A multicenter prospective study of the short-term outcome of a newly developed partially covered self-expandable metallic biliary stent (WallFlex(®))

A finite element investigation on design parameters of bare and polymer-covered self-expanding wire braided stents

Self-expanding covered braided stents are routinely used across a diverse range of clinical applications, but few computational studies have attempted to replicate their complex behaviour. In this study, a computational framework was developed to predict the functional performance of bare and covered self-expanding wire braided stents, with a systematic evaluation on the effect of various braid and cover parameters presented. Simulated radial force and kink deformation tests show good agreement to experimental data for covered braided stents across a range of braid angles and cover thicknesses. Our results demonstrate that braid angle is a key governing parameter that dictates the radial and kink performance of both bare-metal and covered wire braided stents. It was also demonstrated that addition of a polymeric cover to a wire braided stent causes a stiffer radial response across all braid angles, particularly when thicker and/or stiffer covering systems were considered. This study represents the first experimentally-validated computational model for covered wire braided stent systems and has excellent potential to be used in future design of these devices for a range of applications.

Usefulness of half-covered metallic stent placement in preventing acute cholecystitis complication in pancreatic cancer-induced distal biliary stricture

Background and Aim

A self-expandable metallic stent (SEMS) is commonly used for biliary stricture caused by pancreatic cancer. Covered SEMS may obstruct the cystic duct, causing acute cholecystitis. This study aimed to determine the outcomes of using a half-covered SEMS with an offset covered portion for preventing cystic duct obstruction.

Methods

Among 80 patients with half-covered SEMS placement for the treatment of pancreatic cancer-induced distal biliary stricture, 74 were followed up. The half-covered SEMS has a total length of 6 or 7 cm, and the offset covered part was 0.5-4.5 or 0.5-5.5 cm, respectively. Intraductal ultrasonography (IDUS) and endoscopic nasobiliary drainage (ENBD) were performed during the initial endoscopic retrograde cholangiopancreatography (ERCP). IDUS findings and ENBD tube cholangiogram confirmed the cystic duct confluence. SEMS placement was performed on the second ERCP or several weeks after the initial tube stent placement.

Results

Half-covered SEMS placement was successful in all patients. However, four (5.4%) patients exhibited early complications, including acute cholecystitis in one patient and stent displacement in another. Over 30 days, cholangitis, tumor growth, and stent displacement occurred in nine (11.3%), five (6.3%), and two (2.5%) patients, respectively. The median stent patency was 71.1 weeks, and the median overall survival in patients with and without chemotherapy was 31.8 and 12.2 weeks, respectively.

Conclusions

With confirmation of the cystic duct confluence, half-covered SEMS placement may become a treatment option for distal biliary stricture caused by pancreatic cancer to prevent acute cholecystitis. Half-covered SEMS patency was comparable with that of covered SEMS.

Palliative therapy in pancreatic cancer-interventional treatment with stents

Interventional treatment with stents in pancreatic cancer is a topic that developed during recent years and new fields of palliative stent therapy have evolved. The increasing life expectancy of patients with unresectable pancreatic cancer increases the need for clinical and cost effective therapeutic interventions. Current literature, guidelines, practice and evidence were reviewed. Besides the most obvious biliary stenting via endoscopic retrograde cholangiopancreatography (ERCP), pancreatic and gastroduodenal stenting as well as percutaneous transhepatic cholangiography (PTC) and the rapidly growing field of endosonographic stent implantation in the palliative care of patients with pancreatic cancer are being discussed from several points of view in this review.

A Prospective Multicenter Study of a Fully Covered Metal Stent in Patients with Distal Malignant Biliary Obstruction: WATCH-2 Study

BACKGROUND

Both fully covered (FC) and partially covered (PC) self-expandable metal stents (SEMSs) are now commercially available for distal malignant biliary obstruction (MBO). While FCSEMS can be easily removed at the time of re-interventions, it is theoretically prone to migration. However, few comparative data between FC and PC SEMSs have been reported.

AIMS

The aim of this study was to compare clinical outcomes of FCSEMS with those of PCSEMS.

METHODS

This was a multicenter, prospective study of FCSEMS for unresectable distal MBO with a historical control of PCSEMS, which was previously reported as the WATCH study. The primary outcome was recurrent biliary obstruction (RBO), and secondary outcomes were stent migration, stent removal, stent-related adverse events, and survival.

RESULTS

A total of 151 cases with unresectable distal MBO undergoing FCSEMS placement were enrolled and compared with a historical cohort of 141 cases undergoing PCSEMS placement. No significant differences were found in the rate of RBO (29 vs. 33%; P = 0.451), time to RBO (318 vs. 373 days; P = 0.382), and survival (229 vs. 196 days; P = 0.177) between FCSEMS and PCSEMS. The rate of stent migration also did not differ significantly between the two groups (14 vs. 8%; P = 0.113). The removal of FCSEMSs was successful in all 24 attempted cases (100%).

CONCLUSIONS

FCSEMSs appeared comparable to PCSEMSs in terms of RBO without a significant increase in stent migration rate in patients with unresectable distal MBO.

CLINICAL TRIAL REGISTRATION NUMBER

UMIN000007131.

Metal stents placement for refractory pancreatic duct stricture in children

AIM

To evaluate the use of fully covered self-expandable metal stents (FCSEMSs) for pancreatic duct strictures in children with chronic pancreatitis.

METHODS

Eight patients with refractory benign dominant stricture of the main pancreatic duct (MPD) were enrolled through chart reviews between December 2014 and June 2017 in a single center. Endoscopic retrograde cholangiopancreatography (ERCP) with placement of a 6-mm FCSEMS with dual flaps was performed. Endoscopic removal of FCSEMSs was performed with a snare or rat-tooth forceps. All procedures were performed by a pediatric gastroenterologist. For the assessment of outcomes, technical and clinical success, adverse events, and stent patency were evaluated retrospectively.

RESULTS

The placement and removal of the FCSEMSs were successful in all 8 patients. Five patients were boys and 3 were girls. The median age at initial FCSEMS placement was 12 years (range, 5-18 years). The diameters of all the inserted stents were 6 mm, and the lengths were 4-7 cm. The median indwelling time was 6 mo (range, 3-10 mo). No pancreatic sepsis, pancreatitis, cholestasis, or mortality occurred. There was no proximal and distal migration. All subjects showed a patent stent. On follow-up ERCP, the mean diameter of the stricture improved from 1.1 mm to 2.8 mm (P < 0.05), whereas that of upstream dilation improved from 8.4 mm to 6.3 mm (P < 0.05).

CONCLUSION

This initial experience showed that temporary FCSEMS placement is feasible and safe for the management of refractory benign MPD stricture in children.

Palliation With Endoscopic Metal Stents May Be Preferable to Surgical Intervention for Patients With Obstructive Pancreatic Head Adenocarcinoma

The aim of this study was to evaluate the efficacy of endoscopically placed metal stents in comparison with operative procedures, in patients with obstructive pancreatic head cancer. Endoscopic stenting techniques and materials for gastrointestinal malignancies are constantly improving. Despite this evolution, many still consider operative procedures to be the gold standard for palliation in patients with unresectable obstructive pancreatic head cancer. This is a retrospective study of 52 patients who were diagnosed with obstructive (biliary, duodenal, or both) adenocarcinoma of the pancreatic head. Twenty-nine patients (endoscopy group) underwent endoscopic stenting. Eleven patients (bypass group) underwent biliodigestive bypass. Twelve patients (Whipple group) underwent Whipple operation with curative intent; however, histopathology revealed R1 resection (palliative Whipple). T4 disease was identified in 13 (44.8%), 7 (63.6%), and 3 (25%) patients in the endoscopy, bypass, and Whipple groups, respectively. Metastatic disease was present only in the endoscopy group (n = 12; 41.3%). There was no intervention-related mortality. Median survival was 280 days [95% confidence interval (95% CI), 103, 456 days], 157 days (95% CI, 0, 411 days), and 647 days (95% CI, 300, 993 days) for the endoscopy, bypass, and Whipple groups, respectively (P = 0.111). In patients with obstructive pancreatic head cancer, endoscopic stenting may offer equally good palliation compared with surgical double bypass. The numerically (not statistically) better survival after palliative Whipple might be explained by the smaller tumor burden in this subgroup of patients and not by the superior efficacy of this operation.

Covered versus Uncovered Self-Expandable Metal Stents for Managing Malignant Distal Biliary Obstruction: A Meta-Analysis

AIM

To compare the efficacy of using covered self-expandable metal stents (CSEMSs) and uncovered self-expandable metal stents (UCSEMSs) to treat objective jaundice caused by an unresectable malignant tumor.

METHODS

We performed a comprehensive electronic search from 1980 to May 2015. All randomized controlled trials comparing the use of CSEMSs and UCSEMSs to treat malignant distal biliary obstruction were included.

RESULTS

The analysis included 1417 patients enrolled in 14 trials. We did not detect significant differences between the UCSEMS group and the CSEMS group in terms of cumulative stent patency (hazard ratio (HR) 0.93, 95% confidence interval (CI) 0.19-4.53; p = 0.93, I2 = 0%), patient survival (HR 0.77, 95% CI 0.05-10.87; p = 0.85, I2 = 0%), overall stent dysfunction (relative ratio (RR) 0.85, M-H, random, 95% CI 0.57-1.25; p = 0.83, I2 = 63%), the overall complication rate (RR 1.26, M-H, fixed, 95% CI 0.94-1.68; p = 0.12, I2 = 0%) or the change in serum bilirubin (weighted mean difference (WMD) -0.13, IV fixed, 95% CI 0.56-0.3; p = 0.55, I2 = 0%). However, we did detect a significant difference in the main causes of stent dysfunction between the two groups. In particular, the CSEMS group exhibited a lower rate of tumor ingrowth (RR 0.25, M-H, random, 95% CI 0.12-0.52; p = 0.002, I2 = 40%) but a higher rate of tumor overgrowth (RR 1.76, M-H, fixed, 95% CI 1.03-3.02; p = 0.04, I2 = 0%). Patients with CSEMSs also exhibited a higher migration rate (RR 9.33, M-H, fixed, 95% CI 2.54-34.24; p = 0.008, I2 = 0%) and a higher rate of sludge formation (RR 2.47, M-H, fixed, 95% CI 1.36-4.50; p = 0.003, I2 = 0%).

CONCLUSIONS

Our meta-analysis indicates that there is no significant difference in primary stent patency and stent dysfunction between CSEMSs and UCSEMSs during the period from primary stent insertion to primary stent dysfunction or patient death. However, when taking further management for occluded stents into consideration, CSEMSs is a better choice for patients with malignant biliary obstruction due to their removability.

No benefit of endoscopic sphincterotomy before biliary placement of self-expandable metal stents for unresectable pancreatic cancer

BACKGROUND & AIMS

Endoscopic sphincterotomy (ES) is performed routinely before self-expandable metallic stents (SEMS) are placed in malignant distal biliary strictures to prevent postprocedural pancreatitis. However, it is not clear whether ES actually prevents pancreatitis or affects other adverse events (AEs). We conducted a noninferiority trial to examine the necessity of ES before SEMS placement.

METHODS

Two hundred patients with distal biliary strictures caused by unresectable pancreatic cancer were assigned randomly to groups that received ES or did not receive ES (non-ES) before SEMS placement, at 25 hospitals in Hokkaido, Japan, from August 2010 through November 2012. The primary outcome was early AEs (≤30 d) specifically related to the presence or absence of ES (pancreatitis, bleeding, or perforation). Secondary outcomes measured included the effect of ES omission on time to SEMS dysfunction and patient survival times.

RESULTS

The proportions of patients with early AEs were 9.2% in the non-ES group and 10.4% in the ES group (a difference of 1.2%, noninferior). The median times to SEMS dysfunction was longer than 594 days in the non-ES group and 541 days in the ES group (P = .88). The median overall survival times were 202 in the ES group vs 255 days in the non-ES group; P = .20).

CONCLUSIONS

ES before SEMS does not affect the incidence of AEs, SEMS patency, or patient survival times. Our data provide no evidence for a benefit of ES to patients undergoing SEMS placement for a biliary stricture caused by pancreatic cancer. UMIN clinical trials registry number: 000004044.

Intraprocedural quality in endoscopic retrograde cholangiopancreatography: a meta-analysis

OBJECTIVES

In 2006, the American College of Gastroenterology (ACG)/the American Society for Gastrointestinal Endoscopy (ASGE) Taskforce on Quality in Endoscopy published quality indicators for the major gastrointestinal procedures. Our primary aim was to use the published literature to assess current endoscopic retrograde cholangiopancreatography (ERCP) intraprocedural performance and compare it to the targets set by the ACG/ASGE taskforce. Our secondary aim was to determine whether performance varies across different health-care settings (academic and community), study designs (prospective and retrospective), and trainee participation.

METHODS

A PubMed and EMBASE literature search from 1/1/2006 to 2/1/2013 was conducted. Articles were selected based on title, abstract, full text, and reporting of success rates for the intraprocedural quality indicators. Success rates, represented as numerical proportions, were collected from each study. For each success rate, a standard error and a 95% confidence interval (CI) was calculated. A random-effects meta-analysis model was used to weight each study, and a cumulative, weighted success rate (or effect size) for each indicator was determined. Random-effects meta-regression was then used to examine the impact of study setting, design, and trainee involvement on each quality indicator.

RESULTS

A total of 8,005 articles were initially retrieved. Following the application of predefined criteria, 52 articles remained. The cumulative, weighted bile duct cannulation success rate was 89.3% (95% CI 0.866-0.919); pancreatic duct cannulation was 85.0% (95% CI 0.813-0.886); precut utilization rate was 10.5% (95% CI 0.087-0.123); common bile duct stone extraction rate was 88.3% (95% CI 0.825-0.941); and the rate of successful biliary stenting below the common bile duct bifurcation was 97.5% (95% CI 0.967-0.984). Subgroup analysis with meta-regression showed no statistically significant differences between academic and community settings, prospective and retrospective study designs, and trainee participation on success across bile duct cannulation, precut utilization, and common bile duct stone extraction (insufficient observations/variance for pancreatic duct cannulation and biliary stent placement).

CONCLUSIONS

ERCP intraprocedural quality is in good standing. On the basis of this analysis, the two targets that could be potentially revised are precut utilization and biliary stenting. This analysis was confined to the published literature and therefore, in general, reflects the ERCP performance of institutions, primarily academic, that are conducting clinical research. Thus, it is difficult to generalize this performance assessment to the broader ERCP community as a whole.

Impact of anticancer treatment on recurrent obstruction in covered metallic stents for malignant biliary obstruction

BACKGROUND

In patients with unresectable malignant biliary obstruction (MBO), anticancer treatment is often administered. The impact of anticancer treatment on recurrent biliary obstruction in covered self-expandable metallic stents (SEMS) has not been fully elucidated.

METHODS

Data on 279 patients enrolled in a multicenter prospective cohort study of two different covered SEMS for distal MBO, WATCH study (141 partially covered WallFlex stents and 138 partially covered Wallstents) were retrospectively analyzed. The rates and causes of recurrent biliary obstruction (stent occlusion or migration) were compared between anticancer treatment group (n = 173) and best supportive care alone (BSC) group (n = 106). Cumulative time and prognostic factors for recurrent biliary obstruction were analyzed, using a proportional hazards model with death without recurrent biliary obstruction as a competing risk.

RESULTS

The overall rate (43 vs. 25%, P = 0.002) and the cumulative incidence (16.1 vs. 8.2, 27.9 vs. 18.9 and 44.1 vs. 26.6% at 3, 6 and 12 months, P = 0.030 by Gray's test) of recurrent biliary obstruction were significantly higher in anticancer treatment group compared with BSC group. The multivariate analysis revealed anticancer treatment [subdistribution hazard ratio (SHR) 1.93, P = 0.007) as well as the use of a partially covered WallFlex stent (SHR 0.65, P = 0.049) as prognostic factors.

CONCLUSIONS

Anticancer treatment was a risk factor for recurrent biliary obstruction in covered SEMS for distal MBO. The superiority of a partially covered WallFlex stent was again confirmed in this competing risk analysis; UMIN-CTR: UMIN000002293.

Biliary stents in the millennium

Biliary stents have now been in use for over two decades. Although a plethora of literature has been published on them, this review article is unique in its attempt to summarize important landmark trials and their implications on the management of various pancreatico-biliary disorders. This article will cover the various types of stents currently being used, established and upcoming indications, techniques of placement, and complications associated with stent use.