Predictors of Initial Response of Thyroid Nodules Treated With RFA, a Multi-Endocrinology Centers Experience From the United States.

Context: Given the growing utilization of radiofrequency ablation in the management of benign thyroid nodules, the identification of factors predicting successful outcomes is increasingly relevant for optimizing patient selection. Objective: This study is looking for potential factors influencing volume reduction (VR) after RFA in benign thyroid nodules. Methods: This is a multicenter, retrospective study of 275 benign thyroid nodules in 240 patients who underwent treatment with radiofrequency ablation (RFA) between November 2018 and March 2022. Results: The study included 240 patients (82.2% women) with 275 benign nodules (191 nonfunctional). Median age was 50 years (interquartile range [IQR] 22.5). After a mean (SD) follow-up of 186.1 (138.7) days, most patients experienced a 50% or more reduction in nodule volume after RFA, with a median volume reduction percentage (VRP) of 63.5% (IQR 48.1%-75.16%), and median absolute volume reduction (AVR) of 6.54 mL (IQR 2.85-14.97). Factors that predict AVR post RFA are female sex, ethnicity, and larger nodule volume before RFA and inversely duration of ablation time. Factors that predict VRP post RFA are age, non-Hispanic ethnicity, American Thyroid Association category very low risk and low risk, higher energy, and pre-RFA thyrotropin level. In a subgroup analysis of autonomously functioning thyroid nodules (AFTNs), the strongest predictor for achieving a normal thyroid function test was the severity of hyperthyroidism before the procedure, with better performance in subclinical hyperthyroidism. Conclusion: Our study suggests that larger nodules may still have successful ablation with higher AVR. A longer time of ablation or higher energy delivered may indicate a less responsive thyroid nodule, hence lower AVR and VRP. In AFTN, severity of hyperthyroidism is the strongest predictor of achieving normal euthyroid state post RFA.