Radioactive Iodine Ablation Can Reduce the Structural Recurrence Rate of Intermediate-Risk Papillary Thyroid Microcarcinoma: A Meta-Analysis

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Background. The incidence of papillary thyroid microcarcinoma (PTMC) has significantly increased in recent years, and the decision to use radioactive iodine (RAI) ablation in low-risk (LR) and intermediate-risk (IR) patients is controversial. The aim of this study was to evaluate whether RAI ablation can reduce the recurrence rate in LR-IR PTMC patients. Methods. A comprehensive literature search of the PubMed, Embase, Cochrane Library, and Web of Science was conducted according to the PRISMA statement. Results. There were 8 studies in English that fit our search strategy, and a total of 2847 patients were evaluated. The results of the meta-analysis showed RAI ablation in LR-IR PTMC patients did not reduce cancer recurrence (risk radio (RR) 0.56, 95% CI 0.19-1.70, <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" id="M1"> <a:mi>P</a:mi> <a:mo>=</a:mo> <a:mn>0.31</a:mn> </a:math> ). Nevertheless, we further performed data analysis and found that IR PTMC patients without RAI ablation had a higher rate of cancer recurrence than those who underwent RAI ablation (RR 0.23, 95% CI 0.11-0.49, <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" id="M2"> <c:mi>P</c:mi> <c:mo>=</c:mo> <c:mn>0.0001</c:mn> </c:math> ). Furthermore, patients with risk factors for lymph node metastasis (RR 0.16, 95% CI 0.06-0.42, <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" id="M3"> <e:mi>P</e:mi> <e:mo>=</e:mo> <e:mn>0.0002</e:mn> </e:math> ), microscopic extrathyroidal extension (RR 0.19, 95% CI 0.06-0.60, <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" id="M4"> <g:mi>P</g:mi> <g:mo>=</g:mo> <g:mn>0.005</g:mn> </g:math> ), and multifocality (RR 0.13, 95% CI 0.04-0.45, <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" id="M5"> <i:mi>P</i:mi> <i:mo>=</i:mo> <i:mn>0.001</i:mn> </i:math> ) in the absence of RAI ablation were more likely to have recurrence. Conclusions. Based on our current evidence, RAI ablation can reduce the cancer recurrence rate over 5 years in IR PTMC patients, especially when patients have some risk factors, such as lymph node metastasis, microscopic extrathyroidal extension, and multifocality.