Diagnosis of somatostatin receptor-positive tumours using 99TCM-hynic-toc: clinical evaluation

Objective: The aim of this study was to assess the diagnostic value of a somatostatin analog imaging agent, 99Tcm-octreotide(99Tcm-hydrazinonicotinyl-Tyr3- octreotide), for the localization of somatostatin receptor (SSTR)-positive tumours. Methods: 88 patients with suspicious endocrine tumors were enrolled in this study, including 37 neuroendocrine tumors, 23 non-neuroendrocrine tumors and 28 benign lesions. The diagnoses were confirmed by pathohistology, other examinations or clinical follow-up studies. Regional, whole body and SPECT/CT(in positive cases) imagings were acquired at 1 and 4 hours after an intravenous injection of 350-400 MBq 99Tcm-octreotide. 24 patients underwent also a 131I-MIBG imaging. 99Tcm-octreotide imagings were performed in 5 patients before and after therapy, including chemotherapy (1 patient) and peptide receptor radionuclide therapy (PRRT) with 90Y-DOTATOC (2 patients), or operation (2 patients). Results: Positive findings were obtained in 30 of 88 patients, including 25 neuroendocrine tumors( 12 pheochromocytomas, 2 neuroendocrine cancers, 2 pituitary tumors, 7 medullary thyroid carcinomas, 1 insulinoma, and 1 gastrinoma), 4 non-neuroendrocrine tumors (1 non-Hodgkin's lymphoma, 1 astrocytoma, 1 parathyroid adenoma and 1 parathyroid cancer), and one benign lesion. The sensitivity, specificity and accuracy of 99Tcm-octreotide imaging for somatostatin receptor- positive tumors were 72.5%, 97.9% and 86.4% respectively. One false-positive finding was caused by nonspecific uptake in a thyroid nodule. The semiquantitative region-of-interest analysis showed that the lesion at 4 hours after injection reached a higher tumor-to-normal ratio than at 1 hour. 131I-MIBG imaging was good for localization of pheochromocytoma of the adrenal gland, but 99Tcm-octreotide was better for ectopic pheochromocytoma. 99Tcm-octreotide imaging confirmed the therapeutic effect of PRRT with 90Y-DOTATOC and detected residual lesions after operation. Conclusion: 99Tcm-octreotide imaging is not only helpful for the diagnosis and localization of SSTR-positive tumours but also useful to detect the residual tumor after operation or evaluate therapeutic response. (authors)