A prospective comparison of sequential versus interval retreatment with radiofrequency ablation for predominantly solid, large-volume benign thyroid nodules

Abstract

<h3>Background</h3><p>Radiofrequency ablation is an effective treatment for benign thyroid nodules. For large nodules ≥20 mL, retreatment within 6 months would lead to a higher volume reduction rate at 12 months than a single treatment. However, the optimal timing of retreatment within the 6-month period has not been determined. This prospective study compared sequential versus interval retreatment with radiofrequency ablation for predominantly solid, large benign thyroid nodules ≥20 mL and identified factors associated with a better volume reduction rate.</p><h3>Methods</h3><p>Consecutive patients with predominantly (>80%) solid, cytologically benign large thyroid nodules (≥20 mL) that were undergoing radiofrequency ablation at a tertiary endocrine surgery center were recruited for a planned, 2-session radiofrequency ablation treatment. Group I received sequential retreatment in <1 month, whereas group II received interval retreatment in 4–6 months. For each session, the entire nodule was ablated until it was fully covered with echogenic bubbles. The primary outcome was 18-month volume reduction rate = (baseline volume – 18-month volume)/baseline volume × 100%. Complications, compressive symptoms, and cosmetic symptoms were compared.</p><h3>Results</h3><p>From 2022 to 2023, 31 nodules (group I: 15, group II: 16) from 30 patients were recruited for a total of 62 ablation sessions. Baseline characteristics including nodule volumes (33.5 [25–40] vs 37.2 [23.9–56.1] mL) and symptoms were comparable (<em>P</em> < .05). The overall 12-month and 18-month volume reduction rates were 75.7% (60.4%–80.9%) and 82.7% (64.7%–87.6%). No significant difference in 18-month volume reduction rate was observed between groups (group I: 84.1% [68.1%–88.3%] vs group II: 79.4% [64.7%–87.6%], <em>P</em> = .608). Both groups had significant further nodule shrinkage from 12 months to 18 months (<em>P</em> < .05), at comparable rates (<em>P</em> > .05), and significant improvement in cosmetic and compressive symptoms (<em>P</em> < .001). A higher energy per unit volume delivered at the second ablation session was the only factor associated with an 18-month volume reduction rate of ≥80% (<em>P</em> = .038, odds ratio: 88.3 [1.47–532]). No vocal cord palsy or hematoma occurred, and all patients were discharged on the same day after each treatment session.</p><h3>Conclusion</h3><p>Continued shrinkage beyond 12 months was observed in large, predominantly solid benign thyroid nodules that received 2-session radiofrequency ablation within 6 months. Varying the time interval to retreatment within 6 months did not affect treatment efficacy. A higher energy per unit volume delivered at the second ablation session was associated with greater volume reduction.</p>