Microwave Thermal Ablation of Thyroid Nodules with the MONTREAL Technique: Preliminary Clinical Results

Ultrasound-guided percutaneous Microwave Thermoablation (MWA) is an increasingly popular minimally invasive therapy for the treatment of benign thyroid nodules due to its remarkable heating velocity and resilience to heat sinking. We present a cohort of 26 patients (17 F, 9M, mean age 56.2yy) with 20 goiters (mean volume 34.9cc, min 6.5cc-max 84cc) and 6 autonomously functioning nodules (AFTNs, mean volume 11.6cc, min 3.5cc-max 24cc) treated with MWA, using the moving shot technique and a novel energy delivery algorithm (MONTREAL), based on intra-operative real-time reflectivity measurements: each moving shot was automatically terminated when reflectivity was observed to ramp up. 17G or 18G internally cooled 2.45 GHz applicators were used (AMICA-PROBE, HS HOSPITAL SERVICE SpA), operated at 15-30W. On average, each treatment deposited 9.9±5.5kJ during 696±325s, through 26.7±14.4 moving shots: the mean moving shot duration was 28.1±9.0s, yielding a mean ablation time per unit nodule volume of 34.3±19.1s/cc. No mild nor severe complications were recorded. Post-MWA ultrasound follow-up showed a mean volume reduction ratio of 59.1±10.2% [min 44% - max 80%] at 3 months and of 70.1±8.5% [min 53% - max 91%] at 6 months, with slightly better outcomes in the AFTNs sub-group (volume reduction of 65.3±10.2%/76.0±4.0% at 3/6 months and, in all cases, normal TSH values at 3 months upon pharmacological therapy suspension). MWA treatments of benign nodules with the MONTREAL technique appeared to be safe, fast, and effective. Further research is warranted to confirm these preliminary results.