Introduction: Recently a new somatostatin analogue labelled with ^99mTc (^99mTc-HYNIC-TOC) has been synthetized. Aim of this study was to evaluate the utility of ^99mTc-HYNIC-TOC in the radionuclide imaging in patients with medullary thyroid carcinoma (MTC).
Material and methods: 30 patients with MTC aged 22-83 years in different stages of the disease were investigated. In 6 patients (group 1) scintigraphy was performed before surgery directly after diagnosis of MTC. Four patients (group 2) were qualified to the study in the phase of remission after surgical treatment that had been confirmed by low concentrations of calcitonin. Twenty patients (group 3) were investigated due to stagnation or recurrence confirmed by persistent hypercalcitoninemia. The scintigraphy using ^99mTc-HYNIC-TOC (Tektrotyd, POLATOM) was performed 2 and 4 hours post injection of 20 mCi (740 MBq) of the tracer. Other imaging techniques were also employed and analysed in individual cases (US, CT, ^99mTc(V)-DMSA, ¹³¹I-MIBG, ^99mTc-MDP, ¹¹¹In-octreotide and FDG-PET).
Results: Images obtained 2 and 4 hours p.i. were similar. In group 1, uptake of the tracer was found in the primary tumour of MTC in all patients. In group 2, a false positive result was found in 1 of 6 patients. In the remaining 5 of 6 cases no pathological foci were visualised. In group 3, uptake in the thyroid bed was found in 3 of 20 cases and in the lymph nodes in 14 of 20 patients. In 3 of 20 cases uptake in the bone metastases was found. Globally, sensitivity of the scintigraphy using ^99mTc-HYNIC-TOC was 86.4%, specificity - 75.0%, and accuracy - 84.6%.
Conclusion: The scintigraphy using ^99mTc-HYNIC-TOC showed high utility in the diagnosis of MTC. Confirmation of the presence of somatostatin receptors with this method may be used for treatment planning: surgery or radionuclide therapy.