Role of second high-intensity focused ultrasound (HIFU) treatment for unsatisfactory benign thyroid nodules after first treatment

Background We aimed to assess the efficacy and safety of second high-intensity focused ultrasound (HIFU) ablation treatment in benign thyroid nodules that had failed to shrink by > 50% 6 months after the first treatment. Methods Twenty-eight patients who did not achieve 50% volume reduction at 6 months after the first HIFU treatment underwent a second HIFU treatment. Nodule volume was measured on ultrasound at baseline, 3 months and 6 months. Extent of nodule shrinkage (by volume reduction ratio) (VRR) = [Baseline volume – volume at 6 months]/[Baseline volume] * 100. Treatment success was defined as VRR > 50%. Obstructive symptom score (by 0–10 visual analogue scale, VAS) was evaluated for 6 months after treatment. Results No complications occurred after the second treatment. The mean 6-month VRR was 21.78 ± 16.87% with a median (range) of 16.16 (1.63–54.07)%. At 6 months, only two (7.1%) patients achieved treatment success, while nine (32.1%) patients had VRR < 10%. However, relative to baseline (3.96 ± 1.04), the mean VAS significantly improved at 3 and 6 months (2.96 ± 1.43, p