Thyroid lobe ablation with iodine-131 in patients with differentiated thyroid carcinoma: a randomized comparison between 1.1 and 3.7 GBq activities

Purpose The present study was undertaken to evaluate the ablation rate after administration of 1.1 or 3.7 GBq of iodine-131 (I-131) to patients with low-risk differentiated thyroid carcinoma (DTC) primarily treated by lobectomy. Patients and methods Enrolled were 136 consecutive patients affected by histologically proven low-risk DTC previously treated by lobectomy. Patients were randomized to receive a single dose of 1.1 or 3.7 GBq of I-131 in an equivalence trial. Successful thyroid ablation was defined as a negative diagnostic whole-body scan and stimulated thyroglobulin levels lower than 2 ng/ml in the absence of thyroglobulin antibodies. Results The patient demographic and clinical data were well balanced at baseline. The ablation rate was significantly (P<0.01) higher in patients treated with 3.7 GBq (75%) than in those treated with 1.1 GBq (54%) of radioiodine. No relevant side effects occurred in either group. Conclusion Radioiodine lobe ablation with a single administration of 3.7 GBq is a simple and safe mode of treatment, achieving an ablation rate higher than that of 1.1 GBq. This procedure may be offered as an alternative to completion thyroidectomy in highly selected DTC patients who had experienced complications during initial surgery or for whom completion thyroidectomy is contraindicated.