The Optimal Activity of Radioactive Iodine for Remnant Ablation in Low/Intermediate Risk Differentiated Thyroid Carcinoma: A Continuous Controversy and Meta-Analysis

Radioactive iodine (RAI) is widely used for remnant ablation in low/intermediate differentiated thyroid carcinoma (DTC). However, the optimal effective dose that overweighs the benefits over unwanted side effects is a matter of controversy. This meta-analysis aimed to assess low versus high doses of RAI activity for DTC remnant ablation. Two authors independently searched PubMed and Cochrane Library using the keywords low dose radioactive iodine, high dose radioactive iodine, low-risk/intermediate risk, differentiated thyroid carcinoma, and remnant ablation. Two hundred and twenty references were identified when limiting the engine to controlled trials in English and during the period from January 2010 to December 2020. Nine trials (five from Europe and four from Asia) including 3137 patients fulfilled the inclusion and exclusion criteria. The data were then entered in an extraction sheet detailing the trial information including the author's name, year of publication, country, and type of surgery, preparation for RAI, the patients and control number in the low and high-dose groups, follow-up period, and the results. Out of 220 articles retrieved, nine controlled trials were included (follow-up period range, six months to 12 years, 3137 patients, and low risk of bias). The analysis favored the high dose for remnants ablation, odd ratio, 0.73, 95% CI, 0.50-1.07; P-value for the overall effect was 0.10. However, the results were limited due to the significant heterogeneity observed (56%, P-value 0.03). High-dose RAI was better for DTC remnants ablation. Further studies focusing on intermediate-risk DTC and adjusting for preoperative and postoperative factors are recommended.