Chinese Data of Efficacy of Low- and High-Dose Iodine-131 for the Ablation of Thyroid Remnant

Background: Chinese data on the efficacy of low- and high-dose radioiodine for thyroid remnant are still absent. The aim of the study was to investigate whether a low dose of radioiodine is as effective as a high dose for remnant ablation in Chinese patients. Methods: Patients presenting for radioiodine ablation in the authors' department were included. Inclusion criteria were aged 16 years, total or near-total thyroidectomy, tumor-node-metastasis (TNM) stage of pT1-3, any N stage, and M0. All patients were randomly allocated to either the high-dose group of 3700MBq or the low-dose group of 1850MBq for remnant ablation. The response to treatment was defined as successful or unsuccessful after a six- to nine-month interval. Ablation was considered to be successful if patients fulfilled the following criteria: no tracer uptake in the thyroid bed on diagnosis whole-body scanning and a negative level of serum thyroglobulin. Results: There were 327 patients enrolled between January 2013 and December 2014. More than 95% had papillary thyroid cancer. Data could be analyzed for 278 cases (M-age=44 years; 71.6% women), 155 in the low-dose group and 123 in the high-dose group. The rate of initial successful ablation was 84.2% in all patients, 82.6% in the low-dose group, and 86.2% in the high-dose group. There was no difference between the two groups (p=0.509). Conclusions: In Chinese patients with differentiated thyroid carcinoma, the low dose of 1850MBq radioiodine activity is as effective as a high dose of 3700MBq for thyroid remnant ablation.