Thermal Ablation of Lung Tissue: In Vivo Experimental Comparison of Microwave and Radiofrequency

Single-Stage Image-Guided Percutaneous Ablation with Thoracoscopic Resection for Multiple Pulmonary Lesions in a Hybrid Operating Room: A Retrospective Study

BACKGROUND

Different approaches are required in treating patients with multiple pulmonary lesions. A multistage procedure may increase the risk of complications and patient discomfort. This study reports an initial experience with single-stage management of multiple lung lesions using percutaneous ablation with thoracoscopic resection in a hybrid operating room (HOR).

METHODS

We retrospectively evaluated patients who underwent combined ablation and resection in an HOR between May 2022 and July 2024. All patients received a single anesthesia via endotracheal tube intubation. The clinical data, operative findings, and pathological characteristics of the lung nodules were recorded.

RESULTS

A total of 22 patients were enrolled in this study. Twenty patients underwent unilateral procedures, while the other two patients underwent bilateral procedures. Ablations were performed before lung resection in 21 patients; only 1 patient underwent surgery first. The median global operating room time was 227.0 min. The median total radiation dose (dose area product) was 14,076 μGym2. The median hospital postoperative length of stay was 2 days.

CONCLUSIONS

The single-stage procedure of percutaneous ablation with thoracoscopic resection under general anesthesia in an HOR is feasible and safe. This procedure is an alternative method for managing multiple pulmonary lesions.

Guidelines for power and time variables for microwave ablation in porcine lung in vitro

PURPOSE

Determination of the appropriate ablative parameters is the key to the success and safety of microwave ablation (MWA) of lung tumors. The purpose of this study was to provide guidelines and recommendations for the optimal time and power for lung tumor MWA.

MATERIAL AND METHODS

MWA using a 2450-MHz system was evaluated in a porcine lung. The independent variables were power (30, 40, 50, 60, 70, and 80 W) and time (2, 4, 6, 8, 10, and 12 min), and the outcome variable was the volume of ablation. Lung tissues were procured after MWA for measurement and histological evaluation. Analysis of variance was used for statistical analysis, followed by least significant difference (LSD) t-tests where appropriate. A P value of <0.05 was considered statistically significant.

RESULTS

The outcome variable (ablative volume) was significantly affected by time, power, and time/power interaction (P < 0.05). When the total output energy was kept constant, the combination of higher power and shorter time obtained a larger ablative volume, especially in the low- and medium-energy groups (P < 0.01).

CONCLUSIONS

We propose guidelines for ablative volume based on different time and power variables to provide a reference for clinical applications.

Cone-beam computed tomography image-guided percutaneous microwave ablation for lung nodules in a hybrid operating room: an initial experience

OBJECTIVES

The experience of thermal ablation of lung lesions is limited, especially performing the procedure under localisation by cone-beam CT in the hybrid operation room (HOR). Here, we present the experience of microwave ablation (MWA) of lung nodules in the HOR.

METHODS

We reviewed patients who underwent image-guide percutaneous MWA for lung nodules in the HOR under general anaesthesia between July 2020 and July 2022. The workflow in the HOR including the pre-procedure preparation, anaesthesia consideration, operation methods, and postoperative care was clearly described.

RESULTS

Forty lesions in 33 patients who underwent MWA under general anaesthesia (GA) in the HOR were analysed. Twenty-seven patients had a single pulmonary nodule, and the remaining six patients had multiple nodules. The median procedure time was 41.0 min, and the median ablation time per lesion was 6.75 min. The median global operation room time was 115.0 min. The median total dose area product was 14881 μGym2. The median ablation volume was 111.6 cm3. All patients were discharged from the hospital with a median postoperative stay of 1 day. Four patients had pneumothorax, two patients had pleural effusion during the first month of outpatient follow-up, and one patient reported intercostal neuralgia during the 3-month follow-up.

CONCLUSIONS

Thermal ablation of pulmonary nodules under GA in the HOR can be performed safely and efficiently if we follow the workflow provided. The procedure provides an alternative to managing pulmonary nodules in patients.

CLINICAL RELEVANCE STATEMENT

Thermal ablation of pulmonary nodules under GA in the HOR can be performed safely and efficiently if the provided workflow is followed.

KEY POINTS

• We tested the feasibility of microwave ablation of lung lesions performed in a hybrid operating room. • To this end, we provide a description of microwave ablation of the lung under cone-beam CT localisation. • We describe a workflow by which ablation of the pulmonary nodule can be performed safely under general anaesthesia.

Primary and Metastatic Lung Cancer: Rationale, Indications, and Outcomes of Thermal Ablation

The widespread use of imaging as well as the efforts conducted through screening campaigns has dramatically increased the early detection rate of lung cancer. Historically, the management of lung cancer has heavily relied on surgery. However, the increased proportion of patients with comorbidities has given significance to less invasive therapeutic options like minimally invasive surgery and image-guided thermal ablation, which could precisely target the tumor without requiring general anesthesia or a thoracotomy. Thermal ablation is considered low-risk for lung tumors smaller than 3 cm that are located in peripheral lung and do not involve major blood vessels or airways. The rationale for ablative therapies relies on the fact that focused delivery of energy induces cell death and pathologic necrosis. Image-guided percutaneous thermal ablation therapies are established techniques in the local treatment of hepatic, renal, bone, thyroid and uterine lesions. In the lung, and specifically in the setting of metastatic disease, the 3 main indications for lung ablation are to serve as (1) curative intent, (2) as a strategy to achieve a chemo-holiday in oligometastatic disease, and (3) in oligoprogressive disease. Following these premises, the current paper aims to review the rationale, indications, and outcomes of thermal ablation as a form of local therapy in the treatment of primary and metastatic lung disease.

Nomogram Based on Preoperative Absolute Lymphocyte Count to Predict Local Recurrence in Patients with Non-Small Cell Lung Cancer After Microwave Ablation

Purpose

This study aims to investigate the prognostic value of preoperative absolute lymphocyte count (preALC) for non-small cell lung cancer (NSCLC) after microwave ablation (MWA) and build a combined nomograph with clinical features to predict the local recurrence.

Patients and Methods

A total of 118 NSCLC patients who underwent microwave ablation were enrolled in this study. The median local recurrence-free survival (LRFS) was 35.5 months. Independent prognostic factors obtained by multivariate analysis were included in the prediction model. The prognostic value of the model was assessed by the area under the time-dependent receiver operating characteristic curve (T-AUC).

Results

Histological subtype and preALC were independent risk factors for local relapse-free survival. According to the time-dependent receiver operating characteristic curve (T-ROC), the optimal cut-off value of preALC was 1.965×10⁹/L, the sensitivity was 0.837, and the specificity was 0.594. The area under the T-ROC curve (AUC) of preALC was 0.703. To establish a nomogram to predict the local recurrence rate of NSCLC after MWA based on the prognostic factors revealed by Cox regression.

Conclusion

Preoperative lymphocyte count reduction is associated with poor prognosis of NSCLC. The nomogram model combined with preALC can provide a good individualized prediction of local recurrence after microwave ablation.

Clinical practice guidelines on image-guided thermal ablation of primary and metastatic lung tumors (2022 edition)

The main contents of the Clinical Practice Guidelines on Image-Guided Thermal Ablation (IGTA) of Primary and Metastatic Lung Tumors (2022 Edition) include the following: epidemiology of primary and metastatic lung tumors; the concepts of the IGTA and common technical features; procedures, indications, contraindications, outcomes evaluation, and related complications of IGTA on primary and metastatic lung tumors; and limitations and future development.

CT after Lung Microwave Ablation: Normal Findings and Evolution Patterns of Treated Lesions

Imaging-guided percutaneous ablative treatments, such as radiofrequency ablation (RFA), cryoablation and microwave ablation (MWA), have been developed for the treatment of unresectable primary and secondary lung tumors in patients with advanced-stage disease or comorbidities contraindicating surgery. Among these therapies, MWA has recently shown promising results in the treatment of pulmonary neoplasms. The potential advantages of MWA over RFA include faster ablation times, higher intra-tumoral temperatures, larger ablation zones and lower susceptibility to the heat sink effect, resulting in greater efficacy in proximity to vascular structures. Despite encouraging results supporting its efficacy, there is a relative paucity of data in the literature regarding the role of computer tomography (CT) to monitor MWA-treated lesions, and the CT appearance of their morphologic evolution and complications. For both interventional and non-interventional radiologists, it is crucial to be familiar with the CT features of such treated lesions in order to detect incomplete therapy or recurrent disease at early stage, as well as to recognize initial signs of complications. The aim of this pictorial essay is to describe the typical CT features during follow-up of lung lesions treated with percutaneous MWA and how to interpret and differentiate them from other radiological findings, such as recurrence and complications, that are commonly encountered in this setting.

Imaging following thermal ablation of early lung cancers: expected post-treatment findings and tumour recurrence

Thermal ablation is a minimally invasive technique that is growing in acceptance and popularity in the management of early lung cancers. Although curative resection remains the optimal treatment strategy for stage I pulmonary malignancies, percutaneous ablative treatments may also be considered for selected patients. These techniques can additionally be used in the treatment of oligometastatic disease. Thermal ablation of early lung tumours can be achieved using several different techniques. For example, microwave ablation (MWA) and radiofrequency ablation (RFA) utilise extreme heat, whereas cryoablation uses extremely cold temperatures to cause necrosis and ultimately cell death. Typically, post-ablation imaging studies are performed within the first 1-3 months with subsequent imaging performed at regular intervals to ensure treatment response and to evaluate for signs of recurrent disease. Surveillance imaging is usually undertaken with computed tomography (CT) and integrated positron-emission tomography (PET)/CT. Typical imaging findings are usually seen on CT and PET/CT following thermal ablation of lung tumours, and it is vital that radiologists are familiar with these appearances. In addition, radiologists should be aware of the imaging findings that indicate local recurrence following ablation. The objective of this review is to provide an overview of the expected post-treatment findings on CT and PET/CT following thermal ablation of early primary lung malignancies, as well as describing the imaging appearances of local recurrence.

Outcomes Following Percutaneous Microwave and Cryoablation of Lung Metastases from Adenoid Cystic Carcinoma of the Head and Neck: A Bi-Institutional Retrospective Cohort Study

OBECTIVE

The aim of this study was to report outcomes following percutaneous microwave and cryoablation of lung metastases from adenoid cystic carcinoma (ACC) of the head and neck.

MATERIAL AND METHODS

This bi-institutional retrospective cohort study included 10 patients (6 females, median age 59 years [range 28-81]) who underwent 32 percutaneous ablation sessions (21 cryoablation, 11 microwave) of 60 lung metastases (median 3.5 tumors per patient [range 1-16]) from 2007 to 2019. Median tumor diameter was 16 mm [range 7-40], significantly larger for cryoablation (22 mm, p = 0.002). A median of two tumors were treated per session [range 1-7]. Technical success, local control, complications, and overall survival were assessed.

RESULTS

Primary technical success was achieved for 55/60 tumors (91.7%). Median follow-up was 40.6 months (clinical) and 32.5 months (imaging, per tumor). Local control at 1, 2, and 3 years was 94.7%, 80.8%, and 76.4%, respectively, and did not differ between ablation modalities. Five of fifteen recurrent tumors underwent repeat ablation, and secondary technical success was achieved in four (80%). Assisted local tumor control at 1, 2, and 3 years was 96.2%, 89.8%, and 84.9%, respectively. Complications occurred following 24/32 sessions (75.0%) and 57.2% Common Terminology Criteria for Adverse Events (CTCAE) lower than grade 3. Of 13 pneumothoraces, 7 required chest tube placements. Hemoptysis occurred after 7/21 cryoablation sessions, and bronchopleural fistula developed more frequently with microwave (p = 0.037). Median length of hospital stay was 1 day [range 0-10], and median overall survival was 81.5 months (IQR 40.4-93.1).

CONCLUSION

Percutaneous computed tomography-guided microwave and cryoablation can treat lung metastases from ACC of the head and neck. Complications are common but manageable, with full recovery expected.

The Role of Real-Time Contrast-Enhanced Ultrasound in Guiding Radiofrequency Ablation of Reninoma: Case Report and Literature Review

BACKGROUND

Reninoma is a rare renal endocrine tumor that can cause secondary hypertension, characterized by hypertension, hypokalemia, high renin and aldosterone with normal aldosterone renin ratio (ARR), and occurs more in young female. Mainstream treatment option is surgery, but is less suitable for small or deep lesions, which makes ablation a promising alternative.

CASE PRESENTATION

Two young female with typical manifestations of reninoma, including hypertension, hypokalemia, high renin, high aldosterone and normal ARR, were treated successfully with real-time contrast-enhanced ultrasound guided radiofrequency ablation, and contrast-enhanced ultrasound was also performed before and after treatment for diagnosis and postoperative assessment. Afterward, their blood pressure and laboratory tests became normal and remained steady during the follow-up of 32 and 6 months, respectively.

CONCLUSION

Contrast-enhanced ultrasound guided radiofrequency ablations is a promising alternative for reninoma treatment with comparable safety and efficacy with surgery, and has advantages especially in small or deep lesions.

Transarterial Chemoembolization and Sorafenib Combined with Microwave Ablation for Advanced Primary Hepatocellular Carcinoma: A Preliminary Investigation of Safety and Efficacy

Purpose

The aim of this study was to investigate the safety and efficacy of transarterial chemoembolization and sorafenib (TACE-S) combined with microwave ablation (TACE-S-MWA) for the treatment of patients with advanced primary hepatocellular carcinoma (HCC).

Methods

Between January 2015 and December 2018, 152 consecutive advanced HCC patients, who underwent TACE-S-MWA (MWA group, n=77) or TACE-S (Non-MWA group, n=75), were investigated. Overall survival (OS), time to progression (TTP) and safety were compared between the two groups. Prognostic factors were analyzed using the Cox proportional hazard regression model.

Results

Baseline patient characteristics were balanced between the two groups. MWA group was associated with a higher OS (median, 19.0 vs 13.0 months; P<0.001) and a longer TTP (median, 6.0 vs 3.0 months; P<0.001) compared with non-MWA group. Multivariate analyses showed that portal vein tumor thrombosis (PVTT) (P=0.002), duration of sorafenib (P<0.001), and MWA treatment (P=0.011) were independently associated with OS. MWA treatment strategy (P<0.001) was a significant predictor of TTP. There were no treatment-related mortalities in either group. The rates of minor complications (42.9% vs 38.7%, P=0.599) and major complications (1.29% vs 1.33%, P=0.985) in the MWA group were similar to those in the non-MWA group.

Conclusion

TACE-S-MWA was safe and effective for advanced primary HCC. TACE-S-MWA resulted in better OS and TTP than did TACE-S for treatment of patients with advanced primary HCC.

Bronchoscopic Therapies for Peripheral Lung Malignancies

Current advances in guided bronchoscopy methods permit minimally invasive access to essentially any area of the lungs. This provides a potential means to treat patients with localized lung malignancies who might not otherwise tolerate conventional treatment, which commonly relies on surgical resection. Ablation methods have long been used for bronchoscopic treatment of central airway malignancies and percutaneous treatment of peripheral lung cancer. This article reviews ablation technologies being adapted for use with guided bronchoscopy and the current state of investigation for the treatment of peripheral lung malignancies.

Microwave ablation for lung cancer patients with a single lung: Clinical evaluation of 11 cases

BACKGROUND

The study was conducted to retrospectively evaluate the safety and effectiveness of computed tomography (CT)-guided percutaneous microwave ablation (MWA) for peripheral non-small cell lung cancer (NSCLC) in 11 patients with a single lung after pneumonectomy.

METHODS

From May 2011 to March 2015, 11 single-lung patients (8 men and 3 women; mean age 60.3 years, range 46-71) with peripheral NSCLC underwent 12 sessions of MWA. Eleven tumors measuring 13-52 mm (mean 30.2 mm) were treated. Follow-up was performed via CT scan at 1, 3, 6, 12, 18, and 24 months after the procedure and annually thereafter. Clinical outcomes were evaluated and complications after MWA were summarized.

RESULTS

At a median follow-up period of 20 months (range 6-38), four patients showed evidence of local recurrence at a rate of 36.4% (4/11). Median overall survival was 20 months. The overall survival rates at one, two, and three years after MWA were 88.7%, 63.6%, and 42.3%, respectively. Complications after MWA included pneumothorax (33.3%), hemoptysis (33.3%), intrapulmonary bleeding (25%), pleural effusion (16.7%), and pulmonary infection (8.3%). None of the patients died during the procedure or in the 30 days after MWA.

CONCLUSION

CT-guided percutaneous MWA is safe and effective for the treatment of peripheral NSCLC in patients with a single lung after prior pneumonectomy.

Microwave ablation versus radiofrequency ablation for the treatment of pulmonary tumors

To retrospectively compare the efficacy and safety of radiofrequency ablation (RFA) and microwave ablation (MWA) in the treatment of pulmonary tumors, a total of 75 patients with lung tumor who underwent thermal ablation therapy in Guangdong General Hospital into the study from March 2007 to December 2014 were enrolled. Of the patients, 43 received radiofrequency ablation and 32 received microwaves ablation. The response rates, overall survival (OS), and complications rates between the RFA group and MWA group were compared. There were no significant differences in the baseline characteristics between two groups. The overall response rates of in RFA and MWA groups were 79% (34/43) and 69% (22/32), respectively, and there was no statistically significant difference between two groups (P = 0.309). The 1-, 2-, 3-, 5-year overall survival (OS) rates in RFA group and MWA group were 77%, 55%, 42%, 34% and 75%, 44%, 40%, 27%, respectively. No significant differences were found in the OS rates between two groups (P = 0.653). The complication rates were 49% (21/43) in RFA group and 50% (16/32) in MWA group; there was no significant difference between two groups (P = 0.921). No patients died during the perioperative period. Our study shows that no significant differences exist in efficacy and safety between RFA and MWA for the treatment of pulmonary tumors, which indicates that MWA could be a substitute therapy for RFA in terms of effectiveness and safety for treating pulmonary tumors.

Percutaneous microwave ablation (MWA) increased the serum levels of VEGF and MMP-9 in Stage I non-small cell lung cancer (NSCLC)

BACKGROUND

Lung cancer is the leading cause of cancer death around the world. Percutaneous microwave ablation (MWA) is an emerging treatment strategy for medically inoperable early-stage non-small cell lung cancer (NSCLC). In this study, we investigated the association of MWA and serum angiogensis promoters VEGF and MMP-9 in these patients subgroup.

METHODS

We enrolled 52 patients with Stage I NSCLC patients in this study. For each patient, blood samples were drawn by venous puncture, one immediately prior to MWA and the others on Post-Procedure Days (PPD) 1, 3, 5, 7, 10 and 14. Serum samples were analysed for VEGF and MMP-9 levels with use of commercially available enzyme-linked immunosorbent assay. Also, blood samples of 28 healthy volunteers were set as the healthy controls.

RESULTS

We did not observe a significant difference of serum VEGF and MMP-9 between NSCLC patients and healthy controls. The VEGF levels increased on the first day (256.0 ± 6.16 pg/ml, p < 0.05) after MWA and peaked on the PPD3 (418.0 ± 14.54 pg/ml, p < 0.05). Although it gradually reduced afterwards, its levels on PPD14 (141.2 ± 4.41 pg/ml, p < 0.05) was still higher than pre-procedure level. The serum MMP-9 level was significantly elevated from PPD1 (231.3 ± 7.93 ng/ml, p < 0.05) until PPD10 (155.3 ± 5.62 ng/ml, p < 0.05), while it normalised to pre-procedure level on PPD14 (90.78 ± 3.36 ng/ml, p > 0.05). The highest MMP-9 level was observed on PPD5 (399.7 ± 17.70 ng/ml, p < 0.05).

CONCLUSION

Our preliminary results indicated that percutaneous MWA resulted in increased serum levels of VEGF and MMP-9 in Stage I NSCLC patients. Antiangiogenesis approaches may be helpful for patients defending against metastases during the immediate post-ablation time window.

Microwave ablation of malignant renal tumours: intermediate-term results and usefulness of RENAL and mRENAL scores for predicting outcomes and complications

The aim of this study was to evaluate intermediate-term results after microwave ablation (MWA) of renal tumours and determine the association of RENAL and modified RENAL (mRENAL) scores with oncological outcomes and complications. In May 2008-September 2014, 58 patients affected by early-stage RCC (renal cell carcinoma; T1a or T1b) were judged unsuitable for surgery and treated with percutaneous MWA. Follow-up was performed with contrast-enhanced computed tomography at 1, 3, 6, 12 and 24 months after the procedure. Technical success (TS), primary technical effectiveness (PTE), secondary technical effectiveness (STE), the local tumour progression rate (LTPR), the cancer-specific survival rate (CSSR), disease-free survival (DFS), overall survival (OS) and safety were recorded. All lesions were evaluated using RENAL and mRENAL scores, and complications were assessed with RENAL scores. The TS rate was 100%, PTE was 93%, STE was 100%, LTPR was 15.7% at 1 year, CSSR was 96.5%, DFS was 87.9% at 5 years, and OS was 80.6%. Mean follow-up was 25.7 months (range 3-72). The mean ± standard deviation (SD) RENAL and mRENAL scores of all treated tumours were 6.7 ± 2.05 (range 4-11) and 7 ± 2.3 (range 4-12), respectively. Major complications occurred in two (2/58) and minor complications in three patients (3/58). Overall complications correlated significantly with RENAL scores; in particular, E and L represent negative predictors for safety and effectiveness. MWA is a valuable alternative for treating RCCs. The correlation with outcomes and complications of RENAL and mRENAL scores could help to customise MWA indications in RCC patients.

Local Efficacy and Survival after Microwave Ablation of Lung Tumors: A Retrospective Study in 183 Patients

PURPOSE

To retrospectively evaluate local efficacy and survival after microwave (MW) ablation of lung tumors and identify predictors of prognosis.

MATERIALS AND METHODS

Data from 183 consecutive patients (67 women; mean age, 61.5 y ± 13.4) with lung tumors who had undergone 203 lung MW ablation sessions from January 2011 to May 2013 were assessed. The χ2 test, independent-samples t test, Kaplan-Meier analysis, and Cox regression model analysis were used to estimate survival rates and evaluate significance of factors affecting rates of incomplete ablation, local progression, remote progression-free survival (RPFS), and cancer-specific survival (CSS).

RESULTS

Technical success rate was 100%. Incomplete ablation rate after 183 first MW ablations was 14.2% (26 of 183); maximum diameter of target tumors (P = .00001) was associated with incomplete ablation on univariate analysis. The local progression rate was 19.1% (35 of 183); emphysema (P = .020) and maximum diameter of target tumor (P = .000003) were associated with local progression. Median and 4-year RPFS were 15.0 months (95% confidence interval [CI], 11.1-18.9 mo) and 23.8%, respectively. Tumor stage (P < .01) and incomplete ablation (P = .002) were independent predictors of RPFS. Median and 4-year CSS were 24.9 months (95% CI, 19.9-29.9 mo) and 31.1%, respectively. Median and 4-year overall survival were 23.7 months (95% CI, 20.6-26.8 mo) and 29.6%, respectively. Tumor stage (P < .01) and maximum diameter (P = .009) were independent risk factors for CSS.

CONCLUSIONS

MW ablation is effective for lung tumors, especially small lesions of early-stage primary lung cancer and solitary lung metastasis.

Short-Term Outcomes and Safety of Computed Tomography-Guided Percutaneous Microwave Ablation of Solitary Adrenal Metastasis from Lung Cancer: A Multi-Center Retrospective Study

OBJECTIVE

To retrospectively evaluate the short-term outcomes and safety of computed tomography (CT)-guided percutaneous microwave ablation (MWA) of solitary adrenal metastasis from lung cancer.

MATERIALS AND METHODS

From May 2010 to April 2014, 31 patients with unilateral adrenal metastasis from lung cancer who were treated with CT-guided percutaneous MWA were enrolled. This study was conducted with approval from local Institutional Review Board. Clinical outcomes and complications of MWA were assessed.

RESULTS

Their tumors ranged from 1.5 to 5.4 cm in diameter. After a median follow-up period of 11.1 months, primary efficacy rate was 90.3% (28/31). Local tumor progression was detected in 7 (22.6%) of 31 cases. Their median overall survival time was 12 months. The 1-year overall survival rate was 44.3%. Median local tumor progression-free survival time was 9 months. Local tumor progression-free survival rate was 77.4%. Of 36 MWA sessions, two (5.6%) had major complications (hypertensive crisis).

CONCLUSION

CT-guided percutaneous MWA may be fairly safe and effective for treating solitary adrenal metastasis from lung cancer.

Local microwave ablation with continued EGFR tyrosine kinase inhibitor as a treatment strategy in advanced non-small cell lung cancers that developed extra-central nervous system oligoprogressive disease during EGFR tyrosine kinase inhibitor treatment: A pilot study

The non-small cell lung cancer (NSCLC) patients that experienced good clinical response to epidermal growth factor receptor-tyrosine kinase inhibitor (EGFR-TKIs) will ultimately develop acquired resistance. This retrospective study was performed to explore the potential survival benefit of microwave ablation (MWA) therapy in epidermal growth factor receptor (EGFR)-mutant NSCLC that developed extra-central nervous system (CNS) oligoprogressive disease during TKI treatment.We retrospectively analyzed 54 NSCLC patients with EGFR mutations who showed a clinical benefit from initial EGFR-TKI therapy and developed extra-CNS oligoprogressive disease at our institutions. Twenty eight patients received MWA as a local therapy for the metastatic sites and continued on the same TKIs (MWA group). The following 26 patients received systemic chemotherapy after progression (chemotherapy group). The progression-free survival (PFS1) was calculated from initiation of targeted therapy to first progression. Progression-free survival (PFS2) was defined from first progression to second progression after MWA or chemotherapy. Overall survival (OS) was calculated from the time of diagnosis to the date of last follow-up or death.The median PFS1 for both groups was similar (median 12.6 vs. 12.9 months, HR 0.63). However, the MWA group patients had a significantly longer PFS2 (median 8.8 vs. 5.8 months, hazards ratio [HR] 0.357) and better OS (median 27.7 vs. 20.0, HR 0.238) in comparison with chemotherapy group. Multivariate analysis and the internal validation identified MWA as the main favorable prognostic factor for PFS2 and OS. In the MWA group, the median PFS2 for complete ablation was significantly longer than that for incomplete ablation (11 vs. 4.2 months, HR 0.29, P < 0.05).MWA with continued EGFR inhibition might be associated with favorable progression-free survival (PFS) and OS in patients with extra-CNS oligometastatic disease. MWA as a local therapy for extra-CNS oligometastatic disease should be considered for NSCLC with acquired resistance to EGFR-TKIs.

Pleural puncture that excludes the ablation zone decreases the risk of pneumothorax after percutaneous microwave ablation in porcine lung

PURPOSE

To test the hypothesis that the geometry of probe placement with respect to the pleural puncture site affects the risk of pneumothorax after microwave (MW) ablation in the lung.

MATERIALS AND METHODS

Computed tomography-guided MW ablation of the lung was performed in 8 swine under general anesthesia and mechanical ventilation. The orientation of the 17-gauge probe was either perpendicular (90°) or parallel (< 30°) with respect to the pleural puncture site, and the ablation power was 30 W or 65 W for 5 minutes. After MW ablation, swine were euthanized, and histopathologic changes were assessed. Frequency and factors affecting pneumothorax were evaluated by multivariate analysis.

RESULTS

Among 62 lung MW ablations, 13 (21%) pneumothoraces occurred. No statistically significant difference was noted in the rate of pneumothorax between the perpendicular and the parallel orientations of the probe (31% vs 14%; odds ratio [OR], 2.8; P = .11). The pneumothorax rate was equal for 65-W and 30-W ablation powers (21% and 21%; OR, 1.0; P = .94). Under multivariate analysis, 2 factors were independent positive predictors of pneumothorax: ablation zone inclusive of pleural insertion point (OR, 7.7; P = .02) and time since intubation (hours) (OR, 2.7; P = .02).

CONCLUSIONS

Geometries where the pleural puncture site excluded the ablation zone decreased pneumothorax in swine undergoing MW ablation in the lung. Treatment planning to ensure that the pleural puncture site excludes the subsequent ablation zone may reduce the rate of pneumothorax in patients undergoing MW ablation in the lung.

Chinese expert consensus workshop report: Guidelines for thermal ablation of primary and metastatic lung tumors

Although surgical resection is the primary means of curing both primary and metastatic lung cancers, about 80% of lung cancers cannot be removed by surgery. As most patients with unresectable lung cancer receive only limited benefits from traditional radiotherapy and chemotherapy, many new local treatment methods have emerged, including local ablation therapy. The Minimally Invasive and Comprehensive Treatment of Lung Cancer Branch, Professional Committee of Minimally Invasive Treatment of Cancer of the Chinese Anti-Cancer Association has organized multidisciplinary experts to develop guidelines for this treatment modality. These guidelines aim at standardizing thermal ablation procedures and criteria for selecting treatment candidates and assessing outcomes; and for preventing and managing post-ablation complications.

Percutaneous microwave ablation of stage I medically inoperable non-small cell lung cancer: clinical evaluation of 47 cases

PURPOSE

To retrospectively evaluate safety and effectiveness of CT-guided percutaneous microwave ablation (MWA) in 47 patients with medically inoperable stage I peripheral non-small cell lung cancer (NSCLC).

METHODS

From February 2008 to October 2012, 47 patients with stage I medically inoperable NSCLC were treated in 47 MWA sessions. The clinical outcomes were evaluated. Complications after MWA were also summarized.

RESULTS

At a median follow-up period of 30 months, the median time to the first recurrence was 45.5 months. The local control rates at 1, 3, 5 years after MWA were 96%, 64%, and 48%, respectively. The median cancer-specific and median overall survivals were 47.4 and 33.8 months. The overall survival rates at 1, 2, 3, and 5 years after MWA were 89%, 63%, 43%, and 16%, respectively. Tumors ≤3.5 cm were associated with better survival than were tumors >3.5 cm. The complications after MWA included pneumothorax (63.8%), hemoptysis (31.9%), pleural effusion (34%), pulmonary infection (14.9%), and bronchopleural fistula (2.1%).

CONCLUSIONS

MWA is safe and effective for the treatment of medically inoperable stage I peripheral NSCLC.

Thermal ablation of stage I non-small cell lung carcinoma

Ablation options for the treatment of localized non-small cell lung carcinoma (NSCLC) include radiofrequency ablation, microwave ablation, and cryotherapy. Irreversible electroporation is a novel ablation method with the potential of application to lung tumors in risky locations. This review article describes the established and novel ablation techniques used in the treatment of localized NSCLC, including mechanism of action, indications, potential complications, clinical outcomes, postablation surveillance, and use in combination with other therapies.

Major complications after lung microwave ablation: a single-center experience on 204 sessions

BACKGROUND

The purpose of this study is to retrospectively evaluate the incidence of and risk factors for major complications after microwave ablation (MWA) of lung tumors.

METHODS

From January 2011 to May 2013 in 184 consecutive patients (67 women and 117 men; mean age, 61.5 years; range, 19 to 85 years), 204 sessions of MWA were performed on 253 lung tumor lesions. Records were reviewed to evaluate prevalence of major complications and risk factors, which were analyzed using univariate and multivariate analyses.

RESULTS

Major complications developed after 42 sessions (20.6%), including 32 cases (15.7%) of pneumothorax requiring chest tube placement which that were associated with emphysema (p=0.001); 6 cases (2.9%) of pleural effusions requiring chest tube placement, which were associated with a distance of less than 1 cm from chest wall to target tumor (p=0.014); 6 cases (2.9%) of pneumonia which that were associated with target tumor maximal diameter (p=0.040); number of pleural punctures (p=0.001) and ablation time (p=0.006); and 1 case (0.5%) of pulmonary abscess. Two cases (1.0%) of the large pneumothorax occurred at the same time with extensive subcutaneous emphysema, including 1 case (0.5%) caused by bronchopleural fistula. Death related to the procedures occurred after 1 session (0.5%).

CONCLUSIONS

As a relatively practical and safe modality, lung tumor MWA can induce serious complications. Enough attention should be paid to patients with emphysema, subpleural, or large target tumor, but the indications for lung MWA need not be limited as most major complications were easily managed.

Lung cancer ablation: what is the evidence?

Percutaneous ablation of small non-small cell lung cancer (NSCLC) has been demonstrated to be both feasible and safe in nonsurgical candidates. Radiofrequency ablation (RFA), the most commonly used technique for ablation, has a reported rate of complete ablation of ~90%, with best results obtained in tumors <2 to 3 cm in diameter. The best reported 1-, 3-, and 5-year overall survival rates after RFA of NSCLC are 97.7%, 72.9%, and 55.7%, respectively. It is noteworthy that in most studies, cancer-specific survival is greater than overall survival due to severe comorbidities in patients treated with RFA for NSCLC. Aside from tumor size and tumor stage, these comorbidities are predictive of survival. Other ablation techniques such as microwave and irreversible electroporation may in the future prove to overcome some of the limitations of RFA, namely for large tumors or tumors close to large vessels. Stereotactic body radiation therapy has also been demonstrated to be highly efficacious in treating small lung tumors and will need to be compared with percutaneous ablation. This article reviews the current evidence regarding RFA for lung cancer.

Modern diagnostic and therapeutic interventional radiology in lung cancer

Imaging has an important role in the multidisciplinary management of primary lung cancer. This article reviews the current state-of-the-art imaging modalities used for the evaluation, staging and post-treatment follow-up and surveillance of lung cancers, and image-guided percutaneous techniques for biopsy to confirm the diagnosis and for local therapy in non-surgical candidates.

Microwave ablation of lung tumours: single-centre preliminary experience

PURPOSE

This study was done to evaluate the feasibility, effectiveness and safety of microwave (MW) ablation of lung tumours.

MATERIALS AND METHODS

Twenty-four patients underwent percutaneous MW ablation of 26 intraparenchymal pulmonary masses. All patients were judged to be inoperable on the basis of tumour stage, comorbidities, advanced age and/or refusal to undergo surgery. Ablation was performed using a microwave generator (Evident Microwave Ablation System, Covidien Ltd., Dublin). Lesions with a diameter ≤ 3 cm were treated with a single antenna, lesions with a diameter >3 cm were treated by positioning two or more antennae, simultaneously. All patients underwent computed tomography (CT) follow-up with and without contrast administration at 1, 3 and 6 months and then yearly in combination with complete blood and metabolic tests.

RESULTS

Technical success was 100 %. No major complications were recorded. Asymptomatic grade-1 pneumothorax was recorded in 9 patients (37.5 %). One case of asymptomatic pleural effusion and one of haemoptysis, not requiring transfusion, were observed. No patients were diagnosed with a post-ablation syndrome. Complete necrosis was observed in 16 of 26 lesions (61.6 %). Partial necrosis was obtained in 30.8 % (8/26 lesions); in one case (3.8 %) a progression of the disease was recorded and in another case (3.8 %) a stability was observed.

CONCLUSIONS

Our preliminary experience may be considered in accordance with literature dates, in terms of efficacy and safety.

Healing dynamics of porcine pancreatic parenchyma after radiofrequency ablation - in vivo experimental pilot study

Radiofrequency ablation is a tumour destruction method, widely used in human as well veterinary medicine. Recently, it has been applied to pancreatic disorder treatment. However, little is known about healing of the pancreatic parenchyma after radiofrequency ablation as it is important for the prevention of complications and treatment strategy. The aim of this experimental in vivo study on pigs was to evaluate the pancreatic parenchyma healing dynamics after damage by radiofrequency ablation. Radiofrequency ablations of the duodenal lobe of the pancreas were performed on 8 cross-bred laboratory pigs. They were euthanized in pairs at seven, fourteen, forty and eighty days after the procedure. Histological and cytological changes of the ablated zone were evaluated after autopsy. It was proved that pancreatic necrosis after radiofrequency ablation heals by means of fibrotic scar. There was no sign of exocrine and endocrine regeneration, respectively, during 80 days after the procedure. This is the first study verifying that the healing process of an ablation zone in the pancreatic parenchyma after radiofrequency ablation is similar to healing in the liver, lung, heart and other parenchymal organs.

In vivo evaluation of lung microwave ablation in a porcine tumor mimic model

PURPOSE

To evaluate the microwave ablation of created tumor mimics in the lung of a large animal model (pigs), with examination of the ablative synergy of multiple antennas.

METHODS

Fifty-six tumor-mimic models of various sizes were created in 15 pigs by using barium-enriched minced collected thigh muscle injected into the lung of the same animal. Tumors were ablated under fluoroscopic guidance by single-antenna and multiple-antenna microwaves.

RESULTS

Thirty-five tumor models were treated in 11 pigs with a single antenna at 75 W for 15 min, with 15 measuring 20 mm in diameter, 10 measuring 30 mm, and 10 measuring 40 mm. Mean circularity of the single-antenna ablation zones measured 0.64 ± 0.12, with a diameter of 35.7 ± 8.7 mm along the axis of the antenna and 32.7 ± 12.8 mm perpendicular to the feeding point. Multiple-antenna delivery of 75 W for 15 min caused intraprocedural death of 2 animals; modified protocol to 60 W for 10 min resulted in an ablation zone with a diameter of 43.0 ± 7.7 along the axis of the antenna and 54.8 ± 8.5 mm perpendicular to the feeding point; circularity was 0.70 ± 0.10

CONCLUSIONS

A single microwave antenna can create ablation zones large enough to cover lung tumor mimic models of ≤4 cm with no heat sink effect from vessels of ≤6 mm. Synergic use of 3 antennas allows ablation of larger volumes than single-antenna or radiofrequency ablation, but great caution must be taken when 3 antennas are used simultaneously in the lung in clinical practice.

Experimental study of destruction to porcine spleen in vivo by microwave ablation

AIM: To discuss the safety, feasibility and regularity of destruction to porcine spleen in vivo with congestion and tumescence by microwave ablation (MWA).

METHODS: Ligation of the splenic vein was used to induce congestion and tumescence in vivo in five porcine spleens, and microwave ablation was performed 2-4 h later. A total of 56 ablation points were ablated and the ablation powers were 30-100 W. The ablation time (1, 2, 3, 4, 5, 6, 7, 8, 9 and 10 min) was performed at a power of 60 W. After ablation, the ablation size was measured in pigs A, C, D and E and spleen resection. In pig B, the ablation size was measured and 2 ablation points were sent for pathology analysis and all tissues were sutured following ablation. Pig B was killed 1 wk later and the ablation points were sent for pathology analysis. Bleeding, tissue carbonization surrounding electrodes, and pathological changes were observed, and the effect on destruction volume relative to different ablation powers, times and positions was analyzed.

RESULTS: The incidence of bleeding (only small am-ounts, < 20 mL) in the course of ablation was 5.4% (3/56) and was attributed to tissue carbonization surrounding electrodes, which also exhibited an incidence of 5.4% (3/56). The destruction volume was influenced by different ablation powers, times and points. It showed that the ablation lesion size increased with increased ablation time, from 1 to 10 min, when the ablation power was 60 W. Also, the ablation lesion size increased with the increase of ablation power, ranging from 30 to 100 W when the ablation time was set to 3 min. A direct correlation was seen between the destruction volume and ablation time by the power of 60 W (r = 0.97542, P < 0.0001, and also between the destruction volume and ablation powers at an ablation time of 3 min (r = 0.98258, P < 0.0001). The destruction volume of zone II (the extra-2/3 part of the spleen, relative to the first or second class vascular branches), which was near the hilum of the spleen, was noteably larger than the destruction volume of zoneI(the intra-1/3 part of the spleen) which was distal from the hilum of the spleen (P = 0.0015). Pathological changes of ablation occurring immediately and 1 wk after MWA showed large areas of coagulation. Immediately following ablation, intact spleen tissues were observed in the areas of coagulation necrosis, mainly around arterioles, and there were no obvious signs of hydropsia and inflammation, while 1 wk following the ablation, the coagulation necrosis was well distributed and complete, as many nuclear fragmentations were detected, and there were obvious signs of hydropsia and inflammation.

CONCLUSION: In vivo treatment of congestion and tumescence in the spleen using microwave ablation of water-cooled antenna is a safe and feasible method that is minimally invasive.

Microwave ablation compared with radiofrequency ablation for breast tissue in an ex vivo bovine udder model

PURPOSE

To compare the effectiveness of microwave (MW) ablation with radiofrequency (RF) ablation for treating breast tissue in a nonperfused ex vivo model of healthy bovine udder tissue.

MATERIALS AND METHODS

MW ablations were performed at power outputs of 25W, 35W, and 45W using a 915-MHz frequency generator and a 2-cm active tip antenna. RF ablations were performed with a bipolar RF system with 2- and 3-cm active tip electrodes. Tissue temperatures were continuously monitored during ablation.

RESULTS

The mean short-axis diameters of the coagulation zones were 1.34 ± 0.14, 1.45 ± 0.13, and 1.74 ± 0.11 cm for MW ablation at outputs of 25W, 35W, and 45W. For RF ablation, the corresponding values were 1.16 ± 0.09 and 1.26 ± 0.14 cm with electrodes having 2- and 3-cm active tips, respectively. The mean coagulation volumes were 2.27 ± 0.65, 2.85 ± 0.72, and 4.45 ± 0.47 cm(3) for MW ablation at outputs of 25W, 35W, and 45W and 1.18 ± 0.30 and 2.29 ± 0.55 cm(3) got RF ablation with 2- and 3-cm electrodes, respectively. MW ablations at 35W and 45W achieved significantly longer short-axis diameters than RF ablations (P < 0.05). The highest tissue temperature was achieved with MW ablation at 45W (P < 0.05). On histological examination, the extent of the ablation zone in MW ablations was less affected by tissue heterogeneity than that in RF ablations.

CONCLUSION

MW ablation appears to be advantageous with respect to the volume of ablation and the shape of the margin of necrosis compared with RF ablation in an ex vivo bovine udder.

Thermal ablation of lung tumors

The 5-year survival for all stages of nonsmall cell lung cancer (NSCLC) remains bleak, having increased from 13% to just 16% over the past 30 years. Despite promising results in nonoperative patients with NSCLC and pulmonary metastatic disease, thermal ablation appears to be limited by large tumor size and proximity to large vessels. This article discusses the particular challenges of performing thermal ablation in aerated lung tissue and reviews important considerations in performing ablation including treatment complications and imaging follow-up. The article compares and contrasts the three major thermal ablation modalities: radiofrequency ablation, microwave ablation, and cryoablation.