Low-dose versus high-dose radioactive iodine ablation of differentiated thyroid carcinoma: a prospective randomized study

Abstract

Purpose: Following total thyroidectomy of differentiated thyroid carcinoma (DTC), some patients are ablated with radioactive iodine I-131 (RAI). We compare the success of ablation with 30 millicurie (mCi) versus 80 mCi. Methods: We randomized the patients to 30 mCi or 80 mCi RAI after surgery. T1-T3, N0-N1, M0 tumors were included (based on the AJCC 7th edition). Pre-ablation baseline serum thyroglobulin (sTg), and thyroglobulin antibody (Tg Ab) were performed. Six months post-ablation successful thyroid ablation was defined as a negative whole body scan (WBS) and undetectable sTg. Results: Out of 50 patients with DTC, 45 patients fulfilled the eligibility criteria. Total thyroidectomy was performed in 27/ 45 (60%). 26/45 (57.8%) of patients received 30 mCi while 19/45 (42.2%) patients received 80 mCi. The median age was 37 and 36.5 years in the arms 80 and 30 mCi respectively. Papillary carcinoma predominated in 42/45 (93.3%) of patients. T2 tumors predominated in 10/19 (52.6%), and 15/26 (57.7%) of the 80 and 30 mCi arms respectively. According to the American Thyroid Association (ATA) risk classification, all of the patients had low risk disease. Success of ablation was achieved in 15/19 (78.9%), and in 15/26 (57. 7%) of the arms 80 and 30 mCi respectively. No patients developed distant metastases in both arms. The patients who received 80 mCi had longer hospital isolation than the 30 mCi arm (p 0.008). 6/26 (23.1%) patients in the 30 mCi arm were isolated for 2-4 days, whereas all the 80 mCi arm patients were isolated for 3-5 days. Conclusion: Both 80 mCi and 30 mCi RAI have similar success rate in the ablation of thyroid remnant of low risk DTC patients. The low dose is associated with fewer side effects, shorter hospital admission duration, and is less expensive in low risk DTC patients.