A prospective comparison of sequential versus interval retreatment with radiofrequency ablation for predominantly...

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.

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.

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 (P < .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%], P = .608). Both groups had significant further nodule shrinkage from 12 months to 18 months (P < .05), at comparable rates (P > .05), and significant improvement in cosmetic and compressive symptoms (P < .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% (P = .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.

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.