Evaluating microwave ablation for treating large benign thyroid nodules.

Background: Large benign thyroid nodules (BTNs) (≥4 cm) are often situated in close proximity to critical tissues, posing unique challenges for treatment. Microwave ablation (MWA), known for its ability to generate consistently higher intratumoral temperatures, has emerged as a promising non-surgical alternative. This study aimed to assess the efficacy and safety of MWA when treating patients harboring large BTNs, and explore the strategy for protecting against recurrent laryngeal nerve (RLN) injury. Methods: A retrospective analysis of 205 patients with BTNs who underwent MWA was conducted. Clinical and ultrasound (US) analyses were performed at 1, 6, and 12 months post-ablation. The volume reduction rate (VRR), associated factors, and complications were analyzed. Results: For patients in this cohort, the respective mean nodule diameter and volume were 46.56±7.66 mm and 22.91±15.23 mL. Of the 205 nodules, 59 were solid, and 146 were predominantly solid. At 12 months, the mean VRR was 82.54%, with a technical efficacy rate of 93.66%. Multivariate analysis revealed that VRR was significantly associated with nodule composition at 6 months but not at 12 months. Eighteen cases necessitated repeat ablation owing to difficulties in maintaining an effective isolating fluid width, with this issue being attributable to high levels of tension between the thyroid nodule and the tracheoesophageal groove. One patient developed transient hoarseness, that was fully resolved within 1 month after ablation. Conclusions: MWA can be safely and effectively used to treat large BTNs. Secondary ablation is a crucial strategy for mitigating RLN injury when isolating fluid is insufficient.