Abstract #1403009: Radiofrequency Ablation for Low-Risk Papillary Thyroid Microcarcinoma: First Reported Cases in the US

Abstract

The incidence of papillary thyroid microcarcinoma (PTMC) is rising with increased utility and advancement of radiology imaging. Conservative treatment is highly considered given indolent nature of the disease. There has been a growing trend around the world to treat low risk PTMC with thermal ablation, such as radiofrequency ablation (RFA), a minimally invasive procedure that preserves most of thyroid parenchyma and function. This study is the first to report the efficacy and safety of RFA for low-risk PTMC in a large referral center in the US. The study included 10 patients who underwent RFA to treat low risk PTMC between July 2020 and February 2022. Patients who had cytological confirmation of single PTMC without evidence of metastasis, and ineligibility or refusal to undergo surgery were included. RFA were performed by three interventional radiologists. RFA technique and type of anesthesia were described. Thyroid function, changes in ablated tumor sizes, as well as procedure-related complications were retrospectively analyzed up to 18 months follow-up. Nine females and 1 male were included; median age was 44 years (range 29 – 69). Nine patients had normal thyroid function before and after RFA, and one patient had transient hyperthyroidism at 3 months follow up. Seven patients underwent general anesthesia, 2 patients had deep sedation, and 1 patient had moderate sedation. Mean duration of RFA was 6.32 minutes (SD +/- 4.25) with energy delivered ranging between 25 – 45 Watts. Mean volume of PTMC at baseline was 0.3 mL SD+/- 0.22. There was an increase in ablated volume at 3 months measuring 1.02 mL SD +/- 0.76, followed by a reduction in ablated nodule volume at 6 months measuring 0.42 mL SD +/- 0.38, and at 12 months measuring 0.26 mL SD +/- 0.28. The ablated nodules almost disappeared by 18 months follow-up, measuring 0.05 mL +/- 0.03 with no evidence of recurrence. There were no procedure-related major complications in any of the patients. This is the first reported cases of low risk PTMC treated with RFA in the US. The ablated volume initially increased as expected due to ablation beyond the nodules margin, followed by a gradual decrease in volume. RFA is safe and effective for the treatment of low risk PTMC. This therapy is potentially expanding in the US. Further study with longer follow up is needed to evaluate the risk of recurrence.