Radiofrequency and malignant biliary strictures: An update

Ablation Therapy of the Biliary Tree: Status and Comprehensive Review

Malignant biliary obstruction is typically referred to endoscopists for palliation. A curative resection is indeed rarely an option in this condition. Photodynamic therapy and radiofrequency ablation are 2 modalities that can be offered in those patients. Many studies have demonstrated improved stent patency and survival after ablation. Photodynamic therapy is unfortunately very expensive and is associated with photosensitivity; however, it transmits to the entire biliary tree. Radiofrequency ablation is more affordable and easier to apply but requires contact with the tumor to be efficient. This review explores both modalities in terms of their safety and efficacy for bile duct cancer palliation.

Radiofrequency ablation via an implanted self-expandable metallic stent to treat in-stent restenosis in a rat gastric outlet obstruction model

Background: In-stent restenosis caused by tissue hyperplasia and tumor growth through the wire meshes of an implanted self-expandable metallic stent (SEMS) remains an unresolved obstacle. This study aimed to investigate the safety and efficacy of SEMS-mediated radiofrequency ablation (RFA) for treating stent-induced tissue hyperplasia in a rat gastric outlet obstruction model. Methods: The ablation zone was investigated using extracted porcine liver according to the ablation time. The optimal RFA parameters were evaluated in the dissected rat gastric outlet. We allocated 40 male rats to four groups of 10 rats as follows: group A, SEMS placement only; group B, SEMS-mediated RFA at 4 weeks; group C, SEMS-mediated RFA at 4 weeks and housed until 8 weeks; and group D, SEMS-mediated RFA at 4 and 8 weeks. Endoscopy and fluoroscopy for in vivo imaging and histological and immunohistochemical analysis were performed to compare experimental groups. Results: Stent placement and SEMS-mediated RFA with an optimized RFA parameter were technically successful in all groups. Granulation tissue formation-related variables were significantly higher in group A than in groups B-D (all p < 0.05). Endoscopic and histological findings confirmed that the degrees of stent-induced tissue hyperplasia in group D were significantly lower than in groups B and C (all p < 0.05). Hsp70 and TUNEL expressions were significantly higher in groups B-D than in group A (all p < 0.001). Conclusion: The implanted SEMS-mediated RFA successfully managed stent-induced tissue hyperplasia, and repeated or periodic RFA seems to be more effective in treating in-stent restenosis in a rat gastric outlet obstruction model.

Impact of endobiliary radiofrequency ablation on survival of patients with unresectable cholangiocarcinoma: a narrative review

Cholangiocarcinoma (CCA) is a rare cancer originating from the biliary epithelium and accounts for about 3% of all gastrointestinal malignancies. Unfortunately, the majority of patients are not eligible for surgical resection at the time of diagnosis, because of the locally advanced stage or metastatic disease. The overall survival time of unresectable CCA is generally less than 1 year, despite current chemotherapy regimens. Biliary drainage is often required as a palliative treatment for patients with unresectable CCA. Recurrent jaundice and cholangitis tend to occur because of reobstruction of the biliary stents. This not only jeopardizes the efficacy of chemotherapy, but also causes significant morbidity and mortality. Effective control of tumor growth is crucial for prolonging stent patency and consequently patient survival. Recently, endobiliary radiofrequency ablation (ERFA) has been experimented as a treatment modality to reduce tumor mass, and delay tumor growth, extending stent patency. Ablation is accomplished by means of high-frequency alternating current which is released from the active electrode of an endobiliary probe placed in a biliary stricture. It has been shown that tumor necrosis releases intracellular particles which are highly immunogenic and activate antigen-presenting cells, enhancing local immunity directed against the tumor. This immunogenic response could potentially enhance tumor suppression and be responsible for improved survival of patients with unresectable CCA who undergo ERFA. Several studies have demonstrated that ERFA is associated with an increased median survival of approximately 6 months in patients with unresectable CCA. Furthermore, recent data support the hypothesis that ERFA could ameliorate the efficacy of chemotherapy administered to patients with unresectable CCA, without increasing the risk of complications. This narrative review discusses the results of the studies published in recent years and focuses on the impact that ERFA could have on overall survival of patients with unresectable cholangiocarcinoma.

Image-guided stent-directed irreversible electroporation for circumferential ablation in the rat esophagus

Background: Irreversible electroporation (IRE) has been investigated in the alimentary tract; however, the lack of dedicated electrodes and insufficient tissue responses made its application limited. The aim of this study was to investigate the efficacy and safety of image-guided stent-directed IRE in the rat esophagus. Methods: The bipolar self-expandable electrode (SE) was developed using the braiding technique. A finite element analysis was performed to validate optimal electrical field strength for the rat esophagus. A total of 40 out of 50 rats received stent-directed IRE and were sacrificed at 10 h, 3 days, 7 days, and 28 days of 10 each. The remaining ten rats underwent a sham procedure. The outcomes of stent-directed IRE were assessed by esophagography and histological responses. Results: Stent-directed IRE was technically successful in all rats with mild muscle contraction. The heart rate dropped immediately and gradually recovered at 180 s. TUNEL and caspase-3 with submucosal thickness significantly increased at 10 h and Day 3 compared with those of the sham control (all p < 0.001). The thickness of epithelial layers with collagen deposition significantly decreased at 10 h and Day 3 (all p < 0.001), however, increased at Day 7 compared with that of the sham control (all p < 0.05). The Ki67-positive deposition significantly increased at Day 3 and 7 compared with that of the sham control (all p < 0.001). All variables were similar to those of the sham control at Day 28. Conclusion: Image-guided stent-directed IRE was effective and safe in the rat esophagus. It seems to have effectively and evenly induced cell death and gradually recovered with cellular regeneration.

Stent-based electrode for radiofrequency ablation in the rat esophagus: a preliminary study

Endoluminal radiofrequency (RF) ablation has been widely used as a safe and effective treatment for Barrett's esophagus. However, inadequate RF ablation may occur due to insufficient contact between the electrode and target tissues. Herein, a stent-based monopolar RF electrode (SE) was developed to evenly deliver RF energy to the inner wall of the rat esophagus. The optimal RF parameters were evaluated in the exposed rat esophagus. The temperature in the rat esophagus reached 70 ℃ in 89 s at 30 W, 59 s at 40 W, and 34 s at 50 W. The technical feasibility and efficacy of RF ablation using SE were evaluated based on changes in histological transformation and immunohistochemical parameters of tissues compared at immediately, 1 and 2 weeks after the procedure. The degrees of inflammatory cell infiltration, fibrotic changes, TUNEL, and HSP70 in the RF-ablated rat esophagus were significantly higher than compared with sham control (all p < 0.05). TUNEL-positive deposition gradually decreased, but HSP 70-positive deposition maintained a similar level for 2 weeks. The stent-based RF ablation was technically feasible and effective in evenly inducing thermal damages to the rat esophagus. The RF ablation system using the SE may represent a promising treatment for endoluminal malignancies.

Endobiliary Radiofrequency Ablation for Malignant Biliary Obstruction over 32-Month Follow-Up

Hilar cholangiocellular carcinoma (CCC) is a malignant neoplasm of epithelial origin occurring at the confluence of the right and left hepatic bile ducts. Typically, these tumors are small, poorly differentiated, exhibit aggressive biologic behavior with non-specific symptoms and tend to obstruct the intrahepatic bile ducts. Surgery is the only available curative option. Unfortunately, in less than half of the patients a complete resection is possible with poor survival rate in unresectable cases. In this report, we present the case of a 58-year-old woman with a history of unresectable hilar cholangiocarcinoma. Initially she was treated with intraductal dilatation of malignancy and placement of a plastic stent and chemotherapy (Gemcitabin® and Platinol®). Two years later she underwent a second-line chemotherapy with Gemcitabin® and Oxyplatin® because of tumor progression. Despite a second line chemotherapy and placement of an uncovered self-expandible metal stent (ucSEMS) that was extended later on by stent-in stent technique, there was tumor progression which led to a complex course with relapsing obstructive cholangiosepsis and cholestasis. Because of tumor ingrowth, endobiliary radiofrequency ablation of the malignant stenosis was performed in repeated sessions. This case illustrates that radiofrequency ablation of solitary malignant biliary obstruction is feasible, safe and allows an improvement of quality of life in non-operable patients.

Updated evidence on the clinical impact of endoscopic radiofrequency ablation in the treatment of malignant biliary obstruction

Endoscopic biliary radiofrequency ablation (RFA) was recently developed as a novel adjunctive procedure and a promising therapeutic option in patients with malignant biliary obstruction (MBO). RFA can achieve local tumor control, resulting in improved biliary stent patency and a potential survival benefit. However, the efficacy of biliary RFA remains controversial, and previous studies have shown conflicting results. At present, extrahepatic cholangiocarcinoma is considered the condition most effectively treated by biliary RFA, but there is limited research even on this point. Further, limitations of RFA associated with the devices used during the procedure are an important subject of discussion. In addition to further well-designed clinical trials, development of innovative devices is warranted to investigate and conclusively establish the usefulness of biliary RFA. In this review we summarize the updated evidence regarding the use of endoscopic biliary RFA for MBO and discuss issues that should be addressed in future studies.

Development of Radiofrequency Ablation Generator and Balloon-Based Catheter for Microendoluminal Thin-Layer Ablation Therapy Using the Rat Duodenum as a Model of Low-Impedance Tissue

Radiofrequency ablation (RFA) is a routinely used, safe, and effective method for the tissue destruction. Often, in case of its application in malignant conditions, the extent of tissue destruction is insufficient due to the size of the target lesion, as well as due to the risk of heat-induced damage to the surrounding organs. Nevertheless, there are conditions requiring superficial precise-depth ablation with preservation of deeper layers. These are represented, for example, by mucosal resurfacing in case of Barrett's esophagus or treatment of recurrent mucosal bleeding in case of chronic radiation proctitis. Recently, new indications for intraluminal RFA use emerged, especially in the pancreatobiliary tract. In the case of intraductal use of RFA (e.g., biliary and pancreatic tract), there are currently available rigid and needle tip catheters. An expandable balloon-based RFA catheter suitable for use in such small-diameter tubular organs could be of benefit due to possible increase of contact between the probe and the target tissue; however, to prevent excessive tissue damage, a compatible generator suitable for low-impedance catheter/tissue is essential. This project aimed to develop a radiofrequency ablation generator and bipolar balloon-based catheter optimized for the application in the conditions of low-impedance tissue and (micro)endoluminal environment. Subsequent evaluation of biological effect in vivo was performed using duodenal mucosa in Wistar rat representing conditions of endoluminal radiofrequency ablation of low-impedance tissue. Experiments confirming the safety and feasibility of RFA with our prototype devices were conducted.

Future Directions of Percutaneous Biliary Interventions

We are at an exciting cross-road in biliary interventions. While other services such as surgery and gastroenterology have learned to use imaging guidance to improve the safety and efficacy of their procedures, it is time for interventional radiologist to learn endoscopic interventions to achieve the same. The future of interventional radiologists in managing patients with biliary disease depends on (1) increasing comfort of our procedures, (2) publishing our data on biliary interventions, and (3) increasing collaboration with other services to manage biliary disease. We need to appropriately understand the limitations of interventional radiology to help guide the future directions of our specialty in this very interesting space.

Advancements in Endoscopic Biliary Interventions by Gastroenterology

Endoscopic retrograde cholangiopancreatography (ERCP) is an endoscopic technique in which a specialized side-viewing endoscope is guided into the duodenum, allowing for instruments to access the biliary and pancreatic ducts. ERCP was initially developed as a diagnostic tool as computed tomography was in its infancy during that time. ERCP has evolved since its inception in the 1960s to becoming not only a valuable diagnostic resource but now an effective therapeutic intervention in the treatment of various biliary disorders. The most common biliary interventions performed by ERCP include the management of biliary obstructions for benign and malignant indications. Additionally, endoscopic ultrasound (EUS) has been increasingly utilized in diagnosing and intervening on pancreaticobiliary lesion. This article will discuss the various methods currently available for various endoscopic biliary interventions and future interventional techniques. For the management of biliary strictures, EUS can be utilized with fine need aspiration, while ERCP can be used for the placement of various stents and diagnostic modalities. Another example is radiofrequency ablation, which can be used for the treatment of hilar strictures. Achieving bile duct access can be challenging in patients with complicated clinical scenarios; other techniques that can be used for bile duct access include EUS-guided rendezvous approach, transluminal approach, Choleodochoduodenostomy, and hepatogastrostomy, along with gaining access in complicated anatomy such as in patients with Rou-en-Y anatomy. Another useful endoscopic tool is nonsurgical drainage of the gallbladder, which can be a suitable option when patients are not optimal surgical candidates. There has also been an increase in outpatient utilization of ERCP, which was previously seen as a predominantly inpatient procedure in the past. Possible future evolutions of biliary interventions include robotic manipulation of a duodenoscope and direct infusion of chemotherapeutic or immunomodulatory agents into the pancreaticobiliary tree. These advancements will depend on parallel advancements in other imaging and laboratory as well as breakthrough technology or techniques by other disciplines including interventional radiology and minimally invasive surgery.

Experimental model of occluded biliary metal stent recanalization using irreversible electroporation via a tubular catheter

PURPOSE

To demonstrate the feasibility of irreversible electroporation (IRE) for treating biliary metal stent occlusion in an experimental liver model.

METHODS AND MATERIALS

IRE was performed using an expandable tubular IRE-catheter placed in nitinol stents in the porcine liver. A 3-electrode IRE-catheter was connected to an IRE-generator and one hundred 100μs pulses of constant voltage (300, 650, 1000, and 1300 V) were applied. Stent occlusion was simulated by insertion of liver tissue both ex vivo (n = 94) and in vivo in 3 pigs (n = 14). Three scenarios of the relationship between the stent, electrodes, and inserted tissue (double contact, single contact, and stent mesh contact) were studied. Electric current was measured and resistance and power calculated. Pigs were sacrificed 72 h post-procedure. Harvested samples (14 experimental, 13 controls) underwent histopathological analysis.

RESULTS

IRE application was feasible at 300 and 650 V for the single and double contact setup in both ex vivo and in vivo studies. Significant differences in calculated resistance between double contact and single contact settings were observed (ex-vivo p ˂ 0.0001, in-vivo p = 0.02; Mann-Whitney). A mild temperature increase of the surrounding liver parenchyma was noted with increasing voltage (0.9-5.9 °C for 300-1000 V). The extent of necrotic changes in experimental samples in vivo correlated with the measured electric current (r² = 0.39, p = 0.01). No complications were observed during or after the in-vivo procedure.

CONCLUSION

Endoluminal IRE using an expandable tubular catheter in simulated metal stent occlusion is feasible. The relationship of active catheter electrodes to stent ingrowth tissue can be estimated based on resistance values.

The combination of endoluminal radiofrequency ablation and metal stent implantation for the treatment of malignant biliary stenosis - Randomized study

PURPOSE

To analyse whether endobiliary radiofrequency ablation prior metal stent insertion in malignant biliary stenosis show improved survival or stent patency.

METHODS

76 patients with histologically proven malignant biliary stenosis have been enrolled in a prospective, randomized study. In control arm, 40 patients underwent self-expandable metal stent insertion. In experimental arm, the endoluminal ablation with a bipolar radiofrequency catheter was performed immediately before stent insertion. A subgroup analysis of cholangiocarcinoma was performed (22 vs 21 patients). The objective of the study was to determine the rate of complications, duration of the stent patency and the survival of patients (Kaplan-Meier analysis).

RESULTS

No major complications related to the stent insertion and the endoluminal ablation were found. The mean primary stent patency was 5.2 (95% CI 0.7-12.8) vs 4.8 months (95% CI 0.8-18.2) months (p = 0.79) in control and experimental group, respectively, in the subgroup analysis with cholangiocarcinoma 4.5 (95% CI 0.8-10.3) and 9.6 (95% CI 5.2-11.2) months (p = 0.029). The median survival since the insertion of the stent was 6.8 (95 %CI 3.0-10.6) vs 5.2 (95 %CI 2.4-7.9) months (p = 0.495) and since the initial drainage 9.8 (95 %CI 6.9-12.7) vs 9.1 (95 %CI 5.4-12.7) months (p = 0.720) in the control and experimental arm.

CONCLUSION

Endobiliary radiofrequency ablation prior metal stent insertion showed increased patency rate only in patients with cholangiocarcinoma, on the other hand, no improvement in survival was demonstrated in this randomized clinical study.

Percutaneous intraductal radiofrequency ablation combined with biliary stent placement for treatment of malignant biliary obstruction

PURPOSE

To determine the safety and efficacy of percutaneous intraductal radiofrequency ablation (RFA) combined with biliary metal stent placement for patients with unresectable malignant biliary obstruction.

METHODS

From a cohort of 70 patients with unresectable malignant biliary obstruction, 28 patients received percutaneous intraductal RFA combined with biliary stent placement (group A) and the remaining 42 were treated with biliary metal stent placement only (group B). Stent patency, overall survival (OS), alleviation of jaundice, and postoperative complications were assessed.

RESULTS

The technical success rate for both groups was 100%. No severe complications (e.g., biliary bleeding, perforation) occurred. In both groups, jaundice was relieved and the decrease of the total and direct bilirubin concentration was significant (p < 0.01). The median time of stent patency in group A and group B were 6.6 ± 0.3 months (95% CI 6.1-7.1 months) and 4.9 ± 0.4 months (95% CI 4.2-5.6 months), respectively (p < 0.01). The median overall survival times in Group A were 7.2 ± 0.3 months (95% CI 6.5-7.9 months) versus 5.6 ± 0.4 months (95% CI 4.8-6.4 months) in group B (p < 0.01). In univariate and multivariate analyses, intraductal RFA, stent patency, and decreased baseline serum direct bilirubin concentration were associated with greater OS (p < 0.05).

CONCLUSION

Percutaneous intraductal RFA combined with stent placement is a safe and effective method for patients with malignant biliary obstruction. As compared to stent placement alone, percutaneous intraductal RFA can significantly prolong stent patency and improve the overall survival of patients with malignant biliary obstruction.

Design and Characterization of a Minimally Invasive Bipolar Electrode for Electroporation

OBJECTIVE

To test a new bipolar electrode for electroporation consisting of a single minimally invasive needle.

METHODS

A theoretical study was performed by using Comsol Multiphysics^® software. The prototypes of electrode have been tested on potatoes and pigs, adopting an irreversible electroporation protocol. Different applied voltages and different geometries of bipolar electrode prototype have been evaluated.

RESULTS

Simulations and pre-clinical tests have shown that the volume of ablated area is mainly influenced by applied voltage, while the diameter of the electrode had a lesser impact, making the goal of minimal-invasiveness possible. The conductive pole's length determined an increase of electroporated volume, while the insulated pole length inversely affects the electroporated volume size and shape; when the insulated pole length decreases, a more regular shape of the electric field is obtained. Moreover, the geometry of the electrode determined a different shape of the electroporated volume. A parenchymal damage in the liver of pigs due to irreversible electroporation protocol was observed.

CONCLUSION

The minimally invasive bipolar electrode is able to treat an electroporated volume of about 10 mm in diameter by using a single-needle electrode. Moreover, the geometry and the electric characteristics can be selected to produce ellipsoidal ablation volumes.

Nonsurgical Approaches to Treat Biliary Tract and Liver Tumors

Endoscopic and percutaneous therapies have been shown to prolong life and reduce morbidity for patients with unresectable advanced stages of primary hepatobiliary malignancies. This article reviews pertinent studies published within the last 5 years that involve locoregional techniques to manage hepatocellular carcinoma, perihilar and distal cholangiocarcinoma. A major emphasis is placed on photodynamic therapy, radiofrequency ablation, irreversible electroporation, and microwave ablation. Technical advances, combinational therapies, and postintervention outcomes are discussed. Despite widespread application, high-quality evidence does not show superiority of any particular locoregional technique for treating advanced hepatobiliary cancers.

Novel swine biliary dilatation model with temperature-controlled endobiliary radiofrequency ablation: An effective tool for training in EUS-guided biliary drainage

Background and Objectives:

EUS-guided biliary drainage (EUS-BD) is used as a rescue method after failed endoscopic retrograde cholangiography. However, it is considered a technically challenging procedure. Phantoms and ex vivo biliary dilatation models have been used to enhance the learning of EUS-BD, but they provide a limited level of realism. The aim of this study was to develop a swine biliary dilatation model that uses temperature-controlled endobiliary radiofrequency ablation (EB-RFA) for training in EUS-BD.

Materials and Methods:

Target temperature-controlled (80°C at 7 or 10 W for 60–120 s) EB-RFA was performed on seven pigs. Two weeks after the EB-RFA, EUS examination was performed to confirm biliary dilatation, and EUS-BD was then attempted by performing a hepaticogastrostomy (HGS) or cholecystogastrostomy (CGS).

Results:

Twelve sessions of EB-RFA (11 at the distal common bile duct [CBD] and one at the proximal CBD) were successfully performed on the seven pigs. There were no immediate postprocedural adverse events. Two weeks after the procedures, clinical signs of jaundice were observed in all the pigs. EUS examination revealed massive intrahepatic and extrahepatic biliary dilatations in all the pigs, and EUS-BD was attempted in the same session. HGS was performed on six pigs. Technical success was achieved in five of the six pigs (83.3%). Technical failure in HGS occurred during the stent deployment, and CGS was successfully performed on one pig.

Conclusions:

Our study shows that EB-RFA is an effective minimally invasive method for creating biliary dilatation models. It may be considered suitable for training in EUS-BD.

miR-186 Suppresses the Progression of Cholangiocarcinoma Cells Through Inhibition of Twist1

Deregulation of miR-186 and Twist1 has been identified to be involved in the progression of multiple cancers. However, the detailed molecular mechanisms underlying miR-186-involved cholangiocarcinoma (CCA) are still unknown. In this study, we found that miR-186 was downregulated in CCA tissues and cell lines, and negatively correlated with the expression of Twist1 protein. In vitro assays demonstrated that miR-186 mimics repressed cell proliferation, in vivo tumor formation, and caused cell cycle arrest. miR-186 mimics also inhibited the migration and invasion of CCLP1 and SG-231 cells. Mechanistically, the 3′-untranslated region (3′-UTR) of Twist1 mRNA is a direct target of miR-186. Further, miR-186 inhibited the expressions of Twist1, N-cadherin, vimentin, and matrix metallopeptidase 9 (MMP9) proteins, whereas it increased the expression of E-cadherin in CCLP1 and SG-231 cells. Silencing of Twist1 expression enhanced the inhibitory effects of miR-186 on the proliferation, migration, and invasion of CCLP1 and SG-231 cells. In conclusion, miR-186 inhibited cell proliferation, migration, invasion, and epithelial–mesenchymal transition (EMT) through targeting Twist1 in human CCA. Thus, miR-186/Twist1 axis may benefit the development of therapies for CCA.