Previous studies indicated that covered stents are less likely to become occluded in comparison to bare stents. While the probability of occlusions caused by tumor in-growth is less in covered stents, they are more likely to spontaneously migrate to a position that is distal to the original deployment site. However, newer covered stents with improved designs, such as the partially covered double bare metallic stent used for this study, include features to mitigate the migration issue. The purpose of this study is to confirm whether the difference in patency rate between regular covered stents and bare stents, which has already been well established by existing studies, is also reproducible when double covered stents are compared against double bare stents.