Impact of ablation dose in the treatment of thyroid cancer with I-131

Purpose: To evaluate the efficacy of ablation therapy using Iodine-131 with two different doses on patients with well-differentiated thyroid cancer who had been operated upon with total or near-total thyroidectomy. Methods: A retrospective study was conducted on 42 patients admitted at the Dr. Cipto Mangunkusumo Hospital, Jakarta between 1993-1996. Thyroid ablation was performed with 80 mCi and 100 mCi on each group consisting of 21 patients respectively. Thyroid scan was performed before ablative procedure, and followed by whole body scanning one week after the ablation.. Efficacy of the treatment was evaluated three months after ablation therapy using whole body scanning with 5 mCi of 1-131. Results: The efficacy of ablation therapy with a dose of 100 mCi was 85, 7%, significantly better than 57% with a dose of 80 mCi dose (p=0, 04). Acute side effects were seen in 4, 8% with a dose of 100 mCi and 19% of patients with a dose 80 mCi. Whole body scanning performed one week after ablation therapy revealed 19% distant metastases with the dose of 100 mCi as compared to 4, 8% with the dose of 80 mCi. Conclusions: Thyroid ablation with a dose of 100 mCi 1-131 showed a better result as compared to 80 mCi dose, as side effects of the treatment were not significantly different. Moreover, ablation therapy with a dose of 100 mCi probably could detect more distant metastases as compared to 80 mCi dose.