I-131 for Remnant Ablation in Differentiated Thyroid Cancer After Thyroidectomy: A Meta-Analysis of Randomized Controlled Evidence

BACKGROUND The aim of this study was to compare the success rate of various levels of I-131 activity for use in remnant ablation in low-risk differentiated thyroid cancer. MATERIAL AND METHODS We identified eligible studies in 5 electronic databases up to December 2014 and the reference lists of original studies and review articles were hand searched for additional articles on this topic. Summary relative risks with their 95% confidence intervals were calculated with a random-effects model. Heterogeneity was assessed using I2 statistics. RESULTS Fourteen randomized clinical trials met the eligibility criteria. The data suggest that the pooled successful ablation rate is 5% lower (95% CI, 1-9% lower) when using 30 mCi compared with 100 mCi (test for heterogeneity, p=0.468, I2=0.0%). In stratified analysis, ablation success rates using 30 mCi are similar to 100 mCi in Asia (SRRs=0.91; 95%CI=0.72-1.14). However, the results favor 100 mCi in Europe (SRRs=0.95; 95%CI=0.91-0.99). Ablation success rates using 30 mCi are similar to 100 mCi in patients who underwent TT/NTT (total thyroidectomy/near total thyroidectomy) (SRRs=0.96; 95%CI=0.92-1.00) and TT/STT (SRRs=0.98; 95%CI=0.73-1.31). However, the result favor 100 mCi in patients who underwent ST/HT (subtotal thyroidectomy/ hemithyroidectomy) (SRRs=0.80; 95%CI=0.65-0.99). There was no publication bias in the present meta-analysis. CONCLUSIONS High radioiodine activity is better than low activity in terms of successful ablation rate in low-risk differentiated thyroid cancer, but the advantage of high activity seems to only exist in patients who underwent hemithyroidectomy/subtotal thyroidectomy, but not lymph node involvement, preparation before ablation, and definition of successful ablation.