Predictors of Volume Reduction Rate Following Microwave Ablation for Benign Thyroid Nodules: A Systematic Review and Meta-Analysis.

Thyroid nodules represent a prevalent clinical condition, with the majority being benign. Microwave ablation (MWA) has emerged as a minimally invasive alternative to surgery, yet volume reduction rate (VRR) outcomes following MWA exhibit substantial heterogeneity. This meta-analysis aimed to identify multifactorial predictors of VRR in patients with benign thyroid nodules undergoing MWA. A systematic search was conducted across PubMed, Web of Science, Embase, Cochrane Library and Scopus from inception to July 2025. Sixteen studies involving 2321 patients met the inclusion criteria and reported VRR outcomes stratified by preprocedural characteristics. Pooled odds ratios (OR) and mean differences (MD) were calculated for binary and quantitative outcomes, respectively, with methodological quality assessed via Newcastle-Ottawa Scale (NOS). Cystic nodules showed significantly better treatment response than solid lesions (MD in VRR: 20.38%, 95% confidence intervals [CI]: 13.28%-27.48%). Larger nodule size was associated with reduced procedural success (OR 0.25, 95% CI 0.14-0.43), and hyperechoic nodules had lower success rates compared to hypoechoic ones (OR 0.34, 95% CI 0.21-0.56). No significant associations were observed for age, sex, calcification, margin or enhancement features. Most studies were high-quality (mean NOS score: 7.7/9). In conclusion, nodule composition, size and echogenicity are key MWA efficacy determinants, with cystic and hypoechoic nodules achieving optimal VRR, while large size reduces treatment success. These predictors facilitate evidence-based patient selection and underscore the need for standardized classification criteria.