Computational modeling of microwave ablation with thermal accelerants

PURPOSE

To develop a computational model of microwave ablation (MWA) with a thermal accelerant gel and apply the model toward interpreting experimental observations in ex vivo bovine and in vivo porcine liver.

METHODS

A 3D coupled electromagnetic-heat transfer model was implemented to characterize thermal profiles within ex vivo bovine and in vivo porcine liver tissue during MWA with the HeatSYNC thermal accelerant. Measured temperature dependent dielectric and thermal properties of the HeatSYNC gel were applied within the model. Simulated extents of MWA zones and transient temperature profiles were compared against experimental measurements in ex vivo bovine liver. Model predictions of thermal profiles under in vivo conditions in porcine liver were used to analyze thermal ablations observed in prior experiments in porcine liver in vivo.

RESULTS

Measured electrical conductivity of the HeatSYNC gel was ∼83% higher compared to liver at room temperature, with positive linear temperature dependency, indicating increased microwave absorption within HeatSYNC gel compared to tissue. In ex vivo bovine liver, model predicted ablation zone extents of (31.5 × 36) mm with the HeatSYNC, compared to (32.9 ± 2.6 × 40.2 ± 2.3) mm in experiments (volume differences 4 ± 4.1 cm3). Computational models under in vivo conditions in porcine liver suggest approximating the HeatSYNC gel spreading within liver tissue during ablations as a plausible explanation for larger ablation zones observed in prior in vivo studies.

CONCLUSION

Computational models of MWA with thermal accelerants provide insight into the impact of accelerant on MWA, and with further development, could predict ablations with a variety of gel injection sites.

Technical and safety performance of CT-guided percutaneous microwave ablation for lung tumors: an ablate and resect study

Background

Percutaneous image-guided thermal ablation has an increasing role in the treatment of primary and metastatic lung tumors. Achieving acceptable clinical outcomes requires better tools for pre-procedure prediction of ablation zone size and shape.

Methods

This was a prospective, non-randomized, single-arm, multicenter study conducted by Medtronic (ClinicalTrials.gov ID: NCT02323854). Subjects scheduled for resection of metastatic or primary lung nodules underwent preoperative percutaneous microwave ablation. Ablation zones as measured via CT imaging following ablation immediately and before resection surgically versus predicted ablation zones as prescribed by the investigational system software were compared. This CT scan occurred after the ablation was finished but the antenna still in position. Time (minutes) from antenna placement to removal was 23.7±13.1 (n=14); median: 21.0 (range, 6.0 to 48.0). The definition of the secondary endpoint of complete ablation was 100% non-viable tumor cells based on nicotinamide adenine dinucleotide hydrogen (NADH) staining. Safety endpoints were type, incidence, and severity of adverse events.

Results

Fifteen patients (mean age 58.9 years; 67% male; 33% female) were enrolled in the study, 33.3% (5/15) with previous thoracic surgery, 73% (11/15) with metastasis, and 27% (4/15) with primary lung tumors. All underwent percutaneous microwave ablation followed by surgical resection the same day. Complete ablation was detected in 54.4% (6/11), incomplete ablation in 36.4% (4/11), and delayed necrosis in 9.1% (1/11). There were no device-related adverse events. Ablation zone volume was overestimated in all patients.

Conclusions

Histological complete ablation was observed in 55% of subjects. CT scanning less than an hour after ablation and tissue shrinkage may account for the smaller zone of ablation observed compared to predicted by the investigational system software.

Consensus Guidelines for the Definition of Time-to-Event End Points in Image-guided Tumor Ablation: Results of the SIO and DATECAN Initiative

There is currently no consensus regarding preferred clinical outcome measures following image-guided tumor ablation or clear definitions of oncologic end points. This consensus document proposes standardized definitions for a broad range of oncologic outcome measures with recommendations on how to uniformly document, analyze, and report outcomes. The initiative was coordinated by the Society of Interventional Oncology in collaboration with the Definition for the Assessment of Time-to-Event End Points in Cancer Trials, or DATECAN, group. According to predefined criteria, based on experience with clinical trials, an international panel of 62 experts convened. Recommendations were developed using the validated three-step modified Delphi consensus method. Consensus was reached on when to assess outcomes per patient, per session, or per tumor; on starting and ending time and survival time definitions; and on time-to-event end points. Although no consensus was reached on the preferred classification system to report complications, quality of life, and health economics issues, the panel did agree on using the most recent version of a validated patient-reported outcome questionnaire. This article provides a framework of key opinion leader recommendations with the intent to facilitate a clear interpretation of results and standardize worldwide communication. Widespread adoption will improve reproducibility, allow for accurate comparisons, and avoid misinterpretations in the field of interventional oncology research. Published under a CC BY 4.0 license. Online supplemental material is available for this article. See also the editorial by Liddell in this issue.

Lung Ablation with Irreversible Electroporation Promotes Immune Cell Infiltration by Sparing Extracellular Matrix Proteins and Vasculature: Implications for Immunotherapy

Background: This study investigated the sparing of the extracellular matrix (ECM) and blood vessels at the site of lung irreversible electroporation (IRE), and its impact on postablation T cell and macrophage populations. Materials and Methods: Normal swine (n = 8) lung was treated with either IRE or microwave ablation (MWA), followed by sacrifice at 2 and 28 days (four animals/timepoint) after treatment. En bloc samples of ablated lung were stained for blood vessels (CD31), ECM proteins (Collagen, Heparan sulfate, and Decorin), T cells (CD3), and macrophages (Iba1). Stained slides were analyzed with an image processing software (ImageJ) to count the number of positive staining cells or the percentage area of tissue staining for ECM markers, and the statistical difference was evaluated with Student's t-test. Results: Approximately 50% of the blood vessels and collagen typically seen in healthy lung were evident in IRE treated samples at Day 2, with complete destruction within MWA treated lung. These levels increased threefold by Day 28, indicative of post-IRE tissue remodeling and regeneration. Decorin and Heparan sulfate levels were reduced, and it remained so through the duration of observation. Concurrently, numbers of CD3⁺ T cells and macrophages were not different from healthy lung at Day 2 after IRE, subsequently increasing by 2.5 and 1.5-fold by Day 28. Similar findings were restricted to the peripheral inflammatory rim of MWA samples, wherein the central necrotic regions remained acellular through Day 28. Conclusion: Acute preservation of blood vessels and major ECM components was observed in IRE treated lung at acute time points, and it was associated with the increased infiltration and presence of T cells and macrophages, features that were spatially restricted in MWA treated lung.

Musculoskeletal Oncologic Interventions: Proceedings from the Society of Interventional Radiology and Society of Interventional Oncology Research Consensus Panel

Musculoskeletal interventions are increasingly used with palliative and curative intent in the multidisciplinary treatment of oncology patients with bone and soft-tissue tumors. There is an unmet need for high-quality evidence to guide broader application and adoption of minimally invasive interventional technologies to treat these patients. Therefore, the Society of Interventional Radiology Foundation and the Society of Interventional Oncology collaborated to convene a research consensus panel to prioritize a research agenda addressing the gaps in the current evidence. This article summarizes the panel's proceedings and recommendations for future basic science and clinical investigation to chart the course for interventional oncology within the musculoskeletal system. Key questions that emerged addressed the effectiveness of ablation within specific patient populations, the effect of combination of ablation with radiotherapy and/or immunotherapy, and the potential of standardization of techniques, including modeling and monitoring, to improve the consistency and predictability of treatment outcomes.

Adjuvant Thermal Accelerant Gel Use Increases Microwave Ablation Zone Temperature in Porcine Liver as Measured by MR Thermometry

PURPOSE

To determine the effects of a thermal accelerant gel on temperature parameters during microwave liver ablation.

MATERIALS AND METHODS

Sixteen consecutive liver ablations were performed in 5 domestic swine under general anesthesia with (n = 8) and without (n = 8) administration of thermal accelerant gel. Ablation zone temperature was assessed by real-time MR thermometry, measured as maximum temperature (T_max) and the volume of tissue ≥ 60°C (V₆₀). Tissue heating rate, ablation zone shape, and thermal energy deposition using the temperature degree-minutes at 43°C (TDM43) index were also measured. Differences between groups were analyzed using generalized mixed modeling with significance set at P = .05.

RESULTS

Mean peak ablation zone temperature was significantly greater with thermal accelerant use (mean T_max, thermal accelerant: 120.0°C, 95% confidence interval [CI] 113.0°C-126.9°C; mean T_max, control: 80.3°C, 95% CI 72.7°C-88.0°C; P < .001), and a significantly larger volume of liver tissue achieved or exceeded 60°C when thermal accelerant was administered (mean V₆₀, thermal accelerant: 22.2 cm³; mean V₆₀, control: 15.9 cm³; P < .001). Significantly greater thermal energy deposition was observed during ablations performed with accelerant (mean TDM43, thermal accelerant: 198.4 min, 95% CI 170.7-230.6 min; mean TDM43, control: 82.8 min, 95% CI 80.5-85.1 min; P < .0001). The rate of tissue heating was significantly greater with thermal accelerant use (thermal accelerant: 5.8 min ± 0.4; control: 10.0 min; P < .001), and accelerant gel ablations demonstrated a more spherical temperature distribution (P = .002).

CONCLUSIONS

Thermal accelerant use is associated with higher microwave ablation zone temperatures, greater thermal energy deposition, and faster and more spherical tissue heating compared with control ablations.

Multicenter Study of Metastatic Lung Tumors Targeted by Interventional Cryoablation Evaluation (SOLSTICE)

OBJECTIVE

To assess the safety and local recurrence-free survival in patients after cryoablation for treatment of pulmonary metastases.

METHODS

This multicenter, prospective, single-arm, phase 2 study included 128 patients with 224 lung metastases treated with percutaneous cryoablation, with 12 and 24 months of follow-up. The patients were enrolled on the basis of the outlined key inclusion criteria, which include one to six metastases from extrapulmonary cancers with a maximal diameter of 3.5 cm. Time to progression of the index tumor(s), metastatic disease, and overall survival rates were estimated using the Kaplan-Meier method. Complications were captured for 30 days after the procedure, and changes in performance status and quality of life were also evaluated.

RESULTS

Median size of metastases was 1.0 plus or minus 0.6 cm (0.2-4.5) with a median number of tumors of 1.0 plus or minus 1.2 cm (one to six). Local recurrence-free response (local tumor efficacy) of the treated tumor was 172 of 202 (85.1%) at 12 months and 139 of 180 (77.2%) at 24 months after the initial treatment. After a second cryoablation treatment for recurrent tumor, secondary local recurrence-free response (local tumor efficacy) was 184 of 202 (91.1%) at 12 months and 152 of 180 (84.4%) at 24 months. Kaplan-Meier estimates of 12- and 24-month overall survival rates were 97.6% (95% confidence interval: 92.6-99.2) and 86.6% (95% confidence interval: 78.7-91.7), respectively. Rate of pneumothorax that required pleural catheter placement was 26% (44/169). There were eight grade 3 complication events in 169 procedures (4.7%) and one (0.6%) grade 4 event.

CONCLUSION

Percutaneous cryoablation is a safe and effective treatment for pulmonary metastases.

CT Densitometry and Morphology of Radiofrequency-Ablated Stage IA Non-Small Cell Lung Cancer: Results from the American College of Surgeons Oncology Group Z4033 (Alliance) Trial

PURPOSE

To evaluate tumor and ablation zone morphology and densitometry related to tumor recurrence in participants with Stage IA non-small cell lung cancer undergoing radiofrequency ablation in a prospective, multicenter trial.

MATERIALS AND METHODS

Forty-five participants (median 76 years old; 25 women; 20 men) from 16 sites were followed for 2 years (December 2006 to November 2010) with computed tomography (CT) densitometry. Imaging findings before and after ablation were recorded, including maximum CT attenuation (in Hounsfield units) at precontrast and 45-, 90-, 180-, and 300-s postcontrast.

RESULTS

Every 1-cm increase in the largest axial diameter of the ablation zone at 3-months' follow-up compared to the index tumor reduced the odds of 2-year recurrence by 52% (P = .02). A 1-cm difference performed the best (sensitivity, 0.56; specificity, 0.93; positive likelihood ratio of 8). CT densitometry precontrast and at 45 seconds showed significantly different enhancement patterns in a comparison among pretreated lung cancer (delta = +61.2 HU), tumor recurrence (delta = +57 HU), and treated tumor/ablation zone (delta [change in attenuation] = +16.9 HU), (P < .0001). Densitometry from 45 to 300 s was also different among pretreated tumor (delta = -6.8 HU), recurrence (delta = -11.2 HU), and treated tumor (delta = +12.1 HU; P = .01). Untreated and residual tumor demonstrated washout, whereas treated tumor demonstrated increased attenuation.

CONCLUSIONS

An ablation zone ≥1 cm larger than the initial tumor, based on 3-month follow-up imaging, is recommended to decrease odds of recurrence. CT densitometry can delineate tumor versus treatment zones.

Effects of a Thermal Accelerant Gel on Microwave Ablation Zone Volumes in Lung: A Porcine Study

Background Thermal ablation of cancers may be associated with high rates of local tumor progression. A thermal accelerant gel has been developed to improve the transmission of microwave energy in biologic tissues with the aim of enlarging the thermal ablation zone. Purpose To determine the effects of a thermal accelerant gel on microwave ablation zone volumes in porcine lung and to compare percutaneous and endobronchial delivery methods. Materials and Methods Thirty-two consecutive microwave lung ablations were performed in nine 12-week-old domestic male swine under general anesthesia by using fluoroscopic guidance between September 2017 and April 2018. Experimental ablations were performed following percutaneous injection of thermal accelerant into the lung (n = 16) or after endobronchial injection by using a flexible bronchoscope (n = 8). Control ablations were performed without accelerant gel (n = 8). Lung tissue was explanted after the animals were killed, and ablation zone volumes were calculated as the primary outcome measure by using triphenyltetrazolium chloride vital staining. Differences in treatment volumes were analyzed by generalized mixed modeling. Results Thermal accelerant ablation zone volumes were larger than control ablations (accelerant vs control ablation, 4.3 cm³ [95% confidence interval: 3.4, 5.5] vs 2.1 cm³ [95% confidence interval: 1.4, 2.9], respectively; P < .001). Among ablations with the thermal accelerant, those performed following percutaneous injection had a larger average ablation zone volume than those performed following endobronchial injection (percutaneous vs endobronchial, 4.8 cm³ [95% confidence interval: 3.6, 6.4] vs 3.3 cm³ [95% confidence interval: 2.9, 3.8], respectively; P = .03). Ablation zones created after endobronchial gel injection were more uniform in size distribution (standard error, percutaneous vs endobronchial: 0.13 vs 0.07, respectively; P = .03). Conclusion Use of thermal accelerant results in larger microwave ablation zone volumes in normal porcine lung tissue. Percutaneous thermal accelerant injection leads to a larger ablation zone volume compared with endobronchial injection, whereas a more homogeneous and precise ablation zone size is observed by using the endobronchial approach. © RSNA, 2019 See also the editorial by Goldberg in this issue.

Evaluation of Probe Angles for Synchronous Waveform 915-MHz Microwave Ablation

BACKGROUND

The purpose of this study is to compare the ablation performance between a synchronous microwave ablation (MWA) system and a commercially available asynchronous system in ex vivo bovine liver and evaluate the efficacy of ablation at varying entrance angles.

MATERIALS AND METHODS

Two 915-MHz MWA systems were used in bench top ex vivo bovine livers with various conditions (synchronous versus asynchronous). Using synchronous technology ablations to liver, kidney, or lung at angles of 0, 15, 30, and 90° were evaluated.

RESULTS

Synchronous and asynchronous MWA systems created mean ablation zone volumes of 26.4 and 15.8 cm³, 62.9 and 45.4 cm³, 90.8 and 56.4, and 75.7 and 54.8 cm³ with single, double (2 microwave probes in use simultaneous) (2 cm spacing), and triple (three probes in use simultaneously) (2 cm and 3 cm spacing) antennae configurations, respectively; adjusted P-values ≤ 0.006. Ablation defects were similar across all groups when evaluated for entrance angle. Specifically, when comparing 0-degree angle to all other angles, achieved zones of ablation (ZA) were similar (mean ± standard deviation for 0-degree versus all other angles: 8.72 ± 4.84 versus 9.38 ± 4.11 cm², P = 0.75). The use of the long-tip probe resulted in a statistically significant increase in the achieved ZA when compared to the short tip probe (10.9 ± 4.3 versus 6.5 ± 2.4, respectively; P = 0.01).

CONCLUSIONS

Newly developed synchronous microwave technology creates significantly larger ablation zones when compared to an existing asynchronous commercially available system. The angle of approach does not affect the resulting ZA. This is clinically relevant as true 0-degree angle is often difficult to obtain.

Optimal CT scanning parameters for commonly used tumor ablation applicators

PURPOSE

CT-beam hardening artifact can make tumor margin visualization and its relationship to the ablation applicator tip challenging. To determine optimal scanning parameters for commonly-used applicators.

MATERIALS AND METHODS

Applicators were placed in ex-vivo cow livers with implanted mock tumors, surrounded by bolus gel. Various CT scans were performed at 440mA with 5mm thickness changing kVp, scan time, ASiR, scan type, pitch, and reconstruction algorithm. Four radiologists blindly scored the images for image quality and artifact quantitatively.

RESULTS

A significant relationship between probe, kVp level, ASiR level, and reconstruction algorithm was observed concerning both image artifact and image quality (both p=<0.0001). Specifically, there are certain combinations of kVp, ASiR, and reconstruction algorithm that yield better images than other combinations. In particular, one probe performed equivalently or better than any competing probe considered here, regardless of kVp, ASiR, and reconstruction algorithm combination.

CONCLUSION

The findings illustrate the overall interaction of the effects of kVp, ASiR, and reconstruction algorithm within and between probes, so that radiologists may easily reference optimal imaging performance for a certain combinations of kVp, ASiR, reconstruction algorithm and probes at their disposal. Optimum combinations for each probe are provided.

Percutaneous Thermal Ablation for Small-Cell Lung Cancer: Initial Experience with Ten Tumors in Nine Patients

PURPOSE

To evaluate outcomes in a small cohort of patients with local or disseminated small-cell lung cancer (SCLC) who received percutaneous thermal ablation therapy.

MATERIALS AND METHODS

Ten biopsy-proven SCLC tumors in 9 consecutive patients (5 men, 4 women; average age, 73.8 y ± 12.4) were retrospectively evaluated. Average tumor sizes were 1.8 cm ± 0.5 and 2.6 cm ± 1.2 among patients with local and disseminated disease, respectively. Microwave and radiofrequency ablation were each used for 5 tumors. None of the patients with local SCLC received adjuvant therapy following thermal ablation. Median follow-up duration was 16 months (range, 2-48 mo). Median and 1-year overall survival (OS) were compared for patients in the local and disseminated disease groups.

RESULTS

Median and 1-year OS were better among patients treated for local SCLC compared with disseminated disease (47.0 vs 5.5 mo and 3 [100%] vs 2 [40%], respectively). Pneumothorax occurred in 5 patients (55.6%), and 3 patients received successful outpatient thoracostomy tube placement. No patients were hospitalized, and there were no major complications.

CONCLUSIONS

This preliminary analysis suggests favorable outcomes in selected patients with local SCLC who undergo percutaneous thermal ablation without adjuvant therapy.

Clinical experiences with microwave thermal ablation of lung malignancies

Approximately 30% of early stage lung cancer patients are not surgical candidates due to medical co-morbidities, poor cardiopulmonary function and advanced age. These patients are traditionally offered chemotherapy and radiation, which have shown relatively modest improvements in mortality. For over a decade, percutaneous image-guided ablation has emerged as a safe, cost-effective, minimally invasive treatment alternative for patients who would otherwise not qualify for surgery. Although radiofrequency ablation (RFA) is currently the most extensively studied and widely utilised technique in the treatment of lung malignancies, there is a growing body of evidence that microwave ablation (MWA) has several unique benefits over RFA and cryoablation in the lung. This article reviews our institution's clinical experiences in the treatment of lung malignancies with MWA including patient selection, procedural technique, imaging follow-up, treatment outcomes and comparison of ablation techniques.

Primary extraskeletal Ewing sarcoma of the stomach: a rare disease in an uncommon location

We report the case of a 63-year-old female undergoing evaluation of symptomatic anemia, gastroesophageal reflux disease, and abdominal pain. After a thorough diagnostic workup, a large, ulcerated mass was identified in the patient's stomach, and surgical pathology in combination with molecular analysis yielded a diagnosis of primary extraskeletal Ewing sarcoma. In our report, we discuss the epidemiologic, clinicopathologic, and radiographic features of this rare disease and provide a review of the existing literature.

Optimizing modality selection for image-guided procedures: an analysis of the challenges to ultrasound guidance

INTRODUCTION

Selection of the most appropriate modality for image guidance is essential for procedural success. We identified specific factors contributing to failure of ultrasound-guided procedures that were subsequently performed using CT guidance.

MATERIALS AND METHODS

This single-center, retrospective study included 164 patients who underwent a CT-guided biopsy, aspiration/drainage, or ablation after initially having the same procedure attempted unsuccessfully with ultrasound guidance. Review of the procedure images, reports, biopsy results, and clinical follow-up was performed and the reasons for inability to perform the procedure with ultrasound guidance were recorded. Patient cross-sectional area and depth to target were calculated. Differences in area and depth were compared using general linear modeling. Depth as a predictor of an unfavorable body habitus designation was modeled using logistic regression.

RESULTS

US guidance was successful in the vast majority of cases (97%). Of the 164 procedures, there were 92 (56%) biopsies, 63 (38%) aspirations/drainages, and 9 (5%) ablations. The most common reason for procedure failure was poor acoustic window (83/164, 51%). Other reasons included target lesion being poorly discerned from adjacent tissue (61/164, 37%), adjacent bowel gas (34/164, 21%), body habitus (27/164, 16%), and gas-containing collection (22/164, 13%). Within the biopsy subgroup, patients for whom body habitus was a limiting factor were found to have on average a larger cross-sectional area and lesion depth relative to patients whose body habitus was not a complicating factor (p < 0.0001 and p = 0.0009).

CONCLUSION

Poor acoustic window was the most common reason for procedural failure with ultrasound guidance. In addition, as lesion depth increased, the odds that body habitus would limit the procedure also increased. If preliminary imaging suggests a limited sonographic window, particularly for deeper lesions, proceeding directly to CT guidance should be considered.

IgG and IgM glycosylation patterns in patients undergoing image-guided tumor ablation

BACKGROUND

Image-guided tumor ablation is a technique whereby needle-like applicators are placed directly into solid tumors under guidance typically with computed tomography or ultrasound. Changes in IgG and IgM antibody glycosylation were studied during ablation-induced immune response to cancer, and the use of glycosylation as a biomarker for diagnosis, prognosis and disease treatment was examined.

METHODS

Plasma from 27 tumor patients was collected immediately before, after and for 6 months following ablation. IgG and IgM antibodies were isolated by use high-throughput chromatography, and analyzed by hydrophilic liquid chromatography. Thorough identification of glycan structures in each chromatography peak was performed by nano-liquid chromatography electrospray ionization mass spectrometry.

RESULTS

Although antibody glycosylation was found to vary with cancer type, discernable patterns of change based on the successful treatment of tumors by ablation were not identified. One patient with renal clear cell carcinoma and poor disease outcome had unexpectedly high amount of oligomannose IgG glycans during the whole period of monitoring. In contrast, IgM antibodies did not follow the same pattern.

CONCLUSIONS

These findings suggest that glycosylation patterns are indicative of an immune system that is unable to prevent different types of cancer, rather than products of the immunostimulatory response to the ablation of tumor itself. Analyses of the outcome effect suggested that IgG glycosylation and IgM glycosylation are not associated with tumor ablation.

GENERAL SIGNIFICANCE

Present work opens a new way for parallel determination of glycosylation changes of both IgG and IgM antibodies by use of high-throughput methods, and their future use as biomarkers for disease diagnosis and prognosis. This article is part of a Special Issue entitled "Glycans in personalised medicine" Guest Editor: Professor Gordan Lauc.

Radiofrequency ablation of stage IA non-small cell lung cancer in medically inoperable patients: Results from the American College of Surgeons Oncology Group Z4033 (Alliance) trial

BACKGROUND

This study evaluated the 2-year overall survival rate, adverse event rate, local control rate, and impact on pulmonary function tests for medically inoperable patients with stage IA non-small cell lung cancer (NSCLC) undergoing computed tomography (CT)-guided radiofrequency ablation (RFA) in a prospective, multicenter trial.

METHODS

Fifty-four patients (25 men and 29 women) with a median age of 76 years (range, 60-89 years) were enrolled from 16 US centers; 51 patients were eligible for evaluation (they had biopsy-proven stage IA NSCLC and were deemed medically inoperable by a board-certified thoracic surgeon). Pulmonary function tests were performed within the 60 days before RFA and 3 and 24 months after RFA. Adverse events were recorded and categorized. Patients were followed with CT and fludeoxyglucose positron emission tomography. Local control rate and recurrence patterns were analyzed.

RESULTS

The overall survival rate was 86.3% at 1 year and 69.8% at 2 years. The local tumor recurrence-free rate was 68.9% at 1 year and 59.8% at 2 years and was worse for tumors > 2 cm. In the 19 patients with local recurrence, 11 were re-treated with RFA, 9 underwent radiation, and 3 underwent chemotherapy. There were 21 grade 3 adverse events, 2 grade 4 adverse events, and 1 grade 5 adverse event in 12 patients within the first 90 days after RFA. None of the grade 4 or 5 adverse events were attributable to RFA. There was no significant change in the forced expiratory volume in the first second of expiration or the diffusing capacity of lung for carbon monoxide after RFA. A tumor size less than 2.0 cm and a performance status of 0 or 1 were associated with statistically significant improved survival of 83% and 78%, respectively, at 2 years.

CONCLUSIONS

RFA is a single, minimally invasive procedure that is well tolerated in medically inoperable patients, does not adversely affect pulmonary function tests, and provides a 2-year overall survival rate that is comparable to the rate reported after stereotactic body radiotherapy in similar patients.

Microwave ablation of focal hepatic malignancies regardless of size: A 9-year retrospective study of 64 patients

PURPOSE

To retrospectively evaluate the safety and efficacy of microwave ablation (MWA) as treatment for single, focal hepatic malignancies.

MATERIALS AND METHODS

Institutional review board approval was obtained for this HIPAA-compliant study. From December 2003 to May 2012, 64 patients were treated with MWA for a single hepatic lesion, in 64 sessions. Hepatocellular carcinoma (HCC) was treated in 25 patients (geometric mean tumor size, 3.33-cm; 95% CI, 2.65-4.18-cm; range, 1.0-12.0-cm), metastatic colorectal cancer (CRC) was treated in 27 patients (geometric mean tumor size, 2.7-cm; 95% CI, 2.20-3.40-cm; range, 0.8-6.0-cm), and other histological-types were treated in 12 patients (geometric mean tumor size, 3.79-cm; 95% CI, 2.72-5.26-cm; range, 1.7-8.0-cm). Kaplan-Meier (K-M) method was used to analyze time event data. Chi-square and correlation evaluated the relationship between tumor size and treatment parameters.

RESULTS

Technical success rate was 95.3% (61/64). Treatment parameters were tailored to tumor size; as size increased more antennae were used (p<0.001), treatment with multiple activations increased (p<0.028), and treatment time increased (p<0.001). There was no statistically significant relationship between time to recurrence and tumor size, number of activations, number of antennae, and treatment time. At one-year, K-M analysis predicted a likelihood of local recurrence of 39.8% in HCC patients, 45.7% in CRC metastases patients, and 70.8% in patients with other metastases. Median cancer specific survivals for patients were 38.3 months for HCC patients, 36.3 months for CRC metastases, and 13.9 months for other histological-types. Complications occurred in 23.4% (15/64) of sessions.

CONCLUSION

In our sample, tumor size did not appear to impact complete ablation rates or local recurrence rates for focal hepatic malignancies treated with MWA.

Image-guided tumor ablation: standardization of terminology and reporting criteria--a 10-year update

Image-guided tumor ablation has become a well-established hallmark of local cancer therapy. The breadth of options available in this growing field increases the need for standardization of terminology and reporting criteria to facilitate effective communication of ideas and appropriate comparison among treatments that use different technologies, such as chemical (eg, ethanol or acetic acid) ablation, thermal therapies (eg, radiofrequency, laser, microwave, focused ultrasound, and cryoablation) and newer ablative modalities such as irreversible electroporation. This updated consensus document provides a framework that will facilitate the clearest communication among investigators regarding ablative technologies. An appropriate vehicle is proposed for reporting the various aspects of image-guided ablation therapy including classification of therapies, procedure terms, descriptors of imaging guidance, and terminology for imaging and pathologic findings. Methods are addressed for standardizing reporting of technique, follow-up, complications, and clinical results. As noted in the original document from 2003, adherence to the recommendations will improve the precision of communications in this field, leading to more accurate comparison of technologies and results, and ultimately to improved patient outcomes.

How to set up a successful tumor ablation practice

Tumor ablation services have increased in prevalence across the country and can now be found in modern health care systems of all sizes. These services have become an integral part of the coordinated multidisciplinary approach to patient care that must take place at any oncologic center of excellence. However, building a reputable tumor ablation practice at an institutional level can be a very difficult task as there are many financial, political, and material considerations that must be addressed during the early phases of operation to ensure its success. This article discusses each of these considerations in turn and provides insight into ways to overcome the inherent challenges faced when bringing all of the necessary elements together to create a thriving tumor ablation practice at an institutional level.

Lung cancer ablation: technologies and techniques

The incidence of lung cancers in 2012 is estimated to reach 226,160 new cases, with only a third of patients suitable surgical candidates. Tumor ablation has emerged as an important and efficacious treatment option for nonsurgical lung cancer patients. This localized minimally invasive therapy is best suited for small oligonodular lesions or favorably located metastatic tumors. Radiofrequency ablation has been in use for over a decade, and newer modalities including microwave ablation, cryoablation, and irreversible electroporation have emerged as additional treatment options for patients. Ablation therapies can offer patients and clinicians a repeatable and effective therapy for palliation and, in some cases, cure of thoracic malignancies. This article discusses the available technologies and techniques available for tumor ablation of thoracic malignancies including patient selection, basic aspects of procedure technique, imaging follow-up, treatment outcomes, and comparisons between various therapies.

Percutaneous ablation for small renal masses-imaging follow-up

Image-guided percutaneous thermal ablation is a safe and effective nephron-sparing alternative to surgical resection for the treatment of small renal tumors. Assessment of treatment efficacy relies heavily on interval follow-up imaging after treatment. Contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI) both play a pivotal role in evaluating the treatment zone, identifying residual tumor, and detecting early and delayed procedure-related complications. This article discusses a surveillance imaging protocol for patients who undergo percutaneous thermal ablation of renal tumors, and also illustrates the typical appearances of both successfully treated tumors and residual disease on contrast-enhanced CT or MRI. In addition, it discusses the imaging appearance of potential early and delayed treatment-related complications to facilitate their prompt detection and management.

Image-guided tumor ablation: standardization of terminology and reporting criteria--a 10-year update

Image-guided tumor ablation has become a well-established hallmark of local cancer therapy. The breadth of options available in this growing field increases the need for standardization of terminology and reporting criteria to facilitate effective communication of ideas and appropriate comparison among treatments that use different technologies, such as chemical (eg, ethanol or acetic acid) ablation, thermal therapies (eg, radiofrequency, laser, microwave, focused ultrasound, and cryoablation) and newer ablative modalities such as irreversible electroporation. This updated consensus document provides a framework that will facilitate the clearest communication among investigators regarding ablative technologies. An appropriate vehicle is proposed for reporting the various aspects of image-guided ablation therapy including classification of therapies, procedure terms, descriptors of imaging guidance, and terminology for imaging and pathologic findings. Methods are addressed for standardizing reporting of technique, follow-up, complications, and clinical results. As noted in the original document from 2003, adherence to the recommendations will improve the precision of communications in this field, leading to more accurate comparison of technologies and results, and ultimately to improved patient outcomes. Online supplemental material is available for this article .

Thermal ablation of tumours: biological mechanisms and advances in therapy

Minimally invasive thermal ablation of tumours has become common since the advent of modern imaging. From the ablation of small, unresectable tumours to experimental therapies, percutaneous radiofrequency ablation, microwave ablation, cryoablation and irreversible electroporation have an increasing role in the treatment of solid neoplasms. This Opinion article examines the mechanisms of tumour cell death that are induced by the most common thermoablative techniques and discusses the rapidly developing areas of research in the field, including combinatorial ablation and immunotherapy, synergy with conventional chemotherapy and radiation, and the development of a new ablation modality in irreversible electroporation.

Microwave ablation devices for interventional oncology

Microwave ablation is one of the several options in the ablation armamentarium for the treatment of malignancy, offering several potential benefits when compared with other ablation, radiation, surgical and medical treatment modalities. The basic microwave system consists of the generator, power distribution system and antennas. Often under image (computed tomography or ultrasound) guidance, a needle-like antenna is inserted percutaneously into the tumor, where local microwave electromagnetic radiation is emitted from the probe's active tip, producing frictional tissue heating, capable of causing cell death by coagulation necrosis. Half of the microwave ablation systems use a 915 MHz generator and the other half use a 2450 MHz generator. To date, there are no completed clinical trials comparing microwave devices head-to-head. Prospective comparisons of microwave technology with other treatment alternatives, as well as head-to-head comparison with each microwave device, is needed if this promising field will garner more widespread support and use in the oncology community.

Ask the Experts: How important is radiofrequency ablation in lung cancer?

Terrance T Healey is the director of Thoracic Radiology at Rhode Island Hospital (RI, USA) and an Assistant Professor of Diagnostic Imaging at the Alpert Medical School of Brown University (RI, USA). Healey received his medical degree from the combined Dartmouth Medical School–Brown Medical School Program in 2003, completed his residency in radiology at Brown University in 2008 and a thoracic radiology fellowship at the Massachusetts General Hospital (MA, USA) in 2009. He joined the faculty staff at Rhode Island Hospital and Brown University in 2009.

Robert C Ward is one of the chief residents within the Department of Diagnostic Imaging at Rhode Island Hospital (RI, USA) and the Alpert Medical School of Brown University (RI, USA). Ward received his medical degree from the George Washington University (Washington, DC, USA) in 2010.

Damian E Dupuy is the director of Tumor Ablation at Rhode Island Hospital (RI, USA) and a Professor of Diagnostic Imaging at The Warren Alpert Medical School of Brown University (RI, USA). Dupuy received his medical degree from the University of Massachusetts Medical School (MA, USA) in 1988 and completed his residency in radiology at The New England Deaconess Hospital (MA, USA) and Harvard Medical School (MA, USA) in 1993. After residency, Dupuy joined the staff at Massachusetts General Hospital (MA, USA) where he worked in the Abdominal Imaging and Bone and Joint Divisions. In 1997, Dupuy joined the Department of Diagnostic Imaging at Rhode Island Hospital and Brown University. Dupuy, a pioneer in the use of image-guided ablation, helped broaden clinical applications to successfully combat cancer involving the kidney, liver, lung, head and neck, adrenal gland and skeleton. Other newer technologies, such as percutaneous microwave ablation, cryoablation and combination therapies using radiofrequency ablation with external radiation or brachytherapy, have been pioneered by Dupuy who has been the principal investigator of two National Cancer Institute-funded multicenter trials. Dupuy has received national awards for research and teaching from the American College of Radiology Imaging Network and the Radiological Society of North America where he is currently the Chair of the Interventional Oncology Symposium featured at the Annual Meeting of the Radiological Society of North America and a Fellow of the American College of Radiology. Dupuy is a member of the Radiological Society of North America, The New England Roentgen Ray Society, The American College of Radiology, Rhode Island Radiological Society and the Society of Interventional Radiology. Dupuy has published over 150 publications and given over 120 invited lectures in the field of radiology and image-guided ablation, both nationally and internationally.

Solitary painful osseous metastases: correlation of imaging features with pain palliation after radiofrequency ablation--a multicenter american college of radiology imaging network study

PURPOSE

To identify the correlation of pre- and postablation imaging features with pain relief, pain intensity, and patient mood after radiofrequency (RF) ablation of solitary painful osseous metastases.

MATERIALS AND METHODS

This prospective, multicenter group trial was approved by each institutional review board. Participants were enrolled between November 1, 2001, and April 6, 2006. Written informed consent was obtained from all subjects, and patient confidentiality protocols were followed in compliance with HIPAA. Computed tomography (CT)-guided RF ablation and contrast material-enhanced 1-month follow-up CT and/or magnetic resonance imaging were performed in 49 subjects (24 men, 25 women; age range, 34-83 years) with a confirmed malignant solitary bone lesion of maximum dimension of 8 cm or smaller that was causing intractable pain. Pain intensity and patient mood were measured before and after RF ablation. Tumor imaging features were recorded. Unadjusted and adjusted linear mixed-effects models, with a random intercept for each subject, were used to model patient mood, pain relief, and pain intensity scores at three times after ablation as a function of each tumor characteristic.

RESULTS

Decreased postablation tumor pain correlated with preablation tumor volume (P = .02) and pathologic fracture (P = .01), while pain relief correlated with pathologic fracture (P = .03) and percentage of bone-tumor interface (BTI) ablated (P = .02). Conversely, presence of an irregular rim after ablation (P = .02) and rim thickness (P = .01) correlated with increased pain. There was no evidence in this study that RF ablation of larger tumor percentage or larger volume leads to better pain relief or decreased pain (P > .05).

CONCLUSION

Existing pathologic fracture and smaller tumor size appear to be predictive parameters of success when selecting patients for palliative RF ablation of painful solitary osseous metastases. Successful palliation also appears to be related to the percentage of BTI ablated.

Cost and effectiveness of radiofrequency ablation versus limited surgical resection for stage I non-small-cell lung cancer in elderly patients: is less more?

PURPOSE

To retrospectively evaluate cost and mortality in 84 patients older than 65 years of age with stage IA or IB non-small-cell lung cancer treated with radiofrequency (RF) ablation or limited surgical resection (ie, wedge resection or segmentectomy) from the perspective of the payer, Medicare.

MATERIALS AND METHODS

From August 2000 to November 2009, 56 patients were treated with RF ablation and 28 with surgery who met the inclusion criteria. Patient health histories and billing charges from initial treatment to the study endpoint were collected. Charges were converted to 2009 Medicare reimbursement fees and cumulated by month. Time-event data were analyzed by using the Kaplan-Meier method. Survival functions and median survival estimates were reported with standard errors. Patient cohorts' survival functions were compared based on the Wilcoxon weighted χ(2) statistic.

RESULTS

Group demographics were comparable with the exception of age, with patients treated with RF ablation an average of 4 years older (95% confidence interval, 0.85-6.76). The overall mortality rate was lower in patients treated with surgery than in those treated with RF ablation (χ(2) = 8.0225, P = .0046), with a median cost per month lived for RF ablation recipients of $620.74, versus $1,195.92 for those treated with surgery (P = .0002, Wilcoxon rank-sum test).

CONCLUSIONS

Patients treated with surgery showed a significant increase in survival; however, those treated with RF ablation were significantly older. For patients who are not surgical candidates, RF ablation provides an alternative treatment option at a significantly lower cost.

Rib fractures after percutaneous radiofrequency and microwave ablation of lung tumors: incidence and relevance

PURPOSE

To retrospectively identify the incidence and probable risk factors for rib fractures after percutaneous radiofrequency ablation (RFA) and microwave ablation (MWA) of neoplasms in the lung and to identify complications related to these fractures.

MATERIALS AND METHODS

Institutional review board approval was obtained for this HIPAA-compliant retrospective study. Study population was 163 patients treated with MWA and/or RFA for 195 lung neoplasms between February 2004 and April 2010. Follow-up computed tomographic images of at least 3 months were retrospectively reviewed by board-certified radiologists to determine the presence of rib fractures. Generalized estimating equations were performed to assess the effect that patient demographics, tumor characteristics, treatment parameters, and ablation zone characteristics had on development of rib fractures. Kaplan-Meier curve was used to estimate patients' probability of rib fracture after ablation as a function of time. Clinical parameters (ie, pain in ribs or chest, organ damage caused by fractured rib) were evaluated for patients with confirmed fracture.

RESULTS

Rib fractures in proximity to the ablation zone were found in 13.5% (22 of 163) of patients. Estimated probability of fracture was 9% at 1 year and 22% at 3 years. Women were more likely than were men to develop fracture after ablation (P = .041). Patients with tumors closer to the chest wall were more likely to develop fracture (P = .0009), as were patients with ablation zones that involved visceral pleura (P = .039). No patients with rib fractures that were apparently induced by RFA and MWA had organ injury or damage related to fracture, and 9.1% (2 of 22) of patients reported mild pain.

CONCLUSION

Rib fractures were present in 13.5% of patients after percutaneous RFA and MWA of lung neoplasms. Patients who had ablations performed close to the chest wall should be monitored for rib fractures.

Solid renal masses: effectiveness and safety of image-guided percutaneous radiofrequency ablation

With increasing emphasis on minimally invasive nephron-sparing techniques for treatment of renal tumors, image-guided percutaneous radiofrequency ablation (RFA) has emerged as a safe and effective method of tumor eradication that may be performed on an outpatient basis, with relatively low morbidity and mortality. This review addresses the clinical and technical considerations, risks, complications, and currently reported efficacy data pertaining to RFA of renal tumors, as well as the standardized approach to treatment and follow-up currently used in our practice.

Treatment of stage I lung cancer in high-risk and inoperable patients: comparison of prospective clinical trials using stereotactic body radiotherapy (RTOG 0236), sublobar resection (ACOSOG Z4032), and radiofrequency ablation (ACOSOG Z4033)

OBJECTIVE

The purpose of the present study was to compare the selection criteria and short-term outcomes among 3 prospective clinical trials using stereotactic body radiotherapy (Radiation Therapy Oncology Group [RTOG] trial 0236), sublobar resection (American College of Surgeons Oncology Group [ACOSOG] trial Z4032), and radiofrequency ablation (ACOSOG trial Z4033).

METHODS

The selection criteria and outcomes were compared among RTOG 0236 (n = 55), ACOSOG Z4032 (n = 211), and ACOSOG Z4033 (n = 51). Age, Eastern Cooperative Oncology Group performance status, percentage of predicted forced expiratory volume in 1 second, and percentage of predicted carbon monoxide diffusing capacity of the lung were used to perform a propensity-matched analysis among patients with clinical stage 1A in RTOG 0236 and ACOSOG Z4032.

RESULTS

The patients in ACOSOG Z4033 undergoing radiofrequency ablation were older (75.6 ± 7.5 years) than those in RTOG 0236 (72.5 ± 8.8 years) and ACOSOG Z4032 (70.2 ± 8.5 years; P = .0003). The pretreatment percentage of predicted forced expiratory volume in 1 second was 61.3% ± 33.4% for RTOG 0236, 53.8% ± 19.6% for ACOSOG Z4032, and 48.8% ± 20.3% for ACOSOG Z4033 (P = .15). The pretreatment percentage of predicted carbon monoxide diffusing capacity of the lung was 61.6% ± 30.2% for RTOG 0236, 46.4% ± 15.6% for ACOSOG Z4032, and 43.7% ± 18.0% for ACOSOG Z4033 (P = .001). The overall 90-day mortality for stereotactic body radiotherapy, surgery, and radiofrequency ablation was 0%, 2.4% (5/211), and 2.0% (1/51), respectively (P = .5). Overall, the unadjusted 30-day grade 3+ adverse events were more common with surgery than with stereotactic body radiotherapy (28% vs 9.1%, P = .004), although no difference was between the 2 groups at 90 days. Among the patients with clinical stage IA in ACOSOG Z4032, 29.3% had a more advanced pathologic stage at surgery. A propensity-matched comparison showed no difference between stereotactic body radiotherapy and surgery for 30-day grade 3+ adverse events (odds ratio, 2.37; 95% confidence interval, 0.75-9.90; P = .18).

CONCLUSIONS

Among appropriately matched patients, no difference was seen in early morbidity between sublobar resection and stereotactic body radiotherapy. These results underscore the need for a randomized trial to delineate the relative survival benefit of each modality and to help stratify patients considered high risk.

Percutaneous image-guided cryoablation of painful metastases involving bone: multicenter trial

BACKGROUND

This study sought to describe the results of a single-arm multicenter clinical trial using image-guided percutaneous cryoablation for the palliation of painful metastatic tumors involving bone.

METHODS

Over a 44-month period, 61 adult patients with 1 or 2 painful bone metastases with a score of 4 or more on a scale of 0 to 10 (≥4/10) worst pain in a 24-hour period who had failed or refused conventional treatment were treated with percutaneous image-guided cryoablation. Patient pain and quality of life was measured using the Brief Pain Inventory prior to treatment, 1 and 4 days after the procedure, weekly for 4 weeks, and every 2 weeks thereafter for a total of 6 months. Patient analgesic use was also recorded at these same follow-up intervals. Complications were monitored. Analysis of the primary endpoint was undertaken via paired comparison procedures.

RESULTS

A total of 69 treated tumors ranged in size from 1 to 11 cm. Prior to cryoablation, the mean score for worst pain in a 24-hour period was 7.1/10 with a range of 4/10 to 10/10. At 1, 4, 8, and 24 weeks after treatment, the mean score for worst pain in a 24-hour period decreased to 5.1/10 (P < .0001), 4.0/10 (P < .0001), 3.6/10 (P < .0001), and 1.4/10 (P < .0001), respectively. One of 61 (2%) patients had a major complication with osteomyelitis at the site of ablation.

CONCLUSIONS

Percutaneous cryoablation is a safe, effective, and durable method for palliation of pain due to metastatic disease involving bone.

Current status of thermal ablation treatments for lung malignancies

About 75% of lung cancer patients are not surgical candidates, either due to advanced disease or medical comorbidities. Furthermore, conventional treatments that can be offered to these patients are beneficial only to a small percentage of them. Thermal ablation is a minimally invasive treatment that is commonly used in this group of patients, and which has shown promising results. Currently, the most widely used ablation techniques in the treatment of lung malignancies are radiofrequency ablation (RFA), microwave ablation, and cryoablation. Although the most studied technique is RFA, recent studies with microwave ablation and cryoablation have shown some advantages over RFA. This article reviews the application of thermal ablation in the thorax, including patient selection, basic aspects of procedure technique, imaging follow-up, treatment outcomes, and comparison of ablation techniques.

Image-guided thermal ablation of lung malignancies

Primary and secondary lung malignancies are often treated with surgery. Many patients are poor surgical candidates owing to advanced age or medical comorbidities. Alternatives to surgery for localized disease include radiation therapy and the newer treatments known as image-guided thermal ablation. Image-guided thermal ablation involves the use of needlelike applicators that are placed directly into tumors by using imaging guidance. Tumors are destroyed by the application of either intense heat or cold. The specific ablative modalities of radiofrequency ablation, microwave ablation, laser ablation, and cryoablation are reviewed with respect to the various clinical indications for treatment of both primary and secondary lung malignancies.

Intraoperative microwave ablation of pulmonary malignancies with tumor permittivity feedback control: ablation and resection study in 10 consecutive patients

PURPOSE

To determine histologic changes induced by microwave ablation (MWA) in patients with pulmonary malignancy by using an ablation system with tumor permittivity feedback control, enabling real-time modulation of energy power and frequency.

MATERIALS AND METHODS

Institutional review board approval and patient informed consent were obtained for this prospective HIPAA-complaint ablation and resection study. Between March 2009 and January 2010, 10 patients (four women, six men; mean age, 71 years; age range, 52-82 years) underwent intraoperative MWA of pulmonary malignancies. Power (10-32 W) and frequency (908-928 MHz) were continuously adjusted by the generator to maintain a temperature of 110°-120°C at the 14-gauge antenna tip for one 10-minute application. After testing for an air leak, tumors were resected surgically. Gross inspection, slicing, and hematoxylin-eosin (10 specimens) and nicotinamide adenine dinucleotide (six specimens) staining were performed.

RESULTS

Tumors included adenocarcinomas (n = 5), squamous cell carcinomas (n = 3), and metastases from endometrial (n = 1) and colorectal (n = 1) primary carcinomas. Mean maximum tumor diameter was 2.4 cm (range, 0.9-5.0 cm), and mean maximum volume was 8.6 cm(3) (range, 0.5-52.7 cm(3)). One air leak was detected. Five of 10 specimens were grossly measurable, revealing a mean maximum ablation zone diameter of 4.8 cm (range, 3.0-6.5 cm) and a mean maximum ablation zone volume of 15.1 cm(3) (range, 7.3-25.1 cm(3)). At hematoxylin-eosin staining, coagulation necrosis was observed in all ablation zones, extended into the normal lung in nine of 10 specimens, and up to blood vessel walls without evidence of vessel (>4 mm) thrombosis. Nicotinamide adenine dinucleotide staining enabled confirmation of no viability within ablation zones extending into normal lung in five of six specimens.

CONCLUSION

MWA with tumor permittivity feedback control results in cytotoxic intratumoral temperatures and extension of ablation zones into aerated peritumoral pulmonary parenchyma, possibly forming the equivalent of an oncologic resection margin.