Histologic influence of paclitaxel-eluting covered metallic stents in a canine biliary model

Abstract

Metallic stents for malignant biliary obstruction are susceptible to occlusion by tumor ingrowth or overgrowth. Paclitaxel-eluting metallic stents (PEMSs), however, may prevent occlusion from tumor ingrowth. We evaluated the safety of PEMSs in a canine biliary model by analyzing tissue reactions by histologic examination. Animal study. Six PEMSs and 5 control stents (CSs) were endoscopically placed in the bile ducts of 11 mongrel dogs and followed up for 6 weeks. The animals were euthanized at 6 weeks, and gross and microhistologic examinations were done. A comparison was made between dogs with PEMSs and dogs with CSs. All 11 stents were successfully placed in the bile ducts, although the distal ends of 2 PEMSs were partially exposed to the duodenal lumen. All 11 dogs survived until death without evidence of jaundice. Gross histologic examination showed mucosal hyperplasia in 3 of 6 dogs in the PEMS group, but there was no evidence of mucosal hyperplasia in the CS group. Microscopically, the epithelial layers at the middle and distal ends of the stented segments were significantly thicker in the PEMS dogs than in the CS group. Placement of PEMSs in normal canine bile ducts was without significant technical complications; however, local drug delivery from the PEMS resulted in significant histologic changes. Therefore, it is important to choose a drug in adequate concentrations to exert an antitumor effect without damaging the adjacent normal bilary mucosa.