Thyroid nodules (TNs) are a common clinical disease, discovered by palpation in 3 to 7% and by ultrasound in about 50% of the general population [
A total 115 patients with 144 benign thyroid nodules were recruited from January to December 2015 in a thyroid center of one medical institution. The inclusion criteria for all the patients were as follows according to the current RFA guidelines [
Demographic characteristics of the ablation group and control group. Normal ranges of the hormones are TSH 0.34~5.6 mIU/l, FT3 3.8~6.0 pmol/l, and FT4 7.86~14.41 pmol/l.
Ablation group | Control group |
| |
---|---|---|---|
Cases ( |
75 | 40 | — |
Nodules ( |
90 | 54 | — |
Age (y) | 39.38 ± 10.09 | 43.36 ± 9.88 | 0.187 |
Gender | |||
Male | 11 (14.7) | 11 (27.5) | — |
Female | 64 (85.3) | 29 (72.5) | 0.096 |
Ablation time (s) | 418.2 ± 308.36 | — | — |
Power (w) | 35.00 | — | — |
Location | |||
Left lobe ( |
36 | 23 | — |
Right lobe ( |
46 | 26 | 0.942 |
Isthmus ( |
8 | 5 | — |
TSH (mIU/l) | 1.73 ± 1.88 | 1.34 ± 0.68 | 0.523 |
FT3 (pmol/l) | 4.32 ± 0.55 | 4.30 ± 0.67 | 0.928 |
FT4 (pmol/l) | 11.43 ± 4.30 | 10.12 ± 2.44 | 0.360 |
Nanjing YIGAO company ECO-100 multifunctional microwave therapeutic instrument was applied with disposable microwave ablation needle antenna (16 G). The antenna type (10 cm in total length, 1.6 mm in diameter, and 3 mm in length of active tip) is suitable for superficial organs. Output power setting was 35 W, with a frequency of 2450 MHz, and the internally cooled needle antenna with normal saline for cold circulation fluid was used. The diameters, composition, and vascularity of nodules were examined by Phillip iU22 color Doppler ultrasonic diagnostic apparatus, probe frequency 5~12 MHz. Preoperative, intraoperative, and postoperative of thyroid nodules were examined by a two-dimensional color Doppler flow, and contrast-enhanced ultrasonography (CEUS) examination was also performed.
Laboratory data including blood biochemistry analysis, complete blood count, blood coagulation test, and thyroid function (thyroid stimulating hormone, triiodothyronine, thyroxine, free triiodothyronine, and free thyroxine) were assayed, and electrocardiogram was examined. A multiparametric monitor was connected to the patient showing continuous blood pressure, oxyhemoglobin saturation, and electrocardiogram during the procedure.
With the supine cervical extension, local anesthesia with 2% lidocaine was performed on the puncture site. After a small incision(<2 mm in length) was made, under the US guidance, a mixture of 2% lidocaine and 0.9% normal saline was infused into the surrounding thyroid capsule, a so-called “hydrodissection technique” to provide a safe barrier to prevent thermal damage to carotid artery and “danger triangle” where the trachea, esophagus, and recurrent laryngeal nerve are located [
Before ablation and after that of 1, 3, 6, 9, and 12 months, respectively, the patients in both groups returned to our hospital for a follow-up review. Preoperative and postoperative thyroid function tests, thyroid globulin antibody, thyroid peroxidase antibody, and thyroid ultrasonography were performed. Changes in volume, echogenicity, and intranodular vascularity were all evaluated. Ultrasonography was performed by fixed technologists in the same ultrasound machine, and three orthogonal diameters of thyroid nodules were measured. The volume of the nodules was calculated by the following equation:
The volume reduce rate (VRR) was assessed by a US imaging and was calculated by the following equation: volume reduction rate (%) = 100 × (initial volume − final volume)/initial volume. The complications during or after the ablation were also evaluated by the clinical signs and symptoms.
Clinical symptoms were evaluated using the symptom grading scores (visual analog scale, 0–10 cm), and the cosmetic grading scores (grade 1: no palpable mass; grade 2: invisible but palpable mass; grade 3: visible mass only by experienced clinician’s eyes; and grade 4: easily visible mass) [
Data analysis was performed with statistical software (SPSS for Windows version 19.0 SPSS IBM Corp., New York, NY). Quantitative data were expressed as mean ± standard deviation (SD), and
Ninety nodules were performed procedure in the MWA group for single-session treatment. The mean ablation time was 6.97 ± 5.13 minutes. The mean thyroid nodular volume of the MWA group decreased from 6.61 ± 4.65 ml (range, 1.11~22.6 ml) to 0.87 ± 0.99 ml (range, 0.05 ml~4.34 ml) (
Outcomes of the microwave ablation for thyroid nodules.
Nodule volume (ml) | Cosmetic scores | Clinical symptoms | ||||||||
---|---|---|---|---|---|---|---|---|---|---|
Baseline | 1 month | 3 months | 6 months | 9 months | 12 months | Before | 12 m (after) | Before | 12 m (after) | |
Control | 5.34 ± 3.88 | — | 5.18 ± 3.13 | 5.64 ± 3.86 | 6.35 ± 4.82 | 6.50 ± 4.36a | 3.07 ± 0.61 | 2.92 ± 0.83 | 4.35 ± 1.27 | 4.07 ± 1.20 |
MWA | 6.61 ± 4.65 | 4.03 ± 3.30 | 2.48 ± 2.27b | 1.94 ± 1.73b | 1.33 ± 1.45b | 0.87 ± 0.99b | 2.81 ± 0.71 | 1.11 ± 0.31b | 3.81 ± 1.99 | 0.96 ± 0.82b |
|
0.229 | — | 0.001 | <0.001 | <0.001 | <0.001 | 0.209 | <0.001 | 0.206 | <0.001 |
Mean volumes as mean ± standard deviation. a
After treatment, all nodules in the MWA group decreased in volume. The VRR in the MWA group was 30.53%, 55.98%, 69.31%, 76.65%, and 84.67% at the 1-, 3-, 6-,9-, and 12-month follow-ups, respectively. The largest diameter of thyroid nodules decreased from 2.92 ± 0.55 cm at baseline to 2.27 ± 0.99 cm, 1.82 ± 0.91 cm, 1.81 ± 0.59 cm, 1.58 ± 0.68 cm, and 1.38 ± 0.56 cm at 1-, 3-, 6-, 9-, and 12-month visits (
A 21-year-old female had a solid nodule in the left lobe of her thyroid gland. (a) The transverse of US examination showed a mainly solid nodule (arrow) which caused cosmetic problem in the superficial layer, and the volume of index nodule was approximately 5.40 ml (2.72 × 1.56 × 2.43 cm). (b) The long axis of index nodule. (c) At 1-month follow-up, US examination showed a little reduction in volume, and the volume was approximately 4.79 ml. (d) Three months after microwave ablation, the volume of the nodule significantly decreased to 3.75 ml. (e) Six months after the procedure, the index nodule shrunk to a volume of 0.96 ml. (f) At 1-year follow-up, the volume of the nodule greatly decreased to 0.08 ml, the VRR was 98.51%, and cosmetic grade significantly improved.
Comparison of the mean volume reduction rate (VRR) of the nodules at baseline (time of microwave ablation) and at follow-up after treatment. The VRR at 3-, 6-, 9-, and 12-month follow-ups was 55.98%, 69.31%, 76.65%, and 84.67% in the MWA group, respectively, while the VRR at 3-, 6-, 9-, and 12-month follow-up in the control group was 2.07%, −13.03%, −16.67%, and −24.53%, respectively.
The changes in volume and diameter before MWA and at each follow-up.
Baseline | 1 month | 3 months | 6 months | 9 months | 12 months | |
---|---|---|---|---|---|---|
Largest diameter (cm) | 2.92 ± 0.55 | 2.27 ± 0.99c | 1.82 ± 0.91c | 1.81 ± 0.59c | 1.58 ± 0.68c | 1.38 ± 0.56c |
Volume (ml) | 6.61 ± 4.65 | 4.03 ± 3.30 | 2.48 ± 2.27d | 1.94 ± 1.73d | 1.33 ± 1.45d | 0.87 ± 0.99d |
VRR (%) | — | 30.53 ± 38.94 | 55.98 ± 25.59 | 69.31 ± 22.03 | 76.65 ± 20.45 | 84.67 ± 17.37 |
Variates shown as mean ± standard deviation. c
In the enrolled patients, with the diameter > 2 cm, though the nodule volume has greatly reduced after the procedure, no nodules showed complete disappearance at 12-month follow-up.
The symptom grading score was significantly reduced from 3.81 ± 1.99 to 0.96 ± 0.82 (
There was no correlation between VRR with the index volume. There was a linear positive correlation between the ablation time and baseline volume of the thyroid nodules, and the correlation coefficient was 0.68 (
Positive correlation between ablation time and index nodule volume.
All the patients who received microwave ablation are well tolerated to the procedure. Ten patients (13.3%) complained of various degrees of pain at the ablated site or pain radiating to the ear, shoulder, or teeth. The pain was totally relieved when the ablation was finished. No one needed analgesics. There was no hematoma formation developed. Ten patients (13.3%) that complained transient voice change due to lidocaine injection recovered within 24 hours after procedure. However, two patients (2.7%) that encountered voice change recovered within 2 months. Slight skin burn happened in one case (1.3%). One patient (1.3%) who suffered from Horner syndrome, mainly for ptosis and pupil shrinks, within 2 months recovered to normal. There were no serious complications such as esophageal perforation and tracheal injury.
Thyroid nodules are very common disease. Most thyroid nodules are benign and asymptomatic, which do not need any treatment [
Microwave ablation is a minimally invasive technique to treat hepatic tumors that has been proven reliable, efficient, and safe [
The results among patients undergoing MWA in this study were superior to those among patients acting as control. It revealed that MWA significantly decreased TN volume in comparison with untreated patients who did experience TN size increase. The magnitude of volume reduction in this study is similar to studies conducted by RFA and other MWA studies [
Procedure-related major complications including recurrent laryngeal nerve paralysis and Horner syndrome occurred in two and one cases, respectively. Since the recurrent laryngeal nerve was close to the treated nodule when it was located in the danger triangle, we believe it was a technical error caused by directing the thermal energy too close to this region [
This study has some limitations and shortcomings. Firstly, the major complication rate is a little higher than previous studies [
In conclusion, MWA is an effective modality in decreasing volumes of benign thyroid nodules, as well as improving cosmetic grading and clinical symptoms, compared with the control group. However, prospective study with large-scale and long-term follow-up is necessary to be developed.
No potential conflict of interests relevant to this article was reported.
This research was supported by the Clinical Scientific Research Program of Zhejiang Medical Association (2015ZYC-A25) and Scientific Incubation Program funded by Wenzhou Medical University First Affiliated Hospital (FHY2015022).