Interventional radiofrequency ablation: A promising therapeutic modality in the management of malignant biliary and pancreatic duct obstruction

Advances in Image-Guided Ablation Therapies for Solid Tumors

Image-guided solid tumor ablation methods have significantly advanced in their capability to target primary and metastatic tumors. These techniques involve noninvasive or percutaneous insertion of applicators to induce thermal, electrochemical, or mechanical stress on malignant tissue to cause tissue destruction and apoptosis of the tumor margins. Ablation offers substantially lower risks compared to traditional methods. Benefits include shorter recovery periods, reduced bleeding, and greater preservation of organ parenchyma compared to surgical intervention. Due to the reduced morbidity and mortality, image-guided tumor ablation offers new opportunities for treatment in cancer patients who are not candidates for resection. Currently, image-guided ablation techniques are utilized for treating primary and metastatic tumors in various organs with both curative and palliative intent, including the liver, pancreas, kidneys, thyroid, parathyroid, prostate, lung, breast, bone, and soft tissue. The invention of new equipment and techniques is expanding the criteria of eligible patients for therapy, as now larger and more high-risk tumors near critical structures can be ablated. This article provides an overview of the different imaging modalities, noninvasive, and percutaneous ablation techniques available and discusses their applications and associated complications across various organs.

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.

Pancreatic duct stents

Pancreatic duct stenting using endoscopy or surgery is widely used for the management of benign and malignant pancreatic diseases. Endoscopic pancreatic stents are mainly used to relieve pain caused by chronic pancreatitis and pancreas divisum, and to treat pancreatic duct disruption and stenotic pancreaticointestinal anastomosis after surgery. They are also used to prevent postendoscopic retrograde cholangiopancreatography pancreatitis and postoperative pancreatic fistula, treat pancreatic cancer, and locate radiolucent stones. Recent advances in endoscopic techniques, such as endoscopic ultrasonography and balloon enteroscopy, and newly designed stents have broadened the indications for pancreatic duct stenting. In this review we outlined the types, insertion procedures, efficacy, and complications of endoscopic pancreatic duct stent placement, and summarized the applications of pancreatic duct stents in surgery.

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.

Percutaneous Endoluminal Radiofrequency Ablation of Occluded Biliary Metal Stent in Malignancy Using Monopolar Technique: A Feasibility Study

PURPOSE

To prove feasibility and safety of percutaneous endoluminal radiofrequency ablation (eRFA) using a monopolar approach in treatment of occluded biliary stent in malignancy.

MATERIALS AND METHODS

The study included 11 patients with occluded biliary metal stent that had been implanted due to malignant biliary obstruction. All underwent metal stent recanalization by percutaneous eRFA in monopolar setting. Sixteen eRFA procedures were performed under fluoroscopic guidance with an EndoHPB 8F radiofrequency ablation catheter. The effect of stent recanalization was assessed based upon change from pre- to post-procedural diameter of the patent lumen of the metal stent (Wilcoxon test), primary and secondary stent patency (compared by log-rank test), catheter-free period, and overall survival. Adverse events were evaluated according to Common Terminology Criteria for Adverse Events (CTCEA) 4.0.

RESULTS

Recanalization of the metal stent by monopolar radiofrequency ablation was successful in all 11 patients. Diameter of the patent lumen of the stent significantly widened after the eRFA inside the stent (median 2 vs. 7 mm, p = 0.003). Grade 1 complications were observed in one-third of procedures. Median stent patency after recanalization by eRFA was non-inferior to primary metal stent patency (154 vs. 161 days, p = 0.27). Median catheter-free survival and overall survival after stent recanalization were 149 and 210 days, respectively.

CONCLUSION

Endoluminal radiofrequency ablation in monopolar setting was shown to be a feasible and safe method for recanalization of occluded biliary metal stents.

LEVEL OF EVIDENCE

Level 4, Case Series.

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.

Stent placement combined with intraluminal radiofrequency ablation and hepatic arterial infusion chemotherapy for advanced biliary tract cancers with biliary obstruction: a multicentre, retrospective, controlled study

OBJECTIVE

To evaluate the efficacy and safety of stent placement combined with intraluminal radiofrequency ablation (intra-RFA) and hepatic arterial infusion chemotherapy (HAIC) for patients with advanced biliary tract cancers (Ad-BTCs) and biliary obstruction (BO).

METHODS

We retrospectively reviewed data for patients with Ad-BTCs and BO who underwent stent placement with or without intra-RFA and HAIC in three centres between November 2013 and November 2018. The stent patency time (SPT), overall survival (OS), and adverse events (AEs) were analysed.

RESULTS

Of the 135 enrolled patients, 64 underwent stent placement combined with intra-RFA and HAIC, while 71 underwent only stent placement. The median SPT was significantly longer in the combination group (8.2 months, 95% confidence interval [CI]: 7.1-9.3) than in the control group (4.3 months, 95% CI: 3.6-5.0; p < 0.001). A similar result was observed for OS (combination: 13.2 months, 95% CI: 11.1-16.5; control: 8.5 months, 95% CI: 7.6-9.6; p < 0.001). The incidence of AEs related to biliary tract operation was not significantly different between the two groups (p > 0.05). The most common AE and serious AE related to HAIC were alanine aminotransferase elevation (24/64; 37.5%) and thrombocytopenia (8/64; 12.5%), respectively. All AEs were tolerable, and there was no death from AEs.

CONCLUSIONS

Stent placement combined with intra-RFA and HAIC may be a safe, potential treatment strategy for patients with Ad-BTCs and BO.

KEY POINTS

• Advanced biliary cancers (Ad-BTCs) with biliary obstruction (BO) can rapidly result in liver failure and cachexia with an extremely poor prognosis. • Stent placement combined with intraluminal radiofrequency ablation and hepatic arterial infusion chemotherapy may be safe and effective for patients with Ad-BTCs and BO. • The long-term efficacy and safety of the combined treatment is promising.

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.

Improving biliary stent patency for malignant obstructive jaundice using endobiliary radiofrequency ablation: experience in 150 patients

BACKGROUND

Although self-expandable mental stents (SEMS) placement is the standard care for relieving obstructive jaundice caused by unresectable malignant biliary stricture, how to maintain stent potency remains an intractable problem. This study was to evaluate the efficacy and safety of endobiliary radiofrequency ablation (RFA) through percutaneous transhepatic cholangiography (PTC) pathway in treating such patients.

METHODS

Consecutive patients who were performed endobiliary RFA as well as SEMS placement because of unresectable malignant obstructive jaundice in single institution in recent 8 years were retrospectively reviewed. As comparison, patients who underwent only percutaneous SEMS placement for unresectable malignant biliary stricture during the contemporary period were reviewed. Stent patency, complications, complications, and overall survival (OS) were investigated and analyzed.

RESULTS

One hundred and fifty patients who underwent endobiliary RFA and 127 patients who underwent only stent placement were included in this study. In the study group of endobiliary RFA, 87 patients (58.0%) underwent ablation for 1 time, 49 (32.7%) for 2 times, and 14 (9.3%) for 3 times. Complications related to RFA as well as SEMS placement happened in 113 patients (75.3%), without severe complications that needed emergent surgery or interventional therapy. The median duration of stent patency after ablation was 11.2 month, and the median survival time was 12.3 month. As comparison, difference was found in the number of interventional procedures and stents placed, duration of initial stent patency, and the incidence of moderate bleeding and pain. In the study group, only the type of tumor that caused biliary obstruction (intrahepatic carcinoma vs. extrahepatic carcinoma) was a poor independent factor (P = 0.035) for recurrent biliary obstruction. Repeated interventional therapy and adoption of subsequent therapy were only independent factors for OS.

CONCLUSIONS

Endobiliary RFA and SEMS placement is technically safe and feasible for unresectable malignant obstructive jaundice to improve the quality of life and prolong survival.

Role of Radiofrequency Ablation in the Management of Unresectable Pancreatic Cancer

Pancreatic cancer is one of the most aggressive malignancies of the digestive tract and carries a poor prognosis. The majority of patients have advanced disease at the time of diagnosis. Surgical resection offers the only curative treatment, but only a small proportion of patients can undergo surgical resection. Radiofrequency ablation (RFA) is a well-known modality in the management of solid organ tumors, however, its utility in the management of pancreatic cancer is under investigation. Since the past decade, there is increasing use of RFA as it provides a feasible palliation treatment in the management of unresectable pancreatic cancer. RFA causes tumor cytoreduction through multiple mechanisms such as coagulative necrosis, protein denaturation, and activation of anticancer immunity. The safety profile of RFA is controversial because of the high risk for complications, however, small prospective and retrospective studies have shown promising results in its applicability for palliative management of unresectable pancreatic malignancies. In this review, we discuss different approaches of RFA, their indications, technical accessibility, safety, and major complications in the management of unresectable pancreatic cancer.

Percutaneous Intraductal Microwave Ablation of Malignant Biliary Strictures: Initial Experience

OBJECTIVE. Metallic stenting of malignant biliary strictures is the preferred method of palliation, because most patients present when the condition is inoperable. Most metallic stents, however, are occluded 6-8 months after deployment. Intraductal radiofrequency ablation has been used in previous studies to improve stent patency. The purpose of this study was to assess a single-center experience with percutaneous intraductal microwave ablation of malignant biliary strictures. MATERIALS AND METHODS. In this retrospective case series study, data on 12 patients with malignant biliary obstruction who underwent percutaneous intraductal microwave ablation followed by metallic stenting were evaluated. Ablation procedures were performed with generator frequencies of 902-928 MHz, power set at 6-10 W, and ablation time of 60-90 seconds in a temperature-controlled manner with target temperature set at 80°C. RESULTS. Causes of malignant biliary obstruction were pancreatic carcinoma in four patients, gastric antrum carcinoma in three, cholangiocarcinoma in two, metastasis in two, and gallbladder carcinoma in one patient. Percutaneous intraductal microwave ablation and metallic stenting were performed successfully in all patients. There was no procedural mortality or major complication. The most common minor complication was abdominal pain. Biliary decompression was achieved in all patients at the end of the first month. The mean follow-up time was 9.4 months. The median primary stent patency period was 231 days. There were two stent occlusions due to sludge formation, and two patients died during follow-up. CONCLUSION. Percutaneous intraductal microwave ablation of malignant biliary strictures is safe and feasible. Prospective randomized controlled studies with long-term results are warranted to determine the effectiveness of this technique in lengthening the stent patency period.

Current Endoscopic Management of Malignant Biliary Stricture

Biliary and pancreatic cancers occur silently in the initial stage and become unresectable within a short time. When these diseases become symptomatic, biliary obstruction, either with or without infection, occurs frequently due to the anatomy associated with these cancers. The endoscopic management of these patients has changed, both with time and with improvements in medical devices. In this review, we present updated and integrated concepts for the endoscopic management of malignant biliary stricture. Endoscopic biliary drainage had been indicated in malignant biliary obstruction, but the concept of endoscopic management has changed with time. Although routine endoscopic stenting should not be performed in resectable malignant distal biliary obstruction (MDBO) patients, endoscopic biliary drainage is the treatment of choice for palliation in unresectable MDBO patients. Self-expanding metal stents (SEMS) have better stent patency and lower costs compared with plastic stents (PS). For malignant hilum obstruction, PS and uncovered SEMS yield similar short-term outcomes, while a covered stent is not usually used due to a potential unintentional obstruction of contralateral ducts.