Microwave coagulation therapy in canine peripheral lung tissue

Local thermal ablative therapies for extracranial oligometastatic disease of non-small-cell lung cancer

Non-small cell lung cancer (NSCLC) is the most common type of lung cancer. Clinically, 40-50% of patients with NSCLC are found to have systemic metastasis at the initial diagnosis. Meanwhile, 30-75% of patients with lung cancer who have undergone radical surgical resection have local recurrence and distant metastases. However, not all distant metastases are multiple, and some are potentially curable. In this study, among the patients with NSCLC having distant organ metastasis, approximately 7% showed extrapulmonary solitary metastasis and remained in this relatively stable state for a long time. This form of metastasis is known as NSCLC oligometastases. This review describes the concept and classification of oligometastases, as well as the local treatment and prognosis of extracranial oligometastases.

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.

Radiofrequency versus microwave ablation for treatment of the lung tumours: LUMIRA (lung microwave radiofrequency) randomized trial

The LUMIRA trial evaluated the effectiveness of radiofrequency (RFA) and microwave ablation (MWA) in lung tumours ablation and defining more precisely their fields of application. It is a controlled prospective multi-centre random trial with 1:1 randomization. Fifty-two patients in stage IV disease (15 females and 37 males, mean age 69 y.o., range 40-87) were included. We randomized the patients in two different subgroups: MWA group and RFA group. For each group, we evaluated the technical and clinical success, the overall survival and complication rate. Inter-group difference was compared using Chi-square test or Fisher's exact test for categorical variables and one-way ANOVA test for continuous variables. For RFA group, there was a significant reduction in tumour size only between 6 and 12 months (p value = 0.0014). For MWA group, there was a significant reduction in tumour size between 6 and 12 months (p value = 0.0003) and between pre-therapy and 12 months (p value = 0.0215). There were not significant differences between the two groups in terms of survival time (p value = 0.883), while the pain level in MWA group was significantly less than in RFA group (1.79 < 3.25, p value = 0.0043). In conclusion, our trial confirms RFA and MWA are both excellent choices in terms of efficacy and safety in lung tumour treatments. However, when compared to RFA therapy, MWA produced a less intraprocedural pain and a significant reduction in tumour mass.

Percutaneous High-Energy Microwave Ablation for the Treatment of Pulmonary Tumors: A Retrospective Single-Center Experience

PURPOSE

To evaluate the safety and efficacy of percutaneous high-energy microwave ablation (MWA) for the treatment for pulmonary tumors.

MATERIALS AND METHODS

A retrospective review was undertaken of 44 patients (21 men, 23 women; median age, 66 y; range, 17-89 y) who underwent 62 sessions of high-energy MWA for 87 pulmonary tumors at a single tertiary referral center between June 2012 and June 2014. Primary tumor origin was sarcoma (n = 23), colorectal (n = 16), lung (n = 2), esophageal (n = 1), breast (n = 1), and bladder (n = 1). Median tumor size was 12 mm (range, 6-45 mm). Technical success was recorded contemporaneously, complication rate at 30 days was recorded prospectively, and technique effectiveness was assessed by longitudinal follow-up CT scan.

RESULTS

Primary technical success was achieved in 94% of ablation sessions. The median follow-up interval was 15 months (range, 6.2-29.5 mo) during which time local tumor progression was observed in two of 87 tumors (technique effectiveness 98%). Pneumothorax requiring chest tube insertion occurred in 19%; delayed pneumothorax occurred in four patients. No hemoptysis, infection, or other complications were recorded.

CONCLUSIONS

High-energy MWA is safe and effective for the destruction of lung tumors.

Patients' survival in lung malignancies treated by microwave ablation: our experience on 56 patients

OBJECTIVES

We retrospectively evaluated percutaneous CT-guided microwave (MW) ablation safety and efficacy in unresectable lung malignancies focusing on patients' survival.

MATERIALS AND METHODS

All procedures were approved by the hospital ethical committee. From 2008 to 2012 we treated 69 unresectable lesions (44 lung cancer, 25 lung metastases) in 56 patients (35 men/21 women; mean age: 61.5 years). Treatment was performed under CT guidance using 14 G needles with a 3 cm active tip and a 55 W MW generator (Vivawave Microwave Coagulation System; Valley Lab). Treatment was performed at 45 W for 6-10 min. Patients were scheduled for a 3 and 6 month CT follow-up to evaluate lesion diameter and enhancement. Survival rate was evaluated by Kaplan-Meier analysis.

RESULTS

Ablation procedures were completed according to protocol in all patients. Pneumothorax occurred in 18 patients and 8 required chest tube. Four lesions (all >4.3 cm) were retreated 20 days after the ablation because of peripheral focal areas of residual tumor. Follow-up CT evaluation showed a decrease in maximum diameter in 44/69 lesions (64%) and in 42/59 lesions (71%) at 3 and 6 months, respectively. In all cases no pathologic enhancement was observed. Cancer-specific mortality yielded a survival rate of 69% at 12 months, 54% at 24 months and 49% at 36 months, respectively. An estimate mean for survival time was 27.8 months with a standard error of 2.8 months (95% confidence interval: 22.4-33.2 months).

CONCLUSION

Based on our experience, MW ablation seems to represent a potential safe and effective percutaneous technique in the treatment of lung malignancies. MW ablation may improve survival in patients not suitable to surgery.

CT-guided percutaneous microwave ablation of pulmonary malignancies: Results in 69 cases

Background

Microwave ablation (MWA) has attracted a worldwide attention gradually in treating inoperable pulmonary malignancies. However, in the lung tissues treated with MWA recurrence of tumor may still occur and few data in large patient groups till now were reported about the safety or effectiveness of microwave ablation in treating primary lung cancer and metastatic pulmonary malignancies. The purpose of this study is to evaluate the clinical curative effect (local control, survival data) MWA and its safety as well.

Methods

From 1 January 2005 to 1 January 2008, retrospective analyses, 69 patients underwent computed tomography (CT)-guided percutaneous MWA of pulmonary malignancies. All patients were deemed medically inoperable. The correlation of tumor sizes and local progression after ablation was analyzed and the survival rates within 3 years post surgery were compared between non-small-cell lung cancer and pulmonary metastases groups also.

Results

Pneumothorax was the most frequent complication and occurred in 24.64% patients after ablation. Neither needle track implantation was found nor did patient death occur in these patients within 30 days. The 1-, 2-, and 3-year overall survival rates were 66.7%, 44.9% and 24.6%, respectively. The overall survival rates for NSCLC patients in 1 year, 2 years, and 3 years were 75.0%, 54.2%, and 29.2%, respectively. The overall survival rates for pulmonary metastatic tumor patients in 1 year, 2 years, and 3 years were 47.6%, 23.8%, and 14.3%, respectively. The recurrence-free survival rates for NSCLC patients in 1 year, 2 years, and 3 years were 72.9%, 50.0%, and 27.1%, respectively. The mortality rates for pulmonary metastatic tumor patients in 1 year, 2 years, and 3 years were 47.6%, 19.0%, and 14.3%, respectively.

Conclusions

Percutaneous microwave coagulation therapy was one safe and effective method and could be beneficial for the improvement of inoperable pulmonary malignancies treatment effect.

Microwave thermal ablation for hepatocarcinoma: six liver transplantation cases

Surgical resection for malignant hepatic tumors, especially hepatocarcinoma (HCC), has been demonstrated to increase overall survival; however, the majority of patients are not suitable for resection. Radiofrequency ablation (RFA) is the most widely used modality for radical treatment of small HCC (<3 cm). It improves 5-year survival compared with standard chemotherapy and chemical ablation, allowing down-staging of unresectable hepatic masses. Microwave ablation (MWA) has been extensively applied in Asia and was recently introduced in the United States of America and Europe with excellent results, especially with regard to large unresectable HCC. Our single-center experience between May 2009 and October 2010 included application of MWA to 154 patients of median age ± standard deviation of 63.5 ± 8.5 years, 6 males, and 1 female, of mean Model for End-Stage Liver Disease (MELD) score (10.1 ± 3.8). The HCC included, hepatitis C virus (HCV)-related (n=70; 45.5%); alcool (ETOH)-related (n=42; 27%), hepatitis B virus (HBV)-related (n=16; 10.5%); and cryptogenic cases (n=26; 17%). The cases were performed for radical treatment down-staging for multifocal pathology or bridging liver transplantation to orthotopic (OLT) in selected patients with single nodules. A computed tomography (CT) scan was performed at 1 month after the surgical procedure to evalue responses to treatment. Among 6 selected patients who underwent OLT; 5 (83.3%) showed disease-free survival at one-year follow-up. The radical treatment achieved no intraoperative evidence of tumor spread or of pathological signs of active HCC among the explanted liver specimens. In conclusion, a MWA seemed to be a safe novel approach to treat HCC and could serve as a "bridge" to OLT and down-staging for patients with HCC.

Microwave tumor ablation: mechanism of action, clinical results, and devices

Microwave ablation uses dielectric hysteresis to produce direct volume heating of tissue. Microwaves are capable of propagating through many tissue types, even those with high impedance such as lung or bone, with less susceptibility to "heat-sink" effects along vessels. Microwaves are highly conducive to the use of multiple applicators, showing the synergy seen with other energies, but also the potential capability for phasing of the electromagnetic field. As a result, larger, more customizable ablation zones may be created in less time. Although multiple microwave ablation systems are currently available, further study and continued development are needed.

Microwave tissue ablation: biophysics, technology, and applications

Microwave ablation is an emerging treatment option for many cancers, cardiac arrhythmias, and other medical conditions. During treatment, microwaves are applied directly to tissues to produce rapid temperature elevations sufficient to produce immediate coagulative necrosis. The engineering design criteria for each application differ, with individual consideration for factors such as desired ablation zone size, treatment duration, and procedural invasiveness. Recent technological developments in applicator cooling, power control, and system optimization for specific applications promise to increase the utilization of microwave ablation in the future. This article reviews the basic biophysics of microwave tissue heating, provides an overview of the design and operation of current equipment, and outlines areas for future research.

Radiofrequency and microwave ablation of the liver, lung, kidney, and bone: what are the differences?

Radiofrequency (RF) ablation is becoming an accepted treatment modality for many tumors of the liver and is being explored for tumors in the lung, kidney, and bone. While RF energy is the most familiar heat source for tissue ablation, it has certain limitations that may hamper its efficacy in these new organ systems. Microwave energy may be a better source for tissue ablation but has technical hurdles that must be overcome as well. This article outlines the physics behind RF and microwave heating, discusses relevant properties of the liver, lung, kidney, and bone for thermal ablation and examines the roles of RF and microwave ablation in these tissues.

Pulmonary thermal ablation: comparison of radiofrequency and microwave devices by using gross pathologic and CT findings in a swine model

PURPOSE

To compare the performance of equivalently sized radiofrequency and microwave ablation applicators in a normal porcine lung model.

MATERIALS AND METHODS

All experiments were approved by an institutional animal care and use committee. A total of 18 ablations were performed in vivo in normal porcine lungs. By using computed tomographic (CT) fluoroscopic guidance, a 17-gauge cooled triaxial microwave antenna (n = 9) and a 17-gauge cooled radiofrequency (RF) electrode (n = 9) were placed percutaneously. Ablations were performed for 10 minutes by using either 125 W of microwave power or 200 W of RF power delivered with an impedance-based pulsing algorithm. CT images were acquired every minute during ablation to monitor growth. Animals were sacrificed after the procedure. Ablation zones were then excised and sectioned transverse to the applicator in 5-mm increments. Minimum and maximum diameter, cross-sectional area, length, and circularity were measured from gross specimens and CT images. Comparisons of each measurement were performed by using a mixed-effects model; P < .05 was considered to indicate a significant difference.

RESULTS

Mean diameter (3.32 cm +/- 0.19 [standard deviation] vs 2.70 cm +/- 0.23, P < .001) was 25% larger with microwave ablation and mean cross-sectional area (8.25 cm(2) +/- 0.92 vs 5.45 cm(2) +/- 1.14, P < .001) was 50% larger with microwave ablation, compared with RF ablation. With microwave ablation, the zones of ablation were also significantly more circular in cross section (mean circularity, 0.90 +/- 0.06 vs 0.82 +/- 0.09; P < .05). One small pneumothorax was noted during RF ablation but stabilized without intervention.

CONCLUSION

Microwave ablation with a 17-gauge high-power triaxial antenna creates larger and more circular zones of ablation than does a similarly sized RF applicator in a preclinical animal model. Microwave ablation may be a more effective treatment of lung tumors.

Ablative treatments for lung tumors: radiofrequency ablation, stereotactic radiosurgery, and microwave ablation

RFA and SRS have been demonstrated to be safe with reasonable efficacy in the treatment of small lung tumors. It is unclear which option is the most effective in the treatment of NSCLC, with both RFA and SRS demonstrating similar early response and progression rates. RFA can be performed in one treatment session, whereas it now seems that SRS is more effective if larger doses of radiation over two to three fractions are performed. RFA is not recommended for centrally based tumors. There are also some tumors (eg, small apical tumors, posteriorly positioned tumors close to the diaphragm, and tumors close to the scapula) where it may be difficult percutaneously to position an active electrode. Such patients are more optimally treated with SRS. In certain circumstances, a combined approach may be beneficial (RFA and SRS). At this point in time, MWA is the least well developed modality. Although treatment times and heat-sink effect may be less compared with RFA, larger trials are needed to understand better the impact of this factor on effectiveness and safety. The heat-sink effect may be protective, minimizing the necrosis of large blood vessels and the risk of subsequent fatal hemoptysis. Future studies need to address long-term outcomes using standardized assessments of treatment response between centers. Comparisons between different RFA systems and ablation modalities need to be undertaken to delineate the optimal use of these strategies in the treatment of early stage lung cancer. Until long-term data with these ablative techniques become available, surgical resection should be performed when clinically possible.