Treating thyroid nodules by radiofrequency: is the delivered energy correlated with the volume reduction rate? A pilot study.

Objective: Radiofrequency ablation (RFA) was proven as effective in reducing thyroid nodules' volume. However, whether technical procedure aspects could influence the volume reduction rate (VRR) has not been clarified. This retrospective pilot study aimed to analyze the correlation of RFA power, duration, and energy with VRR.

Methods: During the period from June to December 2018 two primary-care centers treated benign thyroid nodules of adult outpatients according to the same RFA procedure. Technical parameters to be investigated were the following: median power (P), effective time of treatment (T), energy calculated as P × T (E), and energy delivered per mL as Kcal × 4184 × nodule's volume (E). Continuous variables were analyzed by the Mann-Whitney test. Data of 1-year posttreatment follow-up were collected on December 2019 and the correlation of the above parameters with VRR was analyzed by linear regression.

Results: Forty-one nodules were included and their 1-year VRR was 66.6%. RFA was performed with a P of 55 W, T 10.24 min, E 31,380 J, and E 1473 J/mL. E was significantly correlated with VRR (p = 0.014) while P, T, and E not. A strong correlation of E with VRR was found in nodules <10 mL (p = 0.001) while no significant correlation was observed in nodules >10 mL.

Conclusions: This study showed that the energy delivered with RFA is the only technical parameter significantly correlated with the VRR of thyroid nodules.