Functional self-expandable metal stents in biliary obstruction

A machine learning-based predictive model for biliary stricture attributable to malignant tumors: a dual-center retrospective study

Background

Biliary stricture caused by malignant tumors is known as Malignant Biliary Stricture (MBS). MBS is challenging to differentiate clinically, and accurate diagnosis is crucial for patient prognosis and treatment. This study aims to identify the risk factors for malignancy in all patients diagnosed with biliary stricture by Endoscopic Retrograde Cholangiopancreatography (ERCP), and to develop an effective clinical predictive model to enhance diagnostic outcomes.

Methodology

Through a retrospective study, data from 398 patients diagnosed with biliary stricture using ERCP between January 2019 and January 2023 at two institutions: the First People's Hospital affiliated with Jiangsu University and the Second People's Hospital affiliated with Soochow University. The study began with a preliminary screening of risk factors using univariate regression. Lasso regression was then applied for feature selection. The dataset was divided into a training set and a validation set in an 8:2 ratio. We analyzed the selected features using seven machine learning algorithms. The best model was selected based on the Area Under the Receiver Operating Characteristic (ROC) Curve (AUROC) and other evaluation indicators. We further evaluated the model's accuracy using calibration curves and confusion matrices. Additionally, we used the SHAP method for interpretability and visualization of the model's predictions.

Results

RF model is the best model, achieved an AUROC of 0.988. Shap result indicate that age, stricture location, stricture length, carbohydrate antigen 199 (CA199), total bilirubin (TBil), alkaline phosphatase (ALP), (Direct Bilirubin) DBil/TBil, and CA199/C-Reactive Protein (CRP) were risk factors for MBS, and the CRP is a protective factor.

Conclusion

The model's effectiveness and stability were confirmed, accurately identifying high-risk patients to guide clinical decisions and improve patient prognosis.

Anti-fibrotic and anti-stricture effects of biodegradable biliary stents braided with dexamethasone-impregnated sheath/core structured monofilaments

Endoscopic biliary stent insertion has been widely used for the treatment of benign biliary stricture (BBS). Thus, the development of stent materials in the perspectives of structure, mechanical properties, and biocompatibility has been also studied. However, conventional metal and plastic stents have several disadvantages, such as repeated procedures to remove or exchange them, dislodgment, restenosis, biocompatibility, and poor mechanical properties. Sustainable effectiveness, attenuation and prevention of fibrosis, and biocompatibility are key factors for the clinical application of stents to BBS treatment. In addition, loading drugs could show synergistic effects with stents' own performance. We developed a dexamethasone-eluting biodegradable stent (DBS) consisting of a sheath/core structure with outstanding mechanical properties and sustained release of dexamethasone, which maintained its functions in a BBS duct over 12 weeks in a swine model. The insertion of our DBS not only expanded BBS areas but also healed secondary ulcers as a result of the attenuation of fibrosis. After 16 weeks from the insertion, BBS areas were totally improved, and the DBS was degraded and thoroughly disappeared without re-intervention for stent removal. Our DBS would be an effective clinical tool for non-vascular diseases. STATEMENT OF SIGNIFICANCE: This study describes the insertion of a drug-eluting biodegradable stent (DBS) into the bile duct. The sheath/core structure of DBS confers substantial durability and a sustained drug release profile. Drug released from the DBS exhibited anti-fibrotic effects without inflammatory responses in both in vitro and in vivo experiments. The DBS maintained its function over 12 weeks after insertion into the common bile duct, expanding benign biliary stricture (BBS) and reducing inflammation to heal secondary ulcers in a swine BBS model. After 16 weeks from the DBS insertion, the DBS thoroughly disappeared without re-intervention for stent removal, resulting in totally improved BBS areas. Our findings not only spotlight the understanding of the sheath/core structure of the biodegradable stent, but also pave the way for the further application for non-vascular diseases.

CT imaging features of bile duct stent complications

Biliary stents have been widely used to treat both malignant and benign biliary obstruction. Biliary stenting serves as a temporary measure to maintain ductal patency and promote bile drainage. Biliary decompression can help relieve clinical symptoms of pain, obstructive jaundice, pruritis, fat malabsorption, and failure to thrive and prevent disease progression, such as secondary biliary cirrhosis and end-stage liver failure. Endoscopic placement of biliary endoprosthesis is a minimally invasive procedure well tolerated by most patients but is not without problems. Multiple early and late complications have been reported in the literature and Computed Tomography (CT) is the most used modality to assess normal positions and evaluate patients suspected of stent complications. The aim of this article is to provide a review various of biliary stent related complications, as seen on CT. Current literature on risk factors, diagnosis and management is also discussed.

Emerging Trends in Biliary Stents: A Materials and Manufacturing Perspective

Biliary stent technology has come a long way since its inception. There have been significant advancements in materials used, designs, and deployment strategies. Options have expanded from thermoplastic and metallic...

Preliminary application of brachytherapy with double-strand 125I seeds and biliary drainage for malignant obstructive jaundice

AIM

To evaluate the efficacy and safety of brachytherapy with double-strand ¹²⁵I seeds and biliary drainage for malignant obstructive jaundice.

METHODS AND MATERIALS

42 patients with obstructive jaundice because of extrahepatic cholangiocarcinoma were enrolled. 22 patients (group A) received a biliary stent with common drainage tube implantation, and 20 patients (group B) received a biliary stent with double-strand ¹²⁵I seeds radiotherapy drainage tube placement. The length, location and pathological stage of biliary stricture were recorded in the two groups. Total bilirubin (TBIL), direct bilirubin (DBIL), IgA, IgG, IgM, alanine aminotransferase and white blood cell (WBC) count were measured before and after percutaneous transhepatic cholangial drainage (PTCD). Tumor diameter was measured before and three months after PTCD, and the difference were calculated. Stent patency time, survival time, and complications were recorded.

RESULTS

There was no significant difference in the length, location and pathological stage of biliary stenosis between the two groups. There was no significant difference in TBIL, DBIL, IgA, IgG, IgM, alanine aminotransferase and WBC count between the two groups before or after PTCD (P > 0.05). Three months after PTCD, tumors growth in group A and tumors shrinkage in group B. The difference in tumor size between the two groups before and after PTCD was statistically significant (P < 0.05). The average stent patency times in groups A and B were 3.55 ± 0.76 months and 8.76 ± 1.85 months, respectively (P < 0.05). The average survival times in groups A and B were 133.5 ± 27.8 days and 252.5 ± 114.5 days, respectively (P < 0.05). There was no statistically significant difference in the incidence of complications between the two groups (P > 0.05).

CONCLUSION

Double-strand ¹²⁵I seeds radiotherapy biliary drainage tubes can safely and effectively control tumors, prolong the patency of biliary stents, and prolong patient survival.

Mechanical properties and degradation process of biliary self-expandable biodegradable stents

OBJECTIVES

The clinical outcomes and prevalence of adverse events associated with biliary biodegradable stents (BS) can differ according to degradation process and time. The aim of this study was to observe the degradation process and time of different BS prototypes, and to evaluate sequential changes in their mechanical properties.

METHODS

Using an in vitro bile flow phantom model, we compared degradation time, radial force changes, and morphologic changes among four different BS prototypes: polydioxanone (PDO) BS, polyglycolide (PGA) BS, polydioxanone/poly-l-lactic acid (PDO/PLLA) sheath-core BS, and polydioxaone/magnesium (PDO/Mg) sheath-core BS. Using an in vivo swine bile duct dilation model, we performed a direct peroral cholangioscopy (DPOC) examination to observe the biodegradation process and related adverse events at regular intervals.

RESULTS

In the bile flow phantom model, the PGA BS and PDO/Mg BS prototypes showed rapid radial force reduction and morphological changes and complete degradation within six weeks. PDO/PLLA BS maintained high radial force and kept their original shape for longer than the PDO BS, up to 16 weeks. A total of 24 BS were inserted into the dilated bile ducts of 12 swine. In this animal model, DPOC examination revealed that PDO BS and PDO/PLLA BS maintained their original shapes for approximately 12 weeks, but PDO BS showed a greater degree of fragmentation and induced biliary stones and bile duct obstruction.

CONCLUSION

Our results showed that PDO/PLLA BS maintained their original shape and radial force for a relatively long time and minimized adverse events.

Antireflux metal stent for biliary obstruction: Any benefits?

Endoscopic retrograde cholangiopancreatography with stent placement has been utilized as standard palliative management of distal malignant biliary obstruction (MBO). Compared to plastic stents, metal stents can provide longer-term relief of symptoms. When a large-bore metal stent is placed across the ampulla, patients are predisposed to the risk of cholangitis or stent dysfunction due to reflux of duodenal contents. To mitigate the risk of adverse events associated with the duodenobiliary reflux, efforts have been directed to development of antireflux metal stents (ARMSs). The antireflux property has been introduced through adding of an antireflux valve to the duodenal stent end. Evidence from clinical studies indicates that ARMSs may not only reduce the risk of ascending cholangitis during follow-up but also prolong stent patency time. However, the results of clinical studies testing ARMSs are inconsistent owing to heterogeneous designs of antireflux valves and stent bodies. Metal stents are increasingly indicated for benign biliary strictures and MBO in the setting of neoadjuvant chemotherapy, and therefore, research is warranted to evaluate ARMSs for those indications. Given that endoscopic ultrasound (EUS)-guided transmural biliary drainage has gained popularity, the optimal timing of placing an ARMS in relation to EUS-guided and percutaneous drainage should be investigated. Development and evaluation of ARMSs require an integrative approach utilizing phantom and animal models, measurements of stent mechanical properties, and in vivo functional study after stent placement. In this review article, we summarize updated evidence on ARMSs for MBO and discuss issues that should be addressed in future studies.

[Mechanisms and prevention of biliary stent occlusion]

One of significant achievements of modern endoscopy is development of retrograde biliary stenting for obstructive jaundice. This method ensured widespread application of endoscopic decompression in the treatment of patients with malignant biliary obstruction as preparation before radical surgery and final palliative care. Endoscopic retrograde transpapillary stenting firmly took its place together with antegrade and percutaneous stenting. There are certain advantages of this technique including minimally invasiveness and favorable quality of life. However, this approach is associated with some drawbacks associated with stent occlusion and difficult correction of this complication. The maximum diameter of the plastic stent (PS) is determined by the width of the working channel of the duodenoscope. In this regard, self-expandable metal stents (SEMS) were developed to increase the diameter of bile drainage channel. SEMS are associated with prolonged function. However, there is another problem. It is a germination of SEMS followed by impossible removal of the stent for its subsequent replacement. A further step in development of endoscopic biliary stents was the use of special SEMS coating to exclude tumor or granulation ingrowth. The problem of biliary stent occlusion remains relevant despite some improvement of stenting results. Mechanisms of occlusion of biliary stents and prevention of these events are discussed in this review.

[Relief of Obstruction in the Management of Pancreatic Cancer]

Pancreatic cancer is a major cause of cancer-related mortality and morbidity, and its incidence is increasing as the population is aging. On the other hand, significant improvement in the prognosis has not occurred. The absence of early diagnosis means that many patients are diagnosed only when they develop symptoms, such as jaundice, due to a biliary obstruction. The role of endoscopy in multidisciplinary care for patients with pancreatic cancer continues to evolve. Controversy remains regarding the best preoperative biliary drainage in patients with surgically resectable pancreatic head cancer. In general, patients undergoing a surgical resection usually do not require preoperative biliary drainage unless they have cholangitis or receive neoadjuvant chemotherapy. If biliary drainage is performed prior to surgery, the patient's condition and a multidisciplinary approach should be considered. With the increasing life expectancy of patients with pancreatic cancer, the need for more long-time biliary drainage or pre-operative biliary drainage is also increasing. Strong evidence of endoscopic retrograde cholangiopancreatography (ERCP) as a first-line and essential treatment for biliary decompression has been provided. On the other hand, the use of endoscopic ultrasound-guided biliary drainage as well as percutaneous biliary drainage has been also recommended. During ERCP, self-expandable metal stent could be recommended instead of a plastic stent for the purpose of long stent patency and minimizing stent-induced complications. In this review, several points of view regarding the relief of obstruction in patients with pancreatic cancer, and optimal techniques are being discussed.

Endoscopic management of anastomotic stricture after living-donor liver transplantation

The most effective and fundamental treatment for end-stage liver disease is liver transplantation. Deceased-donor liver transplantation has been performed for many of these cases. However, living-donor liver transplantation (LDLT) has emerged as an alternative because it enables timely procurement of the donor organ. The success rate of LDLT has been improved by development of the surgical technique, use of immunosuppressant drugs, and accumulation of post-transplantation care experience. However, the occurrence of biliary stricture after LDLT remains a problem. This article reviews the pathogenesis, diagnosis, endoscopic management, and long-term outcomes of post-liver transplantation biliary stricture, with a focus on anastomotic stricture.

Bile Flow Phantom Model and Animal Bile Duct Dilation Model for Evaluating Biliary Plastic Stents with Advanced Hydrophilic Coating

Background/Aims

The efforts to improve biliary plastic stents (PSs) for decreasing biofilm formation and overcome short patency time have been continued. The aim of this study is to evaluate the effect of advanced hydrophilic coating for patency and biodurability of PS.

Methods

Using an in vitro bile flow phantom model, we compared patency between prototype PS with hydrophilic coating (PS+HC) and prototype PS without hydrophilic coating (PS−HC). We performed an analysis of the degree of luminal narrowing by microscopic examination. Using an in vivo swine bile duct dilation model made by endoscopic papillary closure and stent insertion, we evaluated biodurability of hydrophilic coating.

Results

In the phantom model, PS+HC showed less biofilm formation and luminal narrowing than PS−HC at 8 weeks (p<0.05). A total of 31 stents were inserted into the dilated bile duct of seven swine models, and 24 stents were successfully retrieved 8 weeks later. There was no statistical difference of stent patency between the polyethylene PS+HC and the polyurethane PS+HC. The biodurability of hydrophilic coating was sustained up to 8 weeks, when assessing the coating layer by scanning electron microscopy examination.

Conclusions

Advanced hydrophilic coating technology may extend the patency of PS compared to uncoated PS.

The Stent Patency and Migration Rate of Different Shaped Plastic Stents in Bile Flow Phantom Model and In Vivo Animal Bile Duct Dilation Model

BACKGROUND/AIM

In research and development of biliary plastic stents (PS), continuous efforts have been made to overcome short patency time and high rate of migration. The aim of this study was to evaluate the patency and migration rate of different PS shapes for a given period of time.

METHODS

Using an in vitro bile phantom model, we compared the patency among different shapes of PS (three straight PS, four double-pigtail PS, and a new screw-shaped PS). We performed an analysis of the degree of luminal narrowing by light microscopic examination. Using an in vivo swine model, we compared the patency and migration rate among the three different types of PS.

RESULTS

Eight weeks after the bile exposure in the bile flow phantom model, 80 PS were retrieved and analyzed. The straight PS showed less biofilm formation and luminal narrowing than other types of PS (p < 0.05). Forty-nine PS were inserted into the dilated bile ducts of 10 swine models, and 39 PS were successfully retrieved 8 weeks later. The stent migration occurred less frequently in the double-pigtail PS and the screw-shaped PS than it did in the straight PS (11.1, 10, and 27.3%, respectively). However, there was no statistical difference in stent patency among the different shapes.

CONCLUSIONS

Stent patency may not be significantly different depending on the shape of PS for 8 weeks. The screw-shaped PS showed similar patency and migration rate to the double-pigtail PS. These results may help guiding future PS development and clinical decisions.

Reintervention for occluded metal stent in malignant bile duct obstruction: A prospective randomized trial comparing covered and uncovered metal stent

BACKGROUND AND AIM

No prospective data are available on comparing covered and uncovered self-expandable metal stent (SEMS) for reintervention of occluded uncovered metal stents during endoscopic retrograde cholangiopancreatography in patients with malignant distal biliary obstruction.

METHODS

From June 2010 to November 2014, 43 patients with inoperable distal biliary obstruction of a previously placed uncovered SEMS were enrolled from three centers in Korea and randomly assigned to covered (n = 22) or uncovered SEMS group (n = 21). The primary outcome was overall stent patency. Secondary outcome was time-to-stent occlusion, patient survival, cause of stent occlusion, and adverse events.

RESULTS

Overall median patency of secondary stent was 112.0 days. Median stent patency of covered and uncovered SEMS was 112.0 and 181.0 days, respectively, (P = 0.373). There was a tendency towards a longer time-to-stent occlusion in uncovered SEMS group (median: 112.0 vs 181.0 days). However, it did not reach statistical significance (P = 0.214). Most common causes of occlusion were stent clogging (36.4%) and tumor ingrowth (33.3%) in covered and uncovered SEMS groups, respectively. There was no significant difference in median survival between the groups (median: 308 vs 300 days; P = 0.325). Acute cholangitis occurred in four patients (three in covered vs one in uncovered SEMS group, P = 0.607).

CONCLUSIONS

In this exploratory trial, there were no statistically significant differences in stent patency, time-to-stent occlusion, patient survival, and complication rates between covered and uncovered SEMS groups. Larger confirmatory multicenter trial is needed for the clear conclusion (ClinicalTrials.gov: NCT01315522).

Time Sequence Evaluation of Biliary Stent Occlusion by Dissection Analysis of Retrieved Stents

BACKGROUND AND AIMS

Multiple factors can affect the occlusion of plastic stents. Previous data demonstrate that side holes may induce more biofilm formation probably via microturbulence and bile flow disturbances that could lead to occlusion. These results, however, have not been replicated in subsequent clinical studies with different methods. The objective of this study is to evaluate the physical characteristics of plastic stent occlusion over time.

METHODS

This is a plastic stent sequential analysis study. Biliary stents removed via ERCP from February 24, 2015, to June 2, 2015, were included. One hundred and forty-eight retrieved straight-type plastic stents were longitudinally cut by a custom-made cutting device. These dissected stents were then evaluated in detail with regard to the location of stent occlusion and the stent patency period. Location of stent occlusive debris was the primary outcome in this study.

RESULTS

Biofilm formations and occlusions by debris were sequentially but separately tallied. Biofilm formations were initially seen around the side hole areas within 30 days and spread to the entire stent by 60 days. Then, occlusion process by debris was mainly initiated by 80 days and progressed to full occlusion by median of 90 days. Although some occlusions were also observed around the side hole areas within 30 days, affected areas were more widely observed after biofilm formation.

CONCLUSIONS

This study is the first to attempt to describe the distribution of stent occlusions over time. These observations may help guide future stent development.

Mechanisms of Biliary Plastic Stent Occlusion and Efforts at Prevention

Biliary stenting via endoscopic retrograde cholangiopancreatography has greatly improved the quality of patient care over the last 30 years. Plastic stent occlusion limits the life span of such stents. Attempts to improve plastic stent patency duration have mostly failed. Metal stents (self-expandable metal stents [SEMSs]) have therefore replaced plastic stents, especially for malignant biliary strictures. SEMS are at least 10 times more expensive than plastic stents. In this focused review, we will discuss basic mechanisms of plastic stent occlusion, along with a systematic summary of previous efforts and related studies to improve stent patency and potential new techniques to overcome existing limitations.

Role of endoscopic retrograde cholangiopancreatography in the management of benign biliary strictures: What’s new?

Benign biliary strictures comprise a heterogeneous group of diseases. The most common strictures amenable to endoscopic treatment are post-cholecystectomy, post-liver transplantation, related to primary sclerosing cholangitis and to chronic pancreatitis. Endoscopic treatment of benign biliary strictures is widely used as first line therapy, since it is effective, safe, noninvasive and repeatable. Endoscopic techniques currently used are dilation, multiple plastic stents insertion and fully covered self-expandable metal stents. The main indication for dilation alone is primary sclerosing cholangitis related strictures. In the vast majority of the remaining cases, temporary placement of multiple plastic stents with/without dilation is considered the treatment of choice. Although this approach is effective, it requires multiple endoscopic sessions due to the short duration of stent patency. Fully covered self-expandable metal stents appear as a good alternative to plastic stents, since they have an increased radial diameter, longer stent patency, easier insertion technique and similar efficacy. Recent advances in endoscopic technique and various devices have allowed successful treatment in most cases. The development of novel endoscopic techniques and devices is still ongoing.

Current Status of Biliary Metal Stents

Many advances have been achieved in biliary stenting over the past 30 years. Endoscopic stent placement has become the primary management therapy to relieve obstruction in patients with benign or malignant biliary tract diseases. Compared with plastic stents, a self-expandable metallic stent (SEMS) has been used for management in patients with malignant strictures because of a larger lumen and longer stent patency. Recently, SEMS has been used for various benign biliary strictures and leaks. In this article, we briefly review the characteristics of SEMS as well as complications of stent placement. We review the current guidelines for managing malignant and benign biliary obstructions. Recent developments in biliary stenting are also discussed.

Initial experience with endoscopic retrograde cholangiography and endoscopic retrograde biliary stenting for treatment of extrahepatic bile duct obstruction in dogs

OBJECTIVE

To describe techniques for endoscopic retrograde cholangiography (ERC) and endoscopic retrograde biliary stenting of the common bile duct (CBD) for minimally invasive treatment of extrahepatic bile duct obstruction (EHBDO) in dogs.

DESIGN

Experimental study and clinical report.

ANIMALS

7 healthy research dogs and 2 canine patients.

PROCEDURES

ERC and endoscopic retrograde biliary stenting were performed in healthy purpose-bred research dogs and client-owned dogs with a diagnosis of EHBDO that underwent an attempted biliary stent procedure. Research dogs were euthanized after completion of the procedure and underwent necropsy. With dogs under general anesthesia, the pylorus was cannulated with a side-view duodenoscope, and the duodenum was entered. The major duodenal papilla (MDP) and minor duodenal papilla were then identified, and the MDP was cannulated. Endoscopic retrograde cholangiography and endoscopic retrograde biliary stenting were attempted with the aid of endoscopy and fluoroscopy in all dogs. Procedure time, outcome for duodenal and MDP cannulation, and success of stent placement were recorded.

RESULTS

Endoscopic retrograde cholangiography was successfully performed in 5 of 7 research dogs and in 1 of 2 patients. Biliary stenting was achieved in 4 of 7 research dogs and 1 of 2 patients, with a polyurethane (n = 4) or self-expanding metallic stent (1). One patient had a mass such that visualization of the MDP was impossible and no attempt at biliary cannulation could be made. After placement, stent patency was documented by means of contrast cholangiography and visualization of biliary drainage into the duodenum intra-operatively. No major complications occurred during or after the procedure in any patient. Follow-up information 685 days after stent placement in 1 patient provided evidence of biliary patency on serial repeated ultrasonography and no evidence of complications. CONCLUSIONS and

CLINICAL RELEVANCE

ERC and endoscopic retrograde biliary stenting were successfully performed in a small group of healthy dogs and 1 patient with EHBDO, but were technically challenging procedures. Further investigation of this minimally invasive technique for the treatment of EHBDO in dogs is necessary before this may be considered a viable alternative to current treatment methods.

Recent Advances in Gastrointestinal Stent Development

Endoscopic stenting is increasingly being used in the management of gastrointestinal luminal obstruction, and has become the current treatment of choice for the palliation of blockage caused by malignant or benign growths. A variety of stents have been developed to enhance the efficacy of the procedure, and improvements are ongoing. In this article, we review the history of, and recent advances in, gastrointestinal stenting. We describe the rationale behind the design as well as the resulting outcome for each stent type.

Recent Advances in Gastrointestinal Stent Development

Endoscopic stenting is increasingly being used in the management of gastrointestinal luminal obstruction, and has become the current treatment of choice for the palliation of blockage caused by malignant or benign growths. A variety of stents have been developed to enhance the efficacy of the procedure, and improvements are ongoing. In this article, we review the history of, and recent advances in, gastrointestinal stenting. We describe the rationale behind the design as well as the resulting outcome for each stent type.

Resolution of pneumobilia as a predictor of biliary stent occlusion

OBJECTIVE

To predict biliary stent occlusion on computed tomography (CT) from the loss of pneumobilia.

METHODS

A total of 66 patients with common bile duct stents with pneumobilia after initial stent placement had a follow-up CT and diagnostic endoscopic retrograde cholangiopancreatography (ERCP). Two readers evaluated all CT exams for pneumobilia. Resolution or decrease of pneumobilia on CT was compared with ERCP findings.

RESULTS

Sensitivity and specificity was 60-64% and 95% with a positive predictive value of 97% and a negative predictive value of 49-51%.

CONCLUSION

Resolution or reduction of pneumobilia after stent placement is specific (95%) and is moderately accurate (70-73%) for predicting biliary stent occlusion.

Polyurethane membrane with porous surface for controlled drug release in drug eluting stent

Background

Membrane covered drug eluting stents (DES) were prepared to prevent tumor ingrowth and to control drug release. Polyurethane (PU) is commonly used for DES coating material because of high tensile strength. The release of paclitaxel (PTX) may increase from porous PU membrane.

Results

Polyethylene glycol (PEG) was incorporated into PU membranes to form porous structure and control the release of hydrophobic anti-cancer drug such as PTX. The bare metal stents were coated with PEG incorporated PU and then, PEG was washed out to form porous structure. The crystallization of PTX was inhibited in porous PU membranes and the release of PTX from porous PU membranes was approximately 8.6% more extended over 19 days.

Conclusions

The enhanced release of PTX from porous PU membranes may increase the patency for the DES covering materials.