Radionuclide diagnostic algorithm for detecting relapses and metastases in patients with iodine-negative forms of differentiated thyroid cancer. Dosimetric support of patients’ examination
Solodyannуkova O.I., Poliakova I.O. , Kmetiuk Ya.V.
Summary. The purpose of the work is to develop an algorithm for postoperative management of patients with iodine-negative metastases of differentiated thyroid cancer (DTC) with the introduction of individual dosimetric planning methods to optimize radiation exposure to critical organs and tissues. Materials and methods. The study group consisted of 115 patients with iodine-negative metastases of thyroid cancer, of which 30 patients underwent whole body scintigraphy (WBS) with methoxy-isobutyl-isonitrile technetium (99mTc-MIBI), 30 — with WBS with dimercapto-amber acid technetium (99mTc-DMCA), 30 — 18F-fluorodeoxyglucose with positron emission tomography (PET with 18F-FDG), 25 patients underwent computed tomography (CT). 10 patients from the group in which WBS was performed with 99mTc-MIBI were additionally subjected to a comprehensive scintigraphic study with 99mTc-pertechnetate, which included dynamic and static scintigraphy in order to obtain angiographic curves from metastatic foci of DTC. For the diagnosis of iodine-negative metastases of thyroid cancer, the following methods were used using non-iodine radiopharmaceuticals (RPC), namely, labeled 99mTc-MIBI, 99mTc-DMCA, 99mTc-pertechnetate and 18F-FDG. Radionuclide studies were performed on a Mediso two-detector gamma camera (Hungary) and a E. CAM 180 single-photon emission computed tomograph (SPECT) from Siemens (Germany). PET / CT were performed on a Biograph 64-TruePoint-Siemens combined tomography scanner (Germany), according to the European Association of Nuclear Medicine (EANM) recommendation for Siemens devices with a 3D mode of data collection. Radiation exposure planning and dosimetric monitoring of diagnostic procedures were carried out to minimize radiation risk and optimize the diagnostic value of examinations for each patient. Depending on the imaging technique used, the calculation of individual and group doses obtained when using RPC was carried out taking into account the activity of the administered isotope and anthropometric indicators of patients. For patients undergoing scintigraphic examinations (SPECT and dynamic / static scintigraphy) using 99mTc-MIBI, 99mTc-DMCA, and 99mTc-pertechnetate, the calculation of absorbed and effective doses was performed according to standard internal dosimetry schemes medical internal radiation dose (MIRD) and current International Commission on Radiological Protection (ICRP) recommendations for technetium-labeled compounds. When conducting PET / CT examinations on a combined tomograph «Biograph-64-TruePoint-Siemens», a comprehensive calculation of the total dose was carried out. It consisted of internal radiation from the positron-emitting radionuclide 18F-FDG, synthesized on a cyclotron «Siemens-RDS-Eclipse-RD», and external X-ray radiation from the diagnostic CT component. CT dose load control was carried out by monitoring the computed tomography dose volume index (CTDIvol) and the dose-length product (DLP), which allowed standardizing the effective equivalent dose. The obtained quantitative dosimetric indicators, together with the results of statistical processing in Excel, Statistica 6.0, and Primer of Biostatistics v 3.0 packages, were integrated into a common data matrix for mathematical justification and formation of the developed postoperative patient management algorithm. Results. Studies have confirmed the possibility of using techniques with non-iodine RPC (99mTc-MIBI, 99mTc-DMCA) to detect iodine-negative metastases of thyroid cancer. PET / CT with 18F-FDG is a highly informative technique for identifying iodine-negative metastases of thyroid cancer during prolongation of the process to the lungs. A comparative assessment of non-iodine RPC, CT, and PET / CT with 18F-FDG revealed that the highest sensitivity indicator is characteristic of PET with 18F-FDG (p <0.05). The specificity is the highest (100%) at WBS with 99mTc-MIBI and 99mTc-DMSA (p <0.05). X-ray CT is characterized by significantly lower indices of both sensitivity and specificity and accuracy (p >0.05). The creation and use of an algorithm for postoperative management of patients with iodine-negative forms of thyroid cancer will allow timely detection of relapses and metastases and appropriate treatment, namely, surgical, radiation and targeted. Conclusions. The results obtained made it possible to optimize the postoperative management of patients with iodine-negative forms of thyroid cancer based on the capabilities of radionuclide diagnostics with non-iodine RPC, which are more affordable, which makes it possible to reduce the cost of diagnostic support for this category of patients. The place of morphological diagnostic methods was determined and the phasing of monitoring of patients with iodine-negative metastases was established. For the first time in Ukraine, the possibilities of PET studies with 18F-FDG for the early diagnosis of iodine-negative metastases in patients with thyroid cancer were investigated and substantiated. The developed complex radiation algorithm for long-term monitoring of this category of patients allows timely detection of relapses and metastases of thyroid cancer and correction further treatment. The social and economic significance of the results is to improve the overall and relapse-free survival of the able-bodied part of patients with DTC, and reduce the cost of monitoring iodine-negative forms of DTC.
Leave a comment