Clinical Effects of Microwave Ablation in the Treatment of Low-Risk Papillary Thyroid Microcarcinomas and Related Histopathological Changes

Histologic Evaluation of Thyroid Nodules Treated with Thermal Ablation: An Institutional Experience

Thyroid nodules are a common, benign condition with a higher prevalence in women, individuals with iodine deficiency, and radiation exposure. Treatment options for benign thyroid nodules include pharmaceutical therapy, thyroidectomy, and thermal ablation (TA). TA, including laser ablation (LA), radiofrequency ablation (RFA), and microwave ablation (MWA), is a procedure that uses heat to cause tissue necrosis. It is commonly used for large, firm, benign, non-functioning thyroid nodules that cause severe symptoms or pain when surgery is not recommended or desired. When thyroid nodules do not respond to TA, they undergo surgery to resolve the symptoms and clarify the diagnosis. This study aims to analyze the histological alterations found in surgically excised TA-treated thyroid nodules and to evaluate the morphological criteria of differential diagnosis between benign and malignant nodules, establishing whether the alterations observed on the histological sample are a consequence of TA or indicative of neoplastic disease. For this purpose, the adoption of ancillary methods, such as immunohistochemistry, is fundamental to distinguish the artifacts induced by TA from the typical morphological characteristics of malignant neoplasms.

Complications of ultrasound-guided thermal ablation of thyroid nodules and associated risk factors: an experience from 9667 cases

OBJECTIVES

To evaluate the safety of ultrasound-guided thermal ablation (UGTA) for thyroid nodules (TNs) by analysing complications and related risks.

MATERIALS AND METHODS

This retrospective, single-centre study reviewed patients who underwent UGTA (microwave or radiofrequency ablation) between January 2018 and March 2023. The incidence of complications was recorded and assessed during and immediately after ablation,1-3 h later, and at 1 month, 3 months, and 6 months. Univariate and multivariate analyses were performed to identify risk factors for hoarseness and haemorrhagic complications.

RESULTS

We reviewed 9667 cases in this study. Overall, 4494 (46.49%) cases underwent microwave ablation, while 5173 (53.51%) cases underwent radiofrequency ablation. The overall complication rate was 4.43%. The incidence of major complications was 1.94% (haemorrhage, 1.32%; hoarseness, 0.54%; and symptomatic aseptic necrosis, 0.08%). The incidence of minor complications was 2.45%. A large nodule volume, radiofrequency ablation, hyper-enhancing nodules, benign nodules, higher preoperative blood pressure, hyperthyroidism, and higher ablation power were independent risk factors for haemorrhage. Dorsal nodules and a higher ablation power were independent risk factors for hoarseness. All complications were resolved.

CONCLUSION

This study suggests that UGTA is a safe treatment for TNs. Several risk factors for haemorrhage and hoarseness should be considered before performing UGTA. Different ablation modalities should be considered for patients with different conditions.

CLINICAL RELEVANCE STATEMENT

Thermal ablation may be a safe treatment for eligible patients with TNs.

KEY POINTS

We analysed the complications and risk factors associated with UGTA in 9667 cases. The complication rate was 4.43%; 1.94% were major complications. Risk factors of haemorrhage and hoarseness should be considered. UGTA was a safe method for the treatment of TNs.

Ultrasound-guided microwave ablation versus surgery for solitary T1bN0M0 papillary thyroid carcinoma: a prospective multicenter study

OBJECTIVE

Microwave ablation (MWA) has emerged as a minimally invasive technology for papillary thyroid microcarcinoma (PTMC), but it has not been widely applied to treat T1bN0M0 PTC with high-level evidence. This study was designed to compare the real-world efficacy and safety of MWA or surgery for treating T1bN0M0 PTC.

METHODS

From December 2019 to April 2021, 123 continuous unifocal T1bN0M0 PTC patients without lymph node metastasis (LNM) or distant metastasis (DM) were included from 10 hospitals. Patients were allocated into the MWA or surgery group based on their willingness. The main outcomes were local tumour progression (LTP), new thyroid cancer, LNM, and DM. The secondary outcomes included changes in tumour size and volume, complications, and cosmetic results. Subgroup analyses were conducted to identify influencing factors.

RESULTS

Fifty-two patients chose MWA, and 71 patients chose surgery. Patients had similar demographic information and tumour characteristics in the two groups. The follow-up durations after MWA and surgery were 10.6 ± 4.2 and 10.4 ± 3.4 months, respectively. The LNM rate was 5.8% in the MWA group and 1.4% in the surgery group (p = 0.177). No LTP, new thyroid cancer, or distant metastasis (DM) occurred in either group. Five (9.6%) of the 52 patients in the MWA group and 8 (11.3%) of the 71 patients in the surgery group had complications (p = 0.27). Better cosmetic results were found in the MWA group (p < 0.01).

CONCLUSION

MWA achieved comparable short-term treatment efficacy with surgery. MWA might be an optional choice for surgery for low-risk T1bN0M0 PTC but concerns about LNM need to be studied further.

CLINICAL RELEVANCE STATEMENT

MWA achieved comparable short-time treatment efficacy with surgery. MWA might be an optional choice for surgery for low-risk T1bN0M0 PTC.

KEY POINTS

• MWA achieved comparable short-term treatment efficacy with surgery. MWA might be an optional choice for surgery for low-risk T1bN0M0 PTC but concerns about LNM need to be studied further. • The complication rate in the surgery group was higher than that in the MWA group without a significant difference. • There was no statistically significant difference in the LNM rate between the MWA and surgery groups.

Efficacy and safety of ultrasound-guided radiofrequency, microwave and laser ablation for the treatment of T1N0M0 papillary thyroid carcinoma on a large scale: a systematic review and meta-analysis

BACKGROUND

To analyze the efficacy and safety of radiofrequency ablation (RFA), microwave ablation (MWA) and laser ablation (LA) in T1N0M0 papillary thyroid carcinoma (PTC) patients by evaluating data on several outcomes on a large scale.

MATERIALS AND METHODS

Literature searches were conducted in PUBMED, EMBASE and the Cochrane Library for studies of thermal ablation (TA) for treating T1N0M0 PTC. Data on the volume reduction rate (VRR) at the 12-month follow-up and final follow-up, complete disappearance rate, local recurrence rate, lymph node metastasis rate, and complication rate of RFA, MWA and LA were evaluated separately. RFA effects were compared between T1aN0M0 and T1bN0M0 patients.

RESULTS

A total of 36 eligible studies were included. RFA presented superior efficacy than MWA in 12-month VRR. At the final follow-up, the difference was slight in subgroups, showing a significant reduction. The complete disappearance rate of LA (93.00%) was higher than that of RFA (81.00%) and MWA (71.00%). Additionally, the local recurrence rate pooled proportions of MWA and RFA were both 2.00%, lower than that of the LA group (3.00%). There was no event of distant metastasis. The lymph node metastasis rates were similar, as RFA (1.00%) had the lowest. For minor complication rates, the pooled proportions of RFA (3.00%) were smaller than those of LA (6.00%) and MWA (13.00%). T1aN0M0 lesions presented with better outcomes than T1bN0M0 lesions.

CONCLUSION

RFA, MWA and LA were reliable in curing PTC, and RFA presented advantages in most outcomes. T1aN0M0 patients may experience fewer side effects than T1bN0M0 patients.

Ultrasound-guided thermal ablation for papillary thyroid microcarcinoma: the devil is in the details

Thermal ablation (TA) has harvested favorable outcomes in treating low-risk papillary thyroid microcarcinoma (PTMC). Preoperative assessment, intraoperative procedures and postoperative follow-up are all closely linked with the success and safety of TA on PTMC. However, many details in these aspects have not been systematically reviewed. This review firstly described the influence of preoperative assessment, especially for the risk of lymph node metastasis (LNM), as well as the molecular testing on the selection of TA for PTMC. Besides, we also summarized the experiences in treating special PTMC cases by TA, like multifocal lesions, PTMC located in the isthmus or adjacent to the dorsal capsule. At last, we discussed the follow-up strategies, the influence of the thyroid-stimulating hormone (TSH) level on the prognosis of PTMCs, and the management for recurrent cases. In conclusion, the procedures during the entire perioperative period should be standardized to improve the outcomes of TA in treating PTMC patients.

Initial ablation ratio predicts the recurrence of low-risk papillary thyroid microcarcinomas treated with microwave ablation: a 5-year, single-institution cohort study

Objective

To assess the long-term efficacy and safety of microwave ablation (MWA) in treating low-risk papillary thyroid microcarcinomas (PTMC) and to identify predictive factors for the postoperative local tumor progression of PTMC.

Methods

A total of 154 low-risk PTMC patients treated with MWA who were followed up for at least 3 months were retrospectively recruited. Ultrasonography was performed after MWA to assess the local tumor progression. Adverse events associated with MWA were recorded. The ablated volume (Va) and initial ablation ratio (IAR) were measured to assess their influences on the recurrence risk of PTMC.

Results

The mean tumor volume of PTMC before MWA was 0.071 (0.039, 0.121) cm3, with a maximum diameter of 0.60 ± 0.18 cm. All PTMC patients were followed up for 6 (3, 18) months. Va increased immediately after MWA, then gradually decreased over time, till significantly smaller at 12 months than that before MWA (P < 0.05). The median volume reduction ratio at 24 months reached 100%, which was maintained during a 60-month follow-up. A total of 7 (4.55%) cases of local tumor progression were recorded during the follow-up. Kaplan-Meier survival analysis revealed that the rate of local tumor progression was significantly lower in PTMC patients with a maximum tumor diameter < 0.70 cm than in those with ≥0.70 cm (P = 0.031). A significant better prognosis was achieved in PTMC patients with IAR ≥ 15 than in those with IAR < 15 (P = 0.015). Sex, age (<55 years) and preoperative thyroid-stimulating hormone (>2.0 mU/L) of PTMC patients were not correlated with local tumor progression.

Conclusion

MWA is an effective therapeutic strategy for low-risk PTMC with high safety. The maximum tumor diameter and IAR are predictive factors for the local tumor progression of PTMC after MWA.

Prediction of ablation zone disappearance after microwave ablation for the patients with papillary thyroid microcarcinoma using nomograph

Objectives

To construct a prognostic nomogram to predict the ablation zone disappearance for patients with papillary thyroid microcarcinoma (PTMC) after microwave ablation (MWA).

Materials and methods

From April 2020 to April 2022, patients with PTMC who underwent MWA treatment were collected retrospectively. Ultrasound (US) or contrast-enhanced ultrasound (CEUS) was performed at 1 day, 1, 3, 6, 12, 18 and 24 months after MWA to observe the curative effect after ablation. The volume, volume reduction rate (VRR) and complete disappearance rate of the ablation zone at each time point were calculated. Univariate and multivariate logistic regression analysis were used to determine the prognostic factors associated with the disappearance of the ablation zone after MWA, and the nomogram was established and validated.

Results

72 patients with PTMCs underwent MWA were enrolled into this study. After MWA, no tumor progression (residual, recurrence or lymph node metastasis) and major postoperative complications occurred. The ablation zone in 28 (38.89%) patients did not completely disappear after MWA in the follow-up period. Three variables, including age (odds ratio [OR]: 1.216), calcification type (OR: 12.283), initial maximum diameter (OR: 2.051) were found to be independent prognostic factors predicting ablation zone status after MWA by multivariate analysis. The above variables and outcomes were visualized by nomogram (C-index=0.847).

Conclusions

MWA was a safe and effective treatment for PTMC. Older patients with macrocalcification and larger size PTMCs were more unlikely to obtain complete disappearance of ablation zones. Incomplete disappearance of ablation zone was not related to recurrence.

Analysis of Therapeutic Effect and Influencing Factors of Ultrasound-Guided Radiofrequency Ablation in the Treatment of Papillary Thyroid Microcarcinoma

OBJECTIVES

The current study sought to explore the effects of ultrasound (US)-guided radiofrequency ablation (RFA) on papillary thyroid microcarcinoma (PTMC) and influencing factors.

METHODS

PTMC patients were assigned to observation (US-guided RFA) and control (surgical operation) groups. A series of operation-related indexes (operation time, intraoperative bleeding, wound closure time, hospital stay, and expenses), visual analogue scale score, lesion size, and thyroid function-related indexes (thyroid-stimulating hormone [TSH], free triiodothyronine*** [FT3], free thyroxine [FT4]), inflammatory factors, and thyroglobulin antibody (TgAb) were assessed and compared. After a 6-month follow-up period, the complications and recurrence were recorded, in addition to analyses of postoperative recurrence cumulative incidence and evaluation of recurrence risk factors.

RESULTS

Operation-related indexes of the observation group were relatively decreased compared with the control group. In addition, the lesion volume in the observation group was lower compared to that in the control group at the 6th month after operation, whereas the volume reduction rate was higher. There were no significant differences in regard to thyroid function-related indexes in the observation group before/after operation. After operation, serum TSH levels and inflammatory factors, and TgAb levels were all diminished, while the FT3 and FT4 levels were both elevated in the observation group relative to the control group, and postoperative recurrence cumulative incidence was lower in the observation group. TSH and TgAb were established as the independent risk factors for recurrence after RFA in PTMC patients.

CONCLUSIONS

Our findings highlighted that US-guided RFA exhibits better efficacy, safety, and postoperative recovery and lower recurrence risk for PTMC.

Ultrasound-guided thermal ablation for papillary thyroid microcarcinoma: A systematic review

OBJECTIVE

Thyroidectomy is the first-line treatment for papillary thyroid microcarcinoma (PTMC), but often involves aggressive overtreatment. Thermal ablation (TA) has been gradually used for the treatment of recurrent PTMC. However, it is not recommended for the treatment of primary PTMC according to the Korean and Italian guidelines. Therefore, this systematic review aimed to analyse the indications, efficacy, and safety of TA in the treatment of PTMC.

DESIGN

Systematic review.

PATIENTS AND MEASUREMENTS

A search strategy was developed in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement. A total of 27 articles were included in this study until January 2022.

RESULTS

According to current guidelines and studies, we divided the indications of TA for PTMC into six primary and three secondary indications. Laser ablation (LA) has the advantages of a small needle, accurate output energy and precision ablation, and it is safe to important organs around the lesion. The patients recover quickly after radiofrequency ablation (RFA), with no major complications, recurrence, or lymph node metastasis. The volume reduction rate after RFA was the highest, followed by microwave ablation and LA, and the improvement in patient quality of life after TA was significantly better than after thyroidectomy.

CONCLUSIONS

TA is an effective alternative method for surgery in the treatment of low-risk PTMC and has the advantages of being minimally invasive, economical, having less bleeding and having a high postoperative quality of life.

The influence of nodule size on clinical efficacy of ethanol ablation and microwave ablation on cystic or predominantly cystic thyroid nodules

Objective

To compare the efficacy and safety of ethanol ablation (EA) and microwave ablation (MWA) in the treatment of cystic or predominantly cystic thyroid nodules.

Methods

Patients with cystic or predominantly cystic thyroid nodules intervened with EA or MWA were retrospectively enrolled and divided into EA group (n = 30) and MWA group (n = 31). The volume and volume reduction rate (VRR) of thyroid nodules before ablation, and at 3 and 12 months after ablation were compared between the two groups. The effective rate (ER) and incidence of adverse events in both groups were recorded.

Results

The median VRR and ER at 3 months after ablation were significantly higher in EA group than in MWA group (81.30% vs 75.76%, P = 0.011; 76.67% (23/30) vs 51.61% (16/31), P = 0.040), while no significant difference was detected at 12 months (93.39% vs 88.78%, P = 0.141; 86.67% (26/30) vs 87.10% (27/31), P = 0.960). The median VRR of small nodules in EA group was significantly higher than that in MWA group (81.30% vs 71.18%, P = 0.006; 93.40% vs 83.14%, P = 0.032). There was no significant difference of median VRR in medium nodules at final follow-up between MWA and EA group (93.01% vs 89.68%, P = 0.482). Serious adverse events were not reported in both groups.

Conclusion

EA and MWA are both effective and safe in the treatment of cystic or predominantly cystic thyroid nodules. EA is more cost-effective and effective than MWA for small nodules, but it requires more cycles of treatment and may pose a higher risk of postoperative pain compared with MWA.

Clinical application status and prospect of the combined anti-tumor strategy of ablation and immunotherapy

Image-guided tumor ablation eliminates tumor cells by physical or chemical stimulation, which shows less invasive and more precise in local tumor treatment. Tumor ablation provides a treatment option for medically inoperable patients. Currently, clinical ablation techniques are widely used in clinical practice, including cryoablation, radiofrequency ablation (RFA), and microwave ablation (MWA). Previous clinical studies indicated that ablation treatment activated immune responses besides killing tumor cells directly, such as short-term anti-tumor response, immunosuppression reduction, specific and non-specific immune enhancement, and the reduction or disappearance of distant tumor foci. However, tumor ablation transiently induced immune response. The combination of ablation and immunotherapy is expected to achieve better therapeutic results in clinical application. In this paper, we provided a summary of the principle, clinical application status, and immune effects of tumor ablation technologies for tumor treatment. Moreover, we discussed the clinical application of different combination of ablation techniques with immunotherapy and proposed possible solutions for the challenges encountered by combined therapy. It is hoped to provide a new idea and reference for the clinical application of combinate treatment of tumor ablation and immunotherapy.

Hyperthermia combined with immune checkpoint inhibitor therapy in the treatment of primary and metastatic tumors

According to the difference in temperature, thermotherapy can be divided into thermal ablation and mild hyperthermia. The main advantage of thermal ablation is that it can efficiently target tumors in situ, while mild hyperthermia has a good inhibitory effect on distant metastasis. There are some similarities and differences between the two therapies with respect to inducing anti-tumor immune responses, but neither of them results in sustained systemic immunity. Malignant tumors (such as breast cancer, pancreatic cancer, nasopharyngeal carcinoma, and brain cancer) are recurrent, highly metastatic, and highly invasive even after treatment, hence a single therapy rarely resolves the clinical issues. A more effective and comprehensive treatment strategy using a combination of hyperthermia and immune checkpoint inhibitor (ICI) therapies has gained attention. This paper summarizes the relevant preclinical and clinical studies on hyperthermia combined with ICI therapies and compares the efficacy of two types of hyperthermia combined with ICIs, in order to provide a better treatment for the recurrence and metastasis of clinically malignant tumors.

Research Review of Thermal Ablation in the Treatment of Papillary Thyroid Carcinoma

Background

Minimally invasive treatment of thyroid tumors has become increasingly common, but has mainly focused on benign thyroid tumors, whereas thermal ablation of thyroid cancer remains controversial. Clinical studies analyzing the efficacy of thermal ablation of papillary thyroid carcinoma (PTC) have been conducted in several countries to verify its safety. Here, we screened and reviewed recent studies on the efficacy and safety of thermal ablation of PTC as well as psychological assessment, patient prognosis, recurrence, and factors affecting ablation.

Summary

The most significant controversy surrounding ablative treatment of PTC centers on its effectiveness and safety, and >40 studies have been conducted to address this issue. The studies include papillary thyroid microcarcinoma (PTMC) and non-PTMC, single PTC and multiple PTC, and controlled studies of ablative therapy and surgical treatment. In general, ablation techniques can be carefully performed and promoted under certain conditions and with active follow-up of postoperative patients. Ablation is a promising alternative treatment especially in patients who are inoperable.

Conclusions

Clinical studies on PTC ablation have provided new perspectives on local treatment. However, because PTC grows very slowly, it is an indolent tumor; therefore, studies with larger sample sizes and extended post-procedure follow-ups are necessary to confirm the investigators’ hypotheses.

Pathology confirmation of the efficacy and safety of microwave ablation in papillary thyroid carcinoma

BACKGROUND

The incidence of papillary thyroid carcinoma (PTC) has rapidly increased in recent years. Microwave ablation (MWA) was proposed as an alternative treatment for PTC. This study aimed to investigate the efficacy and safety of MWA by exploring the postoperative pathology results of post-ablation lesions in patients with PTC.

METHODS

This study retrospectively analyzed data from 12 patients who underwent thyroid surgery after MWA treatment for primary PTC between January 2015 and November 2021 in six hospitals.

RESULTS

The average age of the 12 patients (8 female) was 45.3 ± 9.7 years. There was one patient with PTC (size > 1 cm) and 11 patients with micro-PTC (size ≤ 1 cm), of which eight patients had unifocal micro-PTC and three patients had multifocal micro-PTC. A total of 17 tumor foci with mean size of 6.2 ± 2.6 mm were treated by MWA. The median interval time between MWA and surgery was 6.6 months (range: 0.4-21.9 months). Intraoperatively, adherence to the anterior cervical muscle group was observed in three cases (3/12). Upon postoperative pathologic examination, all the post-ablation lesions of the eight unifocal micro-PTC and two multifocal micro-PTC showed no residual carcinomas. Outside the ablation zone, PTCs were detected in three cases, including two of the eight patients with unifocal micro-PTC and one of the three patients with multifocal micro-PTC. Cervical lymph node metastases were detected in seven patients (7/12).

CONCLUSION

MWA was feasible for the treatment of primary unifocal low-risk micro-PTC (T1aN0M0) with good efficacy and safety. However, the use of MWA for treating PTC (size > 1 cm) and multifocal micro-PTC remains controversial.

Efficacy and safety of ultrasound-guided microwave ablation versus surgical resection for Bethesda category IV thyroid nodules: A retrospective comparative study

OBJECTIVE

The objective of this study was to assess the efficacy and safety of ultrasound-guided microwave ablation (MWA) for Bethesda IV thyroid nodules and to compare the outcomes, complications, and costs of MWA and thyroidectomy.

METHODS

A total of 130 patients with Bethesda IV nodules were retrospectively reviewed, involving 46 in the MWA group and 84 in the surgery group. The local institutional review board approved this study. Patients in the MWA group were followed up at 1, 3, 6, and 12 months after the intervention. Postoperative complications, treatment time, and cost in the two groups were compared.

RESULTS

Among 84 patients with 85 Bethesda IV nodules in the surgery group, postoperative pathology was benign lesions, borderline tumors, papillary thyroid carcinoma, follicular variant papillary thyroid carcinoma, follicular thyroid carcinoma, and medullary carcinoma in 44, 4, 27, 6, 3, and 1 cases, respectively. Malignant thyroid nodules were more prone to solid echostructure (86.11% vs. 72.72%), hypoechogenicity (55.56% vs. 13.63%), and irregular margin (47.22% vs. 13.63%) than benign lesions. The nodule volume reduction rate of patients at 12 months after MWA was 85.01% ± 10.86%. Recurrence and lymphatic and distant metastases were not reported during the follow-up period. The incidence of complications, treatment time, hospitalization time, incision length, and cost were significantly lower in the MWA group than in the surgery group (all p < 0.001).

CONCLUSIONS

MWA significantly reduces the volume of Bethesda IV nodules with high safety and is recommended for those with surgical contraindications or those who refuse surgical resection. Patients with suspicious ultrasound features for malignancy should be actively treated with surgery.

Safety and efficacy of ultrasound-guided thermal ablation in treating T1aN0M0 and T1bN0M0 papillary thyroid carcinoma: A meta-analysis

BACKGROUND

Papillary thyroid cancer (PTC) is the most common thyroid tumor, and early diagnosis and treatment can effectively improve prognosis. Many controversies surround the treatment method of T1N0M0 PTC. Recently, thermal ablation (TA) has shown some benefits in the treatment of PTC patients, but the safety and efficacy of its treatment remain controversial. This article performs a meta-analysis of TA in patients with T1aN0M0 and T1bN0M0 PTC.

METHODS

The PubMed, Embase, Web of Science, and Cochrane Library databases were systematically searched for retrospective or prospective studies of TA for treating patients with T1N0M0 PTC from the database establishment to May 1, 2022. Data on volume reduction rate (VRR), disease progress, and complication rate were collected. In addition, a meta-analysis was performed using the Stata 12.0 and Review Manager 5.3.

RESULTS

A total of 9 eligible studies were included. Our study demonstrated the effectiveness of VRR and disease progress. The VRR was reduced after 3 months (-75.90%; 95% CI [-118.46-33.34%]), 6 months (34.33%; 95% CI [15.01-53.65%]), 12 months (78.69%; 95% CI [71.69-85.68%]), and 24 months (89.97%; 95% CI [84.00-95.94%]). The disease progress was 1.9% (95% CI [1.1-3.0]). Safety is justified by the complication rate, which was 6.5% (95% CI [3.5-10.2]). Pain and hoarseness were the most common complications, and no life-threatening complications were reported. Egger's test demonstrated that publication bias was acceptable.

CONCLUSIONS

TA is an effective and safe method for managing T1aN0M0 and T1bN0M0 papillary thyroid nodules.