Bipolar radiofrequency ablation for nodular thyroid disease--ex vivo and in vivo evaluation of a dose-response relationship

Thyroid dysfunction following radiofrequency ablation for benign thyroid nodules: more likely to occur within one-week and in high-risk population

BACKGROUND

Radiofrequency ablation (RFA) has been recommended as the treatment for benign thyroid nodules (BTNs) by some guidelines. However, detailed follow-up instructions for thyroid function about the timing and affected populations after RFA are lacked due to insufficient researches. This 12-month prospective study aimed to evaluate the incidence and risk factors of thyroid dysfunction at different time points after RFA, especially within 1 week that previous studies didn't concern.

METHODS

Seventy-five euthyroid patients who underwent RFA for symptomatic BTNs were enrolled (ChiCTR-INR-16007884). The incidence of thyroid dysfunction within 1 week, at 1, 6, and 12 months after RFA was evaluated. The risk factors for different types of thyroid dysfunction in the different terms were further analyzed.

RESULTS

Within 1 week after RFA, the incidence of thyroid dysfunction was as high as 36.00% unexpectedly, and only overt thyrotoxicosis and subclinical thyrotoxicosis occurred, which were significantly associated with the low-normal baseline thyrotropin (TSH) level (p = 0.001) and high ablation volume ratio (p = 0.008). From 1 to 12 months (the long term), the incidence dropped significantly and remained low (8.00-12.00%); and thyroid dysfunction presented as overt thyrotoxicosis, subclinical thyrotoxicosis, and subclinical hypothyroidism. The long-term thyrotoxicosis group had more cases with diabetes and lower baseline TSH levels. The long-term subclinical hypothyroidism group had more cases with positive thyroid peroxidase antibodies, higher baseline TSH levels, and higher ablation volume ratios.

CONCLUSIONS

After the RFA of BTNs, thyroid dysfunction was more likely to occur within 1 week and in populations with risk factors.

Efficacy and safety of radiofrequency ablation for benign thyroid nodules in patients with previous thyroid lobectomy

Background

Radiofrequency ablation (RFA) is recommended for the treatment of benign thyroid nodules. However, data on the clinical role of RFA for benign thyroid nodules in patients with history of thyroid lobectomy are insufficient. The purpose of this study was to evaluate the efficacy and safety of radiofrequency ablation (RFA) for benign thyroid nodules in patients who had previously undergoing thyroid lobectomy.

Methods

From May 2015 to October 2018, a total of 20 patients (19 females, 1 male, mean age 49.50 ± 14.26 years, range 22–74 years) with 20 benign thyroid nodules (mean volume 15.04 ± 21.17 ml, range 0.40–69.67 ml) who had undergone previous thyroid lobectomy were included in this retrospective study. Patients were followed up at 3, 6, 12 months after RFA and every 12 months thereafter by ultrasound, clinical evaluation and thyroid function. Volume, volume reduction rate (VRR), symptom score and cosmetic score were evaluated.

Results

During the mean follow-up time of 21.24 ± 16.41 months, the mean nodule volume decreased significantly from 15.04 ± 21.17 ml to 1.29 ± 1.17 ml (P = 0.018) with a mean VRR of 85.41 ± 12.17%. Therapeutic success was achieved in a single session for all thyroid nodules. The symptom score (P = 0.001) and cosmetic score (P = 0.001) were both significantly reduced at the last follow-up. The levels of free triiodothyronine (fT3), free thyroxine (fT4) and thyroid stimulating hormone were not significantly different at the last follow-up from those prior to treatment (all P > 0.05). No life-threatening complications or sequelae occurred after RFA.

Conclusions

As a minimally invasive modality, RFA was a safe, effective, and thyroid function-preserving option for patients with symptomatic benign thyroid nodules after a previous lobectomy.

Radiofrequency Thermoablation On Ex Vivo Animal Tissues: Changes on Isolated Swine Thyroids

The use of Radiofrequency thermoablation (RFA) for treating large thyroid nodules is limited by the modest efficiency of the available systems in terms of volume of the ablation zones (AZs). This increases the risk of incomplete ablation of the nodule. Systems employing perfused electrodes have been developed to increase the volume of the AZ. Aim of this study is to compare the size of the AZ induced by RFA systems using internally cooled perfused vs. non-perfused electrodes in swine thyroids. RFAs were performed on 40 freshly isolated swine thyroids using both systems. The perfused system was tested using 0.9% saline, 7% and 18% hypertonic saline solutions. Energy delivery to the tissue was stopped when tissue conductivity dropped (real life simulations) and after an established time of 20 seconds (controlled duration). Following RFA, thyroids were transversally and longitudinally cut. Photographs were taken for macroscopic morphometry of the ablated zones before and after formalin fixation, to evaluate tissue shrinkage. Microscopic morphometry was performed on PAS stained sections. In real life simulation experiments, gross morphometry revealed that AZs produced with electrodes perfused using 7.0% saline are larger compared to isotonic saline. Microscopically, all the conditions tested using the perfused system produced larger AZs compared to non-perfused system after 20 seconds of RFA. In conclusion, the perfusion with 7.0% NaCl solution increased the electrical conductivity of the tissue in real life simulations, resulting in larger ablated areas compared to the use of isotonic saline.

Comparison of the Ablation and Hyperechoic Zones in Different Tissues Using Microwave and Radio Frequency Ablation

OBJECTIVES

The aim of this study was to compare the differences between the ablation region and hyperechoic zones in microwave and radio frequency ablation of different tissues.

METHODS

Microwave and radio frequency ablation were performed on fresh porcine muscle and liver with different power levels for 90 seconds. These 2 ablation methods were then performed on rabbit liver in vivo using 20 W for 60 seconds. The volumes of the ablation and hyperechoic zones were compared following different ablation methods.

RESULTS

The ablation zones were significantly greater than the hyperechoic zones (P < .05) with the same power and duration when using 2 ablation methods. The differences of the ablation and hyperechoic zones between muscle and liver tissues were significantly different (P < .05). The difference values of the ablation and hyperechoic zones were also significantly different (P < .05) using 2 ablation methods.

CONCLUSIONS

The hyperechoic zone may have underestimated the extent of ablation using a specified ablation time. In the same tissue, the hyperechoic zone could more accurately estimate the ablation zones using microwave ablation.

Morphological Changes Induced by Bipolar Radiofrequency Ablation in Thyroid Nodules - a Preclinical Ex Vivo Investigation

Introduction: Recently, radiofrequency ablation (RFA) has been increasingly used for the treatment of thyroid nodules. However, immediate morphological changes associated with bipolar devices are poorly shown. Aims: To present the results of analysis of gross and microscopic alterations in human thyroid tissue induced by RFA delivered through the application of the original patented device. Materials and methods: In total, there were 37 surgically removed thyroid glands in females aged 32-67 at presentation: 16 nodules were follicular adenoma (labelled as 'parenchymal' solid benign nodules) and adenomatous colloid goitre was represented by 21 cases. The thyroid gland was routinely processed and the nodules were sliced into two parts - one was a subject for histological routine processing according to the principles that universally apply in surgical pathology, the other one was used for the RFA procedure. Results: No significant difference in size reduction between parenchymal and colloid nodules was revealed (p>0.1, t-test) straight after the treatment. In addition, RFA equally effectively induced necrosis in follicular adenoma and adenomatous colloid goitre (p>0.1, analysis of variance test). As expected, tumour size correlated with size reduction (the smaller the size of the nodule, the greater percentage of the nodule volume that was ablated): r=-0.48 (p<0.0001). Conclusion: The results make it possible to move from ex vivo experiments to clinical practice.

Treatment efficacy and safety of ultrasound-guided percutaneous bipolar radiofrequency ablation for benign thyroid nodules

OBJECTIVE

To evaluate the therapeutic efficacy and safety of ultrasound-guided percutaneous bipolar radiofrequency ablation (BRFA) of benign thyroid nodules by comparison with a matched untreated control group.

METHODS

The therapeutic efficacy and safety in 35 patients who were subjected to a single session of ultrasound-guided percutaneous BRFA (Group A) for benign thyroid nodules were compared with those in 35 untreated patients (Group B) with benign nodules. The benign nature of all the nodules was confirmed by ultrasound-guided fine-needle aspiration biopsy (FNAB), and all the patients had normal thyroid functions. BRFA was performed with a bipolar electrode (CelonProSurge 150-T20) with an output power of 20 W. Nodule volume, thyroid function and clinical symptoms of all the patients were compared before treatment and during follow-up.

RESULTS

In Group A, the BRFA procedures were completed with a mean time of 10.02 ± 3.30 min (range, 5.47-16.03 min) and with a mean total energy deposition of 10.747 ± 3704 J (range, 5510-17.770 J). The procedures were tolerated well in all the patients without causing any major complications. At the 6-month follow-up, all of the nodule volume decreased significantly (from 8.81 ± 8.66 to 1.59 ± 1.55 ml, p < 0.001) in Group A, whereas the nodule volume increased from 6.90 ± 3.77 to 7.87 ± 3.95 ml in Group B (p < 0.001). All (100%) the 35 nodules in Group A had volume reduction ratios (VRRs) of >50%, among which 3 (8.57%) had VRRs >90%. In Group A, the clinical symptoms of the patients who had symptoms before BRFA disappeared, whereas in Group B, the patients had no resolution of clinical symptoms at the 6-month follow-up.

CONCLUSION

Ultrasound-guided percutaneous BRFA seems to be an effective and safe method for the treatment of benign thyroid nodules. It may gain a wide use in clinical practice.

ADVANCES IN KNOWLEDGE

Based on the comparable efficacy and clinical symptoms between the BRFA and untreated groups, the technique of BRFA can be used as an effective and safe method for the treatment of benign thyroid nodules.

Advances in nonsurgical treatment of benign thyroid nodules

Ethanol ablation has traditionally been used for treatment of cystic thyroid nodules. Laser ablation and radiofrequency ablation were introduced later and used for treatment of solid thyroid nodules. However, how to select the best treatment modality among the different techniques has, so far, not been determined and causes confusion in clinical practice. Therefore, the necessity for a proper guideline regarding the choice of the preferable treatment modality has been suggested as the use of nonsurgical treatment for benign thyroid nodules has been increasing. This article provides an up-to-date review of nonsurgical treatment of benign thyroid nodules focusing on how to select the best treatment modality according to the composition of thyroid nodules based on the clinical evidence.