Thyroid Remnant Ablation of Differentiated Thyroid Carcinoma: a comparison of Ablation success with High and Low Doses of Radio-iodine

Abstract

Aim of study: To assess efficiency of low dose I131 in thyroid remnant ablation of patients with differentiated thyroid cancer after surgical treatment. Material and Method: A randomized double‐armed trial comparing low‐dose and high‐dose radioiodine ablation. 128 patients (age 20‐75 years) with differentiated thyroid cancer, tumor stage T1 to T3, with disease confined to the thyroid or cervical lymph nodes were treated with I131 after total thyroidectomy and pathologic lymph node resection, if present. Results were available for 88 cases. 39 patients received low dose [1110MBq (30mCi)] and 49 patients received high dose [2960‐3700 MBq (80‐ 100mCi)]. Six months after the administration of radioiodine, measurements of Tg, anti‐Tg antibodies together with neck ultrasound exam and I131 whole‐body scan were performed. The success rate of ablation is determined by negative whole body I131 scan, negative neck ultrasonography and serum thyroglobulin level less than 2 ng/mL. Results: Successful ablation reported in 23 out of 39 cases (58.9 %) in the group receiving low‐dose radioiodine [1110 MBq] versus 37 out of 49 cases (75.5 %) in the group receiving the high dose [2960‐3700 MBq]. (P value= 0.098). Six months later (1 year after the ablative dose) a second follow up was performed for the cases who had successive ablation from both groups. In the low dose group it was available for 12 out of 23 patients (52%), all of them didn't show disease recurrence, versus 17 cases out of 37 from the high dose group, 16 of them didn't had recurrence (43.2%), while in one case there was a recurrent disease at the thyroid bed. Conclusion: Initial results show no significant difference in successful ablation with low and high dose of 131‐iodine. This is work in progress.