# Comparison of microwave ablation versus lauromacrogol injection ablation for 50–75% cystic thyroid nodules: a two-center retrospective study

## TL;DR

Microwave ablation is more effective than lauromacrogol injection for treating 50–75% cystic thyroid nodules, especially for larger nodules.

## Contribution

This study provides a two-center comparison of microwave ablation and lauromacrogol injection for thyroid nodules with 50–75% cystic components.

## Key findings

- Microwave ablation achieved a higher 12-month volume reduction rate (91.5%) compared to lauromacrogol injection (81.1%).
- Microwave ablation showed significantly lower regrowth rates (3.9%) compared to lauromacrogol injection (20.0%).
- Microwave ablation was more effective for nodules larger than 10 ml but not for smaller nodules.

## Abstract

To compare the efficacy between microwave ablation (MWA) and lauromacrogol injection ablation (LIA) for treating 50-75% cystic thyroid nodules and systematically identify the factors influencing outcomes.

This retrospective study included 106 patients with predominantly cystic thyroid nodules (PCTNs) with 50-75% proportion of cystic components (simple as 50–75% cystic thyroid nodules) who underwent ultrasound-guided MWA (n=51) or LIA (n=55) in two hospitals between April 2017 and November 2023. The primary endpoint was 12-month volume reduction rate (VRR). ANCOVA was used to compare adjusted 12-month VRR between groups after adjusting for confounders. Secondary endpoints included effective treatment rate (VRR >50% at 6 or 12 months), recurrence, and stratified analysis analyses by initial nodule volume (>10 ml and ≤10 ml) and vascularity (Grades 0–1 and 2-3). Regrowth-free survival was estimated by Kaplan-Meier (KM) analysis and compared with the Log-rank test.

At 12 months postoperatively, the mean VRR for MWA was 91.5 ± 9.8% and 81.1 ± 2.4% for LIA (F = 4.40, P = 0.005). MWA yielded higher VRR than LIA at 6 and 12 months across both low- and high-vascularity subgroups (P<0.05). For nodules >10 ml, MWA produced significantly greater VRR at 3, 6 and 12 months (P<0.05); no significant difference was observed for nodules ≤10 ml (P>0.05). The 12-month effective treatment rate was 96.1% (49/51) after MWA versus 81.8% (46/55) after LIA (P = 0.018). Regrowth rates were 3.9% (2/51) for MWA and 20.0% (11/55) for LIA (P = 0.006). The KM analysis showed significantly longer regrowth-free survival following MWA (Log-rank P = 0.010).

Both MWA and LIA exhibit favorable efficacy in the treatment of 50–75% cystic thyroid nodules. Importantly, based on the approximately 12-month follow-up, MWA demonstrates superior efficacy and improved control of regrowth compared to LIA. This advantage of MWA is further amplified in the management of larger nodules.