Ablation outcomes of low versus high doses of radioiodine (131^I) in patients with differentiated thyroid carcinoma following thyroidectomy

Objective: The aim was to compare the ablative efficacy of low vs high doses of radioactive iodine-131 (131I) in patients with differentiated thyroid carcinoma (DTC) after total or near total thyroidectomy. Materials and methods: A randomized, double-armed clinical study compared the ablation outcomes of patients with low and intermediate risk DTC after administration of low (30 mCi) vs high doses (80–120 mCi) of 131I for 20 and 25 patients, respectively. All the included patients were re-examined under thyroid-stimulating hormone stimulation 6–8 months after 131I administration. Successful ablation is defined as follows: Absence of any significant 131I uptake at the thyroid bed or abnormal uptake elsewhere in the body in the diagnostic whole-body scan, stimulated serum thyroglobulin less than 2 ng/ml with negative antithyroglobulin antibodies, and free neck ultrasonography (no thyroid residue or pathological cervical lymph nodes). Results: Overall successful ablation after a single dose of 131I was reported in 34/45 patients representing 75.6% of the whole patient population, while unsuccessful ablation was reported in the remaining 11 (24.4%) patients. Successful ablation was reported in 15 out of 20 patients (75%) in the low-dose group and in 19 out of 25 cases in the high-dose group (76%) (P=1.000). Conclusion: Ablation with low-dose radioactive iodine (30 mCi) in patients with DTC who did not have gross residual disease or cervical lymphadenopathy after surgical treatment is as effective as the high one (80–120 mCi).