Irreversible electroporation ablation (IRE) of unresectable soft tissue tumors: learning curve evaluation in the first 150 patients treated

Effects of bipolar irreversible electroporation with different pulse durations in a prostate cancer mouse model

Irreversible electroporation (IRE) is a non-thermal ablation technique for local tumor treatment known to be influenced by pulse duration and voltage settings, affecting its efficacy. This study aims to investigate the effects of bipolar IRE with different pulse durations in a prostate cancer mouse model. The therapeutic effectiveness was assessed with in vitro cell experiments, in vivo tumor volume changes with magnetic resonance imaging, and gross and histological analysis in a mouse model. The tumor volume continuously decreased over time in all IRE-treated groups. The tumor volume changes, necroptosis (%), necrosis (%), the degree of TUNEL-positive cell expression, and ROS1-positive cell (%) in the long pulse duration-treated groups (300 μs) were significantly increased compared to the short pulse duration-treated groups (100 μs) (all p < 0.001). The bipolar IRE with a relatively long pulse duration at the same voltage significantly increased IRE-induced cell death in a prostate cancer mouse model.

In silico study about the influence of electroporation parameters on the cellular internalization, spatial uniformity, and cytotoxic effects of chemotherapeutic drugs using the Method of Fundamental Solutions

Reversible electroporation is a suitable technique to aid the internalization of medicaments in cancer tissues without inducing permanent cellular damage, allowing the enhancement of cytotoxic effects without incurring in electric-driven necrotic or apoptotic processes by the presence of non-reversible aqueous pores. An adequate selection of electroporation parameters acquires relevance to reach these goals and avoid opposite effects. This work applies the Method of Fundamental Solutions (MFS) for drug transport simulations in electroporated cancer tissues, using a continuum tumor cord approach and considering both electro-permeabilization and vasoconstriction effects. The MFS algorithm is validated with published results, obtaining satisfactory accuracy and convergence. Then, MFS simulations are executed to study the influence of electric field magnitude [Formula: see text], number of electroporation treatments [Formula: see text], and electroporation time [Formula: see text] on three assessment parameters of electrochemotherapy: the internationalization efficacy accounting for the ability of the therapy to introduce moles into viable cells, cell-kill capacity indicating the faculty to reduce the survival fraction of cancer cells, and distribution uniformity specifying the competence to supply drug homogeneously through the whole tissue domain. According to numerical results, when [Formula: see text] is the reversibility threshold, a positive influence on the first two parameters is only possible once specific values of [Formula: see text] and [Formula: see text] have been exceeded; when [Formula: see text] is just the irreversibility threshold, any combination of [Formula: see text] and [Formula: see text] is beneficial. On the other hand, the drug distribution uniformity is always adversely affected by the application of electric pulses, being this more noticeable as [Formula: see text], [Formula: see text], and [Formula: see text] increases.

Characterizing reversible, irreversible, and calcium electroporation to generate a burst-dependent dynamic conductivity curve

The relationships between burst number, reversible, irreversible, and calcium electroporation have not been comprehensively evaluated in tumor tissue-mimics. Our findings indicate that electroporation effects saturate with a rate constant (τ) of 20 bursts for both conventional and high frequency waveforms (R2 > 0.88), with the separation between reversible and irreversible electroporation thresholds converging at 50 bursts. We find the lethal thresholds for calcium electroporation are statistically similar to reversible electroporation (R2 > 0.99). We then develop a burst-dependent dynamic conductivity curve that now incorporates electroporation effects due to both the electric field magnitude and burst number. Simulated ablation and thermal damage volumes vary significantly between finite element models using either the conventional or new burst-dependent dynamic conductivity curve (p < 0.05). Lastly, for clinically relevant protocols, thermal damage is indicated to not begin until 50 bursts, with maximum nonthermal ablation volumes at 100 bursts (1.5-13% thermal damage by volume). We find that >100 bursts generated negligible increases in ablation volumes with 40-70% thermal damage by volume at 300 bursts. Our results illustrate the need for considering burst number in minimizing thermal damage, choosing adjuvant therapies, and in modeling electroporation effects at low burst numbers.

Infection reporting in patients undergoing irreversible electroporation of locally advanced pancreatic cancer

BACKGROUND

Intraoperative bile cultures (IOBCs) taken during pancreatic surgery are commonly performed and there has been limited evidence that a positive IOBC could aid in perioperative adverse event (AE) management. Therefore, this study aims to describe infection management in patients undergoing irreversible electroporation (IRE).

METHODS

An Institutional Review Board (IRB)-approved prospective database was utilized from 8/2016 to 6/2022, with 127 pancreatic adenocarcinoma patients included.

RESULTS

A total of 28 patients that underwent IRE also had a simultaneous positive IOBC and the remaining 99 patients that underwent IRE had negative IOBC. A total of 11(39%) of the patients with a positive IOBC had AE's, and 38 (38%) of the patients with negative IOBC had AE's. Both groups had similar rates of AEs leading to new hospitalization and prolonged hospitalizations. Overall, there was no correlation between a positive IOBC and a patient developing an AE.

CONCLUSIONS

The findings of this study provide insights that improve the infectious management of patients undergoing IRE.

Real-Time Temperature Rise Estimation during Irreversible Electroporation Treatment through State-Space Modeling

To evaluate the feasibility of real-time temperature monitoring during an electroporation-based therapy procedure, a data-driven state-space model was developed. Agar phantoms mimicking low conductivity (LC) and high conductivity (HC) tissues were tested under the influences of high (HV) and low (LV) applied voltages. Real-time changes in impedance, measured by Fourier Analysis SpecTroscopy (FAST) along with the known tissue conductivity and applied voltages, were used to train the model. A theoretical finite element model was used for external validation of the model, producing model fits of 95.8, 88.4, 90.7, and 93.7% at 4 mm and 93.2, 58.9, 90.0, and 90.1% at 10 mm for the HV-HC, LV-LC, HV-LC, and LV-HC groups, respectively. The proposed model suggests that real-time temperature monitoring may be achieved with good accuracy through the use of real-time impedance monitoring.

Intratumoral electroporation of a self-amplifying RNA expressing IL-12 induces antitumor effects in mouse models of cancer

Alphavirus vectors based on self-amplifying RNA (saRNA) generate high and transient levels of transgene expression and induce innate immune responses, making them an interesting tool for antitumor therapy. These vectors are usually delivered as viral particles, but it is also possible to administer them as RNA. We evaluated this possibility by in vivo electroporation of Semliki Forest virus (SFV) saRNA for local treatment of murine colorectal MC38 subcutaneous tumors. Optimization of saRNA electroporation conditions in tumors was performed using an SFV vector coding for luciferase. Then we evaluated the therapeutic potential of this approach using an SFV saRNA coding for interleukin-12 (SFV-IL-12), a proinflammatory cytokine with potent antitumor effects. Delivery of SFV-IL-12 saRNA by electroporation led to improvement in tumor control and higher survival compared with mice treated with electroporation or with SFV-IL-12 saRNA alone. The antitumor efficacy of SFV-IL-12 saRNA electroporation increased by combination with systemic PD-1 blockade. This therapy, which was also validated in a hepatocellular carcinoma tumor model, suggests that local delivery of saRNA by electroporation could be an attractive strategy for cancer immunotherapy. This approach could have easy translation to the clinical practice, especially for percutaneously accessible tumors.

Pancreatic Ductal Adenocarcinoma: Current and Emerging Therapeutic Uses of Focused Ultrasound

Simple Summary

Pancreatic ductal adenocarcinoma (PDAC) is an increasingly prevalent form of cancer with a low patient survival rate following diagnosis. Focused Ultrasound is an emerging modality that provides exciting opportunities in treating PDAC. This review provides an overview of the clinical application and scientific research of therapeutic focused ultrasound for the treatment of PDAC for use by clinicians and scientific researchers. In addition to providing a description of various physical mechanism underlying therapeutic applications, the current benefits, challenges, and possible future avenues for the application and development of focused ultrasound in the treatment of PDAC are summarized.

Abstract

Pancreatic ductal adenocarcinoma (PDAC) diagnosis accompanies a somber prognosis for the patient, with dismal survival odds: 5% at 5 years. Despite extensive research, PDAC is expected to become the second leading cause of mortality by cancer by 2030. Ultrasound (US) has been used successfully in treating other types of cancer and evidence is flourishing that it could benefit PDAC patients. High-intensity focused US (HIFU) is currently used for pain management in palliative care. In addition, clinical work is being performed to use US to downstage borderline resectable tumors and increase the proportion of patients eligible for surgical ablation. Focused US (FUS) can also induce mechanical effects, which may elicit an anti-tumor response through disruption of the stroma and can be used for targeted drug delivery. More recently, sonodynamic therapy (akin to photodynamic therapy) and immunomodulation have brought new perspectives in treating PDAC. The aim of this review is to summarize the current state of those techniques and share our opinion on their future and challenges.

Treatment of unresectable locally advanced pancreatic cancer with percutaneous irreversible electroporation (IRE) following initial systemic chemotherapy (LAP-PIE) trial: study protocol for a feasibility randomised controlled trial

BACKGROUND

Approximately 30% of patients with pancreas cancer have unresectable locally advanced disease, which is currently treated with systemic chemotherapy. A new treatment option of irreversible electroporation (IRE) has been investigated for these patients since 2005. Cohort studies suggest that IRE confers a survival advantage, but with associated, procedure-related complications. Selection bias may account for improved survival and there have been no prospective randomised trials evaluating the harms and benefits of therapy. The aim of this trial is to evaluate the feasibility of a randomised comparison of IRE therapy with chemotherapy versus chemotherapy alone in patients with locally advanced pancreatic cancer (LAPC).

METHODS AND ANALYSIS

Eligible patients with LAPC who have undergone first-line 5-FluoroUracil, Leucovorin, Irinotecan and Oxaliplatin chemotherapy will be randomised to receive either a single session of IRE followed by (if indicated) further chemotherapy or to chemotherapy alone (standard of care). Fifty patients from up to seven specialist pancreas centres in the UK will be recruited over a period of 15 months. Trial follow-up will be 12 months. The primary outcome measure is ability to recruit. Secondary objectives include practicality and technical success of treatment, acceptability of treatment to patients and clinicians and safety of treatment. A qualitative study has been incorporated to evaluate the patient and clinician perspective of the locally advanced pancreatic cancer with percutaneous irreversible electroporation trial. It is likely that the data obtained will guide the structure, the primary outcome measure, the power and the duration of a subsequent multicentre randomised controlled trial aimed at establishing the clinical efficiency of pancreas IRE therapy. Indicative procedure-related costings will be collected in this feasibility trial, which will inform the cost evaluation in the subsequent study on efficiency.

ETHICS AND DISSEMINATION

The protocol has received approval by London-Brent Research Ethics Committee reference number 21/LO/0077.Results will be analysed following completion of trial recruitment and follow-up. Results will be presented to international conferences with an interest in oncology, hepatopancreaticobiliary surgery and interventional radiology and be published in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

ISRCTN14986389.

A Comparative Modeling Study of Thermal Mitigation Strategies in Irreversible Electroporation Treatments

Irreversible electroporation (IRE), also referred to as nonthermal pulsed field ablation (PFA), is an attractive focal ablation modality for solid tumors and cardiac tissue due to its ability to destroy aberrant cells with limited disruption of the underlying tissue architecture. Despite its nonthermal cell death mechanism, application of electrical energy results in Joule heating that, if ignored, can cause undesired thermal injury. Engineered thermal mitigation (TM) technologies including phase change materials (PCMs) and active cooling (AC) have been reported and tested as a potential means to limit thermal damage. However, several variables affect TM performance including the pulsing paradigm, electrode geometry, PCM composition, and chosen active cooling parameters, meaning direct comparisons between approaches are lacking. In this study, we developed a computational model of conventional bipolar and monopolar probes with solid, PCM-filled, or actively cooled cores to simulate clinical IRE treatments in pancreatic tissue. This approach reveals that probes with integrated PCM cores can be tuned to drastically limit thermal damage compared to existing solid probes. Furthermore, actively cooled probes provide additional control over thermal effects within the probe vicinity and can altogether abrogate thermal damage. In practice, such differences in performance must be weighed against the increased time, expense, and effort required for modified probes compared to existing solid probes.

Optimizing Patient Selection for Irreversible Electroporation of Locally Advanced Pancreatic Cancer: Analyses of Survival

Background

Irreversible electroporation (IRE) has emerged as a viable consolidative therapy after induction chemotherapy, in which this combination has improved overall survival of locally advanced pancreatic cancer (LAPC). Optimal timing and patient selection for irreversible electroporation remains a clinically unmet need. The aim of this study was to investigate preoperative factors that may assist in predicting progression-free and overall survival following IRE.

Methods

A multi-institutional, prospectively maintained database was reviewed for patients with LAPC treated with induction chemotherapy followed by open-technique irreversible electroporation from 7/2015-5/2019. RECIST 1.1 criteria were used to assess tumor response and radiological progression. Overall survival (OS) and progression-free survival (PFS) were recorded. Survival analyses were performed using Kaplan Meier and Cox multivariable regression analyses.

Results

187 LAPC patients (median age 62 years range, 21 – 91, 65% men, 35% women) were treated with IRE. Median PFS was 21.7 months and median OS from diagnosis was 25.5 months. On multivariable analysis, age ≤ 61 (HR 0.41, 95%CI 0.21-0.78, p<0.008) and no prior radiation (HR 0.49, 95%CI 0.26-0.94, p=0.03) were positive predictors of OS after IRE. Age ≤ 61(HR 0.53, 95%CI, 0.28-.99, p=0.046) and FOLFIRINOX followed by gemcitabine/abraxane induction chemotherapy (HR 0.37,95%CI 0.15-0.89, p=0.027) predicted prolonged PFS after IRE. Abnormal CA19-9 values at the time of surgery negatively impacted both OS (HR 2.46, 95%CI 1.28-4.72, p<0.007) and PFS (HR 2.192, 95%CI 1.143-4.201, p=0.018) following IRE.

Conclusions

Age, CA 19-9 response, avoidance of pre-IRE radiation, and FOLFIRINOX plus gemcitabine/abraxane induction chemotherapy are prominent factors to consider when referring or selecting LAPC patients to undergo IRE.

Intraoperative HIFU Ablation of the Pancreas Using a Toroidal Transducer in a Porcine Model. The First Step towards a Clinical Treatment of Locally Advanced Pancreatic Cancer

Apart from palliative chemotherapy, no other therapy has been proven effective for the treatment of locally advanced pancreatic tumors. In this study, an intraoperative high-intensity focused ultrasound (HIFU) device was tested in vivo to demonstrate the feasibility of treating the pancreatic parenchyma and tissues surrounding the superior mesenteric vessels prior to clinical translation of this technique. Twenty pigs were included and treated using a HIFU device equipped with a toroidal transducer and an integrated ultrasound imaging probe. Treatments were performed with energy escalation (from 30 kJ to 52 kJ). All treatments resulted in visible (macroscopically and in ultrasound images) homogeneous thermal damage, which was confirmed by histology. The dimensions of thermal lesions measured in ultrasound images and those measured macroscopically were correlated (r = 0.82, p < 0.05). No arterial spasms or occlusion were observed at the lowest energy setting. Temporary spasm of the peripancreatic artery was observed when using an energy setting greater than 30 kJ. The possibility of treating the pancreas and tissues around mesenteric vessels without vascular thrombosis holds great promise for the treatment of locally advanced pancreatic cancers. If clinically successful, chemotherapy followed by HIFU treatment could rapidly become a novel treatment option for locally advanced pancreatic cancer.

Early Detection of Local Tumor Progression after Irreversible Electroporation (IRE) of a Hepatocellular Carcinoma Using Gd-EOB-DTPA-Based MR Imaging at 3T

Simple Summary

Liver tumors like hepatocellular carcinoma (HCC) can be treated minimally invasive, e.g., by Irreversible Electroporation (IRE), which destroys the cancer. As it is possible that the tumor re-grows due to single tumor cells inadvertently not covered by the treatment, follow-up imaging of the liver is important for early detection of local tumor progression. As ablation leaves scarred tissue, recurrent tumor after IRE can appear vastly different than before treatment and thus can be hard to detect on MRI via classical imaging features. We here examined cases of local tumor progression after IRE of HCC and found distinct MR-imaging features helpful for the identification of re-grown viable tumor, namely T2 BLADE and diffusion weighted images (DWI) at the ablation zone border and T1 portal-venous and delayed phase post-contrast images in the center of the ablation zone. This knowledge will help in early detection and re-treatment of HCC for a prolonged survival.

Abstract

This single-center retrospective study was conducted to improve the early detection of local tumor progression (LTP) after irreversible electroporation (IRE) of a hepatocellular carcinoma (HCC) using gadolinium ethoxybenzyl diethylenetriamine pentaacetic acid (Gd-EOB-DTPA)-based 3T MR imaging and to identify helpful signal characteristics by comparing 23 patients with and 60 patients without LTP. To identify the differences in the sensitivity of MRI sequences, the specificity, positive prediction value, negative prediction value (NPV) and diagnostic odds ratio were calculated. A chi-squared test, two-tailed student’s t-test and binary logistic regression model were used to detect distinct patient characteristics and variables for the prediction of LTP. LTP was mostly detected in the peripheral ablation zone (82.6%) within the first six months (87.0%). The central LTP ablation area presented more hypointensities in T1 p.v. (sensitivity: 95.0%; NPV: 90.0%) and in T1 d.p. (sensitivity: 100.0%; NPV: 100.0) while its peripheral part showed more hyperintensities in T2 BLADE (sensitivity: 95.5%; NPV: 80.0%) and in diffusion sequences (sensitivity: 90.0%). Liver cirrhosis seems to be an unfavorable prognosticator for LTP (p = 0.039). In conclusion, LTP mostly occurs in the peripheral ablation zone within six months after IRE. Despite often exhibiting atypical Gd-EOB-DTPA MR signal characteristics, T2 BLADE and diffusion sequences were helpful for their detection in the peripheral zone while T1 p.v. and T1 d.p. had the highest sensitivity in the central zone.

Clinical Phase I/II Study: Local Disease Control and Survival in Locally Advanced Pancreatic Cancer Treated with Electrochemotherapy

Objective. To assess local disease control rates (LDCR) and overall survival (OS) in locally advanced pancreatic cancer (LAPC) treated with electrochemotherapy (ECT). Methods. Electrochemotherapy with bleomycin was performed in 25 LAPC patients who underwent baseline Magnetic Resonance Imaging (MRI) and/or Computed Tomography (CT) and Position Emission Tomography (PET) scans before ECT and 1 and 6 months post ECT. LDCR were assessed using Response Evaluation Criteria in Solid Tumors (RECIST 1.1) and Choi criteria. Needle electrodes with fixed linear (N-30-4B) or fixed hexagonal configurations (N-30-HG or I-40-HG or H-30-ST) or variable geometry (VGD1230 or VGD1240) (IGEA S.p.A., Carpi, Italy) were used to apply electric pulses. Pain evaluation was performed pre-ECT, after 1 month and after 6 months with ECT. Overall survival estimates were calculated by means of a Kaplan-Meier analysis. Results. At 1 month after ECT, 76% of patients were in partial response (PR) and 20% in stable disease (SD). Six months after ECT, 44.0% patients were still in PR and 12.0% in SD. A LDCR of 56.0% was reached six months after ECT: 13 patients treated with fixed geometry had a LDCR of 46.1%, while for the 12 patients treated with variable geometry, the LDCR was 66.7%. The overall survival median value was 11.5 months: for patients treated with fixed geometry the OS was 6 months, while for patients treated with variable geometry it was 12 months. Electrochemotherapy was well-tolerated and abdominal pain was rapidly resolved. Conclusions. Electrochemotherapy obtained good results in terms of LDCR and OS in LAPC. Multiple needle insertion in a variable geometry configuration optimized by pre-treatment planning determined an increase in LDCR and OS compared to a fixed geometry configuration.

Efficacy and safety of irreversible electroporation for malignant liver tumors: a systematic review and meta-analysis

OBJECTIVE

The data regarding overall survival (OS) and progression-free survival (PFS) following irreversible electroporation (IRE) is scarce. We performed a systematic review of the safety and efficacy of IRE for liver malignancies.

METHODS

Searches of MEDLINE, EMBASE, and SCOPUS databases were performed through September 1, 2019. Studies reporting the survival data (OS and PFS) and complications (graded according to the Society of interventional Radiology classification) were included. A generalized linear mixed method with a random-effects model was used for assessing pooled incidence rates and corresponding 95% confidence intervals (CIs).

RESULTS

A total of 25 studies (n = 776, 15 prospective, 10 retrospective) were included. Metastasis, hepatocellular carcinoma, and cholangiocarcinoma were present in 354, 285, and 100 patients, respectively. The pooled OS at 6, 12, 24, and 36 months was 93.28% (95% CI: 63.23-99.12, I²= 67%), 81.29% (95% CI: 69.80-89.22, I² = 73%), 61.47% (95% CI: 52.81-69.46, I² = 0%), and 40.88% (95% CI: 28.43-54.61, I² = 64%), respectively. The pooled PFS at 6, 12, and 24 months was 79.72% (95% CI: 67.88-87.97, I² = 70%), 64.19% (95% CI: 56.68-71.06, I² = 57%), 49.05% (95% CI: 11.47-87.73, I² = 96%), respectively. Overall complication rate was 23.7%. Major complications (grade C-F) occurred in 6.9% patients.

CONCLUSION

IRE is associated with favorable OS and PFS. Although the overall complication rate is high, most complications are graded as minor.

KEY POINTS

• The pooled OS and PFS at 6, 12, and 24 months for all the tumor types was 93.28% and 79.72%, 81.29% and 64.19%, and 61.47% and 49.05%, respectively. • HCC was associated with a better OS at 12 and 36 months. • The overall complication rate was 23.7%, with major complications (SIR grade C-F) comprising 6.9%.

Intratumoral STING Agonist Injection Combined with Irreversible Electroporation Delays Tumor Growth in a Model of Hepatocarcinoma

BACKGROUND/AIM

Irreversible electroporation (IRE) showed promising results for small-size tumors and very early cancers. However, further development is needed to evolve this procedure into a more efficient ablation technique for long-term control of tumor growth. In this work, we show that it is possible to increase the antitumor efficiency of IRE by simmultaneously injecting c-di-GMP, a STING agonist, intratumorally.

MATERIALS AND METHODS

Intratumoral administration of c-di-GMP simultaneously to IRE was evaluated in murine models of melanona (B16.OVA) and hepatocellular carcinoma (PM299L).

RESULTS

The combined therapy increased the number of tumor-infiltrating IFN-γ/TNF-α-producing CD4 and CD8 T cells and delayed tumor growth, as compared to the effect observed in groups treated with c-di-GMP or IRE alone.

CONCLUSION

These results can lead to the development of a new therapeutic strategy for the treatment of cancer patients refractory to other therapies.

Combinatorial effect of radium-223 and irreversible electroporation on prostate cancer bone metastasis in mice

BACKGROUND

Metastatic prostate cancer in bone is difficult to treat as the tumor cells are relatively resistant to hormonal or chemotherapies when compared to primary prostate cancer. Irreversible electroporation (IRE) is a minimally invasive ablation procedure that has potential applications in the management of prostate cancer in bone. However, a common limitation of IRE is tumor recurrence, which arises from incomplete ablation that allows remaining cancer cells to proliferate. In this study, we combined IRE with radium-223 (Ra-223), a bone-seeking radionuclide that emits short track length alpha particles and thus is associated with reduced damage to the bone marrow and evaluated the impact of the combination treatment on bone-forming prostate cancer tumors.

METHODS

The antitumor activity of IRE and Ra-223 as single agents and in combination was tested in vitro against three bone morphogenetic protein 4 (BMP4)-expressing prostate cancer cell lines (C4-2B-BMP4, Myc-CaP-BMP4, and TRAMP-C2-BMP4). Similar evaluation was performed in vivo using a bone-forming C4-2B-BMP4 tumor model in nude mice.

RESULTS

IRE and Ra-223 as monotherapy inhibited prostate cancer cell proliferation in vitro, and their combination resulted in significant reduction in cell viability compared to monotherapy. In vivo evaluation revealed that IRE with single-dose administration of Ra-233, compared to IRE alone, reduced the rate of tumor recurrence by 40% following initial apparent complete ablation and decreased the rate of proliferation of incompletely ablated tumor as quantified in Ki-67 staining (53.58 ± 16.0% for IRE vs. 20.12 ± 1.63%; for IRE plus Ra-223; p = 0.004). Histological analysis qualitatively showed the enhanced killing of tumor cells adjacent to bone by Ra-223 compared to those treated with IRE alone.

CONCLUSION

IRE in combination with Ra-223, which enhanced the destruction of cancer cells that are adjacent to bone, resulted in reduction of tumor recurrence through improved clearance of proliferative cells in the tumor region.

Ureteral Stent Fracture After Irreversible Electroporation for Treatment of Metastatic Rectal Adenocarcinoma

Background: Irreversible electroporation (IRE) is a soft tissue ablation technique using electrical pulses without thermal energy to create pores in the cell membrane, resulting in death from apoptosis rather than necrosis. Advantages include protection of blood vessels, nerves, and surrounding structures. Documented complications include periprocedure nausea/vomiting, infection, and severe pain. Ureteral stents are frequently used in management of hydronephrosis caused by malignant obstruction. We describe what is to our knowledge the first documentation of stent fragmentation secondary to IRE and subsequent management. Case Presentation: This is a 61-year-old male with history of metastatic rectal adenocarcinoma treated initially with chemotherapy and surgery. Follow-up imaging revealed hydronephrosis and enlarged right iliac lymph node. Ureteral stent was placed for management of the hydronephrosis and the patient was referred to undergo IRE for management of metastatic disease. After treatment, the patient had imaging performed that showed fractured right ureteral stent with proximal portion in the ureter and distal portion floating freely in the bladder. This complication was managed with staged endoscopic procedure involving adjacent ureteral stent placement and subsequent ureteroscopy and stent removal using delta grasper. Conclusion: We describe to our knowledge the first incidence as well as subsequent management of ureteral stent fracture from an increasingly common treatment modality for metastatic disease. Given the frequency of malignant ureteral obstruction managed with ureteral stents, knowledge of potential complications pertaining to the urologist is imperative.

Irreversible electroporation in patients with liver tumours: treated-area patterns with contrast-enhanced ultrasound

BACKGROUND

Familiarity with post-IRE imaging interpretation is of considerable importance in determining ablation success and detecting recurrence. CEUS can be used to assess the tumour response and characteristics of the ablation zone. It is of clinical interest to describe the ultrasonographic findings of liver tumours after irreversible electroporation (IRE) percutaneous ablation.

METHODS

A prospective study of 24 cases of malignant liver tumours (22 cases of primary liver tumours and 2 cases of liver metastases) treated by IRE ablation was conducted. Two inspectors evaluated the ablation zone in a consensus reading performed immediately, 1 day, and 1 month after IRE ablation. The gold standard method, magnetic resonance imaging (MRI), was used to evaluate the effectiveness of the treatment at 1 month.

RESULTS

Immediately after IRE ablation and up to 1 month later, the ablation zones gradually changed from hypo-echogenicity to hyper-echogenicity on conventional ultrasound and showed non-enhancement on contrast-enhanced ultrasound (CEUS). One month after IRE ablation, CEUS and MRI results were highly consistent (κ = 0.78, p < 0.05).

CONCLUSIONS

We conclude that CEUS may be an effective tool for assessing post-IRE ablation changes after 1 month. CEUS enables the depiction of tumour vascularity in real time and serves as an easy, repeatable method.

Changes in gadoxetic-acid-enhanced MR imaging during the first year after irreversible electroporation of malignant hepatic tumors

PURPOSE

To evaluate the appearance and size of ablation zones in gadoxetic-acid-enhanced magnetic resonance imaging (MRI) during the first year after irreversible electroporation (IRE) of primary or secondary hepatic malignancies and to investigate potential correlations to clinical features.

MATERIAL AND METHODS

The MRI-appearance of the ablation area was assessed 1-3 days, 6 weeks, 3 months, 6 months, 9 months and 1 year after IRE. The size of the ablation zone and signal intensities of each follow-up control were compared. Moreover, relationships between clinical features and the MRI-appearance of the ablation area 1-3 days after IRE were analyzed.

RESULTS

The ablation zone size decreased from 5.6 ± 1.4 cm (1-3 days) to 3.7±1.2 cm (1 year). A significant decrease of central hypointensities was observed in T2-blade- (3 months), T2 haste- (6 weeks; 3 months; 6 months; 1 year), T1 arterial phase- (3 months; 1 year), and diffusion-sequences (6 weeks; 3 months; 6 months; 9 months; 1 year). The unenhanced T1-sequences showed significantly increasing central hypointensities (6 weeks; 3 months; 6 months; 9 months; 1 year). Significantly increasing peripheral hypointensities were detected in T1 arterial phase- (3 months; 6 months; 9 months; 1 year) and in T1 portal venous phase-sequences (6 weeks; 3 months; 6 months; 9 months; 1 year). Peripheral hypointensities of unenhanced T1-sequences decreased significantly 1 year after IRE. 1-3 days after IRE central T1 portal venous hypo- or isointensities were detected significantly more often than hyperintensities, if more than 3 IRE electrodes were used.

CONCLUSION

Hepatic IRE results in continuous reduction of ablation zone size during the first postinterventional year. In addition to centrally decreasing T1-signal and almost steadily increasing signal in the enhanced T2 haste-, diffusion- and T1 arterial phase-sequences, there is a trend toward long-term decreasing T1 arterial- and portal venous MRI-signal intensity of the peripheral ablation area, probably representing a region of reversible electroporation.

Clinical impact of irreversible electroporation ablation for unresectable hilar cholangiocarcinoma

Irreversible electroporation (IRE) is a non-thermal ablation modality that has been shown to be safe and effective in its application to tumors that are close to risky areas. This study aims to assess the safety and efficacy of IRE for unresectable hilar cholangiocarcinoma. Nine patients from two medical centers in Asia received IRE treatment between June 2015 and July 2017. Before IRE treatment, percutaneous biliary decompressions had been performed on eight patients, and internal stenting had been performed on one patient. All patients tolerated the procedure well without high-grade complications. The ablated tumors had constant size without contrast enhancement for more than three months in eight patients and the level of CA19-9 decreased significantly in all patients. The percutaneous biliary drainage tube was removed from two patients with recanalization of the bile duct. The internal stent in one patient was removed without further stenting. The median overall survival period was 26 months, and the progression-free survival was 18 months. Bile ducts remained narrow in the majority (2/3) of the treated patients. Nevertheless, IRE ablation of unresectable hilar cholangiocarcinoma involving vital structures is a safe and feasible primary treatment for local tumor control and is effective in prolonging survival.

Cardiac synchronization and arrhythmia during irreversible electroporation

BACKGROUND AND OBJECTIVES

Irreversible electroporation (IRE) is a nonthermal electrical tumor ablative strategy for unresectable tumors. IRE is relatively safe around critical structures but may induce cardiac arrhythmia when its delivery is not synchronized to the cardiac cycle. We performed a systematic literature review to determine rates of arrhythmia when IRE was utilized with or without cardiac synchronization.

METHODS

An online literature search was conducted with additional hand selection of articles. Data were extracted and pooled analyses were performed.

RESULTS

Twelve articles were included in analysis. IRE was performed for 481 patients; 46% hepatic tumors (n = 223), 36% pancreatic lesions (n = 168), and multiple other locations including prostate. Synchronization was performed on 422 patients. Arrhythmias were noted in 3.7% of cases (n = 18/481); cardiac synchronization: 1.2% (n = 5/422) vs unsynchronized: 22.0% (n = 13/59), P < .0001. These events occurred in every organ except the prostate.

CONCLUSIONS

IRE remains a potent technology for unresectable tumors, but arrhythmia is a clinical concern. This literature review confirms that cardiac gating should be used in all cases outside of prostate to prevent this potentially serious adverse event.

The efficacy and safety of the open approach irreversible electroporation in the treatment of pancreatic cancer: A systematic review

BACKGROUND

Irreversible Electroporation (IRE) is a novel non-thermal ablation technique used in patients with locally advanced pancreatic cancer (LAPC), in the proximity of sensitive structures such as vessels, intestinal wall and the bile duct. Currently, it is only used in the setting of clinical trials. This systematic review aimed to tackle the knowledge gap in the literature, in relation to the safety and efficacy of the open approach IRE.

METHODS

MEDLINE, EMBASE and Cochrane libraries were searched for English language articles published from January 2000 to December 2019. Data related to safety and efficacy were extracted.

RESULTS

Nine studies involving 460 patients with LAPC were included. Open approach IRE was associated with high morbidity (29.4%) but with a survival benefit compared to traditional treatment. Median overall survival (OS) was at 17.15 months. Major morbidity was at 10.2% and mortality at 3.4%.

CONCLUSIONS

Despite the paucity of literature and the low quality of evidence, the results regarding safety and efficacy appear to be encouraging. The high morbidity seems to be mitigated by a demonstrated improvement in OS. The potential of this technique is more evident when mortality and major morbidity are considered, since they are at acceptable levels. The limitations of this review have made it difficult to extract definitive conclusions. Higher quality evidence is needed in the form of large-scale multicentre randomized controlled trials. It remains to be elucidated whether the rate of adverse events decreases as our experience with this technique increases.

Electro-Thermal Therapy Algorithms and Active Internal Electrode Cooling Reduce Thermal Injury in High Frequency Pulsed Electric Field Cancer Therapies

Thermal tissue injury is an unintended consequence in current irreversible electroporation treatments due to the induction of Joule heating during the delivery of high voltage pulsed electric fields. In this study active temperature control measures including internal electrode cooling and dynamic energy delivery were investigated as a process for mitigating thermal injury during treatment. Ex vivo liver was used to examine the extent of thermal injury induced by 5000 V treatments with delivery rates up to five times faster than current clinical practice. Active internal cooling of the electrode resulted in a 36% decrease in peak temperature vs. non-cooled control treatments. A temperature based feedback algorithm (electro-thermal therapy) was demonstrated as capable of maintaining steady state tissue temperatures between 30 and 80 °C with and without internal electrode cooling. Thermal injury volumes of 2.6 cm³ were observed for protocols with 60 °C temperature set points and electrode cooling. This volume reduced to 1.5 and 0.1 cm³ for equivalent treatments with 50 °C and 40 °C set points. Finally, it was demonstrated that the addition of internal electrode cooling and active temperature control algorithms reduced ETT treatment times by 84% (from 343 to 54 s) vs. non-cooled temperature control strategies with equivalent thermal injury volumes.

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.

Time-Dependent Impact of Irreversible Electroporation on Pathology and Ablation Size in the Porcine Liver: A 24-Hour Experimental Study

Irreversible electroporation causes cell death through low frequency, high voltage electrical pulses and is increasingly used to treat non-resectable cancers. A recent systematic review revealed that tissue damage through irreversible electroporation is time-dependent, but the impact of time on the ablation zone size remains unknown. Irreversible electroporation ablations were performed hourly during 24 consecutive hours in the peripheral liver of 2 anaesthetized domestic pigs using clinical treatment settings. Immediately after the 24th ablation, the livers were harvested and examined for tissue response in time based on macroscopic and microscopic pathology. The impact of time on these outcomes was assessed with Spearman rank correlation test. Ablation zones were sharply demarcated as early as 1 hour after treatment. During 24 hours, the ablation zones showed a significant increase in diameter (rs = 0.493, P = .014) and total surface (rs = 0.499, P = .013), whereas the impact of time on the homogeneous ablated area was not significant (rs = 0.172, P = .421). Therefore, the increase in size could mainly be attributed to an increase in the transition zone. Microscopically, the ablation zones showed progression in cell death and inflammation. This study assessed the dynamics of irreversible electroporation on the porcine liver during 24 consecutive hours and found that the pathological response (ie, cell death/inflammation), and ablation size continue to develop for at least 24 hours. Consequently, future studies on irreversible electroporation should prolong their observation period.

Ablation of soft tissue tumours by long needle variable electrode-geometry electrochemotherapy: final report from a single-arm, single-centre phase-2 study

Standard electrochemotherapy (ECT) is effective in many tumour types but is confined to the treatment of small superficial lesions. Variable electrode-geometry ECT (VEG-ECT) may overcome these limitations by using long freely-placeable electrodes. Patients with bulky or deep-seated soft-tissue malignancies not amenable to resection participated in a single-arm phase-2 study (ISRCTN.11667954) and received a single course of VEG-ECT with intravenous bleomycin (15,000 IU/m²) and concomitant electric pulses applied through an adjustable electrode array. The primary outcome was radiologic complete response rate (CRR) per RECIST; secondary endpoints included feasibility, metabolic response, toxicity (CTCAE), local progression-free survival (LPFS) and patient perception (EQ-5D). During 2009–2014, we enrolled 30 patients with trunk/limb sarcomas, melanoma, Merkel-cell carcinoma, and colorectal/lung cancer. Median tumour size was 4.7 cm. Electrode probes were placed under US/TC guidance (28 and 2 patients, respectively). Median procedure duration was 80 minutes. Tumour coverage rate was 97% (29 of 30 patients). Perioperative side-effects were negligible; one patient experienced grade-3 ulceration and infection. One-month ¹⁸F-FDG-SUV decreased by 86%; CRR was 63% (95% CI 44–79%). Local control was durable in 24 of 30 patients (two-year LPFS, 62%). Patients reported an improvement in “usual activities”, “anxiety/depression”, and “overall health” scores. VEG-ECT demonstrated encouraging antitumour activity in soft-tissue malignancies; a single course of treatment produced high and durable responses, with low complications.

Irreversible Electroporation: Background, Theory, and Review of Recent Developments in Clinical Oncology

Irreversible electroporation (IRE) has established a clinical niche as an alternative to thermal ablation for the eradication of unresectable tumors, particularly those near critical vascular structures. IRE has been used in over 50 independent clinical trials and has shown clinical success when used as a standalone treatment and as a single component within combinatorial treatment paradigms. Recently, many studies evaluating IRE in larger patient cohorts and alongside other novel therapies have been reported. Here, we present the basic principles of reversible electroporation and IRE followed by a review of preclinical and clinical data with a focus on tumors in three organ systems in which IRE has shown great promise: the prostate, pancreas, and liver. Finally, we discuss alternative and future developments, which will likely further advance the use of IRE in the clinic.

Antitumor Efficacy of Liposome-Encapsulated NVP-BEZ235 Combined with Irreversible Electroporation for Head and Neck Cancer

Irreversible electroporation (IRE) kills tumor cells by the delivery of short pulses of strong electric fields. However, the field strength decreases with distance from the treatment center. When IRE cannot eradicate the entire tumor mass, the surviving tumor cells can regrow. NVP-BEZ235 is a dual PI3K/mTOR inhibitor that has been administered orally in clinical trials. However, its hydrophobicity and poor water solubility make NVP-BEZ235 difficult to deliver to target areas. To improve its pharmacokinetics and therapeutic efficacy, we have encapsulated NVP-BEZ235 in a liposome (termed as L-BEZ). Our current study focuses on the long-term antitumor efficacy of IRE and intratumoral injection of L-BEZ in HN5 head and neck cancer xenografts in nude mice. We compared in vitro efficacy, as well as the effect on tumor size and growth rate in vivo, between IRE alone, IRE + oral BEZ, and IRE + L-BEZ over the course of two months. All animals in the control group were sacrificed by day 36, due to excess tumor burden. Tumors treated with IRE alone grew faster and larger than those in the control group. IRE + oral BEZ suppressed tumor growth, but the growth rate increased to that of the controls toward the end of 21 days. Only IRE + L-BEZ eradicated the tumor masses, with no palpable or extractable tumor mass observed after two months. The combination of IRE and L-BEZ could effectively eradicate tumors and prevent recurrence.

Percutaneous image-guided ablation: From techniques to treatments

Image-guided ablation is performed by percutaneously introducing ablation probes to deliver energy into a tumor to destroy it in a controlled and localized fashion. Ablation modalities can be broadly classified as thermal or non-thermal based on the mechanism of tumor destruction and are performed using different types of image guidance for planning, delivering and follow-up of the treatment. Ablation is performed in a minimally invasive fashion, providing greater residual organ preservation with minimal morbidity to the patient. Image-guided ablation is being used in the clinic for the treatment of primary and metastatic tumors, and this article reviews state of the art for the treatment of malignancies in the liver, lung, kidney and musculoskeletal tissue.

Therapeutic Effect of Irreversible Electroporation in Combination with Poly-ICLC Adjuvant in Preclinical Models of Hepatocellular Carcinoma

PURPOSE

To evaluate the therapeutic efficacy of irreversible electroporation (IRE) combined with the intratumoral injection of the immunogenic adjuvant poly-ICLC (polyinosinic-polycytidylic acid and poly-L-lysine, a dsRNA analog mimicking viral RNA) inmediately before IRE.

MATERIALS AND METHODS

Mice and rabbits bearing hepatocellular carcinoma tumors (Hepa.129 and VX2 tumor models, respectively) were treated with IRE (2 pulses of 2500V), with poly-ICLC, or with IRE + poly-ICLC combination therapy. Tumor growth in mice was monitored using a digital caliper and by computed tomography in rabbits.

RESULTS

Intratumoral administration of poly-ICLC immediately before IRE elicited shrinkage of Hepa.129 cell-derived tumors in 70% of mice, compared to 30% and 26% by poly-ICLC or IRE alone, respectively (P = .0004). This combined therapy induced the shrinkage of VX-2-based hepatocellular carcinoma tumors in 40% of rabbits, whereas no response was achieved by either individual treatment (P = .045). The combined therapy activated a systemic antitumor response able to inhibit the growth of other untreated tumors.

CONCLUSIONS

IRE treatment, immediately preceded by the intratumoral administration of an immunogenic adjuvant such as poly-ICLC, might enhance the antitumor effect of the IRE procedure. This combination might facilitate the induction of a long-term systemic response to prevent tumor relapses and the appearance of metastases.

Systematic Review of Surgical and Percutaneous Irreversible Electroporation in the Treatment of Locally Advanced Pancreatic Cancer

OBJECTIVE

The aim of the present systematic review was to collect, analyze, and critically evaluate the role of irreversible electroporation (IRE) in locally advanced pancreatic cancer (LAPC). Furthermore, we sought to analyze the different approaches of IRE (open, laparoscopic, and percutaneous) and assess the relative outcomes.

METHODS

A systematic review was performed according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Using the MEDLINE (1966-2018), Scopus (2004-2018), Google Scholar (2004-2018) and ClinicalTrials.gov databases, eligible articles published up to August 2018 were included. The following keywords were applied: 'irreversible electroporation', 'IRE', 'LAPC', 'unresectable pancreatic cancer', 'palliative treatment', 'locally advanced pancreatic cancer', 'ablation' and 'ablative treatment'.

RESULTS

IRE for LAPC was feasible and safe; however, it was associated with morbidity in approximately one in three patients, some of whom experienced serious complications, particularly after surgical IRE. In addition, while mortality following IRE was uncommon, it did occur in 2% of patients. While some studies suggested a survival benefit, others failed to note an improvement in long-term outcomes following IRE compared with other therapies.

CONCLUSIONS

Providers and patients need to be aware of the potential morbidity and mortality associated with IRE. In addition, based on the literature to date, the survival benefit of IRE for LAPC remains to be elucidated. Conclusive and definitive evidence to support a survival benefit of IRE does not currently exist. Future multicenter, randomized, prospective trials are needed to clarify the role of IRE in patients with LAPC.

Evaluating the Regulatory Immunomodulation Effect of Irreversible Electroporation (IRE) in Pancreatic Adenocarcinoma

BACKGROUND

Irreversible electroporation (IRE) has been demonstrated as an effective local method for locally advanced (stage 3) pancreatic adenocarcinoma. Immune regulatory T cells (Tregs) induce immunosuppression of tumors by inhibiting patients' anti-tumor adaptive immune response. This study aimed to evaluate the immunomodulation effect of IRE to identify an ideal time point for potential adjuvant immunotherapy.

METHODS

This study prospectively evaluated an institutional review board-approved study of patients undergoing either in situ IRE or pancreatectomy. Patient blood samples were collected at different time points (before surgery [preOP] and on postoperative day [POD] 1, POD3, and POD5). Peripheral blood mononuclear cells (PBMCs) were isolated and evaluated for three different CD4 + Treg subsets (CD25 + CD4 +, CD4 + CD25 + FoxP3 +, CD4 + CD25 + FoxP3 -) by flow cytometry and analyzed for median fold change (MFC) between each two consecutive time points (MFC = log2(T2/T1)).

RESULTS

The study analyzed 15 patients with in situ IRE (n = 11) or pancreatectomy (PAN) (n = 4). In both groups, CD25 + CD4 + Tregs decreased on POD1 followed by a steady increase in pancreatectomy, whereas the trend in the IRE group reversed between D3 and D5 (MFC: IRE [- 0.01], PAN [+ 0.39]). For each period, CD4 + CD25 + FoxP3 + Tregs showed the most dramatic inverse effect, with D3 to D5 showing the most change (MFC: IRE [- 0.18], PAN [+ 0.39]). Also, CD4 + CD25 + FoxP3 - Tregs showed an inverse effect between D3 and D5 (MFC: IRE [- 0.25], PAN [+ 0.49]). Altogether, the Treg trend was inversely affected by the in situ IRE procedure, with the greatest cumulative significant change for all three Treg subsets between D3 and D5 (MFC ± SEM: IRE [- 0.24 ± 0.05], PAN [+ 0.37 ± 0.02]; p = 0.016).

CONCLUSIONS

The study data suggest that in situ IRE procedure-mediated Treg attenuation between POD3 and POD5 can provide a clinical window of opportunity for potentiating clinical efficacy in combination with immunotherapy.

Ablation treatments in unresectable pancreatic cancer

Ablation treatments have been increasingly applied as an alternative treatment for unresectable locally advanced pancreatic cancer (LAPC). The goal of LAPC therapy is surgical resection with negative margins (R0); however, that can be achieved only in a minority of patients and only following neoadjuvant treatment. Ablation might be useful for those patients with unresectable LAPC that do not progress towards metastatic stage and do not experience a true downstaging. Indeed, some LAPC that tend to grow locally, might be the subgroup of tumors that could benefit from ablation. Experience is necessary to select patients and the technique to adopt, since serious or fatal complications can occur. This review aims to discuss the role of ablation treatments in LAPC, with a unique focus on radiofrequency ablation and irreversible electroporation.

Irreversible Electroporation in Liver Cancers and Whole Organ Engineering

Liver cancers contribute significantly to cancer-related mortality worldwide and liver transplants remain the cornerstone of curative treatment for select, early-stage patients. Unfortunately, because of a mismatch between demand and supply of donor organs, liver cancer patients must often wait extended periods of time prior to transplant. A variety of local therapies including surgical resection, transarterial chemoembolization, and thermal ablative methods exist in order to bridge to transplant. In recent years, a number of studies have examined the role of irreversible electroporation (IRE) as a non-thermal local ablative method for liver tumors, particularly for those adjacent to critical structures such as the vasculature, gall bladder, or bile duct. In addition to proving its utility as a local treatment modality, IRE has also demonstrated promise as a technique for donor organ decellularization in the context of whole-organ engineering. Through complete non-thermal removal of living cells, IRE allows for the creation of an acellular extra cellular matrix (ECM) scaffold that could theoretically be recellularized and implanted into a living host. Here, we comprehensively review studies investigating IRE, its role in liver cancer treatment, and its utility in whole organ engineering.

Percutaneous Irreversible Electroporation (IRE) of Hepatic Malignancy: A Bi-institutional Analysis of Safety and Outcomes

Aim

Irreversible electroporation (IRE) is a non-thermal ablative option in patients unsuitable for standard thermal ablation, due to its potential to preserve collagenous structures (vessels and ducts) and a reduced susceptibility to heat sink effects. In this series from two large tertiary referral hepatobiliary centres, we aim to assess the safety/outcomes of hepatic IRE.

Materials and Methods

Bi-institutional retrospective, longitudinal follow-up series of IRE for primary hepatic malignancy; [hepatocellular carcinoma (n = 20), cholangiocarcinoma (n = 3)] and secondary metastatic disease; colorectal (n = 28), neuroendocrine (n = 1), pancreatic (n = 1), breast (n = 1), gastrointestinal stromal tumour (GIST, n = 1) and malignant thymoma (n = 1). Outcome measures included procedural safety/effectiveness, time to progression and time to death.

Results

Between 2013 and 2017, 52 patients underwent percutaneous IRE of 59 liver tumours in 53 sessions. All tumours were deemed unsuitable for thermal ablation. Cases were performed using ultrasound (US) or computed tomography (CT) guidance. A complete ablation was achieved in n = 44, (75%) of cases with an overall complication rate of 17% (n = 9). Of the complete ablation group, median time to progression was 8 months. At 12 months, 44% were progression-free (95% CI 30–66%). The data suggest that larger lesion size (> 2 cm) is associated with shorter time to progression and there is highly significant difference with faster time to progression in mCRC compared with HCC. Median survival time was 38 months.

Conclusion

This bi-institutional review is the largest UK series of IRE and suggests this ablative technology can be a useful tool, but appears to mainly induce local tumour control rather than cure with HCC having better outcomes than mCRC.

Safety and efficacy of irreversible electroporation in the treatment of obstructive jaundice in advanced hilar cholangiocarcinoma

BACKGROUND

Irreversible electroporation (IRE) has successfully been used for palliation of pancreatic and liver cancers due to its ability to ablate tumors without destroying nearby vital structures. To date, it has not been evaluated in patients with advanced hilar cholangiocarcinoma (AHC). This study presents a single-institution experience with IRE for management of obstructive jaundice in AHC.

METHODS

A single-institution database was queried for patients undergoing IRE for AHC after PTBD placement for relief of obstructive jaundice from 2010 to 2017 and compared to a control group treated with standard of care only (No IRE).

RESULTS

Twenty-six patients underwent IRE for AHC after PTBD replacement. Three patients experienced complications, with two experiencing severe (≥ grade 3) complications. After IRE, median time to PTBD removal was 122 days (range 0-305 days) and median catheter-free time before requiring PTBD replacement was 305 days (range 92-458 days). In comparison, the 137 control patients had an admission rate of 59% (N = 80 patients) for PTBD infection, occlusion, or catheter related problem.

CONCLUSION

IRE safely achieves biliary decompression via tumor electroporation and allows PTBD removal for an extended period of time. In appropriately selected patients with obstructive jaundice in the setting of AHC, IRE can be used to increase catheter-free days and optimize overall quality of life.

Antitumor efficacy of liposome-encapsulated NVP-BEZ 235 in combination with irreversible electroporation

Irreversible electroporation (IRE) is an emerging minimally invasive tumor ablation technique that delivers short pulses of strong electric fields and kills cancer cells by disrupting their cell membranes with the electric pulses. However, clinical studies report that more than 10% of local tumor recurrences occur at the original ablated site. NVP BEZ-235 (BEZ) is a dual PI3K/mTOR inhibitor that has substantial anticancer effects. However, the clinical trials of BEZ was not satisfactory because of its low bioavailability and high toxicity, which stemmed from the use of oral administration of high doses over a long period of time. In this research, we prepared a liposomal formulation of BEZ (L-BEZ) for intratumoral injection and studied its antitumor efficacy alone and in combination with IRE. We hypothesized that IRE could release BEZ from the liposomes and that the combination could decrease tumor viability. Our results show that IRE released BEZ from its liposomal encapsulation. The combination of L-BEZ and IRE killed more Hep3B tumor cells in vitro than did L-BEZ or IRE alone and also inhibited cancer cell proliferation in nude mice bearing Hep3B xenografts. Combination of chemotherapeutic agent loaded nanoparticles could enhance the antitumor efficacy of IRE.

Non-surgical ablative therapies for inoperable benign insulinoma

PURPOSE

Benign insulinoma is the most common functioning neuroendocrine tumor of the pancreas. The gold-standard therapeutic approach for insulinoma is surgery, which allows for tumor removal, histology and immunochemical analyses. If surgery is not feasible, minimally invasive ablative procedures performed by interventional radiology can lead to partial or complete remission of hormone hypersecretion and tumor control in insulinoma patients.

METHODS

We performed a review of existing literature on non-chemotherapeutic/radioactive ablative techniques employed for the treatment of benign, otherwise inoperable, pancreatic insulinoma. For this purpose, feasibility, effectiveness and safety of ablative treatments for pancreatic insulinoma were reviewed from literature data published from 1982 to date.

RESULTS

A total of 44 insulinoma cases treated with non-surgical ablative techniques were desumed, and divided as follows: 7 cases of tumor embolization, 26 ethanol ablations, 7 radiofrequency ablations, 2 high intensity focused ultrasound ablation, 1 irreversible electroporation and 1 percutaneous microwave ablation. Most cases involved single insulinoma, predominantly located in the pancreas head and body. In the majority of patients, ablation was chosen instead of surgery due to severe comorbidities. After an average follow-up of 16 months, the overall success rate of non-surgical ablative treatments of insulinoma was 84%, the recurrence/persistence rate was 16%, and transient adverse events were noted in 23% of cases. Adverse events were usually self-limiting and medically manageable.

CONCLUSIONS

Non-surgical ablation is a feasible, safe and repeatable procedure in patients with pancreatic insulinoma, who are not candidate to surgery or refuse it. Partial or complete control of symptoms and tumor growth is experienced by the majority of patients.

Irreversible Electroporation in Hepatopancreaticobiliary Tumours

Hepatopancreaticobiliary tumours are often diagnosed at an advanced disease stage, in which encasement or invasion of local biliary or vascular structures has already occurred. Irreversible electroporation (IRE) is an image-guided tumour ablation technique that induces cell death by exposing the tumour to high-voltage electrical pulses. The cellular membrane is disrupted, while sparing the extracellular matrix of critical tubular structures. The preservation of tissue integrity makes IRE an attractive treatment option for tumours in the vicinity of vital structures such as splanchnic blood vessels and major bile ducts. This article reviews current data and discusses future trends of IRE for hepatopancreaticobiliary tumours.

Irreversible electroporation of pancreatic adenocarcinoma: a primer for the radiologist

Irreversible electroporation (IRE) is increasingly used for the ablation of unresectable locally advanced pancreatic adenocarcinoma. Unlike other ablation technologies that cannot be safely used around critical vasculature or ducts for risk of thermal damage, IRE uses high-voltage pulses to disrupt cellular membranes. This causes cell death by apoptosis and inflammation. IRE has been deployed by both open and percutaneous approaches. Generator parameters are the same for both approaches, and settings are pancreas specific. Variations in settings, probe placement, and probe exposure can result in thermal damage or reversible electroporation and resultant treatment failure, morbidity, or mortality. When used properly, IRE appears to improve overall survival and local recurrence, but does not influence the rate of distant recurrence. However, studies of both open and percutaneous approaches have been relatively small, non-controlled, and without appropriate comparisons. It is challenging for the radiologist to interpret treatment effects after IRE because of a dearth of guiding literature and pathologic correlates. This primer describes technical aspects, pathology correlates, post-IRE imaging, and outcomes for percutaneous and open approaches.

Ablative Therapies for Locally Advanced Pancreatic Cancer

The vast majority of patients who present with pancreatic adenocarcinoma have locally advanced or metastatic disease at the time of presentation without possibility of cure. Although in recent years there have been some new promising chemotherapy regimens that improve overall survival by a few months, the prognosis remains dismal. There is, however, a subset of patients who experience durable stable disease or partial responses after initial courses of chemotherapy with locally advanced disease. In these select patients, there remains interest in local ablative therapy with or without resection as a means for local control, palliation of symptoms, and possible improved survival. This review describes the techniques, complications, and expected benefits of several ablative techniques as a treatment modality for locally advanced pancreatic cancer.

An evaluation of irreversible electroporation thresholds in human prostate cancer and potential correlations to physiological measurements

Irreversible electroporation (IRE) is an emerging cancer treatment that utilizes non-thermal electric pulses for tumor ablation. The pulses are delivered through minimally invasive needle electrodes inserted into the target tissue and lead to cell death through the creation of nanoscale membrane defects. IRE has been shown to be safe and effective when performed on tumors in the brain, liver, kidneys, pancreas, and prostate that are located near critical blood vessels and nerves. Accurate treatment planning and prediction of the ablation volume require a priori knowledge of the tissue-specific electric field threshold for cell death. This study addresses the challenge of defining an electric field threshold for human prostate cancer tissue. Three-dimensional reconstructions of the ablation volumes were created from one week post-treatment magnetic resonance imaging (MRIs) of ten patients who completed a clinical trial. The ablation volumes were incorporated into a finite element modeling software that was used to simulate patient-specific treatments, and the electric field threshold was calculated by matching the ablation volume to the field contour encompassing the equivalent volume. Solutions were obtained for static tissue electrical properties and dynamic properties that accounted for electroporation. According to the dynamic model, the electric field threshold was 506 ± 66 V/cm. Additionally, a potentially strong correlation (r = −0.624) was discovered between the electric field threshold and pre-treatment prostate-specific antigen levels, which needs to be validated in higher enrollment studies. Taken together, these findings can be used to guide the development of future IRE protocols.

Raising the pressure: Hemodynamic effects of splanchnic nerve stimulation

A number of cardiovascular and neurological diseases are characterized by a dysregulation of intravascular volume distribution. The veins and arteries of the visceral organs form the so-called splanchnic vascular compartment and are the largest reservoir for intravascular blood. The blood localized in the splanchnic compartment can be mobilized in and out of the compartment via passive compression or active neurohormonal recruitment. We studied the hemodynamic effects of splanchnic nerve stimulation during five cases of irreversible electroporation (IRE) in patients with pancreatic cancer. In IRE, repeated bursts of high-voltage electrical fields are applied to visceral beds for >1 min, which induces rapid increase in blood pressure, heart rate, and cardiac output. We present the first analysis into the hemodynamic changes with splanchnic nerve stimulation and explore potential mechanisms of the hyperdynamic state. Our analysis presents the first human report of splanchnic nerve stimulation to induce hypertension and volume redistribution, introducing the splanchnic nerves as a key component of cardiovascular regulation.

NEW & NOTEWORTHY Our case series provides the first detailed description of human hemodynamic effects with splanchnic nerve stimulation. Splanchnic nerve stimulation results in profound hemodynamic alteration with rapid onset of hypertension and blood mobilization.

Skin regeneration with all accessory organs following ablation with irreversible electroporation

Skin scar formation is a complex process that results in the formation of dense extracellular matrix (ECM) without normal skin appendages such as hair and glands. The absence of a scarless healing model in adult mammals prevents the development of successful therapies. We show that irreversible electroporation of skin drives its regeneration with all accessory organs in normal adult rats. Pulsed electric fields at 500 V, with 70 μs pulse duration and 1000 pulses delivered at 3 Hz, applied through two electrodes separated by 2 mm lead to massive cell death. However, the ECM architecture of the skin was preserved. Six months after the ablation, the epidermis, sebaceous glands, panniculus carnosus, hair follicles, microvasculature and arrector pili muscle were altogether re-formed in the entire ablated area. These results suggest a key role of the ECM architecture in the differentiation, migration and signalling of cells during scarless wound healing. Copyright © 2016 John Wiley & Sons, Ltd.

Multi-disciplinary management of locally advanced pancreatic cancer with irreversible electroporation

The essential diagnosis for LAPC is based on high-quality cross-sectional imaging, which demonstrates tumor invasion into the celiac/superior mesenteric arteries and/or superior mesenteric/portal venous system that is not reconstructable. The optimal management of these patients is evolving quickly with the advent of newer chemotherapeutics, radiation, and non-thermal ablation modalities. This review will present the current status of initial chemotherapy, surgical therapy, ablative therapy, and radiation therapy for patients with nonmetastatic locally advanced unresectable pancreatic cancer.

Single-center nonrandomized clinical trial to assess the safety and efficacy of irreversible electroporation (IRE) ablation of liver tumors in humans: Short to mid-term results

INTRODUCTION

A single-center nonrandomized clinical trial was performed to assess the safety and efficacy of IRE ablation of liver tumors in humans.

METHODS

38 malignant liver tumors on 30 patients were treated with IRE between September 2011 and September 2014. Treatment was with curative intent, and the diagnoses were colorectal cancer with liver metastases (CRLM) (n = 23), hepatocellular carcinoma (HCC) (n = 8) and other metastasis (n = 7). Patients were selected when surgery, radiofrequency ablation (RFA) or microwave ablation (MWA) was not an option, and when they met inclusion criteria (tumor size < 3 cm, 1-2 tumors). Patients were followed-up at 1 and 6 months with a contrast-enhanced computed tomography (CE-CT), and contrast-enhanced ultrasound (CE-US) at 3 months.

RESULTS

Ablation success was defined as no evidence of residual tumor in the ablated area as confirmed by CE-CT and CE-US. At 3 months ablation success was 78.9%, and 65.8% at 6 months. There was no statistically significant difference between tumor volume (<5 cm³ vs >5 cm³, p = 0.518), and between diagnosis (CRLM vs HCC, p = 0.084) in terms of local recurrence. Complications were classified according to the standardized grading system of Society of Interventional Radiology (SIR). A minor complication occurred in six patients (20%), one patient (3.3%) suffered from a major complication (bile duct dilatation and stricture of the portal vein and bile duct). No mortalities occurred at 30 days.

CONCLUSIONS

IRE appears to be a safe treatment modality for a selected group of patients with liver tumors and offers high local tumor control at 3 and 6 months.