Microwave liver ablation: influence of hepatic vein size on heat-sink effect in a porcine model

Determining the Relationship between Delivery Parameters and Ablation Distribution for Novel Gel Ethanol Percutaneous Therapy in Ex Vivo Swine Liver

Ethyl cellulose-ethanol (ECE) is emerging as a promising formulation for ablative injections, with more controllable injection distributions than those from traditional liquid ethanol. This study evaluates the influence of salient injection parameters on forces needed for infusion, depot volume, retention, and shape in a large animal model relevant to human applications. Experiments were conducted to investigate how infusion volume (0.5 mL to 2.5 mL), ECE concentration (6% or 12%), needle gauge (22 G or 27 G), and infusion rate (10 mL/h) impacted the force of infusion into air using a load cell. These parameters, with the addition of manual infusion, were investigated to elucidate their influence on depot volume, retention, and shape (aspect ratio), measured using CT imaging, in an ex vivo swine liver model. Force during injection increased significantly for 12% compared to 6% ECE and for 27 G needles compared to 22 G. Force variability increased with higher ECE concentration and smaller needle diameter. As infusion volume increased, 12% ECE achieved superior depot volume compared to 6% ECE. For all infusion volumes, 12% ECE achieved superior retention compared to 6% ECE. Needle gauge and infusion rate had little influence on the observed depot volume or retention; however, the smaller needles resulted in higher variability in depot shape for 12% ECE. These results help us understand the multivariate nature of injection performance, informing injection protocol designs for ablations using gel ethanol and infusion, with volumes relevant to human applications.

Safety and local efficacy of computed tomography-guided microwave ablation for treating early-stage non-small cell lung cancer adjacent to bronchovascular bundles

OBJECTIVES

To retrospectively evaluate the safety and efficacy of computed tomography (CT)-guided percutaneous microwave ablation in treating early-stage non-small cell lung cancer (NSCLC) adjacent to bronchovascular bundles.

METHODS

Two hundred and thirty-one patients with early-stage NSCLC who underwent CT-guided microwave ablation of the tumor were included for analysis. Among these, 66 lesions were located adjacent to the bronchovascular bundle. Achievement of the specific ablation range (defined as the ablation zone encompassing the tumor and the adjacent vessel) was assessed after ablation. Complications and tumor progression after treatment were examined and compared between the bronchovascular bundle and non-bronchovascular bundle groups.

RESULTS

A total of 231 patients were included. Overall, 1-, 2-, and 3-year local progression-free survival (LPFS) was 77.4%, 70.5%, and 63.8%, respectively. Bronchovascular bundle proximity, pure-solid tumor, tumor size, and ablation margin < 5 mm were independent risk factors for local progression in multivariate analysis. In the bronchovascular bundle group, the 1-, 2- and 3-year LPFS rates were 63.0%, 50.7%, and 43.4%, respectively; vessel proximity and specific ablation range failure were independent risk factors for local progression. Overall survival in the entire cohort was 93.0% at 1 year, 76.1% at 2 years, and 55.0% at 3 years. The incidence of postoperative complications did not significantly differ between the two groups (p > 0.05). The most common complication was pneumothorax. Severe hemoptysis did not occur.

CONCLUSION

Tumor location near the bronchovascular bundles was a significant risk factor for local progression after microwave ablation. Achieving a specific ablation range may increase LPFS for these lesions.

CLINICAL RELEVANCE STATEMENT

Achieving the specific ablation range may improve local efficacy for early-stage non-small cell lung cancer located adjacent to the bronchovascular bundle.

KEY POINTS

• Local efficacy of percutaneous microwave ablation in treating early-stage non-small cell lung cancer was affected by bronchovascular bundle proximity. • Achieving the specific ablation range may improve local efficacy for lesions located adjacent to the bronchovascular bundle.

Technical and Clinical Outcomes of Laparoscopic-Laparotomic Hepatocellular Carcinoma Thermal Ablation with Microwave Technology: Case Series and Review of Literature

PURPOSE

To evaluate technical and clinical outcomes of intraoperative (laparoscopic/laparotomic) microwave ablation on HCC.

MATERIALS AND METHODS

This is a retrospective single-center study evaluating consecutive patients treated for very early/early-stage HCC with intraoperative microwave ablation from 1 July 2017 to 30 June 2023. In these patients, a percutaneous US-guided approach was excluded due to the nodule's suboptimal visibility or harmful location and liver resection for a deep position or adherences. Data about the clinical stage, surgical approach, liver pathology and nodules characteristics, technical success, complications, and follow-up were collected. Technical success was intended as the absence of locoregional persistence at follow-up CT/MRI controls.

RESULTS

A total of 36 cirrhotic patients (M:F = 30:6, median age 67 years) were enrolled; 18/36 (50%) had a single nodule, 13/36 (36%) had two, 4/36 had three (11%), and 1/36 had four (3%). Among the patients, 24 (67%) were treated with laparoscopy, and 12/36 (33%) with a laparotomic approach. Sixty HCCs of 16.5 mm (6-50 mm) were treated for 7 min (2-30 min) with 100 W of power. A total of 55 nodules (92%) were treated successfully and showed no residual enhancement at the first postoperative follow-up; the other 5/60 (8%) underwent chemo/radioembolization. There was one complication (3%): a biliary fistula treated with percutaneous drainage and glue embolization. The average hospital stay was 3.5 days (1-51 days), and patients were followed up on average for 238 days (13-1792 days). During follow-up, 5/36 patients (14%) underwent liver transplantation, 1/36 (2%) died during hospitalization and 1 after discharge.

CONCLUSIONS

Laparoscopic/laparotomic intraoperative HCC MW ablation is feasible in patients unsuitable for percutaneous approach or hepatic resection, with rare complications and with good technical and clinical outcomes.

Heat sink effects in thyroid bipolar radiofrequency ablation: an ex vivo study

The study aimed to investigate heat sink effects in radiofrequency ablation (RFA) under thyroid-specific conditions. In an ex vivo model, bovine thyroid lobes were ablated using bipolar RFA with 2.0 kJ energy input at a power level set to 10 W (n = 35) and 25 W (n = 35). Glass vessels (3.0 mm outer diameter) placed within the ablation zone were used to deliver tissue perfusion at various flow rates (0, 0.25, 0.5, 1, 5, 10, 20 ml/min). Temperature was measured in the proximity of the vessel (Tv) and in the non-perfused contralateral region of the ablation zone (Tc), at equal distances to the ablation electrode (d = 8 mm). Maximum temperature within the perfused zone was significantly lowered with Tv ranging from 54.1 ± 1.5 °C (20 ml/min) to 56.9 ± 1.5 °C (0.25 ml/min), compared to Tc from 63.2 ± 3.5 °C (20 ml/min) to 63.2 ± 2.6 °C (0.25 ml/min) (10 W group). The cross-sectional ablation zone area decreased with increasing flow rates from 184 ± 12 mm2 (0 ml/min) to 141 ± 20 mm2 (20 ml/min) at 10 W, and from 207 ± 22 mm2 (0 ml/min) to 158 ± 31 mm2 (20 ml/min) in the 25 W group. Significant heat sink effects were observed under thyroid-specific conditions even at flow rates ≤ 1 ml/min. In thyroid nodules with prominent vasculature, heat dissipation through perfusion may therefore result in clinically relevant limitations to ablation efficacy.

Intratumoral perfusion may affect microwave ablation area of hepatocellular carcinoma

OBJECTIVES

We aimed to evaluate the effect of intratumoral perfusion on microwave ablation (MWA) area in hepatocellular carcinoma (HCC).

METHODS

Patients who underwent curative MWA for HCC between October 2013 and May 2015 were enrolled. Three days before MWA, contrast-enhanced ultrasound (CEUS) was performed to illustrate the perfusion characteristics of the target lesion. Using the Sonoliver quantification software, time-intensity curves of dynamic CEUS were obtained, and quantitative parameters were extracted. Two microwave antennae were inserted into the center of the tumor and MWA was performed with a continuous power output of 50 W for 5 min. A second CEUS was performed to measure the size of the ablated region. Thereafter, an additional MWA procedure was performed until complete ablation with a 5-10-mm safety margin was achieved.

RESULTS

A total of 38 patients who underwent curative MWA for 39 HCC nodules were enrolled. The mean age was 57 years (34-80 years), and the median maximum diameter of the HCC was 3.4 cm (interquartile range, 2-6.8 cm). Time-intensity curves were obtained and the area under the curve (AUC) was selected as a parameter for intratumoral perfusion. The AUC was inversely and linearly correlated with the size of the MWA area, including long- and short-axis diameters and ablation volume. A 1,000-dB·s change in the AUC produced an average change of 1.17 ± 0.44 mm, 0.725 ± 0.355 mm, and 2.4995 ± 0.6575 cm³ in the long- and short-axis diameters and ablation volume, respectively.

CONCLUSIONS

The intratumoral perfusion of HCC was inversely correlated with MWA area size.

A Comparison of Microwave Ablation and Cryoablation for the Treatment of Renal Cell Carcinoma: A Systematic Literature Review and Meta-analysis

OBJECTIVE

To conduct a systematic review and meta-analysis comparing microwave ablation (MWA) and cryoablation for renal cell carcinoma (RCC).

METHODS

The systematic search was performed in MEDLINE, Embase, and Cochrane databases. Studies published in English from January 2006 to February 2022 that assessed adults with primary RCC who received MWA or cryoablation were included. Study arms from RCTs, comparative observational, and single-arm studies were eligible. The outcomes included local tumor recurrence (LTR), overall survival, disease-free survival, overall/major complications, procedure/ablation time, 1- to 3-month primary technique efficacy, and technical success. Single-arm meta-analyses were performed using the random effects model. Sensitivity analyses excluding low-quality studies assessed using the MINORs scale were performed. Univariable and multivariable examined the effects of prognostic factors.

RESULTS

Baseline characteristics were similar between groups and mean tumor size for MWA and cryoablation were 2.74 and 2.69 cm. Single-arm meta-analyses were similar for LTR and secondary outcomes between cryoablation and MWA. Ablation time was significantly shorter with MWA than with cryoablation (meta-regression weighted mean difference 24.55 minutes, 95% confidence interval -31.71, -17.38, P < .0001). One-year LTR was significantly lower with MWA than cryoablation (odds ratio 0.33, 95% confidence interval 0.10-0.93, P = .04). There were no significant differences for other outcomes.

CONCLUSION

MWA provides significantly improved 1-year LTR and ablation time compared with cryoablation for patients with RCC. Other outcomes appeared similar or favorable for MWA; however, results were not statistically significant. MWA of primary RCC is as safe and effective as cryoablation, which should be confirmed with future comparative studies.

Unresectable Intermediate-Size (3-5 cm) Colorectal Liver Metastases: Stereotactic Ablative Body Radiotherapy Versus Microwave Ablation (COLLISION-XL): Protocol of a Phase II/III Multicentre Randomized Controlled Trial

BACKGROUND

Although microwave ablation (MWA) has a low complication rate and good efficacy for small-size (≤ 3 cm) colorectal liver metastases (CRLM), local control decreases with increasing size. Stereotactic body radiotherapy (SBRT) is gaining interest as a potential means to treat intermediate-size CRLM and might be less susceptible to increasing volume. The objective of this study is to compare the efficacy of MWA to SBRT in patients with unresectable, intermediate-size (3-5 cm) CRLM.

METHODS

In this two-arm, multicentre phase II/ III randomized controlled trial, 68 patients with 1-3 unresectable, intermediate-size CRLM suitable for both MWA and SBRT, will be included. Patients will be treated with MWA or SBRT as randomised. The Primary endpoint is local tumour progression-free survival (LTPFS) at 1 year (intention-to-treat analysis). Main secondary endpoints are overall survival, overall and distant progression-free survival (DPFS), local control (LC) and procedural morbidity and mortality and assessment of pain and quality of life.

DISCUSSION

Current guidelines lack clear recommendations for the local treatment of liver only intermediate-size, unresectable CRLM and studies comparing curative intent SBRT and thermal ablation are scarce. Although safety and feasibility to eradicate tumours ≤ 5 cm have been established, both techniques suffer from lower LTPFS and LC rates for larger-size tumours. For the treatment of unresectable intermediate-size CRLM clinical equipoise has been reached. We have designed a two-armed phase II/ III randomized controlled trial directly comparing SBRT to MWA for unresectable CRLM 3-5 cm.

LEVEL OF EVIDENCE

Level 1, phase II/ III Randomized controlled trial.

TRIAL REGISTRATION

NCT04081168, September 9th 2019.

Ablative strategies for recurrent hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the most common primary liver cancer and is the fifth leading cause of cancer death worldwide and the third leading cause of all diseases worldwide. Liver transplantation, surgical resection and ablation are the three main curative treatments for HCC. Liver transplantation is the optimal treatment option for HCC, but its usage is limited by the shortage of liver sources. Surgical resection is considered the first choice for early-stage HCC, but it does not apply to patients with poor liver function. Therefore, more and more doctors choose ablation for HCC. However, intrahepatic recurrence occurs in up to 70% patients within 5 years after initial treatment. For patients with oligo recurrence after primary treatment, repeated resection and local ablation are both alternative. Only 20% patients with recurrent HCC (rHCC) indicate repeated surgical resection because of limitations in liver function, tumor location and intraperitoneal adhesions. Local ablation has become an option for the waiting period when liver transplantation is unavailable. For patients with intrahepatic recurrence after liver transplantation, local ablation can reduce the tumor burden and prepare them for liver transplantation. This review systematically describes the various ablation treatments for rHCC, including radiofrequency ablation, microwave ablation, laser ablation, high-intensity focused ultrasound ablation, cryablation, irreversible electroporation, percutaneous ethanol injection, and the combination of ablation and other treatment modalities.

An update on locoregional percutaneous treatment technologies in colorectal cancer liver metastatic disease

INTRODUCTION

Liver-dominant metastatic colorectal cancer is noted in approximately 20%-35% of the patients. Systemic chemotherapy remains the first-line treatment for mCRC, but the prognosis is poor due to liver failure. Novel minimally invasive technologies have enabled the optimization of locoregional treatment options.

AREAS COVERED

This is a comprehensive review of novel locoregional treatment technologies, both percutaneous ablation and transcatheter arterial treatments, which can be used to decrease hepatic disease progression in patients with mCRC. Trans-arterial radioembolization is the most recently developed locoregional treatment for metastatic liver disease, and robust evidence has been accumulated over the past years.

EXPERT OPINION

Image-guided techniques, endovascular and ablative, have gained wide acceptance for the treatment of liver malignancies, in selected patients with non-resectable disease. The optimization of dosimetry and microsphere technological advancement will certainly upgrade the role of liver radioembolization segmentectomy or lobectomy in the upcoming years, due to its curative intent. Also, ablative interventions provide local curative intent, offering significant and sustained local tumor control. Standardization protocols in terms of predictability and reliability using immediate treatment assessment and ablation zone software could further ameliorate clinical outcomes.

Microwave ablation for the control of bleeding from disintegrated mammary tumours in two dogs

A 16-year-old intact female Miniature Dachshund (dog 1) and a 13-year-old intact female American Cocker Spaniel (dog 2) presented with a chief complaint of bleeding from a mammary gland tumour ulceration. Dog 1 was transferred to hospital from a local hospital in a haemorrhagic shock state with uncontrolled continuous bleeding. Thoracic radiographs revealed multiple nodular shadows suspected to be pulmonary metastasis. Dog 2 presented with intermittent bleeding from a mass lesion in the right fifth mammary gland. Due to high anaesthetic risk secondary to severe mitral valve insufficiency (ASA status III), the owner declined surgical excision of the tumour. Therefore, microwave ablation (MWA) under local anaesthesia was chosen in order to achieve adequate haemostasis. Both dogs received local anaesthesia around the bleeding mass lesion, and the disintegrated site was microwave-ablated; dog 1 underwent MWA after blood transfusion to improve the haemorrhagic shock. The ablation site was protected using a non-adhesive dressing. Scarring of the ulcerated site led to complete haemostasis in both cases. Dog 1 underwent tumorectomy on the 31st hospital day to prevent rebleeding; histopathology results were consistent with mammary adenocarcinoma with the ablation site covered by a capsule structure. To the authors' knowledge, this is the first case report describing the use of MWA to stop bleeding from mammary tumours in veterinary medicine. MWA is a feasible and potentially effective palliative treatment modality to stop bleeding from disintegrated mammary tumours in dogs under local anaesthesia.

Dynamic Contrast-Enhanced MR Imaging Evaluation of Perfusional Changes and Ablation Zone Size after Combination Embolization and Ablation Therapy

PURPOSE

The objectives of this study were to assess the utility of dynamic contrast-enhanced magnetic resonance (MR) imaging in quantifying parenchymal perfusional changes after embolization and to characterize the association between pharmacokinetic (PK) parameters and final microwave ablation volume.

MATERIALS AND METHODS

PK parameters from dynamic contrast-enhanced MR imaging were used to quantify perfusional changes in the liver after transarterial embolization of the right or left lobe in a swine liver model (n = 5). Each animal subject subsequently underwent microwave ablation (60 W for 5 minutes) of the embolized and nonembolized liver lobes. Changes in PK parameters from dynamic contrast-enhanced MR imaging were correlated with their respective final microwave ablation volumes in each liver lobe.

RESULTS

Microwave ablation volumes of embolized liver lobes were significantly larger than those of nonembolized liver lobes (28.0 mL ± 6.2 vs 15.1 mL ± 5.2, P < .001). PK perfusion parameters were significantly lower in embolized liver lobes than in nonembolized liver lobes (K^trans = 0.69 min^-1 ± 0.15 vs 1.52 min^-1 ± 0.37, P < .001; k_ep = 0.69 min^-1 ± 0.19 vs 1.54 min^-1 ± 0.42, P < .001). There was a moderate but significant correlation between normalized k_ep and ablation volume, with each unit increase in normalized k_ep corresponding to a 9.8-mL decrease in ablation volume (P = .035).

CONCLUSIONS

PK-derived parameters from dynamic contrast-enhanced MR imaging can be used to quantify perfusional changes after transarterial embolization and are directly inversely correlated with final ablation volume.

Study of ultrasound-guided percutaneous microwave ablation combined with portal vein embolization for rapid future liver remnant increase of planned hepatectomy

Purpose

To evaluate the efficacy of ultrasound-guided percutaneous microwave ablation (PMA) combined with portal vein embolization (PVE) for planned hepatectomy.

Methods

We retrospectively reviewed data of 18 patients with multiple right liver tumors or hilar tumor of liver invades the surrounding tissue and insufficient future liver remnant (FLR) for hepatectomy from July 2015 to March 2017. Ultrasound-guided PMA was performed by using PMCT cold circulation microwave treatment apparatus. PVE was performed after PMA. The increase of FLR was evaluated by computed tomography (CT) 6-22 days after PVE. The proportion of FLR, increase in the amplitude of FLR, procedure-related complications, perioperative morbidity and mortality, and overall survival (OS) rates, the median survival time were analyzed.

Results

The median volume of FLR before PMA and PVE was 369.7 ml (range: 239.4-493.1 ml). After a median waiting period of 11.5 days (range: 6-22 days), the median volume of FLR was increased to 523.4 ml (range: 355.4-833.3 ml). The changes in FLR before and after PMA and PVE were statistically significant (p<0.001). No serious perioperative complications or mortality were found. After a median follow-up time of 51.0 months (range: 2-54 months), the 6-month, 1-year, 2-year, 3-year and 4-year survival rates were 88.9%, 72.2%, 44.4%, 33.3%, 22.2%, respectively, and the median survival time was 15.0 ± 7.1 months.

Conclusion

PMA combined with PVE increases FLR rapidly, avoids touching malignant tumors, and produces fewer procedure-related complications. It appears safe and efficacious for planned hepatectomy.

Device safety assessment of bronchoscopic microwave ablation of normal swine peripheral lung using robotic-assisted bronchoscopy

INTRODUCTION

The aim of this study was to assess the safety of bronchoscopic microwave ablation (MWA) of peripheral lung parenchyma using the NEUWAVE™ FLEX Microwave Ablation System, and robotic-assisted bronchoscopy (RAB) using the MONARCH™ Platform in a swine model.

METHODS

Computed tomography (CT)-guided RAB MWA was performed in the peripheral lung parenchyma of 17 Yorkshire swine (40-50 kg) and procedural adverse events (AEs) documented. The acute group (day 0, n = 5) received 4 MWAs at 100 W for 1, 3, 5, and 10 min in 4 different lung lobes. Subacute and chronic groups (days 3 and 30, n = 6 each) received one MWA (100 W, 10 min) per animal.

RESULTS

The study was completed without major procedural complications. No postprocedural AEs including death, pneumothorax, bronchopleural fistula, hemothorax, or pleural effusions were observed. No gross or histological findings suggestive of thromboembolism were found in any organ. One 3-Day and one 30-Day swine exhibited coughing that required no medication (minor AEs), and one 30-Day animal required antibiotic medication (major AE) for a suspected lower respiratory tract infection that subsided after two weeks. CT-based volumetric estimates of ablation zones in the acute group increased in an ablation time-dependent (1-10 min) manner, whereas macroscopy-based estimates showed an increasing trend in ablation zone size.

CONCLUSION

The NEUWAVE FLEX and MONARCH devices were safely used to perform single or multiple RAB MWAs. The preclinical procedural safety profile of RAB MWA supports clinical research of both devices to investigate efficacy in select patients with oligometastatic disease or primary NSCLC.

Creation of an Ex Vivo Renal Perfusion Model to Investigate Microwave Ablation

This study hypothesized that an ex vivo renal perfusion model can create smaller microwave ablation (MWA) measurements during perfused states compared with nonperfused states across multiple device settings. Nine bovine kidneys, a fluoroscopic compatible perfusion model, and a commercially-available clinical MWA system were used to perform 72 ablations (36 perfused and 36 nonperfused) at 9 different device settings. Comparing perfused and nonperfused ablations at each device setting, significant differences in volume existed for 6 of 9 settings (P < .05). Collapsed across time settings, the ablation volumes by power were the following (perfused and nonperfused, P value): 60 W, 2.3 cm³ ± 1.0 and 7.2 cm³ ± 2.7, P < .001; 100 W, 5.4 cm³ ± 2.1 and 11.5 cm³ ± 5.6, P < .01; and 140 W, 11.2 cm³ ± 3.7 and 18.7 cm³ ± 6.3, P < .01. Applied power correlated with ablation volume: perfused, 0.021 cm³/W and R = 0.462, P = .004, and nonperfused, 0.029 cm³/W and R = 0.565, P < .001. These results support that an ex vivo perfused organ system can evaluate MWA systems and demonstrate heat sink perfusion effects of decreased ablation size.

Current perspectives on microwave ablation of liver lesions in difficult locations

Microwave ablation (MWA) is becoming the standard of care in treating liver lesions smaller than 3 cm benefiting from a plethora of radiofrequency ablation (RFA) data in the literature. Some of the advantages of MWA compared to RFA are as follows: Faster ablations, more reproducible and predictable heating, better thermal conductivity in different liver tissue environments, and less susceptibility to heat-sink effect. Despite its many advantages, there are still concerns regarding MWA use in high-risk locations such as near portal veins, near the bile ducts, and near the heart. Some centers have historically considered these tumor locations as a contraindication to percutaneous thermal ablation. In this review, we summarize the current data on the safety of MWA of liver tumors in challenging locations. We also discuss several technical tips with examples provided.

Percutaneous ultrasound-guided microwave ablation for treatment of hepatocellular carcinomas in dogs: four cases (2019-2020)

OBJECTIVES

To describe ultrasound-guided microwave ablation as a minimally invasive treatment option for primary or metastatic hepatocellular carcinomas.

METHODS

Four client-owned dogs underwent percutaneous ultrasound-guided microwave ablation of three primary and one metastatic hepatocellular carcinoma, diagnosed on cytology/histopathology. In each case, multiple ultrasound-guided thermal lesions were created in a 10 to 40 minutes ablation at 30 to 35 W. Real-time monitoring was performed using 10 MHz diagnostic ultrasound transducers. The procedures were performed without complication and CT scans or abdominal ultrasounds were repeated immediately after. Patients were discharged on oral analgesia on the same day or 24 hours later.

RESULTS

Hepatocellular carcinomas were successfully ablated, which in some cases resulted in an improvement in clinical signs and laboratory values. The patients were followed up for a time ranging between 39 and 649 days and no evidence of disease progression was found. Three out of four patients are still alive at the time of writing.

CLINICAL SIGNIFICANCE

In these four patients, minimally invasive ultrasound-guided microwave ablation was feasible and resulted in no immediate complications. Regular imaging follow-up is recommended after the procedure and further studies on microwave ablation are warranted to establish its effectiveness in dogs with hepatocellular carcinomas.

Microwave ablation combined with lipiodol-microsphere mixed or conventional transarterial chemoembolization for the treatment of colorectal liver metastases: A retrospective study

PURPOSE

To investigate the clinical outcomes of microwave ablation (MWA) combined with lipiodol-microsphere mixed transarterial chemoembolization (mTACE) or conventional TACE (cTACE) for patients with colorectal liver metastases (CRLM).

MATERIALS AND METHODS

This retrospective study evaluated the medical records of patients with CRLM who underwent MWA combined with mTACE or cTACE from January 2018 to September 2021. The objective response rate (ORR), disease control rate (DCR), progression-free survival (PFS) and overall survival (OS) were evaluated during the follow-up. In addition, prognostic factors affecting survival were analyzed by univariate and multivariate methods.

RESULTS

A total of 79 patients with CRLM were enrolled in the study (MWA-mTACE group, n = 38; MWA-cTACE group, n = 41). The patients who underwent MWA-mTACE had higher DCR (86.8% vs. 65.9%, P = 0.029) and better PFS (median, 8.1 vs. 5.5 months, P = 0.018) than those who underwent MWA-cTACE, but no significant difference was found in ORR (34.2% vs. 22.0%, P = 0.225) and OS (median, 15.7 vs. 13.0 months, P = 0.231). Further univariate and multivariate analyses indicated that MWA-mTACE was an independent positive factor for PFS, and abnormal carcinoembryonic antigen level was a hazard factor for OS. The postoperative laboratory tests and complications in patients who underwent MWA-mTACE were similar to those who underwent MWA-cTACE.

CONCLUSION

Lipiodol-microsphere mixed TACE might be an effective and safe treatment to combine with microwave ablation for patients with colorectal liver metastases.

Advanced CT techniques for hepatic microwave ablation zone monitoring and follow-up

PURPOSE

To evaluate utility of advanced CT techniques including HighlY constrained back-projection and dual-energy CT for intra- and post-procedure hepatic microwave ablation zone monitoring.

METHODS

8 hepatic microwave ablations were performed in 4 adult swine (5 min/65 W). Low-dose routine CECT and dual-energy CT images were obtained every 1 min during ablation. Images were reconstructed ± HYPR. Image quality and dose metrics were collected. 21 MWA were performed in 4 adult swine. Immediate post-procedure CECT was performed in the arterial, portal venous, and delayed phases using both routine and DECT imaging with full-dose weight-based IV contrast dosing. An additional 16 MWA were subsequently performed in 2 adult swine. Immediate post-procedure CT was performed with half-dose IV contrast using routine and DECT. 12 patients (10 M/2F, mean age 62.4 yrs) with 14 hepatic tumors (4 HCC, 10 metastatic lesions) treated with MWA were prospectively imaged with DECT 1 month post-procedure. 120 kV equivalent images were compared to DECT [51 keV, iodine material density]. Image quality and dose metrics were collected.

RESULTS

Gas created during MWA led to high CNR in all intraprocedural CT datasets. Optimal CNRs were noted at 4 min with CNR 6.7, 15.5,15.9, and 21.5 on LD-CECT, LD-CECT + HYPR, DECT, and DECT + HYPR, respectively (p < 0.001). Image quality scores at 4 min were 1.8, 2.8, 2.4, and 3, respectively (p < 0.001). Mean radiation dose (CTDI_vol) was eightfold higher for the DECT series. For swine, post-procedural DECT images (IMD/51 keV) showed improved CNR compared to routine CT at all time points with full and with reduced dose contrast (CNR 4.6, 3.2, and 1.5, respectively, at half-contrast dose, p < 0.001). For human subjects, the 51 keV and IMD images showed higher CNRs (5.8, 4.8 vs 4.0, p < 0.001) and SNRs (3.7, 5.9 vs 2.8). Ablation zone sharpness was improved with DECT (routine 3.0 ± 0.7, DECT 3.5 ± 0.5). Diagnostic confidence was higher with DECT (routine 2.3 ± 0.9, DECT 2.6 ± 0.8). Mean DLP for DECT was 905.7 ± 606 mGy-cm, CTDI_vol 37.5 ± 21.2 mGy, and effective dose 13.6 ± 9.1 mSv, slightly higher than conventional CT series.

CONCLUSION

Advanced CT techniques can improve CT image quality in peri-procedural hepatic microwave ablation zone evaluation.

Ruptured Hepatocellular Carcinoma: What Do Interventional Radiologists Need to Know?

Rupture of HCC (rHCC) is a life-threatening complication of hepatocellular carcinoma (HCC), and rHCC may lead to a high rate of peritoneal dissemination and affect survival negatively. Treatment for rHCC mainly includes emergency surgery, interventional therapies, and palliative treatment. However, the management of rHCC should be carefully evaluated. For patients with severe bleeding, who are not tolerant to open surgery, quick hemostatic methods such as rupture tissue ablation and TAE/TACE can be performed. We described clinical presentation, prognosis, complication, interventional management, and current evidence of rHCC from the perspective of interventional radiologists. Overall, our review summarized that interventional therapies are necessary for most patients with rHCC to achieve hemostasis, even in some patients with Child–Pugh C. Moreover, TAE/TACE followed by staged hepatectomy is a beneficial treatment for rHCC according to current clinical evidence. TAE/TACE is the first choice for most patients with rHCC, and appropriate interventional treatment may provide staged surgery opportunities for those who are not tolerant to emergency surgery to reach an ideal prognosis.

Ruptured Hepatocellular Carcinoma: What Do Interventional Radiologists Need to Know?

Rupture of HCC (rHCC) is a life-threatening complication of hepatocellular carcinoma (HCC), and rHCC may lead to a high rate of peritoneal dissemination and affect survival negatively. Treatment for rHCC mainly includes emergency surgery, interventional therapies, and palliative treatment. However, the management of rHCC should be carefully evaluated. For patients with severe bleeding, who are not tolerant to open surgery, quick hemostatic methods such as rupture tissue ablation and TAE/TACE can be performed. We described clinical presentation, prognosis, complication, interventional management, and current evidence of rHCC from the perspective of interventional radiologists. Overall, our review summarized that interventional therapies are necessary for most patients with rHCC to achieve hemostasis, even in some patients with Child–Pugh C. Moreover, TAE/TACE followed by staged hepatectomy is a beneficial treatment for rHCC according to current clinical evidence. TAE/TACE is the first choice for most patients with rHCC, and appropriate interventional treatment may provide staged surgery opportunities for those who are not tolerant to emergency surgery to reach an ideal prognosis.

Microwave Ablation of Liver, Kidney and Lung Lesions: One-Month Response and Manufacturer’s Charts’ Reliability in Clinical Practice

Microwave ablation systems allow for performing tumoral destruction in oncology. The objective of this study was to assess the early response and reliability of the microwave ablation zone size at one month for liver, kidney and lung lesions, as compared to the manufacturer’s charts. Patients who underwent microwave ablation with the Emprint^TM ablation system for liver, kidney and lung lesions between June 2016 and June 2018 were retrospectively reviewed. Local response and ablation zone size (major, L, and minor, l, axes) were evaluated on the one-month follow-up imaging. Results were compared to the manufacturers’ charts using the Bland–Altman analysis. Fifty-five patients (mean age 68 ± 11 years; 95 lesions) were included. The one-month complete response was 94%. Liver ablations showed a good agreement with subtle, smaller ablation zones (L: −2 ± 5.7 mm; l: −5.2 ± 5.6 mm). Kidney ablations showed a moderate agreement with larger ablations for L (L: 8.69 ± 7.94 mm; l: 0.36 ± 4.77 mm). Lung ablations showed a moderate agreement, with smaller ablations for l (L: −5.45 ± 4.5 mm; l: −9.32 ± 4.72 mm). With 94% of early complete responses, the system showed reliable ablations for liver lesions, but larger ablations for kidney lesions, and smaller for lung lesions.

Microwave Ablation, Radiofrequency Ablation, Irreversible Electroporation, and Stereotactic Ablative Body Radiotherapy for Intermediate Size (3-5 cm) Unresectable Colorectal Liver Metastases: a Systematic Review and Meta-analysis

Purpose of Review

Based on good local control rates and an excellent safety profile, guidelines consider thermal ablation the gold standard to eliminate small unresectable colorectal liver metastases (CRLM). However, efficacy decreases exponentially with increasing tumour size. The preferred treatment for intermediate-size unresectable CRLM remains uncertain. This systematic review and meta-analysis compare safety and efficacy of local ablative treatments for unresectable intermediate-size CRLM (3–5 cm).

Recent Findings

We systematically searched for publications reporting treatment outcomes of unresectable intermediate-size CRLM treated with thermal ablation, irreversible electroporation (IRE) or stereotactic ablative body-radiotherapy (SABR). No comparative studies or randomized trials were found. Literature to assess effectiveness was limited and there was substantial heterogeneity in outcomes and study populations. Per-patient local control ranged 22–90% for all techniques; 22–89% (8 series) for thermal ablation, 44% (1 series) for IRE, and 67–90% (1 series) for SABR depending on radiation dose.

Summary

Focal ablative therapy is safe and can induce long-term disease control, even for intermediate-size CRLM. Although SABR and tumuor-bracketing techniques such as IRE are suggested to be less susceptible to size, evidence to support any claims of superiority of one technique over the other is unsubstantiated by the available evidence. Future prospective comparative studies should address local-tumour-progression-free-survival, local control rate, overall survival, adverse events, and quality-of-life.

Cooling Effects Occur in Hepatic Microwave Ablation At Low Vascular Flow Rates and in Close Proximity to Liver Vessels - Ex Vivo

Background. The impact of vascular cooling effects in hepatic microwave ablation (MWA) is controversially discussed. The objective of this study was a systematic assessment of vascular cooling effects in hepatic MWA ex vivo. Methods. Microwave ablations were performed in fresh porcine liver ex vivo with a temperature-controlled MWA generator (902-928 MHz) and a non-cooled 14-G-antenna. Energy input was set to 9.0 kJ. Hepatic vessels were simulated by glass tubes. Three different vessel diameters (3.0, 5.0, 8.0 mm) and vessel to antenna distances (5, 10, 20 mm) were examined. Vessels were perfused with saline solution at nine different flow rates (0-500 mL/min). Vascular cooling effects were assessed at the largest cross-sectional ablation area. A quantitative and semi-quantitative/morphologic analysis was carried out. Results. 228 ablations were performed. Vascular cooling effects were observed at close (5 mm) and medium (10 mm) antenna to vessel distances (P < .05). Vascular cooling effects occurred around vessels with flow rates ≥1.0 mL/min (P < .05) and a vessel diameter ≥3 mm (P < .05). Higher flow rates did not result in more distinct cooling effects (P > .05). No cooling effects were measured at large (20 mm) antenna to vessel distances (P > .05). Conclusion. Vascular cooling effects occur in hepatic MWA and should be considered in treatment planning. The vascular cooling effect was mainly affected by antenna to vessel distance. Vessel diameter and vascular flow rate played a minor role in vascular cooling effects.

Ablation Techniques in Cancer Pain

Painful bone metastases are a frequently encountered problem in oncology practice. The skeletal system is the third most common site of metastatic disease and up to 85% of patients with breast, prostate, and lung cancer may develop bone metastases during the course of their disease.

Percutaneous lung and liver CT-guided ablation on swine model using microwave ablation to determine ablation size for clinical practice

PURPOSE

Microwave ablation (MWA) provides an effective treatment of lung and liver tumors but suffers from a lack of reproducibility of ablation size among currently available technologies. In-vitro evaluations are far removed from clinical practices because of uninfused tissue. This study is in-vivo preclinical testing of a new MWA system on swine lungs and liver.

MATERIALS AND METHODS

All ablations were performed under CT guidance and multiple algorithms were tested with a power of 50, 75, and 100 W for durations of 3, 5, 8, 10, and 15 min. A 3 D-evaluation of the ablation zone was carried out using enhanced-CT. The sphericity index, coefficients of variation, and energy efficiency (which corresponds to the volume yield according to the power supplied) were calculated.

RESULTS

Fifty liver and 48 lung ablations were performed in 17 swine. The sphericity index varies from 0.50 to 0.80 for liver ablations and from 0.40 to 0.69 for lung ablations. The coefficient of variation was below 15% for 4/5 and 4/8 protocols for lung and liver ablations, respectively. The energy efficiency seems to decrease with the duration of the ablation from 0.60 × 10^-3 cm³/J (75 W, 3 min) to 0.26 × 10^-3 cm³/J (100 W, 15 min) in the liver and from 0.57 × 10^-3 cm³/J (50 W, 10 min) to 0.42 × 10^-3 cm³/J (100 W, 12 min) in the lungs.

CONCLUSION

A shorter treatment time provides the best energy efficiency, and the best reproducibility is obtained for a 10 min treatment duration. The system tested provides an interesting reproducibility in both lung and liver measurements. Our results may help interventional radiologists in the optimal selection of treatment parameters.

Image-Guided Ablation for Colorectal Liver Metastasis: Principles, Current Evidence, and the Path Forward

Simple Summary

Colorectal cancer is the fourth most common type of cancer globally. Approximately 20% of patients with colorectal cancer present with synchronous liver metastases, and up to 60% will develop metachronous metastases during the course of the disease. Although liver resection is currently considered the local treatment of choice for colorectal liver metastasis (CLM), less than one-third of patients are eligible for surgery at the time of diagnosis of CLM. Ablation is a well-established, less invasive, locoregional therapy for patients with small CLMs, which has shown favorable oncological outcomes in patients with unresectable CLMs, comparable to those in patients eligible for surgery. The increasing knowledge of factors affecting oncological outcomes has allowed selected patients with resectable small volume CLMs to be treated with thermal ablation with curative intent. The continuous technological evolutions in imaging and image guidance have contributed to this paradigm shift in CLM treatment. The importance of patient selection, patient factors, tumor factors, ablation techniques, and clinical applications is discussed in this article.

Abstract

Image-guided ablation can provide effective local tumor control in selected patients with CLM. A randomized controlled trial suggested that radiofrequency ablation combined with systemic chemotherapy resulted in a survival benefit for patients with unresectable CLM, compared to systemic chemotherapy alone. For small tumors, ablation with adequate margins can be considered as an alternative to resection. The improvement of ablation technologies can allow the treatment of tumors close to major vascular structures or bile ducts, on which the applicability of thermal ablation modalities is challenging. Several factors affect the outcomes of ablation, including but not limited to tumor size, number, location, minimal ablation margin, RAS mutation status, prior hepatectomy, and extrahepatic disease. Further understanding of the impact of tumor biology and advanced imaging guidance on overall patient outcomes might help to tailor its application, and improve outcomes of image-guided ablation.

Microwave Ablation of Very-Early- and Early-Stage HCC: Efficacy Evaluation by Correlation with Histology after Liver Transplantation

Microwave (MW) ablation is a worldwide-diffused technique for the percutaneous ablation of hepatocellular carcinoma (HCC). Nevertheless, the efficacy of this technique still needs to be confirmed in pathological specimens. The purpose of this study was to evaluate the efficacy of MW ablation by correlation with histology in excised liver samples at the time of liver transplantation (LT). All patients with MW-ablated HCC who subsequently underwent LT between 2012 and 2020 were retrospectively evaluated. In the explanted livers, the treated lesions were evaluated at pathology, and the necrosis was classified as complete or partial. Thirty-six HCCs were ablated in 30 patients (20.9 ± 6.1 mm, a range of 10-30 mm). Ablations were performed with a single insertion of a MW antenna under ultrasound or CT guidance. A complete radiological response was demonstrated in 30/36 nodules (83.3%) in 24/30 patients (80%) at imaging performed one-month after MW ablation. At pathology, of the 36 treated nodules, 28 (77.8%) showed a complete necrosis, and 8 (22.2%) showed a pathological partial necrosis. Good agreement was found between the imaging performed one-month after treatment and the complete pathological response (Cohen's k = 0.65). The imaging accuracy in detecting a complete response to treatment was 88.9%. All lesions with complete necrosis did not show recurrence at follow-up imaging until transplantation. The rad-path correlation in the explanted livers showed that MW ablation achieved a high rate of complete necrosis if a macroscopical complete ablation was obtained.

Computed tomography-guided microwave ablation of perivascular liver metastases from colorectal cancer: a study of the ablation zone, feasibility, and safety

OBJECTIVES

To compare the ablation margins and safety of microwave ablation (MWA) of perivascular versus non-perivascular liver metastases from colorectal cancer (CRC) and to determine the risk factors for local tumor progression (LTP) after perivascular MWA.

METHODS

Between June 2017 and June 2019, 84 metastases were treated: 39 perivascular (<5 mm from a vessel >3 mm), and 46 non-perivascular. Perivascular metastases were treated with either conventional or optimized protocols (maximum power and/or several heating cycles after repositioning the needle regardless of the initial tumor dimensions). The mean diameter of metastases was 15.4 mm (SD: 7.56).

RESULTS

Vascular proximity did not result in a significant difference in ablation margins. The technical success rate, primary efficacy, and secondary efficacy were 90%, 66%, and 83%, respectively. Perivascular location was not a risk factor for time to LTP (p = 0.49), RFS (p = 0.52), or OS (p = 0.54). LTP was statistically related to the presence of a colonic obstruction (p < 0.05), number of metastases at the time of diagnosis (p < 0.05), type of protocol (p < 0.05), ablation margins (p < 0.001) and LTP was proportional to the number of liver resections before MWA (p < 0.05). There was no LTP in tumors ablated with margins over 10 mm. Two grade 4 complications occurred.

CONCLUSION

MWA is an effective and safe treatment for perivascular liver metastases from CRC, provided that satisfactory margins are achieved. A maximalist attitude could be related to better local control.

A Systematic Review about Imaging and Histopathological Findings for Detecting and Evaluating Electroporation Based Treatments Response

BACKGROUND

Imaging methods and the most appropriate criteria to be used for detecting and evaluating response to oncological treatments depend on the pathology and anatomical site to be treated and on the treatment to be performed. This document provides a general overview of the main imaging and histopathological findings of electroporation-based treatments (Electrochemotherapy-ECT and Irreversible electroporation-IRE) compared to thermal approach, such as radiofrequency ablation (RFA), in deep-seated cancers with a particular attention to pancreatic and liver cancer.

METHODS

Numerous electronic datasets were examined: PubMed, Scopus, Web of Science and Google Scholar. The research covered the years from January 1990 to April 2021. All titles and abstracts were analyzed. The inclusion criteria were the following: studies that report imaging or histopathological findings after ablative thermal and not thermal loco-regional treatments (ECT, IRE, RFA) in deep-seated cancers including pancreatic and liver cancer and articles published in the English language. Exclusion criteria were unavailability of full text and congress abstracts or posters and different topic respect to inclusion criteria.

RESULTS

558 potentially relevant references through electronic searches were identified. A total of 38 articles met the inclusion criteria: 20 studies report imaging findings after RFA or ECT or IRE in pancreatic and liver cancer; 17 studies report histopathological findings after RFA or ECT or IRE; 1 study reports both imaging and histopathological findings after RFA or ECT or IRE.

CONCLUSIONS

Imaging features are related to the type of therapy administrated, to the timing of re-assessment post therapy and to the imaging technique being used to observe the effects. Histological findings after both ECT and IRE show that the treated area becomes necrotic and encapsulated in fibrous tissue, suggesting that the size of the treated lesion cannot be measured as an endpoint to detect response. Moreover, histology frequently reported signs of apoptosis and reduced vital tissue, implying that imaging criteria, which take into account the viability and not the size of the lesion, are more appropriate to evaluate response to treatment.

[Resection of liver segments VII-VIII: is right hepatic vein reconstruction advisable?]

OBJECTIVE

To improve the treatment outcomes in patients with primary and metastatic liver tumors localized in segments VII-VIII involving the right hepatic vein and its branches.

MATERIAL AND METHODS

There were 16 surgical interventions including resection of liver segment VII and/or VIII with resection of the right hepatic vein and its branches without reconstruction. All procedures were carried out at the Department of Liver and Pancreatic Tumors of the Blokhin National Medical Cancer Research Center for the period 2016-2020. The cause of surgery was colorectal cancer liver metastases in 8 patients, hepatocellular carcinoma in 2 cases, angiomyolipoma in 1 case and metastases of uterine cancer in 1 patient. Minor liver resection was additionally performed in 5 cases.

RESULTS

Median surgery time was 150 (80-220) min, intraoperative blood loss - 400 (100-2000) ml. Afferent blood flow was blocked in 4 patients for 14 (12-25) min. None patient had intraoperative signs of impaired venous outflow. Biliary fistula in postoperative period occurred in 1 patient. No complications were noted in other cases. Median postoperative hospital-stay was 13 (9-19) days. There were no specific complications in long-term postoperative period that could be associated with venous outflow blockade through the right hepatic vein.

CONCLUSION

Existing vessels and intrahepatic collaterals de novo can provide adequate venous outflow into the middle hepatic vein and short hepatic veins during resection of liver segments VII and/or VIII with resection of the right hepatic vein and its branches without reconstruction and the absence of inferior right hepatic vein.

Irreversible electroporation of locally advanced pancreatic cancer

Locally advanced pancreatic cancer (LAPC) constitutes approximately one-third of all pancreatic cancer, with standard of care inconsistently defined and achieving modest outcomes at best. While resection after downstaging offers the chance for cure, only a fraction of patients with LAPC become candidates for resection. Chemotherapy remains the mainstay of treatment for the remainder. In these patients, ablative therapy may be given for local control of the tumor. Irreversible electroporation (IRE) is an attractive ablative technique. IRE changes the permeability of tumor cell membranes to induce apoptosis. Unlike other ablative therapies, IRE causes little thermal injury to the target area, making it ideal for LAPC involving major vessels. Compared to systemic chemotherapy alone, IRE seems to offer some survival benefit. Although early studies reported notable morbidity and mortality rates, IRE presents opportunities for those who cannot undergo resection and who otherwise have limited options. Another role of IRE is to extend the margins of resected tumors when there is a concern for R1 resection. Perhaps most exciting, IRE is thought to have effects beyond local ablation. IRE has immunomodulatory effects, which may induce in vivo vaccination and may potentially synergize with immunotherapy. Through electrochemotherapy, IRE may enhance drug delivery to residual tumor cells. Ultimately the role of IRE in the treatment of LAPC still needs to be validated through well designed randomized trials. Investigations of its future possibilities are in the early stages. IRE offers the potential to provide more options to LAPC patients.

Microwave Thermoablation of Colorectal Liver Metastases Close to Large Hepatic Vessels Under Pringle Maneuver Minimizes the "Heat Sink Effect"

BACKGROUND

Liver resection and thermoablation are the mainstay of the surgical management of colorectal liver metastases (CRLM). The main limitation of thermoablation is the "heat-sink" effect for nodules next to large vessels. Herein, we report the preliminary results of microwave ablation (MWA) with associated Pringle maneuver to overcome this flaw.

METHODS

From November 2017, we performed intraoperative MWA with Pringle maneuver for nodules ≤3 cm with immediate proximity to large vessels (distance ≤ 5 mm, diameter ≥ 3 mm). We collected characteristics of nodules, surgical procedures and postoperative morbidity. Diameter of the ablation area, especially the ablative minimal margin, was calculated for each nodule. Recurrence was also evaluated.

RESULTS

Nineteen patients underwent MWA with Pringle maneuver for 23 nodules. Nineteen (83%) ablated nodules were located in segments VI, VII and VIII, and one nodule was in segment I. Median size of nodules was 15 mm (10-21). No deaths occurred. Six patients (38%) experienced complications, among them only one was subsequent to the thermal ablation. Ablative minimal margin was ≥5 mm for 19 (83%) nodules. Margin was not sufficient for four nodules, among them only 2/23 cases (8.7%) of in situ recurrence occurred after 12 months of median follow-up.

CONCLUSIONS

In this preliminary study, MWA with Pringle maneuver was associated with a low related morbidity rate and favorable oncological outcome, especially when the radiological minimal margin was sufficient.

Long-term results of percutaneous microwave ablation for colorectal liver metastases

BACKGROUND

Radiofrequency ablation (RFA) has been used for therapy of colorectal liver metastases (CRLMs) several years, with considerable data confirming its safety and efficacy. However, there are few studies focusing on the long-term results of percrtaneous microwave ablation (PMWA) for CRLMs. The aim of this study was to evaluate the long-term survival and prognostic factors in patients with CRLMs undergoing PMWA.

METHODS

We retrospectively analyzed treatment and survival parameters of 210 patients with CRLMs who had received PMWA in a single center from January 2010 to December 2017. Prognostic factors for survival were evaluated by means of univariate and multivariate analyses.

RESULTS

The median follow-up time after PMWA was 48 months. The median overall survival (OS) time were 40.0 months (95% CI, 31.4 to 48.5 months), with 1-, 2, 3-, 4, and 5-year cumulative survival rates of 98.6%, 73.3%, 53.3%, 42.2%, and 32.9%, respectively. Tumor number (P = 0.004; HR: 1.838; CI: 1.213- 2.784), main tumor size (P = 0.017; HR: 1.631; CI: 1.093- 2.436), and serum CEA level (P = 0.032; HR: 1.559; CI: 1.039-2.340) were found as independent predictors of OS. The median OS time for patients with resectable lesions was 60.91 months (95% CI, 51.36 to 70.47 months), with 5-year cumulative survival rates of 53.5%.

CONCLUSION

PMWA is a safe and effective treatment for CRLMs, with a favorable long-term outcome. Multiple lesions, main tumor diameter>3 cm, and serum CEA >30 ng/ml have a significant negative effect on OS.

Feasibility and efficacy of ultrasonographic and laparoscopic guidance for microwave ablation of clinically normal canine ovaries

OBJECTIVE

To determine the optimal energy profile for and to assess the feasibility and efficacy of ultrasonographic and laparoscopic guidance for microwave ablation (MWA) of clinically normal canine ovaries.

SAMPLE

44 extirpated ovaries from 22 healthy dogs.

PROCEDURES

In the first of 2 trials, 13 dogs underwent oophorectomy by routine laparotomy. Extirpated ovaries underwent MWA at 45 W for 60 (n = 11) or 90 (12) seconds; 3 ovaries did not undergo MWA and served as histologic controls. Ovaries were histologically evaluated for cell viability. Ovaries without viable cells were categorized as completely ablated. Histologic results were used to identify the optimal MWA protocol for use in the subsequent trial. In the second trial, the ovaries of 9 dogs underwent MWA at 45 W for 90 seconds in situ. Ultrasonographic guidance for MWA was deemed unfeasible after evaluation of 1 ovary. The remaining 17 ovaries underwent MWA with laparoscopic guidance, after which routine laparoscopic oophorectomy was performed. Completeness of ablation was histologically assessed for all ovaries.

RESULTS

2 ovaries were excluded from the trial 1 analysis because of equivocal cell viability. Six of 11 ovaries and 10 of 10 ovaries that underwent MWA for 60 and 90 seconds, respectively, were completely ablated. In trial 2, laparoscopic-guided MWA resulted in complete ablation for 12 of 17 ovaries. Dissection of the ovarian bursa for MWA probe placement facilitated complete ablation.

CONCLUSIONS AND CLINICAL RELEVANCE

Laparoscopic-guided MWA at 45 W for 90 seconds was feasible, safe, and effective for complete ablation of clinically normal ovaries in dogs.

Outcome of Laparoscopic Assisted Percutaneous Microwave Ablation for Exophytic Versus Non-exophytic Hepatocellular Carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is one of the most common malignancies and is the third cause of cancer-related death worldwide. Surgery is the optimal treatment for early HCC; however, the majority of cases are not suitable for curative resection at the time of diagnosis. Surgical resection difficulties may be related to size, site, number of tumors, extrahepatic involvement, and patient general condition. Exophytic tumors were considered as relative contraindication for thermal ablation because of the risk of incomplete ablation or major complications as hemorrhage and seeding.

AIM OF THIS STUDY

to evaluate the safety and efficacy of microwave ablation (MWA) of exophytic HCC in comparison with non-exophytic HCC.

METHODS

Prospective comparative study carried on 30 patients having 30 exophytic (six of those patients had another non-exophytic lesion) and 32 patients having 44 non-exophytic HCC lesions (22 had single lesion, 8 patients had 2 lesions, and 2 patients had 3 lesions) within Milan criteria. All patients were child A or B, they were subjected to full clinical assessment, laboratory investigations, and radiological investigations. Laparoscopic assisted percutaneous MWA was the procedure of choice in our study for all patients either having exophytic or non-exophytic lesions using no-touch wedge technique for exophytic lesions and direct puncture for non-exophytic lesions.

RESULTS

Technical success was 100% in both groups, all lesions were completely ablated as confirmed by LIOUS. There were no major complications or perioperative mortality and low incidence of local tumor progression in both exophytic and non-exophytic groups.

CONCLUSION

Laparoscopic assisted MWA of exophytic HCC is safe and effective with comparable results to non-exophytic HCC. Exophytic HCC is not contraindication for MWA with proper technique selection.

Percutaneous Thermal Ablation for Treatment of T1a Renal Cell Carcinomas

Based on Surveillance, Epidemiology, and End Results studies, most renal cancers are low grade and slow growing. Long-term, single-center studies show excellent outcomes for T1a renal cell carcinoma (RCC), comparable to partial nephrectomy without affecting renal function and with much lower rates of complications. However, there are no multicenter randomized controlled trials of multiple ablative modalities or comparison with partial nephrectomy, and most studies are single-arm observational studies with short-term and intermediate follow-up. For treatment of stage T1a RCC, percutaneous TA is an effective alternative to surgery with preservation of renal function, low risk, and comparable overall and disease-specific survival.

In vivo noninvasive three-dimensional (3D) assessment of microwave thermal ablation zone using non-contrast-enhanced x-ray CT

PURPOSE

To develop an image processing methodology for noninvasive three-dimensional (3D) quantification of microwave thermal ablation zones in vivo using x-ray computed tomography (CT) imaging without injection of a contrast enhancing material.

METHODS

Six microwave (MW) thermal ablation procedures were performed in three pigs. The ablations were performed with a constant heating duration of 8 min and power level of 30 W. During the procedure images from sixty 1 mm thick slices were acquired every 30 s. At the end of all ablation procedures for each pig, a contrast-enhanced scan was acquired for reference. Special algorithms for addressing challenges stemming from the 3D in vivo setup and processing the acquired images were prepared. The algorithms first rearranged the data to account for the oblique needle orientation and for breathing motion. Then, the gray level variance changes were analyzed, and optical flow analysis was applied to the treated volume in order to obtain the ablation contours and reconstruct the ablation zone in 3D. The analysis also included a special correction algorithm for eliminating artifacts caused by proximal major blood vessels and blood flow. Finally, 3D reference reconstructions from the contrast-enhanced scan were obtained for quantitative comparison.

RESULTS

For four ablations located >3 mm from a large blood vessel, the mean dice similarity coefficient (DSC) and the mean absolute radial discrepancy between the contours obtained from the reference contrast-enhanced images and the contours produced by the algorithm were 0.82 ± 0.03 and 1.92 ± 1.47 mm, respectively. In two cases of ablation adjacent to large blood vessels, the average DSC and discrepancy were: 0.67 ± 0.6 and 2.96 ± 2.15 mm, respectively. The addition of the special correction algorithm utilizing blood vessels mapping improved the mean DSC and the mean absolute discrepancy to 0.85 ± 0.02 and 1.19 ± 1.00 mm, respectively.

CONCLUSIONS

The developed algorithms provide highly accurate detailed contours in vivo (average error < 2.5 mm) and cope well with the challenges listed above. Clinical implementation of the developed methodology could potentially provide real time noninvasive 3D accurate monitoring of MW thermal ablation in-vivo, provided that the radiation dose can be reduced.

Microwave ablation: How we do it?

Minimally invasive techniques such as Image guided thermal ablation are now widely used in the treatment of tumors. Microwave ablation (MWA) is one of the newer modality of thermal ablation and has proven its safety and efficacy in the management of the tumors amenable for ablation for primary and metastatic diseases. It is used in the treatment of primary and secondary liver malignancies, primary and secondary lung malignancies, renal and adrenal tumors and bone metastases. We wanted to share our initial experience with this newer modality. In this article we will describe the mechanism and technique of MWA, comparison done with RFA, advantages and disadvantages of MWA along with pre procedure workup, post procedure follow-up and review of literature.

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.

Early Outcomes with Single-antenna High-powered Percutaneous Microwave Ablation for Primary and Secondary Hepatic Malignancies: Safety, Effectiveness, and Predictors of Ablative Failure

Objective:

Microwave ablation (MWA) of liver malignancies has gained much traction over the past 5 years. However, MWA carries relatively higher rates of residual disease compared to resection. Likelihood of MWA success is multifactorial and newer devices with more reliable ablation zones are being developed to overcome these drawbacks. This manuscript is a review of our first 100 liver ablations with the newer single antenna high powered MWA system.

Materials and Methods:

Retrospective chart review of patients that underwent MWA for either primary or secondary hepatic malignancies between March 2015 and July 2016 was conducted. The complete ablation rates, rate of new lesions, complications, and short-term survival were analyzed. Multiple statistical tests, including multivariate regression, were used to assess risk factors for local residual and recurrent disease.

Results:

Fifty-three patients (median age 61 ± 9 years, 39 males) underwent 100 MWAs. Of the 100 lesions ablated, 76 were hepatocellular cancers (HCCs) and 24 were metastases. Median lesion size was 16 ± 9 mm. Seventy- five of these patients had multifocal disease targeted in the same session. Seventy patients had cirrhosis (median model for end-stage liver disease score 9 ± 3; Child-Pugh B and C in 42%). An 83% complete lesion ablation rate was seen on follow-up imaging with liver protocol magnetic resonance imaging/computed tomography (median follow-up of 1 year). The minor complication rate was 9.4% with no major complications or 30-day mortality. Despite this, evidence of new foci of hepatic disease was found in 47% of patients, the majority (80%) of which were in HCC patients (P < 0.01) and most of these new lesions were in a different hepatic segment (64%). Degree of cirrhosis (P < 0.01), presence of non-alcoholic steatohepatitis (NASH) (P = 0.01) and lesion’s subcapsular location (P = 0.03) was significant predictors of residual disease. With the subset analysis of only HCC lesions larger than 1 cm, only the presence of NASH remained significant.

Conclusion:

The single probe high power MWA of malignant hepatic lesions is safe and effective with minimal morbidity. Degree of cirrhosis, NASH, and subcapsular location was associated with an increased rate of residual disease on short-term follow-up.

4D Flow MR Imaging to Improve Microwave Ablation Prediction Models: A Feasibility Study in an In Vivo Porcine Liver

PURPOSE

To characterize the effect of hepatic vessel flow using 4-dimensional (4D) flow magnetic resonance (MR) imaging and correlate their effect on microwave ablation volumes in an in vivo non-cirrhotic porcine liver model.

MATERIALS AND METHODS

Microwave ablation antennas were placed under ultrasound guidance in each liver lobe of swine (n = 3 in each animal) for a total of 9 ablations. Pre- and post-ablation 4D flow MR imaging was acquired to quantify flow changes in the hepatic vasculature. Flow measurements, along with encompassed vessel size and vessel-antenna spacing, were then correlated with final ablation volume from segmented MR images.

RESULTS

The linear regression model demonstrated that the preablation measurement of encompassed hepatic vein size (β = -0.80 ± 0.25, 95% confidence interval [CI] -1.15 to -0.22; P = .02) was significantly correlated to final ablation zone volume. The addition of hepatic vein flow rate found via 4D flow MRI (β = -0.83 ± 0.65, 95% CI -2.50 to 0.84; P = .26), and distance from antenna to hepatic vein (β = 0.26 ± 0.26, 95% CI -0.40 to 0.92; P = .36) improved the model accuracy but not significantly so (multivariate adjusted R² = 0.70 vs univariate (vessel size) adjusted R² = 0.63, P = .24).

CONCLUSIONS

Hepatic vein size in an encompassed ablation zone was found to be significantly correlated with final ablation zone volume. Although the univariate 4D flow MR imaging-acquired measurements alone were not found to be statistically significant, its addition to hepatic vein size improved the accuracy of the ablation volume regression model. Pre-ablation 4D flow MR imaging of the liver may assist in prospectively optimizing thermal ablation treatment.

Fully laparoscopic thermo-ablation of liver malignancies with or without liver resection: tumor location is an independent local recurrence risk factor

BACKGROUND

The aim of this study was to analyze risk factors of local recurrence (LR) after exclusive laparoscopic thermo-ablation (TA) with or without associated liver resection.

METHODS

Between 2012 and 2017, among 385 patients who underwent 820 TA in our department, 65 (17%) patients (HCC = 11, LM = 54) had exclusive laparoscopic TA representing 112 lesions (HCC = 17, LM = 95). TA was associated with other procedures in 57% of cases (liver resection 81%). All TA were done without liver clamping. Median tumor size was 1.8 cm [ranges from 0.3 to 4.5], 18% of the lesions were larger than 3 cm in size and 11% close to major liver vessels. Tumors locations were 77.5% in right liver, 36% in S7&S8, and 46% in S7&S8&S4a.

RESULTS

Mortality was nil and morbidity rate 15.4% including Dindo-Clavien > II grade 3%. The median follow-up was 24 months [0.77-75]. Per lesion LR rate after TA was 18% (n = 19 patients) with a mean time of 7.6 months. Among patients with LR, 18 (95%) could have been re-treated successfully (new resection = 11, re-TA = 7). Multivariate analyses revealed that tumor location in S7 alone, S7&S8 and/or S7, S8, or S4a were independent risk factors of LR after TA.

CONCLUSIONS

Exclusive laparoscopic TA is a safe and an effective tool to treat liver malignancies with or without liver resection. Other than classical risk factors, tumor location in upper segments of the liver, are independent risk factors for LR.

Role of thermal ablation in the management of colorectal liver metastasis

With a recent randomized prospective trial revealing that thermal ablative therapy as local tumor control improved overall survival (OS) in patients with unresectable colorectal cancer liver metastases (CRLM), thermal ablation continues to remain as an important treatment option in this patient population. Our aim of this article is to review the current role of the ablative therapy in the management of CRLM patients. Main indications for thermal ablation include (I) unresectable liver lesions; (II) in combination with hepatectomy; (III) in patients with significant medical comorbidities or poor performance status (PS); (IV) a small (<3 cm) solitary lesion, which would otherwise necessitate a major liver resection; and (V) patient preference. There are several approaches and modalities for ablative therapy, including open, percutaneous, and laparoscopic approaches, as well as radiofrequency ablation (RFA) and microwave ablation (MWA). Each approach and ablation modality have its own pros and cons. Percutaneous and laparoscopic approaches are preferred due to minimally invasive nature, yet laparoscopic approach has more benefits from thorough intraoperative ultrasound (US) exam as well as complete peritoneal staging with laparoscopy. Similarly, whereas high local tumor failure rate has been a major concern with RFA, MWA or microwave thermosphere ablation (MTA) have demonstrated significantly improved local tumor control due to homogenous tissue heating, ability to reach higher tissue temperatures, and less susceptible to the "heat-sink" effect. Although liver resection is the standard of care for CRLM, there have been some retrospective studies demonstrating similar oncological outcome between ablative therapy and surgical resection in very selected populations with small (<3 cm) solitary CRLM. Lastly, ablative therapy and liver resection should not be mutually exclusive, especially in the management of bilobar liver metastases. Concomitant ablative therapy with hepatectomy may spare the patients from having two-stage hepatectomy with less morbidity. The role of the thermal ablation will continue to evolve in patients with resectable and ablatable lesions owing to newly emerging technology, in addition to new systemic treatment options, including immunotherapy for metastatic colorectal cancer (CRC).

Toward a clinical real time tissue ablation technology: combining electroporation and electrolysis (E2)

Background

Percutaneous image-guided tissue ablation (IGA) plays a growing role in the clinical management of solid malignancies. Electroporation is used for IGA in several modalities: irreversible electroporation (IRE), and reversible electroporation with chemotoxic drugs, called electrochemotherapy (ECT). It was shown that the combination of electrolysis and electroporation—E2—affords tissue ablation with greater efficiency, that is, lower voltages, lower energy and shorter procedure times than IRE and without the need for chemotoxic additives as in ECT.

Methods

A new E2 waveform was designed that delivers optimal doses of electroporation and electrolysis in a single waveform. A series of experiments were performed in the liver of pigs to evaluate E2 in the context of clinical applications. The goal was to find initial parameter boundaries in terms of electrical field, pulse duration and charge as well as tissue behavior to enable real time tissue ablation of clinically relevant volumes.

Results

Histological results show that a single several hundred millisecond long E2 waveform can ablate large volume of tissue at relatively low voltages while preserving the integrity of large blood vessels and lumen structures in the ablation zone without the use of chemotoxic drugs or paralyzing drugs during anesthesia. This could translate clinically into much shorter treatment times and ease of use compared to other techniques that are currently applied.