99mTc-pertechnetate thyroid scintigraphy predicts clinical outcomes in personalized radioiodine treatment for Graves' disease

Objective: The aim of this study was, first, to ascertain the efficacy of radioiodine therapy (RIT) for Graves' disease (GD) based on a calculated-dose regime and, second, to determine the value of Tc-99m-pertechnetate thyroid scintigraphy in predicting the clinical outcomes of RIT. Methods: One hundred and thirty 9 consecutive GD patients who underwent RIT using a calculated-dose method in our hospital from January 2015 to September 2015 were retrospectively evaluated. Radioiodine dose was calculated based on the Marinelli's formula. Tc-99m-pertechnetate uptake, age, gender, thyroid mass, duration of the disease, previous antithyroid drugs treatment, serum levels of TSH, FT3 and FT4, a positive rate of TPOAb and Anti-TRAb, radioiodine dose and follow-up were evaluated as potential interference factors for RIT success. Results: One hundred and 8 (77.7%) GD patients including 71 (51.1%) euthyroid and 37 (26.6%) hypothyroid were successful, but 31 (22.3%) remained hyperthyroid (treatment failure). Significant differences were found between the treatment success group and the failure group in Tc-99m-pertechnetate uptake (p<0.0001), the duration of disease (P=.0140) and positive rate of Anti-TRAb (P=.0103). Tc-99m-pertechnetate uptake is an independent risk factor for predicting treatment failure (P=.0394). Using a cut-off value of 18.4%, Tc-99m-pertechnetate uptake could predict treatment failure with a sensitivity of 84.3%, and a specificity of 80.6%. Conclusion: Our study has shown that a calculated radioiodine dose is effective in treating GD patients with a consequent low rate of hypothyroid. A Tc-99m-pertechnetate uptake above 18.4% is a significant predictor of treatment failure and these patients should receive a higher radioiodine dose in this scenario. (C) 2018 Published by Elsevier Espana, S.L.U. on behalf of Sociedad Espanola de Medicina Nuclear e Imagen Molecular.