131I therapy for Graves disease: a comparative study for calculating the 131I-iodide activity based on radioactive iodine uptake formula and individualized experience method

Abstract

Objective To prospectively compare the clinical effect of 131I therapy for Graves disease (GD) using the 131I-iodide dose determined by radioactive iodine uptake formula and by individualized experience method respectively. Methods (1) A total of 527 GD patients referred for 131I therapy were enrolled and divided into two groups using interval sampling method. Group 1 consisted of 241 patients with their 131I activity calculated by iodine uptake formula. Group 2 consisted of 286 patients with their 131I activity calculated by individualized method based on clinical experience. (2) The patients who were not cured for the first time were retreated after 3 months in the same way until remission. (3)All patients were followed for more than 1 year after GD was cured. The clinical outcome was compared between the 2 groups. χ2 test and two-sample t test were used for data analysis. Results There were no significant differences in age, gender, disease course, ATD pretreatment, the time of ATD discontinuation, level of thyroid hormone and autoantibody before 131I therapy, 131I uptake rate, size of thyroid and duration of follow-up between the two groups (t=0.156-1.430, χ2=0.159, all P>0.05). Group 1 had less 131I dose than group 2 ((247.9±107.3) MBq vs (329.3±177.6) MBq, t=6.102, P 0.05). Conclusions The first treatment dose of 131I by individualized experience method is slightly higher than that by radioactive iodine uptake formula. Individualized treatment method for GD based on experience might help to control the GD earlier and improve the one-off remission rate without increasing the rate of hypothyroidism. Key words: Graves disease; Radiotherapy; Iodine radioisotopes; Radiotherapy dosage