Radionuclide monitoring of targeted therapy of iodine-negative differentiated thyroid cancer

Background. Current management of treating iodine-negative metastases of differentiated thyroid cancer has its features. In recent years, tyrosine kinase inhibitors (sorafenib, sunitinib) have been registered and indicated to treat refractory forms of differentiated thyroid cancer in Ukraine. However, there were only few studies dealing with cytologic aspects of predicting radioiodine resistance of papillary thyroid cancer, development of radionuclide monitoring and diagnostic algorithm to detect relapses and metastases in patients with iodine-negative forms of differentiated thyroid cancer. At the same time, scientific and clinical aspects of treatment of radioiodineresistant differentiated thyroid cancer in Ukrainian oncology and radiology are barely studied. Thus, the status of treatment and post-therapeutic monitoring of patients with iodine-negative forms of differentiated thyroid cancer, still remains insufficiently studied and requires further scientific and clinical development. Purpose – develop a technique of treatment of iodine-negative metastases of differentiated thyroid cancer. Materials and methods. Thirty-eight patients with iodine-negative metastases of differentiated thyroid cancer were provided with treatment, where in 10 patients the efficiency of treatment was assessed by means of whole body scintigraphy with 99mTc-MIBI, in 10 patients – with 99mTcDMCA. In 10 patients the short-term results of treatment with tyrosine kinase inhibitors were evaluated by PET with 18F-FDG. Eight patients represented a group where the bones were affected and treatment was provided by means of radionuclide or external-beam radiotherapy. The average age of patients varied from 43 to 76, the median was 57.8 + 3.9; out of those: 24 women, 14 men. Pathohistologically, papillary cancer was diagnosed in 31, follicular – in 5, papillary-follicular – in 2. The studies were performed by means of the two-detector gamma camera manufactured by Mediso (Hungary) and the single-photon emission computed tomography (SPECT) E. CAM 180, Siemens (Germany). PET/CT were performed on the Biograph-64-TruePoint-Siemens combined tomograph (Germany), according to the guidelines of the European Association of Nuclear Physicians. Results. Prior to initiating therapy, 10 patients with differentiated thyroid cancer underwent whole body scintigraphy with 99mTc-MIBI and re-examination in three months in order to assess treatment success. After diagnostic examination, the patient was prescribed targeted therapy with Nexavar according to the treatment protocol. Regression of the focus in the lungs was achieved within 70 %. Further monitoring of antitumor treatment success was performed by means of whole body scintigraphy with 99mTc-MIBI. Ten patients, who had PET/CT with 18F-FDG made before treatment, also underwent targeted therapy by means of Nexavar. Diagnostic scanning with 18F-FDG after therapy revealed decreased functional activity of the lesion in the neck, however no decrease in the dimensions of the lesion was observed. Conclusions. Treatment of iodine-negative metastases of differentiated thyroid cancer by means of tyrosine kinase inhibitors was accompanied by a decreasing number of metastatic foci and reducing level of their functional activity. The studies have confirmed the possibility of applying techniques with non-iodine RP (99mTc-MIBI, 99mTc-DMCA) to assess the effectiveness of treatment of iodine-negative metastases of differentiated thyroid cancer . PET/CT with 18F-FDG is a highly informative technique for assessing the effect of tyrosine kinase inhibitors on the functional activity of metastatic foci according to metabolic scans in treatment of iodine-negative metastases of differentiated thyroid cancer. If there are no positive changes after 3–4 courses, external-beam radiotherapy with total radiation dose of 30–50 Gy is indicated, which is capable of reducing the volume of metastatic foci as well as their metabolic activity. The social and economic significance of the obtained findings have made it possible to improve the overall and recurrence-free survival rates in the working population of patients with differentiated thyroid cancer and reduce the cost of following-up patients with iodine-negative forms of differentiated thyroid cancer.