Electrochemotherapy – An easy, highly effective and safe treatment of cutaneous and subcutaneous metastases: Results of ESOPE (European Standard Operating Procedures of Electrochemotherapy) study

Electroporation Enhanced Effect of Dystrophin Splice Switching PNA Oligomers in Normal and Dystrophic Muscle

Peptide nucleic acid (PNA) is a synthetic DNA mimic that has shown potential for discovery of novel splice switching antisense drugs. However, in vivo cellular delivery has been a limiting factor for development, and only few successful studies have been reported. As a possible modality for improvement of in vivo cellular availability, we have investigated the effect of electrotransfer upon intramuscular (i.m.) PNA administration in vivo. Antisense PNA targeting exon 23 of the murine dystrophin gene was administered by i.m. injection to the tibialis anterior (TA) muscle of normal NMRI and dystrophic mdx mice with or without electroporation. At low, single PNA doses (1.5, 3, or 10 µg/TA), electroporation augmented the antisense exon skipping induced by an unmodified PNA by twofold to fourfold in healthy mouse muscle with optimized electric parameters, measured after 7 days. The PNA splice switching was detected at the RNA level up to 4 weeks after a single-dose treatment. In dystrophic muscles of the MDX mouse, electroporation increased the number of dystrophin-positive fibers about 2.5-fold at 2 weeks after a single PNA administration compared to injection only. In conclusion, we find that electroporation can enhance PNA antisense effects in muscle tissue.

Palliative electro-chemotherapy in elderly patients with vulvar cancer: A phase II trial

OBJECTIVE

The primary endpoint of this trial was to assess clinical response (cCR) of squamocellular vulvar cancer (V-SCC) in elderly patients treated with electro-chemotherapy (ECT). Secondary endpoints were symptoms relief and local tumor control.

METHODS

A phase II study was designed and elderly patients with V-SCC unfit for other treatments were treated. Response Evaluation Criteria in Solid Tumors (RECIST criteria) were applied to evaluate tumor response. Quality of life (QoL) was evaluated by visual analogue score (VAS) for pain and four items of vulvar cancer subscale (VCS), of functional assessment of vulvar cancer therapy (FACT-V) [16], before, one month after the procedure and during follow-up.

RESULTS

Median age was 85 years (range 66-96 years). One month after treatment complete response was observed in 13 patients (52%), partial response in 7 (28%), stable disease in 3 (12%), and progressive disease in 2 (8%). Local tumor control at 1 and 6 months was 91% and 53%, respectively. Symptom free survival at 1 and 6 months was 78% and 40%, respectively, with significant reduction of pain (P < 0.01). One-year overall survival was 34%.

CONCLUSIONS

Our study showed that ECT produces high response rate with significant reduction of pain and improvement of local symptoms.

Feasibility of Electroporation in Bone and in the Surrounding Clinically Relevant Structures: A Preclinical Investigation

Skeletal metastases are a common cause of severe morbidity, reduction in quality of life and often early mortality. Consequently, improvements in therapies are necessary. Electroporation uses electric energy to alter cancer cell membrane permeability and enhance the local uptake of chemotherapeutics, thus leading to local tumor control. The aim of this study was to investigate the feasibility and safety of delivering electric field protocols causing electroporation of healthy bone and structures of clinical relevance using small and large animal models. Reversible electroporation was used in the rabbit sciatic nerve by applying 2 series of 8 pulses 100ms long at 1000 V/cm. Irreversible electroporation was used in rabbit distal femur condyles and in sheep vertebral body by applying 120 pulses 100ms long at 1750 V/cm. Any effect on surrounding sensitive structures was investigated. Reversible electroporation of sciatic nerve was associated with transient foot functional deficit that completely recovered at 30 days. Irreversible electroporation removed cells from trabeculae in the femurs of rabbits and in the vertebral body of sheep. After irreversible protocol, histology and microtomography demonstrated that the trabecular structure was maintained, the presence of new bone marrow cells, osteoblasts, and mineral apposition characterized by new trabeculae thinner than controls (P = .005) and a significant reduction in the ablated areas (-225%, P = .0219). Spinal cord, vertebral pedicles and spinal nerves showed transient edema in the absence of functional or structural alterations. Collectively, these results show that electroporation can be safely applied to bone even in the proximity of neuronal structures.

Electrical resistance of human soft tissue sarcomas: an ex vivo study on surgical specimens

This paper presents a study about electrical resistance, which using fixed electrode geometry could be correlated to the tissue resistivity, of different histological types of human soft tissue sarcomas measured during electroporation. The same voltage pulse sequence was applied to the tumor mass shortly after surgical resection by means of a voltage pulse generator currently used in clinical practice for electrochemotherapy that uses reversible electroporation. The voltage pulses were applied by means of a standard hexagonal electrode composed by seven, 20-mm-long equispaced needles. Irrespective of tumor size, the electrode applies electric pulses to the same volume of tissue. The resistance value was computed from the voltage and current recorded by the pulse generator, and it was correlated with the histological characteristics of the tumor tissue which was assessed by a dedicated pathologist. Some differences in resistance values, which could be correlated to a difference in tissue resistivity, were noticed according to sarcoma histotype. Lipomatous tumors (i.e., those rich in adipose tissue) displayed the highest resistance values (up to 1700 Ω), whereas in the other soft tissue sarcomas, such as those originating from muscle, nerve sheath, or fibrous tissue, the electrical resistance measured was between 40 and 110 Ω. A variability in resistance was found also within the same histotype. Among lipomatous tumors, the presence of myxoid tissue between adipocytes reduced the electrical resistance (e.g., 50-100 Ω). This work represents the first step in order to explore the difference in tissue electrical properties of STS. These results may be used to verify whether tuning electric field intensity according to the specific STS histotype could improve tissue electroporation and ultimately treatment efficacy.

Coupling treatment planning with navigation system: a new technological approach in treatment of head and neck tumors by electrochemotherapy

BACKGROUND

Electrochemotherapy provides highly effective local treatment for a variety of tumors. In deep-seated tumors of the head and neck, due to complex anatomy of the region or inability to cover the whole tumor with standard electrodes, the use of long single needle electrodes is mandatory. In such cases, a treatment plan provides the information on the optimal configuration of the electrodes to adequately cover the tumor with electric field, while the accurate placement of the electrodes in the surgical room in patients can remain a problem. Therefore, during electrochemotherapy of two head and neck lymph-node metastases of squamous cell carcinoma origin, a navigation system for placement of electrodes was used.

PATIENT AND METHODS

Electrochemotherapy of two lymph-node metastases of cutaneous squamous cell carcinoma, one in the left parotid gland and the other in the neck just behind the left mandibular angle, was performed using intravenous administration of bleomycin and long single needle electrodes. The tumors were treated according to the prepared treatment plan, and executed with the use of navigation system.

RESULTS

Coupling of treatment plan with the navigation system aided to an accurate placement of the electrodes. The navigation system helped the surgeon to identify the exact location of the tumors, and helped with the positioning of the long needle electrodes during their insertion, according to treatment plan. Five electrodes were inserted for each metastasis, one centrally in the tumor and four in the periphery of the tumor. Five weeks after electrochemotherapy, computed tomography images demonstrated partial response of the first metastasis and complete response of the second one. Six weeks after electrochemotherapy, fine-needle aspiration biopsy specimen obtained from the treated lesions revealed necrosis and inflammatory cells, without any viable tumor cells.

CONCLUSION

We describe a new technological approach for electrochemotherapy of deep-seated head and neck tumors, coupling of the treatment planning with navigation system for accurate placement of the single long needle electrodes into and around the tumors, according to the treatment plan. Evidence of its effectiveness on two lymph-node metastases of cutaneous squamous cell carcinoma origin in neck lymph is provided.

Current density imaging sequence for monitoring current distribution during delivery of electric pulses in irreversible electroporation

Background

Electroporation is gaining its importance in everyday clinical practice of cancer treatment. For its success it is extremely important that coverage of the target tissue, i.e. treated tumor, with electric field is within the specified range. Therefore, an efficient tool for the electric field monitoring in the tumor during delivery of electroporation pulses is needed. The electric field can be reconstructed by the magnetic resonance electric impedance tomography method from current density distribution data. In this study, the use of current density imaging with MRI for monitoring current density distribution during delivery of irreversible electroporation pulses was demonstrated.

Methods

Using a modified single-shot RARE sequence, where four 3000 V and 100 μs long pulses were included at the start, current distribution between a pair of electrodes inserted in a liver tissue sample was imaged. Two repetitions of the sequence with phases of refocusing radiofrequency pulses 90° apart were needed to acquire one current density image. For each sample in total 45 current density images were acquired to follow a standard protocol for irreversible electroporation where 90 electric pulses are delivered at 1 Hz.

Results

Acquired current density images showed that the current density in the middle of the sample increased from first to last electric pulses by 60%, i.e. from 8 kA/m² to 13 kA/m² and that direction of the current path did not change with repeated electric pulses significantly.

Conclusions

The presented single-shot RARE-based current density imaging sequence was used successfully to image current distribution during delivery of short high-voltage electric pulses. The method has a potential to enable monitoring of tumor coverage by electric field during irreversible electroporation tissue ablation.

A rare case of anal porocarcinoma treated by electrochemotherapy

We report the case of an old woman with an eccrine porocarcinoma unusually localized in the perianal area treated by electrochemotherapy, a new technique, emerging as a very effective local treatment of different skin metastases and selected primary tumors. Electrochemotherapy was performed taking into account patient wishes and refusal of demolitive surgery. The electrochemotherapy treatment was well tolerated by the patient, it gave an excellent clinical response and a complete clinical regression with no sphincter dysfunction and signs of relapse observed during follow-up. The case is of particular interest for the exceptional localization of porocarcinoma for the first time treated by electrochemotherapy in this area. Electrochemotherapy could be considered as an alternative option for selected cases of cutaneous tumors.

Electrochemotherapy in the Treatment of Cutaneous Metastases from Breast Cancer: A Multicenter Cohort Analysis

Background

The management of breast cancer (BC) skin metastases represents a therapeutic challenge. Electrochemotherapy (ECT) combines the administration of bleomycin with temporary permeabilization induced by locally administered electric pulses. Preliminary experience with ECT in BC patients is encouraging.

Methods

A total of 125 patients with BC skin metastases who underwent ECT between 2010 and 2013 were enrolled onto a multicenter retrospective cohort study. The treatment was administered following the European Standard Operative Procedures of Electrochemotherapy. Tumor response was clinically assessed adapting the Response Evaluation Criteria in Solid Tumors, and toxicity was evaluated according to Common Terminology Criteria for Adverse Events 4.0. Cox regression analysis was used to identify predictive factors.

Results

Response was evaluable in 113 patients for 214 tumors (median 1 per patient, range 1–3). The overall response rate after 2 months was 90.2 %, while the complete response (CR) rate was 58.4 %. In multivariate analysis, small tumor size (P < 0.001), absence of visceral metastases (P = 0.001), estrogen receptor positivity (P = 0.016), and low Ki-67 index (P = 0.024) were significantly associated with CR. In the first 48 h, 10.4 % of patients reported severe skin pain. Dermatologic toxicity included grade 3 skin ulceration (8.0 %) and grade 2 skin hyperpigmentation (8.8 %). Tumor 1-year local progression-free survival was 86.2 % (95 % confidence interval 79.3–93.8) and 96.4 % (95 % confidence interval 91.6–100) in the subgroup of those with CR.

Conclusions

In this study, small tumor size, absence of visceral metastases, estrogen receptor positivity, and low Ki-67 index were predictors of CR after ECT. Patients who experienced CR had durable local control. ECT represents a valuable skin-directed therapy for selected patients with BC.

Electrochemotherapy as a new approach on pancreatic cancer and on liver metastases

Electrochemotherapy is a local non-thermal treatment for cancer ablation. Currently, many studies and case report have investigated the differences in effectiveness of electrochemotherapy with respect to tumor type, chemotherapeutic drug, and route of drug administration. ESOPE trial validated standard operating procedures [SOP] for ECT using the Cliniporator device and demonstrated that ECT is a simple, highly efficacious, and cost-effective treatment of cutaneous and subcutaneous nodules from different primary tumors for cutaneous or superficial lesions. This review has the purpose to summarize current knowledge about clinical effectiveness of electrochemotherapy and future prospects regarding its use on pancreatic cancer and liver metastasis not only.

Angiosarcoma of the breast: a new therapeutic approach?

INTRODUCTION

Angiosarcomas are highly malignant endothelial cell tumors with poor prognosis. These can be due to breast cancer itself or to subsequent therapeutic modalities. No evidence-based guidelines exist concerning the ideal treatment of angiosarcomas.

PRESENTATION OF THE CASE

We report the case of a 76-year-old woman who developed an exuberant and aggressive post radiation angiosarcoma of the breast and discuss different aspects of therapy for this disease. A total left mastectomy was performed, followed by a right mastectomy. The lesions into the chest wall, and multiple abdominal skin nodules were treated with local Electrochemotherapy (ECT) with intravenous bleomicin.

DISCUSSION

No evidence-based guidelines exist concerning the ideal treatment of angiosarcomas. Electrochemotherapy (ECT) is an efficient palliative treatment of cutaneous and subcutaneous tumor nodules. It consists of the combination of a cytotoxic drug and electroporation, using appropriate electrical parameters; destabilization of the membrane is reversible, ensuring a high survival of permeabilized cells and the delivery of non-permeant molecules inside the cell.

CONCLUSION

Due to the rarity of the disease, prospective studies concerning adjuvant or neoadjuvant therapy are limited and no evidence-based guidelines exist. The response to chemotherapy seems to be poor. Treatment with ECT in addition to systemic chemotherapy achieves a complete response in all the lesions and improving patient body image perception.

Electrical impedance tomography of electrolysis

The primary goal of this study is to explore the hypothesis that changes in pH during electrolysis can be detected with Electrical Impedance Tomography (EIT). The study has relevance to real time control of minimally invasive surgery with electrolytic ablation. To investigate the hypothesis, we compare EIT reconstructed images to optical images acquired using pH-sensitive dyes embedded in a physiological saline agar gel phantom treated with electrolysis. We further demonstrate the biological relevance of our work using a bacterial E.Coli model, grown on the phantom. The results demonstrate the ability of EIT to image pH changes in a physiological saline phantom and show that these changes correlate with cell death in the E.coli model. The results are promising, and invite further experimental explorations.

Assessing a novel immuno-oncology-based combination therapy: Ipilimumab plus electrochemotherapy

Melanoma is responsible for most skin cancer-related deaths and is one of the most common cancers diagnosed in young adults. In melanoma, tumors can become established by activation of the negative regulator of cytotoxic T lymphocytes (CTLs), CTL antigen-4 (CTLA-4). Ipilimumab blocks the interaction of CTLA-4 with CD80/CD86 and augments T-cell activation and proliferation. In electrochemotherapy (ECT), local application of short high-voltage pulses renders cell membranes transiently permeable to chemotherapeutic drugs. The combination of ipilimumab and ECT may be beneficial for the treatment of metastatic melanoma; however, no prospective data are available to date. Here, we report the retrospective analysis of patients treated with ipilimumab in an expanded access program (EAP) who also received ECT. Fifteen patients with previously treated metastatic melanoma who received ipilimumab 3 mg/kg every three weeks for four cycles and underwent ECT for local disease control and/or palliation of cutaneous lesions with bleomycin 15 mg/m2 after the first ipilimumab infusion were included in the analysis. Over the study period, a local objective response was observed in 67% of patients (27% complete response [CR] and 40% partial response [PR]). According to immune-related response criteria, a systemic response was observed in nine patients (five PR and four stable disease [SD]), resulting in a disease control rate of 60%. Evaluation of circulating T-regulatory (T-reg) cells demonstrated significant differences between responders and non-responders. Overall, treatment was well-tolerated and without notable toxicity. In conclusion, the combination of ipilimumab and ECT appears to be beneficial to patients with advanced melanoma, warranting further investigation in prospective trials.

Electrochemotherapy in melanoma patients: a single institution experience

AIM

This study was undertaken to update the outcome of the treated lesions with electrochemotherapy (ECT) plus intravenous injection of bleomycin in patients with in-transit disease or distant cutaneous metastases in melanoma patients.

PATIENTS & METHODS

89 patients with relapsed and refractory cutaneous melanoma metastases or in-transit disease were submitted to 126 treatments of ECT.

RESULTS

34 patients (38.2%) had a partial response and 43 had a complete response (48.3%). 12 patients (13.5%) had no change or progressive disease. The objective response rate was 67.5%.

CONCLUSION

The favorable outcome obtained in the present study demonstrates that ECT is a reliable, easy, fast and effective procedure showing benefits in terms of curative and palliative treatment for unresectable cutaneous lesions respecting the quality of life.

Electrochemotherapy in locally advanced pancreatic cancer: Preliminary results

OBJECTIVE

Report the preliminary results on electrochemotherapy (ECT) in the treatment of locally advanced pancreatic cancer of a phase I/II study and described the new functional imaging tools to assess ECT response in Magnetic Resonance (MR) imaging compared to morphological Computer Tomography (CT), ultrasound (US) without and with contrast enhancement (CEUS) and MR Imaging.

MATERIALS AND METHODS

Thirteen patients were enrolled in an ongoing clinical phase I/II study approved by Ethical Committee of National Cancer Institute G. Pascale Foundation - IRCCS of Naples. ECT with bleomycin was performed during open surgery. All patients underwent US and CT scan, before and after ECT treatment; 7 patients were evaluated using morphological and functional (dynamic contrast enhancement-DCE and diffusion weighted- DW) parameters in MR; 5 patients underwent CEUS. RECIST criteria were used to evaluate ECT response on US, CT and MR images. Functional parameters were also used to evaluate ECT response on MR images.

RESULTS

No acute (intraoperative) and/or postoperative serious adverse events related to electrochemotherapy were observed; no clinically significant electrocardiographic, hemodynamic, or serum biologic changes were noted. No clinically relevant elevation of amylase or lipase levels was observed and no bleeding or damage to surrounding viscera occurred. In three patients had seen splenic infarction without thrombosis of the splenic vessels.

CONCLUSION

Electrochemotherapy is feasible and safe treatment modality in patients with locally advanced pancreatic adenocarcinoma. Dynamic and diffusion MR imaging in comparison to MR morphological sequence alone and to UC and CT imaging is more suitable to assess ECT treatment response. CEUS is not indicated in follow up after ECT.

Evaluation of the Electroporation Efficiency of a Grid Electrode for Electrochemotherapy: From Numerical Model to In Vitro Tests

Electrochemotherapy (ECT) is a local anticancer treatment based on the combination of chemotherapy and short, tumor-permeabilizing, voltage pulses delivered using needle electrodes or plate electrodes. The application of ECT to large skin surface tumors is time consuming due to technical limitations of currently available voltage applicators. The availability of large pulse applicators with few and more spaced needle electrodes could be useful in the clinic, since they could allow managing large and spread tumors while limiting the duration and the invasiveness of the procedure. In this article, a grid electrode with 2-cm spaced needles has been studied by means of numerical models. The electroporation efficiency has been assessed on human osteosarcoma cell line MG63 cultured in monolayer. The computational results show the distribution of the electric field in a model of the treated tissue. These results are helpful to evaluate the effect of the needle distance on the electric field distribution. Furthermore, the in vitro tests showed that the grid electrode proposed is suitable to electropore, by a single application, a cell culture covering an area of 55 cm(2). In conclusion, our data might represent substantial improvement in ECT in order to achieve a more homogeneous and time-saving treatment, with benefits for patients with cancer.

Dose-dependent ATP depletion and cancer cell death following calcium electroporation, relative effect of calcium concentration and electric field strength

Background

Electroporation, a method for increasing the permeability of membranes to ions and small molecules, is used in the clinic with chemotherapeutic drugs for cancer treatment (electrochemotherapy). Electroporation with calcium causes ATP (adenosine triphosphate) depletion and cancer cell death and could be a novel cancer treatment. This study aims at understanding the relationship between applied electric field, calcium concentration, ATP depletion and efficacy.

Methods

In three human cell lines — H69 (small-cell lung cancer), SW780 (bladder cancer), and U937 (leukaemia), viability was determined after treatment with 1, 3, or 5 mM calcium and eight 99 μs pulses with 0.8, 1.0, 1.2, 1.4 or 1.6 kV/cm. Fitting analysis was applied to quantify the cell-killing efficacy in presence of calcium. Post-treatment intracellular ATP was measured in H69 and SW780 cells. Post-treatment intracellular ATP was observed with fluorescence confocal microscopy of quinacrine-labelled U937 cells.

Results

Both H69 and SW780 cells showed dose-dependent (calcium concentration and electric field) decrease in intracellular ATP (p<0.05) and reduced viability. The 50% effective cell kill was found at 3.71 kV/cm (H69) and 3.28 kV/cm (SW780), reduced to 1.40 and 1.15 kV/cm (respectively) with 1 mM calcium (lower EC50 for higher calcium concentrations). Quinacrine fluorescence intensity of calcium-electroporated U937 cells was one third lower than in controls (p<0.0001).

Conclusions

Calcium electroporation dose-dependently reduced cell survival and intracellular ATP. Increasing extracellular calcium allows the use of a lower electric field.

General Significance

This study supports the use of calcium electroporation for treatment of cancer and possibly lowering the applied electric field in future trials.

Tumour cell membrane poration and ablation by pulsed low-intensity electric field with carbon nanotubes

Electroporation is a physical method to increase permeabilization of cell membrane by electrical pulses. Carbon nanotubes (CNTs) can potentially act like "lighting rods" or exhibit direct physical force on cell membrane under alternating electromagnetic fields thus reducing the required field strength. A cell poration/ablation system was built for exploring these effects of CNTs in which two-electrode sets were constructed and two perpendicular electric fields could be generated sequentially. By applying this system to breast cancer cells in the presence of multi-walled CNTs (MWCNTs), the effective pulse amplitude was reduced to 50 V/cm (main field)/15 V/cm (alignment field) at the optimized pulse frequency (5 Hz) of 500 pulses. Under these conditions instant cell membrane permeabilization was increased to 38.62%, 2.77-fold higher than that without CNTs. Moreover, we also observed irreversible electroporation occurred under these conditions, such that only 39.23% of the cells were viable 24 h post treatment, in contrast to 87.01% cell viability without presence of CNTs. These results indicate that CNT-enhanced electroporation has the potential for tumour cell ablation by significantly lower electric fields than that in conventional electroporation therapy thus avoiding potential risks associated with the use of high intensity electric pulses.

Picosecond and Terahertz Perturbation of Interfacial Water and Electropermeabilization of Biological Membranes

Non-thermal probing and stimulation with subnanosecond electric pulses and terahertz electromagnetic radiation may lead to new, minimally invasive diagnostic and therapeutic procedures and to methods for remote monitoring and analysis of biological systems, including plants, animals, and humans. To effectively engineer these still-emerging tools, we need an understanding of the biophysical mechanisms underlying the responses that have been reported to these novel stimuli. We show here that subnanosecond (≤500 ps) electric pulses induce action potentials in neurons and cause calcium transients in neuroblastoma-glioma hybrid cells, and we report complementary molecular dynamics simulations of phospholipid bilayers in electric fields in which membrane permeabilization occurs in less than 1 ns. Water dipoles in the interior of these model membranes respond in less than 1 ps to permeabilizing electric potentials by aligning in the direction of the field, and they re-orient at terahertz frequencies to field reversals. The mechanism for subnanosecond lipid electropore formation is similar to that observed on longer time scales-energy-minimizing intrusions of interfacial water into the membrane interior and subsequent reorganization of the bilayer into hydrophilic, conductive structures.

Predicting patients at risk for pain associated with electrochemotherapy

BACKGROUND

Electrochemotherapy describes the use of electric pulses to enhance chemotherapy uptake, and has proven highly efficient in treating cutaneous metastases. Patients referred for electrochemotherapy present with diverse clinical pictures, from multiple small lesions to large, ulcerated lesions. Post-electrochemotherapy pain has been observed in some patients. The objectives of this study were to evaluate pain scores before and after electrochemotherapy, and to investigate if patients at risk of post-procedure pain could be identified.

METHODS

Seven cancer centres in the International Network for Sharing Practices on Electrochemotherapy (INSPECT) consecutively and prospectively reported to a common database. Electrochemotherapy consisted of intratumoural or intravenous injection of bleomycin, followed by delivery of electric pulses in local or general anesthesia.

RESULTS

Of 121 patients 39% had metastatic melanoma, 18% squamous cell carcinoma, 16% breast cancer, 13% basal-cell carcinoma, and 14% other malignancies. Median size of the largest nodules was 2.3 cm (range 0.3-40 cm). A majority of patients presented with low pain scores, and this continued through follow-up (74%). A subset of patients had moderate (13%) or severe pain (13%) after treatment. Post-procedure pain was statistically significantly associated with: 1) moderate or severe pain before treatment (p<0.0001); 2) size of the largest treated lesion (p<0.01); 3) previous irradiation (p<0.02); and 4) high treatment current value (p<0.0001).

CONCLUSION

The majority of patients had no or mild pain after electrochemotherapy. Patients at risk for post-procedure pain could be identified at the pre-treatment visit, and/or at the time of treatment, enabling a pain management strategy for this group.

Electrochemotherapy: a good idea in recurrent basal cell carcinoma treatment

Basal cell carcinoma (BCC) is the most common skin cancer in Caucasian population. Surgical excision is the gold standard treatment for BCC. Secondary surgical approach in patients presenting surgical scars after multiple surgical excisions or submitted to radiotherapy without obtaining a safe clearance margin, should be avoided. In recent years the use of electrochemotherapy (ECT) in head and neck cancers using intravenous bleomycin was specifically addressed and BCC resulted to be among tumors with the best response to ECT. We report a case of a recurrent nasal BCC treated with ECT with a complete regression of lesions after 8 weeks and a disease free period of 7 months. ECT is a good palliative treatment not affecting survival rate but improving quality of life in patients.

New Formulations of Polysaccharide-Based Hydrogels for Drug Release and Tissue Engineering

Polysaccharide-based hydrogels are very promising materials for a wide range of medical applications, ranging from tissue engineering to controlled drug delivery for local therapy. The most interesting property of this class of materials is the ability to be injected without any alteration of their chemical, mechanical and biological properties, by taking advantage of their thixotropic behavior. It is possible to modulate the rheological and chemical-physical properties of polysaccharide hydrogels by varying the cross-linking agents and exploiting their thixotropic behavior. We present here an overview of our synthetic strategies and applications of innovative polysaccharide-based hydrogels: hyaluronan-based hydrogel and new derivatives of carboxymethylcellulose have been used as matrices in the field of tissue engineering; while guar gum-based hydrogel and hybrid magnetic hydrogels, have been used as promising systems for targeted controlled drug release. Moreover, a new class of materials, interpenetrating hydrogels (IPH), have been obtained by mixing various native thixotropic hydrogels.

Locally enhanced chemotherapy by electroporation: clinical experiences and perspective of use of electrochemotherapy

Electroporation is used to enhance drug diffusion and gene delivery into the cytosol. The combination of electroporation and cytotoxic drugs, electrochemotherapy (ECT), is used to treat metastatic tumor nodules located at the skin and subcutaneous tissue. The objective response rate following a single session of treatment exceeds 80%, with minimal toxicity for the patients. The efficacy of ECT in the bone and visceral metastasis is currently investigated, and Phase II studies have been completed. ECT has been used to treat skin primary tumors, except melanoma, and is under investigation for locally advanced pancreatic cancer. Early evidence suggests that treatment of tumor nodules with ECT recruits components of the immune system and eliciting a systemic immune response against cancer is a challenging clinical perspective. Considering the proven safety in several different clinical applications electroporation should be viewed as a clinical platform technology with wide perspectives for use in ECT, gene therapy and DNA vaccination.

Electrochemotherapy in the treatment of melanoma skin metastases: a report on 31 cases

INTRODUCTION AND OBJECTIVES

Electrochemotherapy is indicated for the treatment of unresectable cutaneous and subcutaneous tumors. The technique involves the synergistic use of electroporation of cell membranes to increase the cytotoxicity of anticancer drugs delivered to the tumor cells. The aim of this study was to analyze the clinical effectiveness and safety of electrochemotherapy in the treatment of unresectable locoregional recurrent or metastatic melanomas.

MATERIAL AND METHODS

We studied 31 patients treated between January 2007 and December 2012. The European Standard Operating Procedures of Electrochemotherapy (ESOPE) were applied in all cases. Treatment response was analyzed as overall patient response (mean response based on results for all lesions treated in a given patient).

RESULTS

Response was classified as partial in 49% of patients and complete in 23%. At 1 year, the level of response achieved had been maintained in 17 patients. Disease progression was observed in 28% of the series. Immediate local complications (pain, swelling, erythema) were mild and resolved within 48hours in most cases. Eight patients developed subsequent local complications, such as ulcers and secondary infections associated with necrosis of the lesions. These complications were brought under control with topical treatments.

CONCLUSIONS

Electrochemotherapy is a very effective, safe, and efficient treatment for advanced locoregional disease in patients with unresectable melanoma lesions.

The role of additional pulses in electropermeabilization protocols

Electropermeabilization (EP) based protocols such as those applied in medicine, food processing or environmental management, are well established and widely used. The applied voltage, as well as tissue electric conductivity, are of utmost importance for assessing final electropermeabilized area and thus EP effectiveness. Experimental results from literature report that, under certain EP protocols, consecutive pulses increase tissue electric conductivity and even the permeabilization amount. Here we introduce a theoretical model that takes into account this effect in the application of an EP-based protocol, and its validation with experimental measurements. The theoretical model describes the electric field distribution by a nonlinear Laplace equation with a variable conductivity coefficient depending on the electric field, the temperature and the quantity of pulses, and the Penne's Bioheat equation for temperature variations. In the experiments, a vegetable tissue model (potato slice) is used for measuring electric currents and tissue electropermeabilized area in different EP protocols. Experimental measurements show that, during sequential pulses and keeping constant the applied voltage, the electric current density and the blackened (electropermeabilized) area increase. This behavior can only be attributed to a rise in the electric conductivity due to a higher number of pulses. Accordingly, we present a theoretical modeling of an EP protocol that predicts correctly the increment in the electric current density observed experimentally during the addition of pulses. The model also demonstrates that the electric current increase is due to a rise in the electric conductivity, in turn induced by temperature and pulse number, with no significant changes in the electric field distribution. The EP model introduced, based on a novel formulation of the electric conductivity, leads to a more realistic description of the EP phenomenon, hopefully providing more accurate predictions of treatment outcomes.

Electrochemotherapy treatment of locally advanced and metastatic soft tissue sarcomas: results of a non-comparative phase II study

AIMS

Our aim was to evaluate the activity, toxicity, and feasibility of electrochemotherapy (ECT) in patients with soft-tissue sarcomas (STS).

METHODS

A two-stage phase II trial was conducted between October 2006 and March 2012. Patients (N = 34) with locally advanced or metastatic STS, unsuitable for standard oncological treatments and with maximum 3-cm deep tumors, received an intravenous bolus of bleomycin (15,000 IU/m(2)), followed by tumor electroporation according to the European Standard Operating Procedures of ECT. Outcome measures included local response according to response evaluation criteria in solid tumors (RECIST), toxicity and tumor control. Feasibility measures included the accuracy of electrode placement and the intensity of electric current flowing in tumor tissue.

RESULTS

Median tumor size was 4.0 cm (range 2-12). Objective response, assessed on 71 target lesions, was 92.2 % (complete 32.3, 95 % CI 28-64). A total of 15 patients received up to four cycles due to incomplete response, but re-treatment did not significantly improve outcome (p = 0.205). After a median follow-up of 19.3 months, 2-year local control rate was 72.5 %. Median time to local failure (N = 11 patients) was 5.1 months. Tumor response (p = 0.041) and control (p = 0.047) correlated with histological grading. Relevant toxicity consisted of G3 skin ulceration and soft tissue necrosis (35 and 23 % of patients, respectively), although this was manageable on an outpatient basis. The accuracy of electrode placement was 47.1 %, and the adequacy of electroporative current 85.3 %.

CONCLUSIONS

ECT may represent an active and safe treatment to achieve local control in advanced STS patients with symptomatic disease. Future research challenges include the improvement of electrode placement and voltage delivery together with the containment of soft tissue toxicity.

In vitro and in vivo experiments on electrochemotherapy for bladder cancer

PURPOSE

Electrochemotherapy is widely performed to treat solid tumors but experience with bladder cancer is limited. We investigated mitomycin C and cisplatin administered with electrochemotherapy for bladder cancer in vitro and in vivo.

MATERIALS AND METHODS

The human bladder cancer cell line SW780 was used. Cells were treated with electroporation, drug alone or electroporation plus increasing concentrations of drug (mitomycin C 0.001 to 2,000 μM or cisplatin 1.56 to 300 μM). Electrochemotherapy parameters were 8 pulses of 1.2 kV/cm for 99 microseconds at 1 Hz. We investigated survival and apoptosis, the latter evaluated by caspase activity. NMRI-Fox1nu nude mice were inoculated subcutaneously and randomized to 1) electrochemotherapy plus NaCl, 2) NaCl alone, 3) electrochemotherapy plus drug or 4) drug alone (mitomycin C 5 mM or cisplatin 250 μM). Tumors were measured 3 times per week. A similar experiment was done to assess necrosis by histology at days 2 and 6.

RESULTS

In vitro mitomycin C cytotoxicity and caspase activity was unaffected by electrochemotherapy (p = 0.9057 and 0.53, respectively). However, electrochemotherapy with cisplatin caused 6.6-fold increased cytotoxicity and higher caspase activity (p <0.0001 and <0.001, respectively). In vivo electrochemotherapy plus mitomycin C resulted in tumor volume reduction (p <0.0005). The survival rate in mice that received electrochemotherapy plus mitomycin C and mitomycin C alone was greater than in controls (p = 0.0004). The tumor response rate was 100% for electrochemotherapy plus mitomycin C, 53% for mitomycin C alone, 14% for electrochemotherapy plus NaCl and 0% for NaCl alone. In vivo electrochemotherapy plus cisplatin was associated with slower tumor growth over other combinations as well as significantly higher survival (p = 0.0005 and 0.0003, respectively). The tumor response rate was 47% for electrochemotherapy plus cisplatin, 0% for cisplatin alone, 0% for electrochemotherapy plus NaCl and 8% for NaCl alone

CONCLUSIONS

In vivo electrochemotherapy with mitomycin C or cisplatin was more effective than chemotherapy alone in a bladder cancer tumor model, opening new perspectives in bladder cancer therapy.

Feasibility and Safety of Intraoperative Electrochemotherapy in Locally Advanced Pancreatic Tumor: A Preliminary Experience

Electrochemotherapy is an effective treatment for various cutaneous tumors and could be translated into treatment of deep-seated tumors. With this aim, a prospective clinical phase I/II study was conducted to evaluate the feasibility and safety of intraoperative Electrochemotherapy (ECT) in locally advanced pancreatic adenocarcinoma: the preliminary results are reported in this study. The secondary endpoint was to assess treatment response in terms of morphological and functional criteria based on Magnetic Resonance Imaging. Eleven consecutive patients were enrolled in a clinical phase I/II study approved by the Ethics Committee of the National Cancer Institute G. Pascale Foundation - IRCCS of Naples. Electrochemotherapy with bleomycin was performed during open surgery. All patients underwent MR and CT scan, before and after ECT treatment, using morphological and functional imaging. RECIST criteria were used to evaluate ECT response on CT and MR images. Functional parameters were also used to evaluate ECT response on MR images. No acute (intraoperative) and/or postoperative serious adverse events related to electrochemotherapy were observed; no clinically significant electrocardiographic, hemodynamic, or serum biologic changes were noted. No clinically relevant elevation of amylase or lipase levels was observed and no bleeding or damage to surrounding viscera occurred. Electrochemotherapy of locally advanced pancreatic adenocarcinoma proved to be a feasible and safe treatment modality. Dynamic and diffusion MR imaging is more suitable to assess ECT treatment response than CT imaging and morphological MR alone, after one month of treatment.

Bleomycin electrochemotherapy in elderly metastatic breast cancer patients: clinical outcome and management considerations

PURPOSE

To evaluate the efficacy and toxicity of electrochemotherapy (ECT) in elderly metastatic breast cancer (BC) patients.

METHODS

Retrospective analysis of 55 patients with superficial metastases who underwent ECT according to the European Standard Operative Procedures of electrochemotherapy. Treatment schedule consisted of intravenous or intratumoral bleomycin followed by locally delivered electric pulses. Statistical comparisons were performed between two groups: the patients aged <70 years (n = 27) and those ≥70 years (n = 28). Treatment outcomes were as follows: complete response (CR) rate, local progression-free survival (LPFS), new lesions-free survival (NLFS), toxicity and patient compliance.

RESULTS

Patient groups were comparable for clinical-pathological features, except for the number of comorbidities (P < .001). The median follow-up was 32 months (range 6-53). Overall, CR rate was 40 % and was significantly higher in elderly patients (57 vs. 26 %, P = .023) and in patients with better performance status (PS = 0-1, 53 vs. PS = 2, 21 %, P = .048), although local tumor control showed a trend for lower values (2-year LPFS, 67 vs. 93 % among elderly and young patients, respectively; P = .061). Older women seemed less likely to progress outside the ECT field (2-year NLFS, 39 vs. 30 %, P = .075), but discontinued treatment more frequently due to impaired performance status (P = .002). Local pain was graded ≥3, according to a 10-point visual analog scale, by 16/28 (57.1 %) and 8/28 (28.6 %) elderly patients at 4 and 8 weeks, respectively. Wound debridement was required in 5/28 (18 %) older women, due to G3 skin ulceration.

CONCLUSIONS

Elderly BC patients are highly responsive to ECT and achieve durable local tumor control. Physicians should be aware of possible debilitating side effects, such as pain and skin toxicity. Performance status and frailty screening could be a helpful addition to improve patient selection.

Efficacy of skin-directed therapy for cutaneous metastases from advanced cancer: a meta-analysis

PURPOSE

To perform the first meta-analysis of the efficacy of skin-directed therapies for cutaneous metastases.

METHODS

MEDLINE, EMBASE, The Cochrane Library, and ClinicalTrials.gov databases were searched for reports of prospective clinical studies published between 1960 and 2013 that assessed the response of skin-directed therapy for cutaneous metastases (47 of 2,955 unique studies were selected). Primary end points of the study were complete and objective response rates. Secondary analyses were preplanned and included subgroup analyses by skin-directed therapy, histology, and recurrence rates. Meta-analyses were performed with random-effect modeling, and extent of heterogeneity between studies was determined with the Cochran Q and I(2) tests.

RESULTS

After applying exclusion criteria, 47 prospective studies of 4,313 cutaneous metastases were assessed. Five skin-directed therapies were identified: electrochemotherapy, photodynamic therapy, radiotherapy, intralesional therapy, and topical therapy. Among all cutaneous metastases, complete response rate was 35.5% (95% CI, 27.6% to 44.3%) and objective response rate was 60.2% (95% CI, 50.6% to 69.0%). Overall recurrence rate was estimated to be 9.2% (95% CI, 3.7% to 21.2%). Melanoma and breast carcinoma comprised 96.8% of all cutaneous metastases studied and had similar objective response rates (54.5% [95% CI, 48.3% to 60.7%] and 54.0% [95% CI, 48.3% to 59.7%], respectively). Grade ≥ 3 toxicity was reported in less than 6% of patients.

CONCLUSION

Response to skin-directed therapy for cutaneous metastases is high but heterogeneous across treatment modalities, with low rates of recurrence post-treatment. Treatment was generally well tolerated and conferred improvements in quality of life. Standardization of response criteria for cutaneous metastases and treatment algorithms to optimally use the available skin-directed therapies are needed.

Comparison of flow cytometry, fluorescence microscopy and spectrofluorometry for analysis of gene electrotransfer efficiency

In this study, we compared three different methods used for quantification of gene electrotransfer efficiency: fluorescence microscopy, flow cytometry and spectrofluorometry. We used CHO and B16 cells in a suspension and plasmid coding for GFP. The aim of this study was to compare and analyse the results obtained by fluorescence microscopy, flow cytometry and spectrofluorometry and in addition to analyse the applicability of spectrofluorometry for quantifying gene electrotransfer on cells in a suspension. Our results show that all the three methods detected similar critical electric field strength, around 0.55 kV/cm for both cell lines. Moreover, results obtained on CHO cells showed that the total fluorescence intensity and percentage of transfection exhibit similar increase in response to increase electric field strength for all the three methods. For B16 cells, there was a good correlation at low electric field strengths, but at high field strengths, flow cytometer results deviated from results obtained by fluorescence microscope and spectrofluorometer. Our study showed that all the three methods detected similar critical electric field strengths and high correlations of results were obtained except for B16 cells at high electric field strengths. The results also demonstrated that flow cytometry measures higher values of percentage transfection compared to microscopy. Furthermore, we have demonstrated that spectrofluorometry can be used as a simple and consistent method to determine gene electrotransfer efficiency on cells in a suspension.

In situ monitoring of electric field distribution in mouse tumor during electroporation

PURPOSE

To investigate the feasibility of magnetic resonance (MR) electric impedance tomography ( EIT electric impedance tomography ) technique for in situ monitoring of electric field distribution during in vivo electroporation of mouse tumors to predict reversibly electroporated tumor areas.

MATERIALS AND METHODS

All experiments received institutional animal care and use committee approval. Group 1 consisted of eight tumors that were used for determination of predicted area of reversibly electroporated tumor cells with MR EIT electric impedance tomography by using a 2.35-T MR imager. In addition, T1-weighted images of tumors were acquired to determine entrapment of contrast agent within the reversibly electroporated area. A correlation between predicted reversible electroporated tumor areas as determined with MR EIT electric impedance tomography and areas of entrapped MR contrast agent was evaluated to verify the accuracy of the prediction. Group 2 consisted of seven tumors that were used for validation of radiologic imaging with histopathologic staining. Histologic analysis results were then compared with predicted reversible electroporated tumor areas from group 1. Results were analyzed with Pearson correlation analysis and one-way analysis of variance.

RESULTS

Mean coverage ± standard deviation of tumors with electric field that leads to reversible electroporation of tumor cells obtained with MR EIT electric impedance tomography (38% ± 9) and mean fraction of tumors with entrapped MR contrast agent (41% ± 13) were correlated (Pearson analysis, r = 0.956, P = .005) and were not statistically different (analysis of variance, P = .11) from mean fraction of tumors from group 2 with entrapped fluorescent dye (39% ± 12).

CONCLUSION

MR EIT electric impedance tomography can be used for determining electric field distribution in situ during electroporation of tissue. Implementation of MR EIT electric impedance tomography in electroporation-based applications, such as electrochemotherapy and irreversible electroporation tissue ablation, would enable corrective interventions before the end of the procedure and would additionally improve the treatment outcome.

A numerical investigation of the electric and thermal cell kill distributions in electroporation-based therapies in tissue

Electroporation-based therapies are powerful biotechnological tools for enhancing the delivery of exogeneous agents or killing tissue with pulsed electric fields (PEFs). Electrochemotherapy (ECT) and gene therapy based on gene electrotransfer (EGT) both use reversible electroporation to deliver chemotherapeutics or plasmid DNA into cells, respectively. In both ECT and EGT, the goal is to permeabilize the cell membrane while maintaining high cell viability in order to facilitate drug or gene transport into the cell cytoplasm and induce a therapeutic response. Irreversible electroporation (IRE) results in cell kill due to exposure to PEFs without drugs and is under clinical evaluation for treating otherwise unresectable tumors. These PEF therapies rely mainly on the electric field distributions and do not require changes in tissue temperature for their effectiveness. However, in immediate vicinity of the electrodes the treatment may results in cell kill due to thermal damage because of the inhomogeneous electric field distribution and high current density during the electroporation-based therapies. Therefore, the main objective of this numerical study is to evaluate the influence of pulse number and electrical conductivity in the predicted cell kill zone due to irreversible electroporation and thermal damage. Specifically, we simulated a typical IRE protocol that employs ninety 100-µs PEFs. Our results confirm that it is possible to achieve predominant cell kill due to electroporation if the PEF parameters are chosen carefully. However, if either the pulse number and/or the tissue conductivity are too high, there is also potential to achieve cell kill due to thermal damage in the immediate vicinity of the electrodes. Therefore, it is critical for physicians to be mindful of placement of electrodes with respect to critical tissue structures and treatment parameters in order to maintain the non-thermal benefits of electroporation and prevent unnecessary damage to surrounding healthy tissue, critical vascular structures, and/or adjacent organs.

Definition of novel electrochemotherapy parameters and validation of their in vitro and in vivo effectiveness

Electrochemotherapy (ECT) is a cancer therapy that conjugates the administration of a chemotherapy agent to the delivery of permeabilizing pulses released singularly or as bursts. This approach results in higher number of anticancer molecules delivered to their biological targets, but is also associated to undesirable side effects such as pain and muscular contractions. A new electroporator delivering train of eight biphasic pulses at the voltage of 1,300 V/cm lasting 50 + 50 µsec each, with a frequency of 1 Hz, and with 10-µsec interpulse intervals (total treatment time: 870 µsec/cm(2) of treated area) was tested in vitro on the human lung cancer cell line A549 and in vivo, both in mice xenografts and privately owned rabbits with spontaneous tumors. The tumor cell line was treated with electroporation using the new parameters, that showed improved drug efficacy in causing cell death. Mice with chemoresistant xenografts were treated as well with either the new parameters and with a previous protocol, confirming the higher tolerability and efficacy of the novel parameters. Finally, a cohort of six pet rabbits with advanced skin neoplasms were enrolled in a compassionate trial using the new parameters in adjuvant fashion. In terms of efficacy, none of the rabbits experienced tumor recurrence, showing minimal discomfort during the ECT sessions. The data described, demonstrate that the new permeabilizing protocol adopting biphasic electric pulses displays a significant higher efficacy compared to previous ECT treatments and substantial reduction of the associated morbidity.

Magnetic resonance electrical impedance tomography for measuring electrical conductivity during electroporation

The electroporation effect on tissue can be assessed by measurement of electrical properties of the tissue undergoing electroporation. The most prominent techniques for measuring electrical properties of electroporated tissues have been voltage-current measurement of applied pulses and electrical impedance tomography (EIT). However, the electrical conductivity of tissue assessed by means of voltage-current measurement was lacking in information on tissue heterogeneity, while EIT requires numerous additional electrodes and produces results with low spatial resolution and high noise. Magnetic resonance EIT (MREIT) is similar to EIT, as it is also used for reconstruction of conductivity images, though voltage and current measurements are not limited to the boundaries in MREIT, hence it yields conductivity images with better spatial resolution. The aim of this study was to investigate and demonstrate the feasibility of the MREIT technique for assessment of conductivity images of tissues undergoing electroporation. Two objects were investigated: agar phantoms and ex vivo liver tissue. As expected, no significant change of electrical conductivity was detected in agar phantoms exposed to pulses of all used amplitudes, while a considerable increase of conductivity was measured in liver tissue exposed to pulses of different amplitudes.

Gene electrotransfer of plasmid antiangiogenic metargidin peptide (AMEP) in disseminated melanoma: safety and efficacy results of a phase I first-in-man study

Antiangiogenic metargidin peptide (AMEP) is a novel anticancer agent exerting antiproliferative and antiangiogenic effects by binding to αvβ3 and α5β1 integrins. Electrotransfer designates the use of electric pulses (electroporation) to transfer plasmid DNA into tissues. This first-in-man phase I study investigated safety and tolerability of intratumoral plasmid AMEP electrotransfer into cutaneous metastatic melanoma. Secondary objectives were efficacy and pharmacokinetics. Five patients with disseminated melanoma without further treatment options were treated at two dose levels (1 and 2 mg DNA). In each patient, two cutaneous lesions were identified (one treated and one control). At day 1 and day 8, plasmid AMEP was injected intratumorally followed by electrotransfer. Patients were monitored weekly until day 29, and at day 64. Local efficacy was assessed at day 29 by direct measurement, and posttreatment biopsies for AMEP mRNA levels were evaluated by reverse transcriptase quantitative polymerase chain reaction. Plasmid copy number in blood and urine was determined by quantitative polymerase chain reaction. Minimal systemic toxicity was observed, including transient fever and transitory increase in C-reactive protein. No related serious adverse events occurred. Plasmid AMEP was detected in plasma but not in urine. AMEP mRNA was found in three of five treated lesions and none of the control lesions. At day 29, all five treated lesions were stable in diameter, whereas four of five control lesions increased more than 20%. No response occurred in distant lesions. This first-in-man study on electrotransfer of plasmid AMEP into cutaneous melanoma shows that the procedure and drug are safe and that local transfection was obtained.

Intraoperative electrochemotherapy of colorectal liver metastases

BACKGROUND AND OBJECTIVES

Electrochemotherapy is effective in treatment of various cutaneous tumors and could be translated into treatment of deep-seated tumors. With this aim a prospective pilot study was conducted to evaluate feasibility, safety, and efficacy of intraoperative electrochemotherapy in the treatment of colorectal liver metastases.

METHODS

Electrochemotherapy with bleomycin was performed during open surgery, by insertion of long needle electrodes into and around the tumor according to the individualized pretreatment plan.

RESULTS

A 29 metastases in 16 patients were treated in 16 electrochemotherapy sessions. No immediate (intraoperative) and/or postoperative serious adverse events related to electrochemotherapy were observed. Radiological evaluation of all the treated metastases showed 85% complete responses and 15% partial responses. In a group of seven patients that underwent a second operation at 6-12 weeks after the first one, during which electrochemotherapy was performed, the histology of resected metastases treated by electrochemotherapy showed less viable tissue (P = 0.001) compared to non-treated ones.

CONCLUSIONS

Electrochemotherapy of colorectal liver metastases proved to be feasible, safe, and efficient treatment modality, providing its specific place in difficult to treat metastases, located in the vicinity of major hepatic vessels, not amenable to surgery or radiofrequency ablation.