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Objective: Neointimal hyperplasia is a major complication of endovascular stent placement with consequent in-stent restenosis or occlusion. Improvements in the biocompatibility of stent designs could reduce stent-associated thrombosis and in-stent restenosis. We hypothesised that the use of a diamond-like carbon (DLC)-coated nitinol stent or a polyethylene glycol (PEG)-DLC-coated nitinol stent could reduce the formation of neointimal hyperplasia, thereby improving stent patency with improved biocompatibility., Methods: A total of 24 stents were implanted, under general anaesthesia, into the iliac arteries of six dogs (four stents in each dog) using the carotid artery approach. The experimental study dogs were divided into three groups: the uncoated nitinol stent group (n = 8), the DLC-nitinol stent group (n = 8) and the PEG-DLC-nitinol stent group (n = 8)., Results: The mean percentage of neointimal hyperplasia was significantly less in the DLC-nitinol stent group (26.7±7.6%) than in the nitinol stent group (40.0±20.3%) (p = 0.021). However, the mean percentage of neointimal hyperplasia was significantly greater in the PEG-DLC-nitinol stent group (58.7±24.7%) than in the nitinol stent group (40.0±20.3%) (p = 0.01)., Conclusion: Our findings indicate that DLC-coated nitinol stents might induce less neointimal hyperplasia than conventional nitinol stents following implantation in a canine iliac artery model; however, the DLC-coated nitinol stent surface when reformed with PEG induces more neointimal hyperplasia than either a conventional or DLC-coated nitinol stent.

Background: Paclitaxel, with its antitumor effect, may improve the function of metallic stents used for biliary drainage. However, clinical studies that use metallic stents covered with a paclitaxel-incorporated membrane (MSCPM) in the biliary tract of human beings have not been previously carried out., Objective: To evaluate the safety and efficacy of an MSCPM for patients with malignant biliary obstruction., Design and Setting: A case series that includes 4 endoscopy centers., Patients: From July 2003 to August 2006, a total of 21 patients diagnosed with unresectable malignant biliary obstruction., Intervention: Endoscopic placement of an MSCPM., Main Outcome Measurements: Stent occlusion, complications, stent patency, patient survival, and the periodic mean concentration of paclitaxel in the blood., Results: Occlusion of the MSCPM was observed in 9 patients and was caused by bile sludge or clog in 4, tumor overgrowth in 3, and tumor ingrowth in 2. Complications included obstructive jaundice in 6, cholangitis in 3, and 1 patient showed stent migration with cholecystitis. The mean patency of a MSCPM was 429 days (median 270 days, range 68-810 days) and cumulative patency rates at 3, 6, and 12 months were 100%, 71%, and 36%, respectively. The mean survival of patients was 350 days (median 281 days, range 68-811 days). The highest concentration of paclitaxel in the blood was found between 1 and 10 days after insertion., Limitations: Small number of patients and low rate of pathologic diagnosis., Conclusions: The endoscopic insertion of MSCPM is technically feasible, safe, and effective in patients with malignant biliary obstruction. In addition, MSCPM may exert local antitumor activity because of the steady release of paclitaxel.

Background: Biliary metallic stents are covered with a membrane to prevent tumor ingrowth and to prolong patency. The only function of these stents is to promote biliary drainage; they have no antitumor effect., Methods: A metallic stent was developed that is covered with a paclitaxel-incorporated membrane. The metallic stents were coated with one of 3 concentrations of paclitaxel (0, 10, and 20 % wt/v) and polyurethane. A stent with each concentration was surgically inserted in the bile duct of two pigs. Four weeks after insertion, the segment of bile duct containing the stent was examined histologically. To determine the efficacy of the drug release, stents were placed in phosphate buffered saline solution for 6 weeks, and the amount of paclitaxel released was measured by high-performance liquid chromatography., Results: The histologic changes in the pig biliary epithelium were acceptable with respect to safety and included inflammatory cell infiltration and fibrous reactions. The changes corresponded to the amount of paclitaxel incorporated within the stent in contact with the bile duct. Epithelial denudation, mucin hypersecretion, and epithelial metaplasia were noted in the bile ducts that were in contact with stents containing 20 % wt/v paclitaxel. Transmural necrosis and perforation were not observed in any animal. In the in vitro experiment, the amounts of paclitaxel released over 1 week and over 6 weeks were similar, regardless of the concentration of paclitaxel incorporated in the stent. The stent with 10% (wt/v) paclitaxel in the covering membrane was found to be better than that with 20 % (wt/v) with respect to histologic changes and the effectiveness of drug release., Conclusions: A paclitaxel-incorporated metallic stent could serve as a basis for the development of a new and safe treatment modality for malignant biliary obstruction. Clinical trials of this stent with other adjuvant therapy are warranted.