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

Abstract

ObjectiveThe 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 99mTc-pertechnetate thyroid scintigraphy in predicting the clinical outcomes of RIT. MethodsOne hundred and thirty nine 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. 99mTc-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. ResultsOne hundred and eight (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 99mTc-pertechnetate uptake (p<0.0001), the duration of disease (p=0.0140) and positive rate of Anti-TRAb (p=0.0103). 99mTc-pertechnetate uptake is an independent risk factor for predicting treatment failure (p=0.0394). Using a cut-off value of 18.4%, 99mTc-pertechnetate uptake could predict treatment failure with a sensitivity of 84.3%, and a specificity of 80.6%. ConclusionOur study has shown that a calculated radioiodine dose is effective in treating GD patients with a consequent low rate of hypothyroid. A 99mTc-pertechnetate uptake above 18.4% is a significant predictor of treatment failure and these patients should receive a higher radioiodine dose in this scenario.