99mTc-EDDA/HYNIC-TOC in gastroenteropancreatic neuro endocrine tumours

Full text: Somatostatin receptors have been identified on most endocrine tumours, including carcinoid tumours, which generally express a high density of the receptors. The aim of this work was to analize the ability in detecting GastroEnteroPancreatic neuroendocrine tumours (GEP NET) by somatostatin receptors with 99mTc-EDDA/HYNICTOCscintigraphy. The conjugated peptide was labeled with 99mTc using a coligand exchange from tricine to EDDA. The radiochemical purity was higher than 95% measured by HPLC and ITLC. We studied twenty-four patients (8 men, 16 women; age range, 16-80 y) with either histologically proven or biologically and clinically suspected GEP neuroendocrine tumours. They were derived to our Department to diagnosis and to determine the staging by somatostatin receptor scintigraphy. Scintigraphy was performed at 3 h (planar and tomographic images) and 24 h (planar images) after injection of 740 MBq of 99mTc- HYNIC-TOC. We compare the 99mTc-HYNIC-TOC scintigraphy with the findings of CT, MRI, ultrasonography, and/or selective angiography. In some cases we performed a fusion images with MRI o CT for tumour localization. Among the tumour location from 24 patients that we included 3 had gastrinoma (Zollinger- Ellison syndrome), 1 MEN I, 1 insulinoma, 3 foregut, 13 midgut and 3 hindgut carcinoids tumours. 99mTc- HYNIC-TOC showed a positive scan in 17 patients: two of them presented a primary tumour and went to surgery, the others 15 had metastatic disease. Seven present a true negative results. One case was a false-negative showed by the others methods of diagnosis CT, MRI and 111In Octreotide scintigraphy. This study revealed a higher sensitivity of 99mTc-HYNIC-TOC as a diagnostic procedure in GEP NET. The scintigraphy allows the localization and staging of tumours, and has benefit in identifying small primary tumours and in detecting metastases. (author)