIOLABELED OCTREOTIDE AND METAIODOBENZYLGUANIDINE (MIBG) SCINTIGRAPHY IN MALIGNANT PHEOCHROMOCYTOMA

Methods: The results of in vivo somatostatin scintigraphy were correla ted with those of MIBG from 14 patients, aged 22-66 yr, with metastati c pheochromocytoma (10 patients), malignant paraganglioma (3 patients) and metastatic ganglioneuroblastoma (1 patient). Twelve patients had elevated catecholamine excretion. A dynamic study and serial whole-bod y scans (4-48 hr) were obtained after injection of 130-187 MBq of In-1 11-DTPA-Phe-1-octreotide. When indicated, SPECT imaging was done. The results were compared to MIBG scans obtained after a diagnostic or a t herapeutic dose. Results: Three patients with more than 20 tumor sites on MIBG scans had only 1-9 sites on In-111-octreotide scintigraphy. T wo patients had no MIBG uptake but one had lung uptake on octreotide s cintigraphy. In the other 9 patients with a total of 41 foci of MIBG u ptake, 33 sites of In-111-octreotide uptake are found. All positive im ages with octreotide scintigraphy were seen at or before 4 hr, but the contrast improved at 24 hr. Uptake intensity was lower with In-111-oc treotide than MIBG and the number of tumor sites was higher with MIBG. However, seven foci were positive only on octreotide scintigraphy and six of them could not be confirmed by other imaging modalities. Concl usion: Use of octreotide to identify somatostatin receptors seems prom ising, especially when results from MIBG scans are negative. Moreover octreotide images could aid in determining a treatment regimen as well as establishing the extent of disease and prognosis.