Ultrasound-Guided Radiofrequency Ablation for Papillary Thyroid Microcarcinoma: Efficacy and Safety in a Cross-Country Multicenter Retrospective Study

Abstract

Objectives: This multicenter cross-country study aimed to assess and compare the short- and long-term efficacy and safety of ultrasound (US)-guided radiofrequency ablation (RFA) for low-risk papillary thyroid microcarcinoma (PTMC) in distinct national treatment settings. Materials and Methods: This retrospective study analyzed low-risk PTMC patients who received US-guided RFA at 6 medical centers in 2 countries (Taiwan and Vietnam) between November 2017 and April 2023. US and computed tomography (CT) were performed to assess and compare the PTMC tumors, changes in tumor size, and disease progression. Repeated measure ANOVA and two-way mixed ANOVA were used to analyze within-group and between-group differences among volume and volume reduction ratio (VRR). Student's t-test and the standard chi-square test were used to compare between-group data, while paired t-test was used to compare within-group data. Results: A total of 206 patients (mean age: 44.8 ± 12.5 years [range, 19-87], 44 men) with 224 PTMC tumors were enrolled and treated. Four (1.9%) patients reported transient hoarseness as complications. All tumors exhibited a reduction in size (p < 0.001) at 12 month post-RFA, while 58.5% (131/224) of PTMCs had completely disappeared under US examination at the last follow-up. One patient had developed ipsilateral cervical LN metastasis at the 6-month follow-up. While the VRR showed a statistical difference between the two countries in the short term (p < 0.001), this difference was not observed at 2 year follow-up (p=0.159). Conclusions: US-guided RFA is an effective and safe procedure for patients with PTMC. Furthermore, we noted no long-term differences in terms of procedural outcomes under the distinct national treatment settings.

Keywords: papillary thyroid microcarcinoma (PTMC); radiofrequency ablation (RFA); thyroid; ultrasound (US)-guided.

Figure 1

The CONSORT flow diagram of the study. PTC = papillary thyroid carcinoma. FNA = fine needle aspiration.

Figure 2

Mean PTMC tumor volume and VRR at each follow-up. (a) The mean tumor volume and (b) the mean VRR of the PTMCs in Taiwan, Vietnam, and both countries before and after RFA at each follow-up. Both countries showed successful treatment responses compared to the baseline, with consistent trends observed in the volume change and VRR between the two countries. PTMC = papillary thyroid microcarcinoma, VRR = volume reduction ratio, RFA = radiofrequency ablation.

Figure 3

A 46-year-old Taiwanese female with PTMC who underwent RFA. (a) US examination and (b) contrast enhanced CT scan revealed the PTMC (arrows) measuring 7 × 6 × 4 mm in the right isthmus of the thyroid adjacent to the trachea. (c) In the beginning of the RFA procedure, a layer of hydrodissection (arrow) was created to prevent thermal injury to the adjacent trachea. (d) During the RFA procedure, the targeted area was transformed to a transient hyperechoic state. (e) Follow-up US examination at 1 year after RFA showed regression of the PTMC, with a remaining linear scar (arrow) measuring 2 mm and atrophy of the right isthmus of the thyroid. (f) Contrast enhanced CT scan 3 years after RFA showed total regression (arrow) of the PTMC. PTMC = papillary thyroid microcarcinoma, RFA = radiofrequency ablation, CT = CT, US = ultrasound.