Minimally Invasive Percutaneous Treatment of Small Renal Tumors with Irreversible Electroporation: A Single-Center Experience

Comparison of Chemotherapy Combined with Percutaneous Electroporation and Chemotherapy Alone in the Management of Locally Advanced Gallbladder Carcinoma (GBC): A Study Protocol

PURPOSE

This study aims to evaluate the feasibility and efficacy of chemotherapy combined with irreversible electroporation (IRE) in patients with locally advanced gallbladder carcinoma (GBC) presenting as gallbladder masses.

MATERIALS AND METHODS

Patients with unresectable GBC masses of size greater than 2 cm and less than 6 cm without evidence of distant metastases and with no contraindication to general anaesthesia will be enrolled in the study. They will be randomized using computer generated table into two arms with 1:1 allocation ratio to include 15 patients in each group. Group I will be the chemotherapy alone arm and Group II will be the combined image-guided irreversible electroporation of the tumour and chemotherapy arm. The primary outcome assessed shall be the clinical benefit rate (complete response, CR; partial response, PR and stable disease, SD) based on the mRECIST criteria and overall survival. The secondary outcome shall be feasibility and safety of the procedure and quality of life pre and post procedure. The quality of life will be assessed by a questionnaire as given by EORTC-Quality of Life Group before starting therapy and 4 weeks after completion of therapy.

EXPECTED GAIN OF KNOWLEDGE

The combined local and systemic effects of irreversible electroporation and systemic chemotherapy respectively may improve the outcomes in inoperable cases of gallbladder carcinoma.

TRIAL REGISTRATION

Clinical Trials Registry - India ( https://ctri.nic.in/Clinicaltrials/advancesearchmain.php ). Identifier: CTRI/2021/05/033803. Primary Register of the International Clinical Trials Registry Platform (WHO ICTRP) ( http://www.who.int/ictrp/search/en/ ).

Design of a System for Magnetic-Resonance-Guided Irreversible Electroporation

Irreversible electroporation (IRE) is a non-thermal tumor ablation method where strong electrical fields between at least two electrodes are used and can be seen as an alternative to thermal ablation techniques. The therapy outcome directly dependents on the position of the electrodes. Real-time monitoring of the IRE by magnetic resonance imaging (MRI) would allow to detect unwanted electrode displacement and to apply visualization methods for the ablation area. This requires that the IRE generator does not significantly interfere with the MRI. Currently, there is no IRE generator available designed for MRI-guided IRE.This paper presents an IRE system specifically developed for use in an MRI environment. The system is initially tested with a standard IRE sequence and then the interference between a clinical 3 T MRI device and the IRE system is investigated using a noise measurement and the signal-to-noise ratio (SNR) of images acquired with a gradient echo (GRE) sequence. The results show, that although the SNR of the images decrease by maximal 36 % when the IRE system is switched on, image quality does not visibly degrade. Hence, MRI-guided IRE is feasible with the proposed system.Clinical relevance- This paper demonstrates the possibility of MRI-guided IRE with only minor image degradation when the IRE system is used in parallel with MRI imaging.

Electroporation-Based Therapy for Brain Tumors: A Review

Electroporation-based therapy (EBT), as a high-voltage-pulse technology has been prevalent with favorable clinical outcomes in the treatment of various solid tumors. This review paper aims to promote the clinical translation of EBT for brain tumors. First, we briefly introduced the mechanism of pore formation in a cell membrane activated by external electric fields using a single cell model. Then, we summarized and discussed the current in vitro and in vivo preclinical studies, in terms of (1) the safety and effectiveness of EBT for brain tumors in animal models, and (2) the blood-brain barrier (BBB) disruption induced by EBT. Two therapeutic effects could be achieved in EBT for brain tumors simultaneously, i.e., the tumor ablation induced by irreversible electroporation (IRE) and transient BBB disruption induced by reversible electroporation (RE). The BBB disruption could potentially improve the uptake of antitumor drugs thereby enhancing brain tumor treatment. The challenges that hinder the application of EBT in the treatment of human brain tumors are discussed in the review paper as well.

Immunomodulatory Effect of Irreversible Electroporation Alone and Its Cooperating With Immunotherapy in Pancreatic Cancer

Emerging studies have showed irreversible electroporation (IRE) focused on pancreatic cancer (PC). However, the effects of IRE treatment on the immune response of PC remain unknown. Moreover, there are few studies on the therapeutic effect of IRE combining with immunotherapy on PC. Thus, we review recent advances in our understanding of IRE alone and its working with immunotherapy towards the immune response of PC, discussing potential opportunities for exploring future treatment strategies.

MRI and CT in the follow-up after irreversible electroporation of small renal masses

PURPOSE

Ablation plays a growing role in the treatment of small renal masses (SRMs) due to its nephron sparing properties and low invasiveness. Irreversible electroporation (IRE) has the potential, although still experimental, to overcome current limitations of thermal ablation. No prospective imaging studies exist of the ablation zone in the follow up after renal IRE in humans. Objectives are to assess computed tomography (CT) and magnetic resonance imaging (MRI) on the ablation zone volume (AZV), enhancement and imaging characteristics after renal IRE.

METHODS

Prospective phase 2 study of IRE in nine patients with ten SRMs. MRI imaging was performed pre-IRE, 1 week, 3 months, 6 months and 12 months after IRE. CT was performed pre-IRE, perioperatively (direct after ablation), 3 months, 6 months and 12 months after IRE. AZVs were assessed by two independent observers. Observer variation was analyzed. Evolution of AZVs, and relation between the needle configuration volume (NCV; planned AZV) and CT- and MRI volumes were evaluated.

RESULTS

Eight SRMs were clear cell renal cell carcinomas, one SRM was a papillary renal cell carcinoma and one patient had a non-diagnostic biopsy. On CT, median AZV increased perioperatively until 3 months post-IRE (respectively, 16.8 cm3 and 6.2 cm3) compared to the NCV (4.8 cm3). On MRI, median AZV increased 1-week post-IRE until 3 months post-IRE (respectively, 14.5 cm3 and 4.6 cm3) compared to the NCV (4.8 cm3). At 6 months the AZV starts decreasing (CT 4.8 cm3; MRI 3.0 cm3), continuing at 12 months (CT 4.2 cm3, MRI 1.1 cm3). Strong correlation was demonstrated between the planning and the post-treatment volumes. Inter-observer agreement between observers was excellent (CT 95% CI 0.82-0.95, MRI 95% CI 0.86-0.96). All SRMs appeared non-enhanced immediately after ablation, except for one residual tumour. Subtraction images confirmed non-enhancement on MRI in unclear enhancement cases (3/9). Directly after IRE, gas bubbles, perinephric stranding and edema were observed in all cases.

CONCLUSION

The AZV increases immediately on CT until 3 months after IRE. On MRI, the AZV increases at 1 week until 3 months post-IRE. At 6 months the AZV starts decreasing until 12 months post-IRE on both CT and MRI. Enhancement was absent post-IRE, except for one residual tumour. Gas bubbles, perinephric stranding and edema are normal findings directly post-IRE.

Irreversible Electroporation for the Treatment of Small Renal Masses: 5-Year Outcomes

Introduction: Irreversible electroporation (IRE) is a nonthermal ablative technology that applies high-voltage short-pulse electrical current to create cellular membrane nanopores and ultimately results in apoptosis. This is thought to overcome thermal limitations of other ablative technologies. We report 5-year oncologic outcomes of percutaneous IRE for small renal masses. Patients and Methods: A single-institution retrospective review of cT1a renal masses treated with IRE from April 2013 to December 2019 was performed. Those with <1 month follow-up were excluded. IRE was performed with the NanoKnife^© System (Angiodynamics, Latham, NY). Renal mass biopsy was obtained before or during ablation in most circumstances; biopsy was excluded in some patients because of concern for IRE probe displacement. Postablation guideline-based surveillance imaging was performed. Initial treatment failure was defined as persistent tumor enhancement on first post-treatment imaging. Survival analysis was performed through the Kaplan-Meier method for effectively treated tumors (SPSS; IBM, Armonk, NY). Results: IRE was used to treat 48 tumors in 47 patients. Twenty-two per 48 tumors (45.8%) were biopsy-confirmed renal cell carcinoma (RCC). No complications ≥ Clavien Grade III occurred and 36 patients (76.6%) were discharged the same day. Initial treatment success rate was 91.7% (n = 44/48); three treatment failures were managed with salvage radiofrequency ablation and one with robotic partial nephrectomy. Median follow-up was 50.4 months (interquartile range 29.0-65.5). The 5-year local recurrence-free survival was 81.4% in biopsy-confirmed RCC patients and 81.0% in all patients. Five-year metastasis-free survival was 93.3% and 97.1%, respectively, and 5-year overall survival was 92.3% and 90.6%, respectively. Five-year cancer-specific survival was 100% for both biopsy-confirmed RCC and all patient groups. Conclusions: IRE has low morbidity, but suboptimal intermediate-term oncologic outcomes compared with conventional thermal ablation techniques for small low-complexity tumors. Use of IRE should be restricted to select cases.

Irreversible electroporation (IRE) in renal cell carcinoma (RCC): a mid-term clinical experience

Objectives

To evaluate the safety and efficacy of CT-guided IRE of clinical T1a (cT1a) renal tumours close to vital structures and to assess factors that may influence the technical success and early oncological durability.

Methods

CT-guided IRE (2015–2020) was prospectively evaluated. Patients’ demographics, technical details/success, Clavien-Dindo (CD) classification of complications (I–V) and oncological outcome were collated. Statistical analysis was performed to determine variables associated with complications. The overall 2- and 3-year cancer-specific (CS), local recurrence-free (LRF) and metastasis-free (MF) survival rates are presented using the Kaplan-Meier curves.

Results

Thirty cT1a RCCs (biopsy-proven/known VHL disease) in 26 patients (age 32–81 years) were treated with IRE. The mean tumour size was 2.5 cm and the median follow-up was 37 months. The primary technical success rate was 73.3%, where 22 RCCs were completely IRE ablated. Seven residual diseases were successfully ablated with cryoablation, achieving an overall technical success rate of 97%. One patient did not have repeat treatment as he died from unexpected stroke at 4-month post-IRE. One patient had CD-III complication with a proximal ureteric injury. Five patients developed > 25% reduction of eGFR immediately post-IRE. All patients have preservation of renal function without the requirement for renal dialysis. The overall 2- and 3-year CS, LRF and MF survival rates are 89%, 96%, 91% and 87%.

Conclusion

CT-guided IRE in cT1a RCC is safe with acceptable complications. The primary technical success rate was suboptimal due to the early operator’s learning curve, and long-term follow-up is required to validate the IRE oncological durability.

Key Points

• Irreversible electroporation should only be considered when surgery or image-guided thermal ablation is not an option for small renal cancer.

• This non-thermal technique is safe in the treatment of small renal cancer and the primary technical success rate was 73.3%.

• This can be used when renal cancer is close to important structure.

In Vitro Study of Calcium Microsecond Electroporation of Prostate Adenocarcinoma Cells

Electroporation, applied as a non-thermal ablation method has proven to be effective for focal prostate treatment. In this study, we performed pre-clinical research, which aims at exploring the specific impact of this so-called calcium electroporation on prostate cancer. First, in an in-vitro study of DU 145 cell lines, microsecond electroporation (μsEP) parameters were optimized. We determined hence the voltage that provides both high permeability and viability of these prostate cancer cells. Subsequently, we compared the effect of μsEP on cells' viability with and without calcium administration. For high-voltage pulses, the cell death's mechanism was evaluated using flow-cytometry and confocal laser microscopy. For lower-voltage pulses, the influence of electroporation on prostate cancer cell mobility was studied using scratch assays. Additionally, we applied calcium-binding fluorescence dye (Fluo-8) to observe the calcium uptake dynamic with the fluorescence microscopy. Moreover, the molecular dynamics simulation visualized the process of calcium ions inflow during μsEP. According to our results calcium electroporation significantly decreases the cells viability by promoting apoptosis. Furthermore, our data shows that the application of pulsed electric fields disassembles the actin cytoskeleton and influences the prostate cancer cells' mobility.

Electroporation-Based Treatments in Urology

The observation that an application of a pulsed electric field (PEF) resulted in an increased permeability of the cell membrane has led to the discovery of the phenomenon called electroporation (EP). Depending on the parameters of the electric current and cell features, electroporation can be either reversible or irreversible. The irreversible electroporation (IRE) found its use in urology as a non-thermal ablative method of prostate and renal cancer. As its mechanism is based on the permeabilization of cell membrane phospholipids, IRE (as well as other treatments based on EP) provides selectivity sparing extracellular proteins and matrix. Reversible EP enables the transfer of genes, drugs, and small exogenous proteins. In clinical practice, reversible EP can locally increase the uptake of cytotoxic drugs such as cisplatin and bleomycin. This approach is known as electrochemotherapy (ECT). Few in vivo and in vitro trials of ECT have been performed on urological cancers. EP provides the possibility of transmission of genes across the cell membrane. As the protocols of gene electrotransfer (GET) over the last few years have improved, EP has become a well-known technique for non-viral cell transfection. GET involves DNA transfection directly to the cancer or the host skin and muscle tissue. Among urological cancers, the GET of several plasmids encoding prostate cancer antigens has been investigated in clinical trials. This review brings into discussion the underlying mechanism of EP and an overview of the latest progress and development perspectives of EP-based treatments in urology.

Ablation of Small Renal Masses

Renal cell carcinoma is most commonly diagnosed in the sixth or seventh decade of life. Historically, surgical extirpation was the gold standard treatment option for small renal masses. However, given the comorbidities in this elderly population, not all patients are candidates for surgery. The development of minimally invasive ablative therapies has solved the surgical dilemma in this patient population. Furthermore, the 2017 American Urological Association guidelines recommends consideration of percutaneous image guided thermal ablation as a treatment option for masses smaller than 3 cm even in healthy individuals. Percutaneous image guided thermal ablation is an attractive treatment option providing excellent local tumor control, fewer complications, better preservation of the renal functions, faster recovery and shorter hospital stay. Various ablative modalities are available in clinical practice. This includes radiofrequency ablation, cryoablation, microwave ablation, irreversible electroporation, high intensity focused ultrasound, and laser ablation. In this review, we focus on the most commonly used modalities including radiofrequency ablation and cryoablation and to a lesser extent microwave ablation and irreversible electroporation.

High-Voltage Electrical Pulses in Oncology: Irreversible Electroporation, Electrochemotherapy, Gene Electrotransfer, Electrofusion, and Electroimmunotherapy

This review summarizes the use of high-voltage electrical pulses (HVEPs) in clinical oncology to treat solid tumors with irreversible electroporation (IRE) and electrochemotherapy (ECT). HVEPs increase the membrane permeability of cells, a phenomenon known as electroporation. Unlike alternative ablative therapies, electroporation does not affect the structural integrity of surrounding tissue, thereby enabling tumors in the vicinity of vital structures to be treated. IRE uses HVEPs to cause cell death by inducing membrane disruption, and it is primarily used as a radical ablative therapy in the treatment of soft-tissue tumors in the liver, kidney, prostate, and pancreas. ECT uses HVEPs to transiently increase membrane permeability, enhancing cellular cytotoxic drug uptake in tumors. IRE and ECT show immunogenic effects that could be augmented when combined with immunomodulatory drugs, a combination therapy the authors term electroimmunotherapy. Additional electroporation-based technologies that may reach clinical importance, such as gene electrotransfer, electrofusion, and electroimmunotherapy, are concisely reviewed. HVEPs represent a substantial advancement in cancer research, and continued improvement and implementation of these presented technologies will require close collaboration between engineers, interventional radiologists, medical oncologists, and immuno-oncologists.

Thermal Ablation of T1a Renal Cell Carcinoma: The Clinical Evidence

Renal cell carcinoma (RCC) is most commonly diagnosed at an early (T1a) stage and is typically amenable to several effective treatments. The current gold standard therapy is partial nephrectomy, given its decreased morbidity and similar oncologic outcomes when compared with radical nephrectomy. Thermal ablation is an evolving definitive therapy for T1a RCC which is even less invasive than partial nephrectomy. This article reviews the evidence for thermal ablation in the treatment of T1a RCC and compares outcomes of existing ablation modalities with surgical management.

Influence of Pulsed Electric Fields and Mitochondria-Cytoskeleton Interactions on Cell Respiration

Pulsed electric fields with microsecond pulse width (μsPEFs) are used clinically; namely, irreversible electroporation/Nanoknife is used for soft tissue tumor ablation. The μsPEF pulse parameters used in irreversible electroporation (0.5-1 kV/cm, 80-100 pulses, ∼100 μs each, 1 Hz frequency) may cause an internal field to develop within the cell because of the disruption of the outer cell membrane and subsequent penetration of the electric field. An internal field may disrupt voltage-sensitive mitochondria, although the research literature has been relatively unclear regarding whether such disruptions occur with μsPEFs. This investigation reports the influence of clinically used μsPEF parameters on mitochondrial respiration in live cells. Using a high-throughput Agilent Seahorse machine, it was observed that μsPEF exposure comprising 80 pulses with amplitudes of 600 or 700 V/cm did not alter mitochondrial respiration in 4T1 cells measured after overnight postexposure recovery. To record alterations in mitochondrial function immediately after μsPEF exposure, high-resolution respirometry was used to measure the electron transport chain state via responses to glutamate-malate and ADP and mitochondrial membrane potential via response to carbonyl cyanide-p-trifluoromethoxyphenylhydrazone. In addition to measuring immediate mitochondrial responses to μsPEF exposure, measurements were also made on cells permeabilized using digitonin and those with compromised cytoskeleton due to actin depolymerization via treatment with the drug latrunculin B. The former treatment was used as a control to tease out the effects of plasma membrane permeabilization, whereas the latter was used to investigate indirect effects on the mitochondria that may occur if μsPEFs impact the cytoskeleton on which the mitochondria are anchored. Based on the results, it was concluded that within the pulse parameters tested, μsPEFs alone do not hinder mitochondrial physiology but can be used to impact the mitochondria upon compromising the actin. Mitochondrial susceptibility to μsPEF after actin depolymerization provides, to our knowledge, a novel avenue for cancer therapeutics.

[Ablative therapy of small renal masses]

Renal cell cancer is nowadays predominantly diagnosed in early stages due to the widespread use of sectional imaging for unrelated symptoms. Small renal masses (<4 cm) feature a largely indolent biology with a very low risk for metastasis or even a benign biology in up to 30% of the cases. Consequently, there is a need for less invasive therapeutic alternatives to nephron-sparing surgery. Meanwhile, there is a broad portfolio of local ablation techniques to treat small renal tumors. These include the extensively studied radiofrequency ablation and cryoablation techniques as well as newer modalities like microwave ablation and irreversible electroporation as more experimental techniques. Tumor ablation can be performed percutaneously under image guidance or laparoscopically. In particular, the percutaneous approach is a less invasive alternative to nephron-sparing surgery with lower risk for complications. Comparative studies and meta-analyses report a higher risk for local recurrence after renal tumor ablation compared to surgery. However, long-term oncological results after treatment of small renal masses are promising and do not seem to differ from partial nephrectomy. The possibility for salvage therapy in case of recurrence also accounts for this finding. Especially old patients with an increased risk of surgical and anesthesiological complications as well as patients with recurrent and multiple hereditary renal cell carcinomas may benefit from tumor ablation. Tumor biopsy prior to intervention is associated with very low morbidity rates and is oncologically safe. It can help to assess the biology of the renal mass and prevent therapy of benign lesions.

Current opinion in urology 2017: focal therapy of small renal lesions

PURPOSE OF REVIEW

With the increasing incidence of small renal masses (SRMs), ablative technologies are becoming more commonly utilized. With any nascent treatment modality, outcomes literature needs to be constantly re-evaluated. The purpose of this review is to revisit the most updated literature regarding the safety and efficacy of ablative treatments of renal lesions.

RECENT FINDINGS

Recent literature demonstrates that small renal tumor ablation is safe and effective. Although it does not have the same oncological efficacy of surgical extirpation, local recurrence-free survival has consistently shown to be around 90%. Cryoablation and radiofrequency ablation have longer-term data demonstrating durable responses. Microwave ablation and irreversible electroporation are promising modalities with longer-term data coming. Complication rates and procedural morbidity of ablation are consistently lower than for partial nephrectomy.

SUMMARY

Image-guided focal ablation is a valuable tool in the management of SRMs. Although it does not have the same efficacy of surgical extirpation, with the ability to perform repeat procedures and salvage surgery if necessary, oncologic outcomes are comparable to those of upfront surgery. Ultimately, longer-term studies and prospective trials are needed to further elucidate these modalities.

A Conceivable Mechanism Responsible for the Synergy of High and Low Voltage Irreversible Electroporation Pulses

Irreversible electroporation (IRE), is a new non-thermal tissue ablation technology in which brief high electric field pulses are delivered across the target tissue to induce cell death by irreversible permeabilization of the cell membrane. A deficiency of conventional IRE is that the ablation zone is relatively small, bounded by the irreversible electroporation isoelectric field margin. In the previous studies we have introduced a new treatment protocol that combines few short high voltage (SHV) pulses with long low-voltage (LLV) pulses. In the previous studies, we also have shown that the addition of few SHV pulses increases by almost a factor of two the area ablated by a protocol that employs only the LLV pulses. This study employs potato and gel phantom to generate a plausible explanation for the mechanism. The study provides circumstantial evidence that the mechanism involved is the production of electrolytic compounds by the LLV pulse sequence, which causes tissue ablation beyond the margin of the irreversible electroporation isoelectric field generated by the SHV pulses, presumable to the reversible electroporation isoelectric field margin generated by the SHV pulses.

Percutaneous irreversible electroporation for the treatment of small renal masses: The first Canadian case series

INTRODUCTION

Irreversible electroporation (IRE) is a novel technology used in the minimally invasive treatment of small solid organ tumours. Currently, there is a paucity of literature studying treatment of small renal masses (SRMs) with IRE. Our pilot study is the first case series in Canada to use IRE in the treatment of SRMs.

METHODS

This retrospective cohort pilot study includes five patients (three females and two males) who presented with a SRM that was deemed not amendable to any other treatment than a radical nephrectomy or IRE. The IRE procedures were carried out by an interventional radiologist in conjunction with a urologist using the Angiodynamics NanoKnife IRE device.

RESULTS

Mean tumour size was 28 mm (range 18-39), with a mean R.E.N.A.L. nephrometry score of 8.4±0.55. Over a mean followup of 22.8 months (range 14-31), four out of the five patients did not have a radiological recurrence. No adverse events were reported after the five IRE procedures. Renal function was stable post-IRE, with no to negligible decreases in estimated glomerular filtration rate detected (range +2 to -13 mL/min/1.73 m²).

CONCLUSIONS

Our pilot study demonstrates that renal percutaneous IRE is safe to use in the context of challenging-to-treat SRMs. Early radiological and renal function outcomes are encouraging, but further study is required to assess oncological success. The small sample size, retrospective nature of the study, relatively short followup, and the lack of routine renal biopsy to confirm malignancy are the major limitations noted.

Available ablation energies to treat cT1 renal cell cancer: emerging technologies

Purpose

An increasing interest in percutaneous ablation of renal tumors has been caused by the increasing incidence of SRMs, the trend toward minimally invasive nephron-sparing treatments and the rapid development of local ablative technologies. In the era of shared decision making, patient preference for non-invasive treatments also leads to an increasing demand for image-guided ablation. Although some guidelines still reserve ablation for poor surgical candidates, indications may soon expand as evidence for the use of the two most validated local ablative techniques, cryoablation (CA) and radiofrequency ablation (RFA), is accumulating. Due to the collaboration between experts in the field in biomedical engineering, urologists, interventional radiologists and radiation oncologists, the improvements in ablation technologies have been evolving rapidly in the last decades, resulting in some new emerging types of ablations.

Methods

A literature search was conducted to identify original research articles investigating the clinical outcomes of new emerging technologies, percutaneous MWA, percutaneous IRE and SABR, in patients with primary cT1 localized renal cell cancer.

Results

Due to the collaboration between experts in the field in biomedical engineering, urologists, interventional radiologists and radiation oncologists, the improvements in ablation technologies have been evolving rapidly in the last decades. New emerging technologies such as microwave ablation (MWA), irreversible electroporation (IRE) and stereotactic ablative radiotherapy (SABR) seem to be getting ready for prime time.

Conclusion

This topical paper describes the new emerging technologies for cT1 localized renal cell cancer and investigates how they compare to CA and RFA.

The Role of Ablation and Minimally Invasive Techniques in the Management of Small Renal Masses

CONTEXT

Nephron-sparing approaches are increasingly recommended for incidental small renal masses. Herein, we review the current literature regarding the safety and efficacy of focal therapy, including percutaneous ablation, for small renal masses.

OBJECTIVE

To summarize the application of ablative therapy in the management of small renal masses.

EVIDENCE ACQUISITION

PubMed and Medline database search was performed to look for findings published since 2000 on focal therapy for small renal masses. After literature review, 64 articles were selected and discussed.

EVIDENCE SYNTHESIS

Radiofrequency ablation and cryotherapy are the most widely used procedures with intermediate-term oncological outcome comparable with surgical series. Cost effectiveness seems excellent and side effects appear acceptable. To date, no randomized trial comparing percutaneous focal therapy with standard surgical approach or active surveillance has been performed.

CONCLUSIONS

Focal ablative therapies are now accepted as effective treatment for small renal tumors. For tumors <3cm, oncological effectiveness of ablative therapies is comparable with that of partial nephrectomy. Percutaneous ablation has fewer complications and a better postoperative profile when compared with minimally invasive partial nephrectomy.

PATIENT SUMMARY

Focal ablative therapies are now accepted as effective treatment for small renal tumors. For tumors <3cm, oncological effectiveness of ablative therapies is comparable with that of partial nephrectomy.

Irreversible Electroporation: A Novel Ultrasound-guided Modality for Non-thermal Tumor Ablation

Ultrasound-guided tumor ablation techniques have been proven to be highly effective and minimally invasive in the treatment of many diseases. Traditional approaches to ablation include microwave and radiofrequency techniques, cryotherapy, and high-intensity focused ultrasound. However, these methods are prone to heat-sink effects that can diminish the effectiveness of treatment and damage adjacent structures, such as bile ducts, blood vessels, the gallbladder, or bowel. Irreversible electroporation (IRE) is a non-thermal ablation modality that induces cell apoptosis through the application of high-voltage current. IRE is not limited by many of the limitation which affects conventional tumor ablation techniques, and is particularly useful in treating sensitive areas of the body. The article reviews the basics of ultrasound-guided technology, including its clinical applications and effectiveness in the treatment of tumors.

Controllable Moderate Heating Enhances the Therapeutic Efficacy of Irreversible Electroporation for Pancreatic Cancer

Irreversible electroporation (IRE) as a non-thermal tumor ablation technology has been studied for the treatment of pancreatic carcinoma and has shown a significant survival benefit. We discovered that moderate heating (MH) at 43 °C for 1-2 minutes significantly enhanced ex vivo IRE tumor ablation of Pan02 cells by 5.67-fold at 750 V/cm and by 1.67-fold at 1500 V/cm. This amount of heating alone did not cause cell death. An integrated IRE system with controllable laser heating and tumor impedance monitoring was developed to treat mouse ectopic pancreatic cancer. With this novel IRE system, we were able to heat and maintain the temperature of a targeted tumor area at 42 °C during IRE treatment. Pre-heating the tumor greatly reduced the impedance of tumor and its fluctuation. Most importantly, MHIRE has been demonstrated to significantly extend median survival and achieve a high rate of complete tumor regression. Median survival was 43, 46 and 84 days, for control, IRE with 100 μs, 1 Hz, 90 pulses and electric fields 2000–2500 V/cm and MHIRE treatment respectively. 55.6% of tumor-bearing mice treated with MHIRE were tumor-free, whereas complete tumor regression was not observed in the control and IRE treatment groups.

Focal ablation therapy for renal cancer in the era of active surveillance and minimally invasive partial nephrectomy

Partial nephrectomy is the optimal surgical approach in the management of small renal masses (SRMs). Focal ablation therapy has an established role in the modern management of SRMs, especially in elderly patients and those with comorbidities. Percutaneous ablation avoids general anaesthesia and laparoscopic ablation can avoid excessive dissection; hence, these techniques can be suitable for patients who are not ideal surgical candidates. Several ablation modalities exist, of which radiofrequency ablation and cryoablation are most widely applied and for which safety and oncological efficacy approach equivalency to partial nephrectomy. Data supporting efficacy and safety of ablation techniques continue to mature, but they originate in institutional case series that are confounded by cohort heterogeneity, selection bias, and lack of long-term follow-up periods. Image guidance and surveillance protocols after ablation vary and no consensus has been established. The importance of SRM biopsy, its optimal timing, the type of biopsy used, and its role in treatment selection continue to be debated. As safety data for active surveillance and experience with minimally invasive partial nephrectomy are expanding, the role of focal ablation therapy in the treatment of patients with SRMs requires continued evaluation.

[Focal therapy for small renal masses : Observation, ablation or surgery]

BACKGROUND

The rising incidence of renal cell carcinoma, its more frequent early detection (stage T1a) and the increasing prevalence of chronic renal failure with higher morbidity and shorter life expectancy underscore the need for multimodal focal nephron-sparing therapy.

DISCUSSION

During the past decade, the gold standard shifted from radical to partial nephrectomy. Depending on the surgeon's experience, the patient's constitution and the tumor's location, the intervention can be performed laparoscopically with the corresponding advantages of lower invasiveness. A treatment alternative can be advantageous for selected patients with high morbidity and/or an increased risk of complications associated with anesthesia or surgery. Corresponding risk stratification necessitates previous confirmation of the small renal mass (cT1a) by histological examination of biopsy samples. Active surveillance represents a controlled delay in the initiation of treatment.

RESULTS

Percutaneous radiofrequency ablation (RFA) and laparoscopic cryoablation are currently the most common treatment alternatives, although there are limitations particularly for renal tumors located centrally near the hilum. More recent ablation procedures such as high intensity focused ultrasound (HIFU), irreversible electroporation, microwave ablation, percutaneous stereotactic ablative radiotherapy and high-dose brachytherapy have high potential in some cases but are currently regarded as experimental for the treatment of renal cell carcinoma.

Irreversible Electroporation for the Ablation of Renal Cell Carcinoma: A Prospective, Human, In Vivo Study Protocol (IDEAL Phase 2b)

Background

Irreversible electroporation (IRE) is an emerging technique delivering electrical pulses to ablate tissue, with the theoretical advantage to overcome the main shortcomings of conventional thermal ablation. Recent short-term research showed that IRE for the ablation of renal masses is a safe and feasible treatment option. In an ablate and resect design, histopathological analysis 4 weeks after radical nephrectomy demonstrated that IRE-targeted renal tumors were completely covered by ablation zone. In order to develop a validated long-term IRE follow-up study, it is essential to obtain clinical confirmation of the efficacy of this novel technology. Additionally, follow-up after IRE ablation obliges verification of a suitable imaging modality.

Objective

The objectives of this study are the clinical efficacy and safety of IRE ablation of renal masses and to evaluate the use of cross-sectional imaging modalities in the follow-up after IRE in renal tumors. This study conforms to the recommendations of the IDEAL Collaboration and can be categorized as a phase 2B exploration trial.

Methods

In this prospective clinical trial, IRE will be performed in 20 patients aged 18 years and older presenting with a solid enhancing small renal mass (SRM) (≤4 cm) who are candidates for ablation. Magnetic resonance imaging (MRI) and contrast-enhanced ultrasound (CEUS) will be performed at 1 day pre-IRE, and 1 week post-IRE. Computed tomography (CT), CEUS, and MRI will be performed at 3 months, 6 months, and 12 months post-IRE.

Results

Presently, recruitment of patients has started and the first inclusions are completed. Preliminary results and outcomes are expected in 2018.

Conclusions

To establish the position of IRE ablation for treating renal tumors, a structured stepwise assessment in clinical practice is required. This study will offer fundamental knowledge on the clinical efficacy of IRE ablation for SRMs, potentially positioning IRE as ablative modality for renal tumors and accrediting future research with long-term follow-up.

Trial Registration

Clinicaltrials.gov registration number NCT02828709; https://clinicaltrials.gov/ct2/show/NCT02828709 (archived by WebCite at http://www.webcitation.org/6nmWK7Uu9). Dutch Central Committee on Research Involving Human Subjects NL56935.018.16

Irreversible Electroporation (IRE) in Renal Tumors

Small renal masses (SRMs) have been traditionally managed with surgical resection. Minimally invasive nephron-sparing treatment methods are preferred to avoid harmful consequences of renal insufficiency, with partial nephrectomy (PN) considered the gold standard. With increase in the incidence of the SRMs and evolution of ablative technologies, percutaneous ablation is now considered a viable treatment alternative to surgical resection with comparable oncologic outcomes and better nephron-sparing property. Traditional thermal ablative techniques suffer from unique set of challenges in treating tumors near vessels or critical structures. Irreversible electroporation (IRE), with its non-thermal nature and connective tissue-sparing properties, has shown utility where traditional ablative techniques face challenges. This review presents the role of IRE in renal tumors based on the most relevant published literature on the IRE technology, animal studies, and human experience.

Irreversible electroporation: state of the art

The field of focal ablative therapy for the treatment of cancer is characterized by abundance of thermal ablative techniques that provide a minimally invasive treatment option in selected tumors. However, the unselective destruction inflicted by thermal ablation modalities can result in damage to vital structures in the vicinity of the tumor. Furthermore, the efficacy of thermal ablation intensity can be impaired due to thermal sink caused by large blood vessels in the proximity of the tumor. Irreversible electroporation (IRE) is a novel ablation modality based on the principle of electroporation or electropermeabilization, in which electric pulses are used to create nanoscale defects in the cell membrane. In theory, IRE has the potential of overcoming the aforementioned limitations of thermal ablation techniques. This review provides a description of the principle of IRE, combined with an overview of in vivo research performed to date in the liver, pancreas, kidney, and prostate.

Percutaneous irreversible electroporation of a renal tumor: Anesthetic management

Percutaneous irreversible electroporation (IRE) is a novel tumour ablation method. The application of short and high-voltage electrical pulses to the target lesion induces alterations in cell membrane permeability, finally causing tumour cell death. The extremely high-voltage that is needed in this technique requires the surveillance and management of an experienced anaesthesiologist, as it involves a significant risk of complications, such as cardiac arrhythmias or seizures. The case is presented of a 66 year-old patient diagnosed with a renal adenocarcinoma, and who received without intention-to-cure IRE under general anaesthesia. This case represents the first time this type of technique is used in Spain.