Results of treatment of patients with diagnosed regional metastases of differentiated thyroid cancer

Objective of research. A number of patients with differentiated thyroid cancer develop iodine- refractory regional metastases, which significantly worsens the prognosis. Given contradictory attitude towards preventive lymph node dissection and an increase in the number of organ- preserving operations, we have searched for a method of preoperative diagnosis of radioiodine- resistance. Materials and methods. We comprised a group of 67 patients operated on thyroid cancer which appeared to have metastatic lymph nodes. All patients underwent radioiodine therapy (61 patients, 90.0%) or diagnostic whole-body scintigraphy (6 patients, 9.0%), which allowed to identify iodine- positive (n=32) and iodine-negative (n=35) subgroups. After removal of metastatic lymph nodes, we carried out an expression analysis of the TERT, TG, SLC5, KRТ19, KRТ5, ERBB2 genes, as well as the two reference genes GUSB and B2M. We also performed an analysis of the mutational status of the BRAF gene (V600E mutation). Results. In iodine-negative and iodine-positive groups, the differences in the SLC5 (NIS) gene expression, in the frequency of the wild-type BRAF alleles and in the ratio of mutant (V600E) 4 BRAF/ wild type BRAF alleles were registered (p=0.05; p=0,013 and p=0,034, respectively). According to the results of the study, we proposed a prediction model consisted of five parameters: the expression level of the SLC5, KRT5, ERBB2 genes, wild-type status of the BRAF gene, and the ratio of mutant (V600E) BRAF/ wild type BRAF alleles. This model allows to predict the probability of accumulation of radioiodine in lymph nodes in 85.7% of cases, herewith radioiodine- resistance - in 90.9% of cases, and the accumulation of 131I in the lymph nodes in 75.0% of cases. Conclusion. The use of the prediction model may help to make the decision in favor of the largest possible volume of lymph node dissection.