PTFE Stents for Treatment of Malignant Biliary Strictures

ERCP (endoscopic retrograde cholangiopancreatography) is the standard method of treating diseases in the biliopancreatic system and the treatment goal is achieved in a very high proportion of the studies. The ERCP is based on the indirect imaging of the bile ducts by injection of contrast medium, which is visualized in X-ray fluoroscopy. Furthermore, the probing of the bile ducts by means of wire and direct interventions within the bile duct system is possible.

Malignant biliary strictures are caused by various, usually cholangiocellular or pancreatic tumors, whose surgical therapy is complex and often impossible due to advanced disease. Tumors of the papillae, lymphomas and lymph node metastases can also lead to stenosis of the extra hepatic bile ducts.

The outcome of patients with malignant biliary strictures is poor, most are already presenting with advanced disease because early symptoms are rare. In particular, the above-mentioned cholangiocellular carcinomas and pancreatic carcinomas are often resectable only in its early form with high recurrence rates. Furthermore, then only palliative concepts are possible. Various studies have shown that stenting of the biliary tract with drainage of more than 50% of the liver volume improves survival. Metal stents seem to be superior to plastic stents at a slightly higher cholangitis rate. It is therefore considered standard therapy to palliatively treat these patients with more than 3 months of life expectancy using a metal stent.

Two types of stents are currently in use, plastic stents and self-expanding metal stents (SEMS). These in turn are coated (cSEMS) and uncoated (uSEMS). In distal malignant stenosis, both cSEMS and uSEMS can be used, with a higher patency rate for cSEMS and a longer duration of uSEMS retention. The disadvantage of the uSEMS is the tumor ingrowth in the stents and the possibility of re-stenosis. Various studies have shown that metal stents are associated with better bile duct drainage and better retention time compared to plastic stents and have fewer early complications, however, a consensus regarding a survival advantage with metal stents has not yet been substantiated, with the data showing a positive trend. Since metal stents, unlike plastic stents, do not need to be changed, a significant advantage for the patient is the significant reduction in endoscopic examinations and associated hospitalization and complication rates.

PTFE stents are a new development that should significantly reduce tumor ingrowth into the stent and, in particular, allow for a significantly reduced stent migration rate. PFTE (Teflon) coating promises improved formability over standard silicone-coated stents, easier removal through the soft surface, and significantly reduced tumor growth through the impermeable surface. At both ends of the stents are "tulips" which are coated with silicone. This in turn reduces the rate of stent closure by sludge, and in particular, the otherwise very high rate of stent migration should be significantly reduced.