Expandable metal stents for the treatment of esophageal malignant obstruction.

Esophageal cancer is the sixth leading cause of death from cancer worldwide [1]. Due to the esophagus distensible characteristics, patients may not recognize any symptoms until 50% of the luminal diameter is compromised explaining why cancer of the esophagus is generally associated with late presentation and poor prognosis [2]. Esophageal stents are devices used to maintain or restore the lumen of the esophagus. it is recommended that stents be placed in patients who have dysphagia caused by esophageal or gastric cardia cancer and a calculated life expectancy of 3 months or less [3]. All metallic stents used in the esophagus are selfexpanding [4, 5]. No balloon-expandable endoprostheses are dedicated for use in the esophagus [5]. stents are inserted using radiologic placement or endoscopic stenting. Both of them have similar success rates and complications [6]. Current self expandable metal stents (sEMs) use nitinol, which is an alloy of nickel and titanium, and is a good material for expandable metal stents [5]. Expandable metal stents based on nitinol are the alloys most frequently used in commercial applications. Nitinol stent exhibits shape memory on the basis of a phase transformation. in recent years, nitinol shape memory stents have been widely accepted for the treatment of gastrointestinal malignant obstruction. importantly, anatomy-conforming nitinol stents or individual stents have been designed and used in patients.