Efficacy, safety and predictors of response to minimally invasive treatments of the thyroid: a prospective study.

PURPOSE: Minimally invasive techniques (MITs), including percutaneous ethanol injection (PEI) and radiofrequency ablation (RFA), are effective non-surgical options for benign thyroid nodules (BTN). However, predictors of response and technical determinants remain incompletely defined. METHODS: We conducted a prospective single-center study including 120 BTNs (45 PEI, 75 RFA) treated between 2022 and 2025, with 12-month follow-up. The primary objective of this study was to identify clinical and procedural predictors of treatment response following MITs for BTNs. The primary outcome measure was the 12-month volume reduction ratio (VRR). Secondary endpoints included changes in cosmetic and symptomatic scores, thyroid function in autonomously functioning nodules (AFTN), and safety outcomes. RESULTS: Baseline mean nodule volume was 22.06 mL SD 14.52, cosmetic score 3.39 SD 0.93, and dysphagia score 3.33 SD 1.8. At 12 months, mean VRR was 84.24% overall, 95.9% after PEI, and 77.4% after RFA, achieving therapeutic success in 96.67% of cases (p < 0.001). In AFTN, MITs, comprising 3 predominantly cystic nodules treated with PEI and 10 solid nodules treated with RFA, achieved a mean VRR of 88.17%, with TSH increasing from 0.12 SD 0.13 to 2.17 SD 2.47 mIU/L; 76.9% of these patients were on antithyroid medication prior to ablation, all discontinued post-procedure. Baseline nodule volume independently predicted VRR (β = - 0.237; p = 0.014), while energy density (kcal/mL) predicted RFA efficacy (β = 1.416; p = 0.047). All adverse events were mild and transient, including local pain (27.5%), transient dysphonia (6.7%), and transient cough or vagal reaction. No permanent complications occurred. CONCLUSION: PEI and RFA are safe and effective minimally invasive options for BTN, achieving durable volume reduction with improved clinical outcomes. Smaller nodules and higher energy delivery/ml predict optimal response.