Solid benign thyroid nodules (>10 ml): a retrospective study on the efficacy and safety of sonographically guided ethanol ablation combined with radiofrequency ablation

Background: Image-guided radiofrequency ablation (RFA) of large solid benign thyroid nodules (BTNs) usually require a high amount of energy. Injection of ethanol into a benign thyroid nodule before RFA can lower the procedural time and patient discomfort. Objective: To investigate the efficacy and safety of ethanol ablation (EA) combined with RFA in the treatment of solid BTNs (>10 ml) and to compare this modified method with RFA treatment alone. Methods: A total of 366 nodules in 366 patients were treated from June 2017 to Mar. 2018, 76 (M:F = 32:44, age 46 +/- 14 years) were treated with EA + RFA and 290 (M:F = 99:191, age 49 +/- 14 years) were treated with RFA. 44 patients (44 nodules) of each group formed a matched cohort after adjustment with propensity score matching. The average time, energy and power of the RFA procedure were retrospectively compared between the two groups. The postoperative nodule volume reduction ratio (VRR), compressive symptoms, cosmetic concerns, comprehensive satisfaction score, thyroid function and complications were retrospectively compared within and between the two groups after 6 months after treatment. Results: No significant differences were observed in the baseline characteristics between groups after propensity score matching adjustment. The mean RFA time (454.7 s (interquartile range (IQR), 290.8-589.0 s vs. 796.0 s (IQR, 554.0-976.30 s), p < .001), energy (3.69 +/- 1.99 kJ vs. 5.10 +/- 2.15 kJ, p = .009) and power (6.17 +/- 1.38 W vs. 7.21 +/- 1.29 W, p < .001) in the EA + RFA group were significantly lower than those in the RFA group. Mean nodule reduction at 6 months in the EA + RFA group and in the RFA group was 69.81 +/- 11.48% vs. 67.43 +/- 12.13% (10-30 ml, p = .454) and 62.75 +/- 11.41% vs. 59.82 +/- 10.53% (>30 ml, p = .456), respectively. The Medium nodules shrunk more than the large nodules (all p < .001), and the pressure symptoms and cosmetic signs significantly improved in the large nodules in both groups (all p < .05). Patients in the EA + RFA group had the highest satisfaction. Conclusions: EA combined with RFA shortened the ablation time of RFA, reduced the total energy and power required and improved patient satisfaction. This modified RFA approach may be considered a low-risk and high-efficacy alternative to treat solid BTNs greater than 10 ml in size.