RATIONALE Insufficient world-wide clinical experience in radioiodine therapy (RIT) for Graves' disease (GD) in children and adolescents, and limited knowledge of the predictors of RIT efficacy. AIMS Analysis and identification of the most significant predictors of the efficacy of RIT in children and adolescents with Graves' disease. MATERIALS AND METHODS A total of 55 patients (48 females and 7 males) aged from 8 to 18 years receiving primary RIT for GD were enrolled. RIT planning was based on the dosimetric method. Analyzed parameters included gender, age, ultrasound thyroid volume before and 6 months after treatment, the presence of endocrine ophthalmopathy, duration of antithyroid drug (ATD) therapy, relapse of thyrotoxicosis after ATD dose reduction, blood fT3, fT4 and TSH levels initially and at 1, 3, 6 months after treatment, TSH receptor Ab initially and at 3 and 6 months after treatment, thyroid 99mTc-pertechnetate uptake at 10-20 minutes (%), maximum thyroid 131I uptake (%), specific 131I uptake (MBq/g) and therapeutic 131I activity (MBq). Fisher exact test, non-parametric Mann-Whitney test, Wilcoxon signed-rank test, logistic regression modelling, ROC-analysis, proportional hazard model (the Cox regression), the Kaplan-Meier method and log-rank test were used for statistical analysis as appropriate. RESULTS Six months after RIT, hypothyroidism was achieved in 45 (81.8%), euthyroid state - in 2 (3.6%), and in 8 (14.6%) patients thyrotoxicosis persisted. On univariate statistical analysis, the smaller thyroid volume, higher fT4 and lower TSH receptor Ab levels, lower 99mTc-pertechnetate uptake and higher specific 131I uptake were associated with hypothyroidism. On multivariate logistic regression analysis, the older patient's age (p=0.011), smaller thyroid volume (p=0.003) and higher fT4 (p=0.024) were independent predictors of RIT efficacy. Thyroid volume was also the only variable associated with achievement of hypothyroidism in time after RIT (p=0.011). CONCLUSION The efficacy of dosimetry-based RIT in children and adolescents with GD 6 months after treatment was 81.2%. Older patients' age, smaller thyroid volume and higher fT4 level were independent predictors of therapy success. Smaller thyroid volume was also a predictor of the favorable time-related outcome. Statistical models obtained in this work may be used to prospectively estimate the chance of efficient RIT for GD in pediatric patients.

Neuroendocrine tumors (NETs) are a heterogeneous group of neoplasms constituting about 0.5 % of all cancer cases. In recent years, there has been a significant increase in the incidence of NETs, which is primarily due to the active development and improvement of medical imaging technologies. Successful treatment and prognosis for patients with NETs strongly depend on the stage of the disease. One of the effective methods of visualization and staging NETs in nuclear medicine is somatostin receptor scintigraphy (SRS), which is based on the use of partial somatostatin receptor agonists labeled with radioactive isotopes. The article presents an analysis of 55 patients with NETs of various localizations who underwent scintigraphy and SPECT/CT. Radiopharmaceutical was used as a tracer for SRS. It was prepared on the basis of a lyophilisate developed by Polatom (Poland) — Tektrotyd, labeled with 99mTc. According to the results of the study SRS with 99mTc-Tektrotyd is informative in the topical diagnosis of NETs, especially when PET/CT scan with 68Ga-labeled peptides is not available. Sensitivity varies depending on the NET localization. It is necessary to continue researches on the diagnostic value of SRS with 99mTc-Tektrotyd for tumors, in the pathogenesis of which somatostatin receptors play a significant role.