Volumetric outcomes of ultrasound-guided microwave ablation for benign thyroid nodules: A single-centre retrospective cohort study

Introduction: Ultrasound-guided microwave ablation is a minimally invasive alternative to surgery for symptomatic benign thyroid nodules, but most outcome data originates from East Asian centres, and evidence from European and Middle Eastern populations is limited. We evaluated the 12-month volumetric response, safety and subgroup outcomes of microwave ablation in a Turkish cohort. Methods: In this single-centre retrospective cohort, 180 consecutive patients with cytologically benign thyroid nodules and complete follow-up underwent ultrasound-guided microwave ablation between January 2019 and May 2025. Thyroid nodule volume was measured by ultrasound at baseline and at 3, 6 and 12 months; volume reduction rate was the primary outcome. Change over time was assessed with repeated-measures analysis of variance (volume) and the Friedman test (volume reduction rate). Results: Mean volume of benign thyroid nodules fell from 10.29 ± 4.15 to 2.86 ± 1.23 cm 3 ( F = 999.7, p &lt; 0.001, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>η</mml:mi> <mml:mi>p</mml:mi> <mml:mn>2</mml:mn> </mml:msubsup> </mml:mrow> </mml:math> = 0.848). The median volume reduction rate rose from 40.9% at 3 months to 62.5% at 6 months and 72.6% at 12 months ( p &lt; 0.001). All patients reached ⩾50% volume reduction rate by 6 months, and 65.6% reached ⩾70% by 12 months. Outcomes were independent of sex and baseline volume. No major complications occurred, and 80.6% reported complete symptom resolution. Conclusion: Ultrasound-guided microwave ablation achieved substantial and safe 12-month volume reduction in benign thyroid nodules, supporting it as a viable alternative to thyroidectomy in carefully selected patients.