Predictive Factors for the Efficacy of Radioactive Iodine Treatment of Graves' Disease

Objective: The utilization of radioactive iodine-131I (RAI) has long been established as a cost-effective and conventional treatment for managing Graves' disease (GD). However, the accurate prediction of the clinical response to RAI treatment remains difficult. The successful resolution of GD through RAI therapy is typically characterized by the induction of hypothyroidism or euthyroidism. Thus, the principal aim of this study was to identify plausible predictors of RAI efficacy in the treatment of GD.Methods: The clinical data of 613 GD patients, who underwent RAI treatment for the first time, were retrospectively analyzed, including age, gender, duration of hyperthyroidism, presence or absence of ocular signs, thyroid volume, thyroid weight, thyroid function (FT3, FT4, and TSH), radioactive iodine uptake (RAIU) at 2 h/6 h/24 h (2-h/6-h/24-h RAIU) prior to RAI treatment, the highest RAIU (RAIUmax), and administered activity of 131I and 131I activity per gram of thyroid tissue. Success of RAI treatment was defined as achieving hypothyroidism or euthyroidism for more than 1 year after the initial treatment. Univariate and multivariate logistics regression analyses were conducted to identify factors that influence the efficacy of RAI treatment for GD. And at last, based on the results of the multivariate logistic regression analysis, a nomogram model was established.Results: In this study, the success rate of RAI treatment for GD was 91.2% (559/613). Univariate analysis demonstrated that several factors, including age (p=0.005), thyroid volume (p=0.001), thyroid-stimulating hormone (TSH, p=0.042), ratio of RAIU at 6 h to 24 h (6-h/24-h RAIU, p=0.048), total 131I activity (p=0.026), and 131I activity per gram of thyroid tissue (p=0.001), were significantly associated with treatment outcome. Multivariate logistic regression analysis indicated thyroid volume and 131I activity per gram of thyroid tissue as significant independent predictors of radioactive iodine therapy (RIT) efficacy. The area under the ROC curve of the established nomogram model was 0.769 (95% confidence interval [CI]: 0.692-0.846), indicating that the model has good discriminatory ability.Conclusion: Calculated-dose RAI is effective in the treatment of GD. The smaller thyroid volume and the higher 131I activity per gram of thyroid tissue are predictors of RAI efficacy in the treatment of GD.