Low versus high radioiodine activity for ablation of the thyroid remnant after thyroidectomy in Han Chinese with low-risk differentiated thyroid cancer

Aim: The aim of this study was to compare the efficacy and adverse effects of radioiodine (I-131) therapy between two groups of patients with low-risk differentiated thyroid cancer (DTC) who received 30 mCi or 100 mCi radioiodine for ablation of the thyroid remnant after total thyroidectomy. Methods: The study cohort was 173 patients, 85 of whom were given 30 mCi of radioiodine and the others were given 100 mCi of radioiodine. Follow-up involved neck ultrasonography, measurement of serum levels of thyroglobulin and whole-body scans to evaluate the response of radioiodine treatment. All patients were assessed for adverse effects. Results: Of the 173 patients, 170 (98.3%) patients finally achieved successful ablation. The prevalence of successful ablation was 77.6% in the low-dose group versus 71.5% in the high-dose group after the first dose administration (P= 0.36), 79% in the low-dose group versus 88% in the high-dose group after the second dose administration (P= 0.416), and 97.6% in the low-dose group versus 98.9% in the high-dose group after the final ablation (P= 0.54). We found no significant differences between the two groups. No patient had an adverse effect with a severity grade >2 and the prevalence of adverse effects in the high-dose group was higher than that in the low-dose group, especially for nausea, neck pain, and sore throat. Conclusion: These data suggest that a low dose of radioiodine is as effective as a high dose of radioiodine for ablation of the thyroid remnant after total thyroidectomy for low-risk DTC. Moreover, low-dose radioiodine therapy is associated with a lower prevalence of adverse events.