The aim of this study was to evaluate the safety and effectiveness of an radioactive airway stent loaded with 125I seeds compared to a conventional airway stent in patients with malignant airway obstruction caused by both primary and metastatic malignant tumors.

Malignant tumors of the lung, esophagus, thyroid, or other mediastinal structures often involve the trachea by direct tumor growth compression and (or) invasion. In addition, extrathoracic cancers metastasize to these lymph nodes as well. However, surgical resection and airway reconstruction are the gold-standard treatment for MAO, many patients with airway involvement are poor surgical candidates based on physiologic or oncologic criteria.There are three main types of malignant airway obstruction: endobronchial obstruction, extrinsic compression, and a mixed pattern. For endobronchial obstruction, ablative techniques that destroy tissue are indicated, including lasers, electrocautery, argon plasma coagulation (APC), photodynamic therapy, microdebriders, and cryotherapy, but primary tracheal cancers are less common than other types of lung cancer. If the obstruction is exclusively or mainly due to compression from outside the airway wall, the only option consists of placement of a stent or endoprosthesis. However, follow-up data has demonstrated that postoperative restenosis of stenting occurs in 5-45% of cases as a result of neoplastic infiltration through the mesh into the lumen or tumor overgrowth above and below the mesh stents. Encouraged by the success of 125I esophageal and biliary stent in esophageal carcinoma , a tracheal stent loaded with 125I radioactive seeds was developed in investigators'institute. After successful in vitro and in vivo evaluations of the delivery system, investigator will prospectively compare responses to treatment with this irradiation tracheal stent versus the conventional self-expandable stent in patients with MAO.

Inclusion Criteria:

1. aged between 18 and 80 years
2. MAO caused by any adenocarcinoma with histologically or cytologically confirmation by biopsy or previous surgical procedures
3. symptoms such as dyspnea related to biliary obstruction
4. unresectability or refusal to be surgically treated
5. willing and able to comply with the study procedures and provide written informed consent to participate

Exclusion Criteria:

1. patients with suspected benign airway obstruction
2. airway obstruction that could not be dilated enough to pass the delivery system
3. perforation of any ducts within the tracheal tree
4. presence of metallic tracheal stent or airway surgery
5. acute or chronic inflammation in the airway
6. uncooperative or could not provide authorization and signature.