US-guided Nanosecond Pulsed Electric Field Ablation of Low-risk PTMC: Interim Results of a Prospective Multicenter Study

CONTEXT: Nanosecond pulsed electric field (nsPEF) ablation has gradually been applied in clinical practice. However, no studies have reported its application in low-risk papillary thyroid microcarcinoma (PTMC). OBJECTIVE: The study aimed to evaluate the efficacy and safety of nsPEF ablation for patients with low-risk PTMC. METHODS: This prospective study (Chinese Clinical Trial Register: ChiCTR-2200064902) included consecutive low-risk patients with PTMC who underwent nsPEF ablation at 6 hospitals in China. Technical feasibility was assessed by recording the technical success of the procedure and therapeutic efficacy at the 1-, 3-, 6-, and 12-month follow-up. Technical success was evaluated using contrast-enhanced ultrasound immediately after ablation, where the target ablation zone exceeded the tumor edge. Therapeutic complications were evaluated. RESULTS: From September 2022 to September 2024, 85 patients (median age, 38 years; interquartile range, 32-47 years; 58 females) with 85 PTMCs were included, all achieving successful nsPEF ablation. At 1-, 3-, 6-, and 12-month follow-up, median tumor volumes were 0.109, 0.054, 0.020, and 0.000 mL, and the associated median volume reduction ratios were -124.0%, -4.8%, 63.5%, and 100%, respectively. At 12 months, 88.0% (66/75) of PTMCs achieved complete disappearance. Fifty-six (65.9%) patients experienced transient thyrotoxicosis. No recurrent tumors, cervical lymph node metastasis, or distant metastasis were observed during follow-up. CONCLUSION: nsPEF ablation under general anesthesia for low-risk PTMC is effective and safe, with the only major complication being transient thyrotoxicosis in more than 50% of patients, which might be caused by the release of thyroid hormones into the bloodstream because of irreversible electroporation. It appears to offer better absorption of the ablated lesions in the short term, potentially increasing its clinical use. Further short- and long-term study is needed.