Thyroid nodules are common in adults and, in population-based cohorts assessed with high-frequency ultrasonography, their prevalence has been reported to range from 20% to 76% [1,2]. In Vietnam, the overall prevalence of thyroid nodules was 48.4%, significantly higher in women than in men (55.2% vs. 42.9%; p < 0.001), with advanced age, hypertension, hyperglycemia, and metabolic abnormalities identified as associated factors [3]. Partially cystic nodules comprise 53.5% of all thyroid nodules, with 13.7% characterized as predominantly cystic, containing more than 75% cystic components [4]. Management of benign cystic thyroid nodules primarily depends on the severity of compressive symptoms or cosmetic concerns [5].

Radiofrequency ablation (RFA) has been demonstrated to be an effective treatment for cystic thyroid nodules, with outcomes influenced by factors such as solid proportion, vascularity, and nodule size [6]. However, the optimal treatment technique for thyroid cystic nodules remains a topic of debate. For purely cystic thyroid nodules, RFA has shown a significantly greater volume reduction within the first three months post-treatment, but this advantage diminishes over longer follow-ups, with similar outcomes observed at six months [6]. For predominantly cystic thyroid nodules (PCTNs), RFA has been associated with a higher volume reduction rate (VRR) and a lower recurrence risk compared to other techniques such as simple aspiration and ethanol ablation (EA), likely due to its ability to address the vascularity and solid components contributing to regrowth or bleeding [7,8]. In a randomized controlled trial, Baek et al. reported that RFA achieved a mean VRR of 87.5 ± 11.5%, compared with 82.4 ± 28.6% obtained with EA after six months [9].

Despite promising results, studies directly comparing the short-term efficacy and safety of single-session RFA for both purely cystic nodules and PCTNs remain limited, particularly in Vietnam. This study aims to evaluate the one-month, 6 months, 12 months outcomes of single-session RFA for these types of nodules.

From June 2023 to April 2025, a total of 38 patients diagnosed with either a purely thyroid cyst or PCTNs were deemed eligible for inclusion through the Ehealth program. Specifically, 36 patients completed the 1-month follow-up, 23 continued to the 6-month follow-up, and 15 remained under observation at the 12-month mark at the end April 2025. Patients lost to follow-up did not return for scheduled visits due to reasons such as relocation, inability to be contacted, or personal scheduling constraints; none of the losses were related to procedure-associated adverse events. The flow of participants through the study is shown in Fig 1. The study was conducted without any complications, either major or minor.

Table 1 shows baseline characteristics of 38 patients. A total of 38 patients were enrolled in the study, including 4 males (10.5%) and 34 females (89.5%), with a mean age of 41.6 ± 18.5 years. The mean largest nodule diameter was 22.8 ± 10.0 mm (range, 10–37.6 mm), and the average nodule volume was 10.1 ± 9.1 mL (range, 0.84–36.96 mL). The mean TSH and FT4 concentrations were 1.37 ± 0.93 mIU/L (range, 0.11–4.77 mIU/L) and 1.22 ± 0.18 ng/dL (range, 0.76–1.52 ng/dL), respectively. Purely thyroid cysts accounted for 26.3% of cases, while 73.7% were PCTNs. The mean aspirated fluid volume was 6.0 ± 7.1 mL (range, 1–35 mL). Regarding anatomical distribution, 53.3% of nodules were located in the right lobe, 42.1% in the left lobe, and 2.6% in the isthmus. The mean baseline cosmetic and symptom scores were 3.00 ± 0.82 and 4.42 ± 0.71, respectively. The procedure duration averaged 16.2 ± 3.1 minutes, with lidocaine used for local anesthesia. The mean energy delivered was 16.72 ± 1.66 kJ, while the minimum and maximum RF powers were 22.5 ± 4.15 watts and 43.15 ± 11.17 watts, respectively.

Table 2 presents the clinical outcomes observed following the initial session of RFA therapy. Following RFA, both the largest diameter and volume of the thyroid nodules showed a significant reduction over time. The mean largest diameter decreased from 32.00 ± 8.55 mm at baseline to 16.21 ± 9.27 mm at 12 months (p < 0.0001), and the mean nodule volume was reduced from 10.14 ± 9.05 mL to 2.04 ± 3.95 mL over the same period (p = 0.0001). These changes indicate a marked and sustained volumetric response to RFA treatment. In contrast, thyroid function tests, including serum TSH and FT4 levels, remained relatively stable throughout the follow-up. The TSH concentration changed slightly from 1.37 ± 0.93 to 1.45 ± 1.01 μIU/mL (p = 0.673), and FT4 levels showed no significant variation (from 1.22 ± 0.18 to 1.24 ± 0.22 ng/dL, p = 0.610)

Table 3 summarizes the outcomes of RFA for thyroid cyst treatment at 1-month, 6-month, and 12-month follow-up intervals. The overall VRR after RFA showed a statistically significant improvement over time, increasing from 65.97 ± 22.19% at 1 month to 83.29 ± 17.33% at 6 months and slightly maintaining at 82.49 ± 23.18% at 12 months (p = 0.001). When stratified by nodule type, purely thyroid cysts exhibited a higher VRR at all time points compared to PCTNs, although the difference was not statistically significant (p = 0.45). Specifically, purely cystic nodules reached a VRR of 77.58 ± 17.04% at 1 month and 91.12 ± 10.86% at 6 months, maintaining a high reduction of 86.87 ± 13.04% at 12 months (p < 0.05). In contrast, the VRR for PCTNs increased from 61.50 ± 22.59% at 1 month to 81.64 ± 8.19% at 6 months and 81.82 ± 24.68% at 12 months.

Regarding treatment efficacy, the overall therapeutic success rate declined over time from 30/36 cases at 1 month to 13/15 at 12 months, with a no statistically significant difference (p = 0.365). Notably, the therapeutic success rate remained consistent and high in purely cystic nodules (from 9/10 at 1 month to 2/2 at 12 months, p > 0.05), whereas in PCTNs, it decreased from 21/26–11/13 over the same timeframe.

According to the multiple linear regression analysis, no significant correlations were observed between the volume reduction ratio (VRR) at one and six months after ablation and any of the evaluated clinical or ultrasonographic parameters, including demographic data, thyroid function indicators, procedural details, and specific nodule features

In recent years, RFA have been one of the minimally invasive alternative treatments of benign thyroid nodule(s) (including solid-cystic nonfunctioning benign nodules, autonomously functioning thyroid nodules), low-risk papillary thyroid carcinoma, and recurrent thyroid cancers [17–24].

Our prospective study conducted from June 2023 to April 2025 evaluated the efficacy and safety of single-session RFA for treating benign cystic thyroid nodules, encompassing both purely cystic nodules (less than 10% solid component) and predominantly cystic thyroid nodules (PCTNs, 10–50% solid component). In our study the mean nodule diameter and volume significantly decreased from 32.0 mm to 16.2 mm and from 10.1 mL to 2.0 mL at 12 months (p < 0.001). The overall VRR improved from 66.0 ± 22.2% at 1 month to 83.3 ± 17.3% at 6 months and 82.5 ± 23.2% at 12 months. Purely cystic nodules achieved higher VRR (up to 91.1% at 6 months) compared with predominantly cystic nodules (81.6%). The therapeutic success rate was 83.3% at 1 month and 86.7% at 12 months, and no major complications or thyroid function changes were observed. Our findings demonstrated that RFA is a safe and effective minimally invasive treatment, achieving significant VRR without major complications or impact on thyroid function.

Our findings are consistent with prior research on RFA for benign thyroid nodules. A randomized controlled trial by Ha et al. (2015) [9] compared RFA and EA for PCTNs and found no significant difference in VRR at 6 months (87.5% ± 11.5% for RFA vs. 82.4% ± 28.6% for EA, p = 0.710). The VRR in our cohort at 1 month was 65.97%. While this is a promising result, comparisons with findings from other studies that differ in design and patient populations cannot be used to infer relative efficacy. This short-term advantage could be attributed to RFA’s ability to target vascular structures and ablate solid components more effectively, as facilitated by the moving-shot technique and Doppler ultrasound used in our study.

Jeong et al. (2022) [25] evaluated the impact of RFA and EA on thyroid-specific quality of life (QoL) in patients with symptomatic benign thyroid nodules. Both treatments significantly improved QoL, but EA demonstrated higher VRR for nodules with a higher fluid component (solidity <50%) at 1, 6, and 12 months (78.7% ± 16.1%, 86.3% ± 21.7%, and 90.9% ± 14.9%, respectively) compared to RFA for nodules with solidity ≥50% (49.1% ± 15.8%, 73.0% ± 14.5%, and 80.3% ± 12.4%). These findings support our observation that purely cystic nodules respond better to RFA than PCTNs, which contain a higher solid component requiring more extensive ablation.

Recurrence remains a significant concern with EA. Sung et al. (2015) [26] reported a recurrence rate of 38.3% after EA for predominantly cystic thyroid nodules, with initial nodule volume >20 mL and high vascularity (grade >1) as independent predictors of recurrence. In contrast, our study reported no recurrences during the 12-month follow-up, although longer-term data are needed to confirm this. The absence of recurrence in our cohort may be due to the targeted ablation of vascular structures using Doppler ultrasound and the moving-shot technique, which enhances the precision and efficacy of RFA.

Lee et al. (2010) (8) proposed RFA as a supplementary treatment for nodules with incomplete resolution after EA, particularly those with residual solid components. This is particularly relevant for PCTNs, where solid portions may persist post-EA, leading to recurrence. Our study’s success with PCTNs, although with lower VRR than purely cystic nodules, supports the role of RFA in managing more complex nodules.

The superior efficacy of RFA for purely cystic nodules can be attributed to the complete removal of cystic fluid followed by ablation of the nodule wall, which prevents fluid reaccumulation. For PCTNs, the presence of solid components necessitates more extensive ablation, potentially explaining the lower VRR compared to purely cystic nodules. The use of the moving-shot technique and Doppler ultrasound to target vascular structures likely enhanced the efficacy of RFA by reducing the risk of incomplete ablation and subsequent recurrence.

Compared to EA, RFA’s ability to ablate both cystic and solid components makes it more versatile, particularly for nodules with higher solid content or those at risk of recurrence. However, EA’s simplicity and lower cost make it a more accessible option in resource-limited settings. The choice between RFA and EA should therefore consider nodule characteristics, patient preferences, and economic factors.

In conclusion, single-session RFA appears to be a safe and effective minimally invasive treatment option for benign cystic thyroid nodules. Further research is needed to refine treatment algorithms and enhance patient outcomes in the management of benign cystic thyroid nodules.