Ultrasound-guided microwave ablation shows volume reduction in small RAS-mutated thyroid nodules in a pilot cohort.

The clinical management of RAS-mutated nodules faces significant challenges. This study aimed to explore the efficacy of microwave ablation (MWA) for the treatment of thyroid nodules ≤ 2 cm with isolated RAS gene mutations. This retrospective study was conducted between February 2022 and July 2024. A total of 23 patients with small RAS-mutated thyroid nodules who underwent MWA and completed at least 12 months of follow-up were enrolled. Data on nodule volume, volume reduction rate (VRR), and MWA-related adverse events were collected. Intra-group comparisons were performed using the Friedman rank sum test with post-hoc pairwise comparisons. Factors affecting VRR were analyzed using linear regression. ROC analysis was conducted as an exploratory approach to determined the optimal diameter cut-off for predicting complete regression. The cohort included 4 males (17.39%) and 19 females (82.61%), with a mean age of 45.35 ± 14.65 years. The median preoperative maximum diameter and volume were 6.20 (5.30-8.70) mm and 81.16 (46.12-256.56) mm³, respectively. All 23 patients completed ≥ 12 months of follow-up, with 6 patients reaching the 24-month follow-up. After an initial transient enlargement, the nodules showed sustained shrinkage. At the 12-month follow-up, the median VRR was 11.84% (P < 0.001), and the complete regression rate was 13.0%. By 24 months, the median VRR had reached 100%, with 83.33% complete regression (5/6). Nodules < 6 mm had higher regression rates. No local recurrence or distant metastasis occurred during the available follow-up period. Preliminary findings suggest that MWA may have favorable short-term efficacy and safety in the treatment of small RAS-mutated thyroid nodules.