Thermal Ablation Modalities Research Articles

Microwave Ablation of Hepatocellular Carcinoma and Liver Metastases: Challenges, Opportunities, and Future Directions

AbstractChronic liver disease predisposes patients to the development of hepatocellular carcinoma (HCC), and the degree of liver dysfunction helps dictate the management of patients with primary hepatic malignancy. Percutaneous ablation is an increasingly utilized treatment modality for patients with hepatocellular carcinoma who are poor surgical candidates, particularly when treatment goals include sparing hepatic parenchyma in the setting of hepatic dysfunction. Various thermal and non-thermal ablation modalities have historically been used to treat HCC. With advances in ablation technology, modern microwave (MW) ablation systems have become increasingly utilized in HCC as well as hepatic metastatic disease management due to larger and more predictable ablation zones. The evolution of ablation technology has resulted in the growth of ablation as a safe and effective treatment option for patients with primary and secondary liver tumors.

Irreversible electroporation in hepatic tumours: a novel ablative modality

Background and Aim: Liver cancer is one of the most common cancers and the cause of cancer-related mortality worldwide. Thermal ablative modalities have stood a test of time in the management of liver cancer. However, the unselective destruction inflicted by them can result in damage to vital structures in the tumoral vicinity. Furthermore, the efficacy of thermal ablation can be impaired due to thermal sink. Close proximity of large vessels, bile ducts, or the gall bladder can cause inconsistent ablation results.

Efficacy and Safety of Different Thermal Ablation Modalities for Papillary Thyroid Microcarcinoma: A Network Meta-Analysis.

Small thyroid-like carcinoma (PTMC) is one of the most common subtypes of thyroid cancer. The main treatment options include surgery and radiofrequency ablation (RFA), microwave ablation (MWA), and laser ablation (LA). Thermal ablation has the advantage of being less invasive and has fewer complications than traditional surgical treatment. The objective is to explore the efficacy and safety of PTMC by different thermal ablation modalities through a network meta-analysis. From the database establishment to October 2021, a computerized search of the Chinese Knowledge Infrastructure (CKNI), VIP Chinese Science and Technology Journal Full-Text Database (VP-CSJFD), WanFang Data journal article resource (WangFang), PubMed, the Cochrane Library, and Embase were performed to include the different methods of thermal ablation for small thyroid carcinoma. A retrospective study of different methods of thermal ablation of small thyroid carcinoma was included. A total of 12 retrospective studies involving 1,926 patients with PTMC were included, all of which were of high quality. This study mainly involved RFA, MWA, LA, and ethanol combined with radiofrequency ablation (EA + RFA). Network meta-analysis showed no significant difference between interventions (p > 0.05) in terms of recurrence rate. Surgical resection may be the measure with the lowest recurrence rate after treatment of PTMC, LA may be the measure with the lowest incidence of complications after treatment, and RFA may be the measure with the least length of hospital stay, operation time, and postoperative lymph node metastasis rate. However, due to the limitations of network meta-analysis, this result still needs to be treated with caution, and more high-quality, large-sample clinical studies are recommended for further verification.

Review of the Economics of Surgical Treatment Options for Benign Prostatic Hyperplasia.

The goal of this paper is to review the literature detailing US-based analyses for cost and cost-effectiveness of surgical treatment options for benign prostatic hypertrophy (BPH) and associated LUTS. TURP offers the greatest degree of symptom improvement with its associated costs dependent upon operating room time, equipment, and length of hospital stay. Other studied surgical treatment modalities, including transurethral laser ablative, thermal ablative, and convective water vapor modalities as well as prostatic urethral lift and transabdominal procedures, generally carry higher costs and lower cost-effectiveness in both inpatient and outpatient settings, with specific exceptions. Compared to TURP, HoLEP and Greenlight PVP have demonstrated superior cost-effectiveness for mild, moderate, and severe BPH. Convective water vapor ablation, as with transurethral microwave/thermoablative therapies, has been observed to be less expensive per procedure than TURP on average. However, it conferred lower degrees of IPSS symptom improvement. Moreover, compared to TURP, prostatic artery embolization has demonstrated lower average costs coupled with inferior objective improvement in maximal flow rate, prostate volume reduction, PSA decline and minimal improvement in IPSS subjective outcome measures. For this review, selection bias, asymmetric patient groups, issues with study aggregation, and understudied cost contributors (including retreatment costs, long-term durability of symptom relief, recovery time, and work productivity limitations) were identified as key limitations. Nevertheless, this overview takes important steps to understand the costs of surgical treatment options for BPH, allowing for more informed clinical and policy decisions.

Current Management of Oligometastatic Lung Cancer and Future Perspectives: Results of Thermal Ablation as a Local Ablative Therapy.

Simple SummaryUp to 56% of lung cancer patients present with metastatic disease at initial diagnosis. Whereas these patients were historically deemed incurable, recent evidence supports the use of thermal ablation in stage IV non-small cell lung carcinoma with limited sites of metastasis (oligometastatic disease). In this review, we discuss the main results (local efficacy, overall survival, progression-free survival, safety and quality of life) of studies evaluating thermal ablation as a local ablative therapy for oligometastatic non-small cell lung carcinoma.A growing body of evidence shows improved overall survival and progression-free survival after thermal ablation in non-small cell lung carcinoma (NSCLC) patients with a limited number of metastases, combined with chemotherapy or tyrosine kinase inhibitors or after local recurrence. Radiofrequency ablation and microwave ablation are the most evaluated modalities, and target tumor size <3 cm (and preferably <2 cm) is a key factor of technical success and efficacy. Although thermal ablation offers some advantages over surgery and radiotherapy in terms of repeatability, safety, and quality of life, optimal management of these patients requires a multidisciplinary approach, and further randomized controlled trials are required to help refine patient selection criteria. In this article, we present a comprehensive review of available thermal ablation modalities and recent results supporting their use in oligometastatic and oligoprogressive NSCLC disease along with their potential future implications in the emerging field of immunotherapy.

Prospective study for commercial and low-cost hyperspectral imaging systems to evaluate thermal tissue effect on bovine liver samples

Thermal ablation modalities, for example radiofrequency ablation (RFA) and microwave ablation, are intended to prompt controlled tumour removal by raising tissue temperature. However, monitoring the size of the resulting tissue damage during the thermal removal procedures is a challenging task. The objective of this study was to evaluate the observation of RFA on an ex vivo liver sample with both a commercial and a low-cost system to distinguish between the normal and the ablated regions as well as the thermally affected regions. RFA trials were conducted on five different ex vivo normal bovine samples and monitored initially by a custom hyperspectral (HS) camera to measure the diffuse reflectance (Rd) utilising a polychromatic light source (tungsten halogen lamp) within the spectral range 348–950 nm. Next, the light source was replaced with monochromatic LEDs (415, 565 and 660 nm) and a commercial charge-coupled device (CCD) camera was used instead of the HS camera. The system algorithm comprises image enhancement (normalisation and moving average filter) and image segmentation with K-means clustering, combining spectral and spatial information to assess the variable responses to polychromatic light and monochromatic LEDs to highlight the differences in the Rd properties of thermally affected/normal tissue regions. The measured spectral signatures of the various regions, besides the calculation of the standard deviations (δ) between the generated six groups, guided us to select three optimal wavelengths (420, 540 and 660 nm) to discriminate between these various regions. Next, we selected six spectral images to apply the image processing to (at 450, 500, 550, 600, 650 and 700 nm). We noticed that the optimum image is the superimposed spectral images at 550, 600, 650 and 700 nm, which are capable of discriminating between the various regions. Later, we measured Rd with the CCD camera and commercially available monochromatic LED light sources at 415, 565 and 660 nm. Compared to the HS camera results, this system was more capable of identifying the ablated and the thermally affected regions of surface RFA than the side-penetration RFA of the investigated ex vivo liver samples. However, we succeeded in developing a low-cost system that provides satisfactory information to highlight the ablated and thermally affected region to improve the outcome of surgical tumour ablation with much shorter time for image capture and processing compared to the HS system.

Histotripsy Ablation Alters the Tumor Microenvironment and Promotes Immune System Activation in a Subcutaneous Model of Pancreatic Cancer.

Pancreatic cancer is a significant cause of cancer-related deaths in the United States with an abysmal five-year overall survival rate that is under 9%. Reasons for this mortality include the lack of late-stage treatment options and the immunosuppressive tumor microenvironment. Histotripsy is an ultrasound-guided, noninvasive, nonthermal tumor ablation therapy that mechanically lyses targeted cells. To study the effects of histotripsy on pancreatic cancer, we utilized an in vitro model of pancreatic adenocarcinoma and compared the release of potential antigens following histotripsy treatment to other ablation modalities. Histotripsy was found to release immune-stimulating molecules at magnitudes similar to other nonthermal ablation modalities and superior to thermal ablation modalities, which corresponded to increased innate immune system activation in vivo. In subsequent in vivo studies, murine Pan02 tumors were grown in mice and treated with histotripsy. Flow cytometry and rtPCR were used to determine changes in the tumor microenvironment over time compared to untreated animals. In mice with pancreatic tumors, we observed significantly increased tumor-progression-freeand general survival, with increased activation of the innate immune system 24 h posttreatment and decreased tumor-associated immune cell populations within 14 days of treatment. This study demonstrates the feasibility of using histotripsy for pancreatic cancer ablation and provides mechanistic insight into the initial innate immune system activation following treatment. Further work is needed to establish the mechanisms behind the immunomodulation of the tumor microenvironment and immune effects.

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

Simple SummaryColorectal 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.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.

Optical Signature Analysis of Liver Ablation Stages Exploiting Spatio-Spectral Imaging

Background and Objective: Thermal ablation modalities such as Radiofrequency ablation (RFA) / Microwave ablation (MWA) are deliberately used for marginally invasive tumor removal by escalating tissue temperature. For precise tumor extinguish, thermal ablation outcomes need routine monitoring for tissue necrosis in a challenging research task. The study aims to exploit hyperspectral imaging (HSI) to evaluate the impact of the liver tissue ablation. Materials and Methods: RFA with temperature range (≥80 °C) was accomplished on the ex vivo animal liver and evaluated using a spectral camera (400~1000 nm). The spectral signatures were extracted from the HSI data after the following processing steps: capturing three spectral data cubes for each liver sample with total 7-samples (before ablation, after ablation, and after ablation with sample slicing) using an HSI optical configuration. The custom HSI processing comprises “Top-hat and Bottom-hat transform” combined with “watershed transform” image segmentation to increase the intensity for a region of interest (ROI) of the investigated tissue, linking spectral and spatial data. Additionally, statistical analysis for HSI data was performed to exclusively select the best spectral band that discriminates between the normal, thermally-damaged, and ablated liver regions. Results: The variation of the optical parameters for the investigated liver samples provides variable interaction with the light diffuse reflection (Ŗd) over the spectrum range (400~1000 nm). Where, the extracting spectral information of the various tissue zones from the induced RFA linked to the hemoglobin, methemoglobin, and water permits variations. The generated spectral image after image enhancement utilizing “Top-hat and Bottom-hat transform” followed by “watershed segmentation”, showed high contrast between normal and thermal regions at a wavelength (600 nm). However, the wavelength (900 nm) shows a high variance between the normal and ablated regions. Finally, delineation of the thermal and ablated regions on the complemented enhanced image. Conclusion: HSI is considered a promising optical noninvasive technique for monitoring the RFA toward enhancing the ablation-based treatment for liver tumor outcomes.

Thermal ablation in non-small cell lung cancer: a review of treatment modalities and the evidence for combination with immune checkpoint inhibitors.

Lung cancer is the leading cause of cancer death worldwide, with approximately 1.6 million cancer related deaths each year. Prognosis is best in patients with early stage disease, though even then five-year survival is only 55% in some groups. Median survival for advanced non-small cell lung cancer (NSCLC) is 8–12 months with conventional treatment. Immune checkpoint inhibitor (ICI) therapy has revolutionised the treatment of NSCLC with significant long-term improvements in survival demonstrated in some patients with advanced NSCLC. However, only a small proportion of patients respond to ICI, suggesting the need for further techniques to harness the potential of ICI therapy. Thermal ablation utilizes the extremes of temperature to cause tumour destruction. Commonly used modalities are radiofrequency ablation (RFA), cryoablation and microwave ablation (MWA). At present thermal ablation is reserved for curative-intent therapy in patients with localized NSCLC who are unable to undergo surgical resection or stereotactic ablative body radiotherapy (SABR). Limited evidence suggests that thermal ablative modalities can upregulate an anticancer immune response in NSCLC. It is postulated that thermal ablation can increase tumour antigen release, which would initiate and upregulated steps in the cancer immunity cycle required to elicit an anticancer immune response. This article will review the current thermal ablative techniques and their ability to modulate an anti-cancer immune response with a view of using thermal ablation in conjunction with ICI therapy.

Hyperthermia and Tumor Immunity.

Simple SummaryMinimally invasive procedures that directly deliver heat into tumors are commonly used to treat a wide range of malignancies. In this review, we discuss the potential role that these procedures can play in not only destroying small tumors but also educating the immune system to recognize and attack tumors throughout the body.Thermal ablation is a cornerstone in the management of cancer patients. Typically, ablation procedures are performed for patients with a solitary or oligometastatic disease with the intention of eradicating all sites of the disease. Ablation has traditionally played a less prominent role for patients with a widely metastatic disease. For such patients, attempting to treat numerous sites of disease compounds potential risks without a clear clinical benefit and, as such, a compelling justification for performing an intervention that is unlikely to alter a patient’s clinical trajectory is uncommon. However, the discovery of immune checkpoints and the development of immune checkpoint inhibitors have brought a new perspective to the relevance of local cancer therapies such as ablation for patients with a metastatic disease. It is becoming increasingly apparent that local cancer therapies can have systemic immune effects. Thus, in the new perspective of cancer care centered upon immunologic principles, there is a strong interest in exploring the utility of ablation for patients with a metastatic disease for its immunologic implications. In this review, we summarize the unmet clinical need for adjuvant interventions such as ablation to broaden the impact of systemic immunotherapies. We additionally highlight the extant preclinical and clinical data for the immunogenicity of common thermal ablation modalities.

A systematic review of outcomes after thermal and nonthermal partial prostate ablation.

We sought to compare oncologic and functional outcomes between thermal and nonthermal energy partial gland ablation (PGA) modalities. We conducted comprehensive, structured literature searches, and 39 papers, abstracts, and presentations met the inclusion criteria of pre-PGA magnetic resonance imaging, oncologic outcomes of at least 6 months, and systematic biopsies after PGA. Twenty-six studies used thermal ablation: high-intensity focused ultrasound (HIFU), cryotherapy, focal laser ablation, or radiofrequency ablation. In-field recurrence rates ranged from 0 to 36% for HIFU, 6 to 24% for cryotherapy, 4 to 50% for focal laser ablation, and 20 to 25% for radiofrequency ablation. Twelve studies used nonthermal technologies of focal brachytherapy, vascular-targeted photodynamic therapy, or irreversible electroporation. Focal brachytherapy had the lowest reported failure rate of 8%, vascular-targeted photodynamic therapy had >30% positive in-field biopsies, and irreversible electroporation had in-field recurrence rates of 12–35%. PGA was well tolerated, and nearly all patients returned to baseline urinary function 12 months later. Most modalities caused transient decreases in erectile function. Persistent erectile dysfunction was highest in patients who underwent HIFU. Although oncologic outcomes vary between treatment modalities, systematic review of existing data demonstrates that PGA is a safe treatment option for patients with localized prostate cancer.

Molecularly targeted photothermal ablation improves tumor specificity and immune modulation in a rat model of hepatocellular carcinoma

Thermal ablation is a standard therapy for patients with hepatocellular carcinoma (HCC). Contemporary ablation devices are imperfect, as they lack tumor specificity. An ideal ablation modality would generate thermal energy only within tumoral tissue. Furthermore, as hyperthermia is known to influence tumor immunity, such a tumor-specific ablation modality may have the ability to favorably modulate the tumor immune landscape. Here we show a clinically relevant thermal ablation modality that generates tumor-specific hyperthermia, termed molecularly targeted photothermal ablation (MTPA), that is based upon the excellent localization of indocyanine green to HCC. In a syngeneic rat model, we demonstrate the tumor-specific hyperthermia generated by MTPA. We also show through spatial and transcriptomic profiling techniques that MTPA favorably modulates the intratumoral myeloid population towards tumor immunogenicity and diminishes the systemic release of oncogenic cytokines relative to conventional ablation modalities.

Prospective comparative study of different endovenous thermal ablation systems for treatment of great saphenous vein reflux

ObjectiveThe aim of our study was to compare three different endovenous thermal ablation (EVTA) modalities in the treatment of great saphenous vein (GSV) incompetence. MethodsWe performed a single-center, prospective, comparative cohort study that included consecutive patients undergoing EVTA of the GSV. Patients were treated with either segmental radiofrequency ablation (sRFA) or endovenous laser ablation (EVLA) with a 1470-nm dual radial fiber or with a 1470-nm jacket-tip fiber. The clinical classification CEAP (clinical, etiologic, anatomic, pathophysiologic), 10-cm visual analog scale scores for pain, Venous Clinical Severity Scores (VCSSs), and chronic venous insufficiency quality-of-life questionnaire (CIVIQ-20) scores were recorded. The primary outcome was clinical success, which was defined as the absence of reflux or recanalization of the GSV and procedure-related complications, assessed at 7 and 30 days and 1 year postoperatively. The secondary outcomes were the assessment of postoperative pain using the VAS and improvement in the VCSSs and CIVIQ-20 scores. ResultsA total of 153 patients (160 limbs) had undergone sRFA (sRFA group; n = 53 limbs), 1470-nm radial fiber EVLA (EVLA-R group; n = 55 limbs), or 1470-nm jacket-tip fiber EVLA (EVLA-J group; n = 52 limbs). The patient demographics, CEAP clinical class, and intraoperative details were comparable among the three groups. The GSV occlusion rate at 1 year was 93% in the sRFA group, 93% in the EVLA-R group, and 95% in the EVLA-J group. No major complications were observed postoperatively. Endothermal heat-induced thrombosis was observed in 2 (4.4%), 1 (2.2%), and 2 (4.4%) patients in the sRFA, EVLA-R, and EVLA-J groups, respectively (P > .5). The VCSS showed greater improvement in the EVLA-R group at 1 week compared with that in the sRFA (P = .05) and EVLA-J (P = .002) groups. Changes in the CIVIQ-20 score were in favor of the EVLA-R group at 7 days (−14.3 ± 10.3 vs −7.9 ± 5.9; adjusted difference, 6.06; 95% confidence interval [CI], 1.57-10.55; P = .01) and 30 days (−12 ± 8 vs −11.2 ± 7; adjusted difference, 5.5; 95% CI, 1.21-9.81; P = .02) postoperatively compared with the sRFA group and at 7 days compared with the EVLA-J group (−14.3 ± 10.3 vs −9.6 ± 7.9; adjusted difference, −4.4; 95% CI, −9.06 to 0.22; P = .05). Analyzing the different components of the CIVIQ-20, pain, and physical scores showed a greater reduction in the EVLA-R group in the early postoperative period compared with that in the sRFA and EVLA-J groups. ConclusionsAll three EVTA modalities showed equal effectiveness and safety for the treatment of GSV reflux. EVLA with the 1470-nm radial fiber showed better outcomes in terms of early postoperative VCSSs and pain and physical CIVIQ scores. The clinical and quality of life benefits were similar for all modalities at 1 year postoperatively.

The ongoing search for clarity regarding the role of cyanoacrylate closure for superficial venous reflux

The development of nonthermal, nontumescent interventions for the closure of incompetent superficial veins seems a natural progression from the thermal ablation modalities that have revolutionized international venous practice during the last two decades. The potential benefits are clear, with the ability to avoid tumescent anesthesia, to avoid the risk of nerve damage, and to readily treat multiple vein segments in a single sitting. However, despite cyanoacrylate closure being approved in Europe in 2011 and gaining Food and Drug Administration approval in the United States in 2015, long-term outcome data are lacking, and the number of published studies is very low in comparison to endothermal techniques. Five-year extension study of patients from a randomized clinical trial (VeClose) comparing cyanoacrylate closure versus radiofrequency ablation for the treatment of incompetent great saphenous veinsJournal of Vascular Surgery: Venous and Lymphatic DisordersVol. 8Issue 6PreviewThe proprietary cyanoacrylate closure (CAC) system vs radiofrequency ablation (RFA) trial (VenaSeal Sapheon Closure System Pivotal Study [VeClose]) showed that CAC, a nontumescent, nonthermal, nonsclerosant ablation technique, was effective and noninferior to RFA in vein closure with good 36-month outcomes. Conducted under a separate protocol, the aim of this extended follow-up was to assess the long-term safety and effectiveness of CAC and RFA for the treatment of incompetent great saphenous veins (GSV) at 5 years (60 months) of follow-up. Full-Text PDF Open Access

Immediate post-thermal ablation biopsy of colorectal liver metastases to predict oncologic outcomes.

4602 Background: Thermal ablation (TA) is used as a local cure for selected colorectal liver metastases (CLM) with minimal risk. A critical limitation of TA has been early local tumor progression (LTP). The goal of this study is to establish the role of ablation zone (AZ) biopsy in predicting LTP. Methods: This institutional review board-approved prospective study included patients with CLM of 5cm or less in maximum diameter, with confined liver disease or stable, limited extrahepatic disease. Both radiofrequency(RF) and microwave(MW) ablation modalities were used. A biopsy of the center and margin of the AZ was performed immediately after ablation. The applicators were also examined for the presence of viable tumor cells. All samples containing morphologically identified tumor cells were further interrogated with immunohistochemistry to determine the proliferative and viability potential of the detected tumor cells. Ablation margin size was evaluated on the first CT scan performed 4–8 weeks after ablation and was confirmed by 3D assessment with Ablation Confirmation Software (Neuwave™). Variables were evaluated as predictors of time to LTP with the competing-risks model (uni- and multivariate analyses). Results: Between November 2009 and February 2019, 102 patients with 182 CLMs were enrolled. Mean tumor size was 2.0 cm (range, 0.6–4.8 cm). MW was used in 95/182 (52%) tumors and RF in 87/182 (48%). Median follow-up was 19 months. Technical effectiveness was evident in 178/182 (97%) ablated tumors on the first contrast material–enhanced CT at 4–8-weeks post-ablation. The cumulative incidence of LTP at 12 months was 19% (95% confidence interval [CI]: 14, 27). Samples from 64 (35%) of the 178 technically successful cases contained viable tumor. At univariate analysis, tumor size, minimal margin size, and biopsy results were significant in predicting LTP. In a multivariate model, margin size of less than 5 mm (P &lt; .001; hazard ratio [HR], 4.3), and positive biopsy results (P = .02; HR, 1.8) remained significant. LTP within 12 months after TA was noted in 3% (95% CI: 1, 6) of tumor-negative biopsy CLMs with margins of at least 5 mm. Conclusions: Biopsy and pathologic examination of the AZ predicts LTP regardless of TA modality used. This can optimize ablation as a potential local cure for patients with limited CLM.

Abstract No. 603 Comparison of thermal ablative modalities for anatomically complex renal tumors: periprocedural complications and treatment outcomes

To evaluate whether the choice of thermal ablative modality impacts the rate of perioperative complications and treatment outcomes for anatomically complex renal cell carcinoma (RCC). A retrospective analysis was performed for 83 patients (M:F = 51:32, mean age = 75 years) who underwent computer tomography (CT)-guided thermal ablation between October 2008 and March 2019. Tumor complexity was assessed by the RENAL nephrometry scoring system, wherein an RCC with a score greater than 10 is considered to be anatomically complex. The rate of complications, residual disease, and local recurrence were compared among radiofrequency ablation (RFA), microwave ablation (MWA) and cryoablation (CA), using the Chi-Square test. The Kaplan-Meier method was used to compute cancer-specific survival rates in each group, which were compared using the log-rank test. A total of 83 anatomically complex RCC measuring between 1.9 to 5.2 cm in diameter were treated with CT-guided MWA (n = 20,24%), RFA (n = 57,69%) or CA (n = 6,7%). There was no significant difference in baseline patient or tumor demographics among the three groups. MWA is associated with significantly decreased ablation time (P = 0.001), procedural time (P = 0.001) and sedation dosage (P = 0.001), when compared to RFA and CA groups. All three ablative modalities resulted in similar rates of complications, residual disease and local recurrence (P = 0.07, P = 0.27, P = 0.10, respectively). CT-guided MWA, RFA and CA resulted in comparable perioperative complications and treatment outcomes for anatomically complex RCC.Table 1Analysis of periprocedural complication and treatment outcome between ablative modalitiesRFACAMWAP valuesProcedural time146 (50)169 (50)67 (18)0.001Fentanyl322 (18)270 (62)159 (12)0.001Versed6.4 (0.8)5.8 (1.1)2.8 (0.4)0.04Radiation dose258 (35)479 (124)208 (22)0.007Major complication3 (5%)0 (0%)1 (5%)0.07Residual disease18 (32%)2 (33%)8 (42%)0.27Local recurrence11 (21%)1 (16%)2 (10%)0.1 Open table in a new tab

Coupled thermo-electro-mechanical models for thermal ablation of biological tissues and heat relaxation time effects

Thermal ablation is a widely applied electrosurgical process in medical treatment of soft biological tissues. Numerical modeling and simulations play an important role in prediction of temperature distribution and damage volume during the treatment planning stage of associated therapies. In this contribution we report a coupled thermo-electro-mechanical model, accounting for heat relaxation time, for more accurate and precise prediction of the temperature distribution, tissue deformation and damage volume during the thermal ablation of biological tissues. Finite element solutions are obtained for most widely used percutaneous thermal ablative techniques, viz., radiofrequency ablation (RFA) and microwave ablation (MWA). Importantly, both tissue expansion and shrinkage have been considered for modeling the tissue deformation in the coupled model of high temperature thermal ablation. The coupled model takes into account the non-Fourier effects, considering both single-phase-lag (SPL) and dual-phase-lag (DPL) models of bio-heat transfer. The temperature-dependent electrical and thermal parameters, damage-dependent blood perfusion rate and phase change effect accounting for tissue vaporization have been accounted for obtaining more clinically relevant model. The proposed model predictions are found to be in good agreement against the temperature distribution and damage volume reported by previous experimental studies. The numerical simulation results revealed that the non-Fourier effects cause a decrease in the predicted temperature distribution, tissue deformation and damage volume during the high temperature thermal ablative procedures. Furthermore, the effects of different magnitudes of phase lags of the heat flux and temperature gradient on the predicted treatment outcomes of the considered thermal ablative modalities are also quantified and discussed in detail.

Simplified Non-Thermal Tissue Ablation With a Single Insertion Device Enabled by Bipolar High-Frequency Pulses.

To demonstrate the feasibility of a single electrode and grounding pad approach for delivering high frequency irreversible electroporation treatments (H-FIRE) in in-vivo hepatic tissue. Ablations were created in porcine liver under surgical anesthesia by adminstereing high frequency bursts of 0.5-5.0μs pulses with amplitudes between 1.1-1.7 kV in the absence of cardiac synchronization or intraoperative paralytics. Finite element simulations were used to determine the electric field strength associated with the ablation margins (ELethal) and predict the ablations feasible with next generation electronics. All animals survived the procedures for the protocol duration without adverse events. ELethal of 2550, 1650, and 875V/cm were found for treatments consisting of 100x bursts containing 0.5μs pulses and 25, 50, and 75μs of energized-time per burst, respectively. Treatments with 1μs pulses consisting of 100 bursts with 100μs energized-time per burst resulted in ELethal of 650V/cm. A single electrode and grounding pad approach was successfully used to create ablations in hepatic tissue. This technique has the potential to reduce challenges associated with placing multiple electrodes in anatomically challenging environments. H-FIRE is an in situ tumor ablation approach in which electrodes are placed within or around a targeted region to deliver high voltage electrical pulses. Electric fields generated around the electrodes induce irrecoverable cell membrane damage leading to predictable cell death in the relative absence of thermal damage. The sparing of architectural integrity means H-FIRE offers potential advantages compared to thermal ablation modalities for ablating tumors near critical structures.

Ablation plus Transarterial Embolic Therapy for Hepatocellular Carcinoma Larger than 3 cm: Science, Evidence, and Future Directions.

Thermal ablation is widely regarded as definitive therapy for early-stage hepatocellular carcinoma, but its efficacy decreases in tumors greater than 3 cm. Extensive clinical studies have supported improved outcomes provided through combining transarterial embolic therapy with ablation in the treatment of larger tumors. This article will provide a survey of the science and data for combination therapy in both thermal and nonthermal ablation modalities, as well as describe emerging applications.