RADIOISOTOPE DIAGNOSTIC ALGORITHM FOR THE RELAPSE AND METASTASES DETECTION IN THE IODINE-NEGATIVE DIFFERENTIATED THYROID CANCER.

Objective: Developing of algorithm for the post-surgical management of patients with iodine-negative metastasesof differentiated thyroid cancer (DTC).

Materials And Methods: The DTC patients with iodine-negative metastases (n = 115) were enrolled in the study.Of them the whole body scintigraphy (WBS) was performed with technetium-99m-hexakis-2-methoxyisobutylisonitrile(99mTc-MIBI) (n = 30), WBS with technetium-99m dimercaptosuccinic acid (99mTc-DMSA) (n = 30), 18FDG PET (n = 30), andcomputer tomography (CT-scan) (n = 25). Complex 99mTc-pertechnetate scans including the dynamic and static scintigraphy was performed supplementary to 99mTc-MIBI WBS in 10 patients to obtain the angiographic curves from DTCmetastatic foci. The non-radioiodine radiopharmaceutical technologies, namely the labeled 99mTc-MIBI, 99mTc-DMSA, 99mTc-pertechnetate, and 18FDG were applied to detect the iodine-negative DTC metastases. Radioisotopic examinationswere performed at the dual-head gamma camera (Mediso Medical Imaging Systems Ltd., Hungary) and single photonemission computed tomography (SPECT) scanner «E.CAM» (Siemens, Germany). PET/CT scans were performed on the«Biograph 64 TruePoint» imaging platform (Siemens, Germany) in accordance with the European Association of NuclearMedicine (EANM) recommendations for the Siemens imaging devices with 3D-mode data acquisition.

Results: The conducted research suggested that it is feasible to use the non-radioiodine (99mTc-MIBI and 99mTc-DMSA)radiopharmaceutical technologies to detect the iodine-negative DTC metastases. 18FDG PET is a highly informativetechnology for the detection of iodine-negative DTC metastases in case of lung involvement in the process. Compareof the non-radioiodine radiopharmaceuticals, CT scan and 18FDG-PET/CT indicated the highest sensitivity of 18FDGPET/CT (p < 0.05). WBS with 99mTc-MIBI and 99mTc-DMSA featured the highest specificity (100 %, p < 0.05). X-ray CTis marked by the significantly lower either sensitivity, specificity, and accuracy rate (p > 0.05). Developing andapplication of algorithm for the post-surgical management of patients with iodine-negative forms of DTC will allowfor the betimes detection of relapses and metastases with administration of adequate surgical, radiation, and targeted treatment.

Conclusions: Obtained results offer the opportunity to optimize the post-surgical management of patients withiodine-negative DTC forms using the options of radionuclide diagnostics with non-radioiodine radiopharmaceuticals. The latter are readily available providing the cost-cutting of diagnostic support in these patients. Place ofmorphological methods of diagnosis is determined and stage of monitoring of patients with the iodine-negativemetastases is established. Possibility of the 18FDG-PET tests for the early diagnosis of iodine-negative metastases inDTC for the first time have been studied and substantiated in Ukraine. A comprehensive radiation algorithm for thelong-term monitoring of this category of patients will allow the timely detection of recurrences and metastases ofDTC and appropriate surgery, radiation and targeted therapy administration. Data obtained as a result of the studyallowed to improve the overall and recurrence-free survival rates in the able-bodied DTC patients and reduce thecosts of follow-up of patients with iodine-negative forms of DTC.