Metallic endoprostheses for malignant tracheobronchial obstruction: initial experience

Evaluation of the Effect of a Tracheal Stent on Radiation Dose Distribution via Micro-CT Imaging

PURPOSE

To study the effect of a metal tracheal stent on radiation dose distribution.

METHOD

A metal tube bracket is placed in a self-made foam tube sleeve, and micro-computed tomography scanning is performed directly. The foam sleeve containing the metal bracket is placed in a nonuniform phantom for a routine computed tomography scan. The stents in conventional computed tomography images are replaced by the stents in micro-computed tomography images. Subsequently, 2 sets of computed tomography images are obtained and then imported to a radiotherapy treatment planning system. A single photon beam at 0° is designed in a field size of 10 cm × 10 cm, a photon beam of 6 MV, and a monitor unit of 200 MU. Monte Carlo algorithm is used to calculate the dose distribution and obtain the dose curve of the central axis of the field. The dose is verified with thermoluminescence dose tablets.

RESULTS

The micro-computed tomography images of the tracheal stent are clearer and less false-like than its conventional computed tomography images. The planned dose curves of the 2 groups are similar. In comparison with the images without any stents in place, the doses at the incident surface of the stent in the conventional computed tomography images and at the stent exit surface in the rear of the stent increase by 1.86% and 2.76%, respectively. In the micro-computed tomography images, the doses at the incident surface of the stent and at the exit surface behind the stent increase by 1.32% and 1.19%, respectively. Conventional computed tomography reveals a large deviation between the measured and calculated values.

CONCLUSION

Tracheal stent based on micro-computed tomography imaging has a less effect on radiotherapy calculation than that based on conventional computed tomography imaging.

Subcarinal ventilation-assisted Y-shaped stent insertion under local anesthesia for patients with complex tracheobronchial stenosis: initial clinical experience

PURPOSE

We aimed to report our preliminary results of subcarinal ventilation-assisted Y-shaped stent insertion under local anesthesia for patients with complex lower tracheal-carinal-main bronchial complex stenosis.

MATERIALS AND METHODS

Seven consecutive patients with lower tracheal-carinal-main bronchial complex stenosis underwent Y-shaped stent insertion under local anesthesia. During the procedure, subcarinal ventilation was performed using a 4 F angiographic catheter, and stent insertion was performed under the protection of ventilation. Data on technical success, clinical outcome, and follow-up were collected and analyzed.

RESULTS

Subcarinal ventilation-assisted Y-shaped stent insertion under local anesthesia was technically successful in all patients without any major procedure-related complications. Seven stents were inserted in seven patients. Respiratory function improved in all patients, with the Hugh-Jones classification of respiratory status improving from grade IV-V before stenting to grade I-II after stenting. During the follow-up, one patient experienced re-stenosis of the stent. Average survival time was 185.7 days (range, 96-285 days) after the stenting procedure.

CONCLUSION

Subcarinal ventilation-assisted Y-shaped stent insertion under local anesthesia can be an effective, simple, and safe method for lower tracheal-carinal-main bronchial complex stenosis.

Fluoroscopic-guided balloon dilatation and stenting in tracheal stenosis with metallic self-expandable stents and long-term follow-up results

The purpose of this study was to assess the safety and long-term efficacy of self-expandable stents in the treatment of benign tracheal stenosis. Nine patients (seven men) with tracheal stenosis (including one with fistula) of varied cause were treated by fluoroscopically guided balloon dilatation and stenting with self-expandable metallic stents. The procedure was carried out under topical spray in eight patients and under general anaesthesia in one patient. The patients were followed up for a period ranging between 13 and 60 months. In eight of the nine patients, satisfactory positioning of the stent was achieved at the first instance, with immediate relief of dyspnoea. One patient with innominate artery aneurysm died 16 days after the procedure because of renal failure. At 1 month of follow up, six out of eight (75%) of our live patients were without any respiratory embarrassment. This dyspnoea-free result reached almost 90% by the end of 1 year especially so in the fibrous strictures. Four out of the eight live patients (50%) had cough for 2 months and two (25%) had mild blood-tinged sputum treated by inhalation and mucolytic agents. Secondary intervention was required in one patient at 1 month because of recurrent symptoms. The patient with tracheo-oesophageal fistula required surgical intervention because of fracture of the stent. Fluoroscopically guided balloon dilatation and stenting of the tracheal stenosis is an effective non-surgical therapy resulting in cure of fibrous strictures and palliation in cases of malignancy.

Palliative Airway Stenting Performed Under Radiological Guidance and Local Anesthesia

PURPOSE

To assess the effectiveness of airway stenting performed exclusively under radiological guidance for the palliation of malignant tracheobronchial strictures.

METHODS

We report our experience in 16 patients with malignant tracheobronchial stricture treated by insertion of 20 Ultraflex self-expandable metal stents performed under fluoroscopic guidance only. Three patients presented dysphagia grade IV due to esophageal malignant infiltration; they therefore underwent combined airway and esophageal stenting. All the procedures were performed under conscious sedation in the radiological room; average procedure time was around 10 min, but the airway impediment never lasted more than 40 sec.

RESULTS

We obtained an overall technical success in 16 cases (100%) and clinical success in 14 patients (88%). All prostheses were successfully placed without procedural complications. Rapid clinical improvement with symptom relief and normalization of respiratory function was obtained in 14 cases. Two patients died within 48 hr from causes unrelated to stent placement. Two cases (13%) of migration were observed; they were successfully treated with another stent. Tumor overgrowth developed in other 2 patients (13%); however, no further treatment was possible because of extensive laryngeal infiltration.

CONCLUSIONS

Tracheobronchial recanalization with self-expandable metal stents is a safe and effective palliative treatment for malignant strictures. Airway stenting performed exclusively under fluoroscopic view was rapid and well tolerated.

Malignant tracheobronchial strictures: palliation with covered retrievable expandable nitinol stent

PURPOSE

To evaluate the safety and clinical effectiveness of a covered retrievable expandable nitinol stent for the treatment of malignant tracheobronchial stricture and/or esophagorespiratory fistula (ERF).

MATERIALS AND METHODS

With fluoroscopic guidance, stents were placed in 35 symptomatic patients with malignant tracheobronchial stricture and/or ERF in most cases caused by lung or esophageal cancer. The site of stricture was most commonly at the trachea or left main bronchus. If there were complications, the stent was removed with a retrieval set. Nine patients had combined symptomatic ERF.

RESULTS

A total of 47 tracheobronchial stents were placed and were technically successful and well-tolerated in all patients. Improvement of dyspnea was achieved in 92% of the patients (24 of 26 patients). Associated ERF in nine patients was effectively treated with tracheobronchial stent placement with or without esophageal stent placement. Stent migration, tumor overgrowth, symptomatic sputum retention, and hemoptysis occurred in 17% (6/35), 6% (2/35), 20% (7/35), and 17% (6/35) of patients, respectively. There were no documented cases of tumor ingrowth. Stent removal was performed easily in five patients when stent migration (n = 2), severe pain (n = 1), tumor overgrowth (n = 1), or persistent gastrobronchial fistula (n = 1) developed. All patients died 2 days to 26 weeks (mean, 9.62 weeks) after stent placement because of disease progression (n = 18), pneumonia (n = 9), hemoptysis (n = 5), or unknown cause (n = 3).

CONCLUSION

Use of a covered retrievable expandable nitinol stent is a safe and effective method for relieving dyspnea. This procedure contributed to improved quality of life for patients with malignant tracheobronchial stricture and/or ERF. Stent retrievability was useful in resolving stent-related complications.

Benign tracheobronchial stenoses: changes in short-term and long-term pulmonary function testing after expandable metallic stent placement

PURPOSE

To determine the short- and long-term improvement in airflow dynamics in patients undergoing tracheobronchial stent placement for benign airway stenoses.

METHODS

Twenty-two patients underwent 34 tracheal and/or bronchial stent placement procedures for benign airway stenoses and had the results of pulmonary function tests available. Stent placement indications included bronchomalacia after lung transplantation (n = 11), postintubation stenoses (n = 6), relapsing polychondritis (n = 2), and 1 each of tracheomalacia, tracheal compression, and histoplasmosis. Six patients underwent more than one stent placement procedure (range: 2-7 procedures). The mean forced expiratory volume in one second (FEV(1) ), forced expiratory flow rate in the midportion of the forced vital capacity curve (FEF(25-75) ), forced vital capacity, and peak flow (PF) rate obtained before stent placement were compared with those immediately after stent placement and with those measurements most remote from stent placement using the paired two-tailed test.

RESULTS

All patients reported improved respiratory function immediately after stent placement. The mean FEV(1), FEF(25-75), and PF rate improved significantly (p < 0.001, p = 0.002, and p = 0.009, respectively) after stent placement. On long-term follow-up averaging 15 months after stent placement, these parameters declined despite patients' subjective sense of improvement. Segregating the population into transplant and nontransplant airway stenosis etiologies, however, FEF(25-75) and PF rate remained significantly improved (p = 0.045, p = 0.027, respectively), over the long term for the latter. FEV increased after subsequent stent placements for patients receiving multiple stents.

CONCLUSION

Stent placement for benign tracheobronchial stenoses provides significant immediate improvement in airflow dynamics. Long-term improvement in airflow obstruction may be expected, and additional stent placements may further improve pulmonary function.

Nd-YAG laser damage to metal and silicone endobronchial stents: delineation of margins of safety using an in vitro experimental model

STUDY OBJECTIVE

To identify margins of safety within which bronchoscopic Nd-YAG laser resection can be performed without damaging indwelling tracheobronchial stents.

DESIGN

Experimental in vitro study simulating a patient-care environment.

METHODS

Uncovered and covered metal Wallstent (Schneider; Zurich, Switzerland) and Dumon (Bryan Corporation; Woburn, MA) silicone stents were deployed in the tracheobronchial tree of a ventilated and oxygenated (fraction of inspired oxygen, 40%) heart-lung block of a dead canine. Rigid bronchoscopic Nd-YAG (1,064 nm) laser procedures were performed in order to deliver laser energy using fiber-to-target distances of 10 mm and 20 mm, and noncontact, continuous-mode, 1-s pulses at power settings of 10 W, 30 W, and 40 W. The major outcome measure was laser-induced stent damage, defined as discoloration, ignition, or breakage. This was assessed using six power densities: 75 W/cm(2), 172 W/cm(2), 225 W/cm(2), 300 W/cm(2), 518 W/cm(2), and 690 W/cm(2).

RESULTS

The uncovered Wallstent and the silicone stent remained intact at power densities of 75 W/cm(2) (10 W, 20 mm) and 172 W/cm(2) (10 W, 10 mm), but were damaged at power densities > 225 W/cm(2) (30 W, 20 mm). The covered Wallstent was damaged at all power densities tested.

CONCLUSION

Uncovered Wallstent and silicone stents are not damaged when Nd-YAG laser energy is delivered using power densities < or = 72 W/cm(2) (10 W, 10 mm). Covered Wallstents, however, had a high likelihood of ignition at all power densities studied.

Treatment of severe carinal stenosis with overlapping metallic endoprosthesis

A 50-year-old man presented with respiratory distress from central airway compression secondary to malignant mediastinal adenopathy. The stenosis involved the carinal triangle and created residual luminal diameters of 6 mm, 6 mm, and pinhole in the distal trachea and right and left mainstem bronchi, respectively. Airway patency at the carina was restored successfully with a stenting method that uses two overlapping Wall stents.

Stenting of the tracheobronchial tree

Endoscopic treatment of endobronchial obstructions is becoming increasingly important. Tracheobronchial stents often are needed in the treatment of obstructions from submucosal or extrabronchial lesions. Tube stents have been available since the early 1960s but are underused because their insertion requires the use of a rigid bronchoscope. With the recent development of metallic stents, interventional radiologists increasingly are involved in the treatment of tracheobronchial obstructions. Metallic stents, easily placed with flexible bronchoscopy, are growing in popularity. All available tracheobronchial stents have been shown in various clinical series to be able to achieve immediate resolution of respiratory symptoms from various tracheobronchial obstructions. A stent's performance, however, should not be based solely on short-term response. Presently, there is no ideal stent because none is free of complications and none are able to consistently maintain life-long patency. Gianturco stents are associated with serious major complications (bronchial perforations and strut fractures) and are no longer recommended for use in the tracheobronchial tree. The Palmaz stent has also fallen into disfavor, because a strong external force, such as a vigorous cough, can recompress it. The Strecker stent can only be used in smaller airways, but may be useful in the accurate stenting of short segment stenoses because it does not foreshorten on deployment. The Wallstent and Ultraflex are our present metallic stents of choice. Both are easy to deploy, available in covered forms, exert adequate radial force, remain relatively stable in position, and have good longitudinal flexibility for use in tortuous airways. Disadvantages include excessive granulation tissue formation and difficulty of removal once the stent has been epithelialized. Metallic stents should be chosen very carefully for use in benign lesions with ongoing active local inflammation or when temporary stenting is needed. In the absence of an ideal stent, technologic advancements will continue. Potential developments include removable metallic stents, biodegradable stents, and chemically and radioactively coated stents. Unquestionably, the expanding stent market will drive scientific research toward the development of the ideal stent. Clearly, physicians need to be ready to assess these technologic advancements.

Tracheobronchial strictures: treatment with a polyurethane-covered retrievable expandable nitinol stent--initial experience

A polyurethane-covered retrievable expandable stent was placed in 13 patients with tracheobronchial strictures. In four patients with benign strictures, the stent was removed with use of a retrieval hook 2-6 months after placement. After stent removal, three of the four patients did not need further treatment. The retrievable stent warrants further investigation in the treatment of tracheobronchial strictures.

Tracheobronchial metal stents: effects of covering a bronchial ostium in pigs

RATIONALE AND OBJECTIVES

The purpose of this study was to examine the effects of placing a metal stent across a bronchial orifice.

MATERIALS AND METHODS

Nine pigs were used as test subjects, because the right upper lobe bronchus comes directly off the trachea in these animals. One of three types of metal stents was placed into the trachea of each pig and covered the orifice of the right upper lobe bronchus. Follow-up studies were performed at 1 and 3 months to evaluate the right upper lobe for signs of bronchial obstruction, infection, and atelectasis. The animals were sacrificed at 3 months to study the histopathologic changes of the trachea and lungs.

RESULTS

Two upper lobe bronchi remained patent; seven were obstructed by granulation tissue or plugs of mucus and inflammatory cells. Right upper lobe infiltration and atelectasis were seen in eight animals. Interestingly, radiographic opacities were also common in other lung segments. There was a tendency toward fewer and less extensive lung opacities at 3 months compared with that at 1 month. At histopathologic examination, areas of both acute and chronic pneumonia were found in the right upper lobe of all animals. The segment of trachea covered by the stent was lined with a thin layer of granulation tissue containing neutrophils, monocytes, and lymphocytes. The stent luminal surface was covered with columnar, cuboidal, and stratified squamous epithelium. Tracheal stenosis was seen in three animals because of excessive granulation tissue in two and a collapsed stent in one.

CONCLUSION

Placement of metal stents in pig trachea covering the orifice of the right upper lobe bronchus resulted in retention of secretions and secondary infection in the right upper lobe and other distant lung segments.

Palliative treatment for tracheal stenoses using carbon dioxide laser and the Gianturco stent. Long-term results

Between September 1992 and March 1998, the self-expandable Gianturco prosthesis was inserted in 23 patients suffering from tracheal stenosis. After radial incision and dilation of the stenosis as described by Shapshay, the positioning of the stent was performed during an endoscopic procedure under optical control. The prosthesis used was a double-ring stent 50 mm long and 20 mm in diameter. The follow-up period ranged between 0.5 and 67 months with an average of 31 +/- 18 months. Pulmonary function tests showed an average improvement of the peak expiratory flow (50%) from preoperative results of 1.06 +/- 0.60 L/s to short-term postoperative results of 2.08 +/- 0.78 L/s and long-term postoperative results of 2.11 +/- 0.78 L/s. The mean peak inspiratory flow (50%) improved from 1.43 +/- 0.85 L/s to 2.40 +/- 1.29 L/s at short term and to 2.56 +/- 1.20 L/s at long term. Eight patients out of the 23 had to undergo a second endoscopic procedure: 3 patients for granuloma vaporization; 1 patient to change a malpositioned stent; 2 patients to add a second stent because of insufficient tracheal enlargement; and 2 patients to resect mucosal membranes between the 2 stent rings and to place a second stent. Optical control of the accurate positioning and use of this model of Gianturco prosthesis helped to avoid the severe complications described in the literature (migration, extrusion, fracture, wall erosion. and hemorrhage). The follow-up must particularly target the prevention of granulomas. The self-expandable Gianturco prosthesis can be advocated for long-term palliative treatment of tracheal stenoses that are inoperable by an external surgical approach.

Interventional radiology and the use of metal stents in nonvascular clinical practice: a systematic overview

PURPOSE

The intent of this systematic overview was to describe the clinical role of metal stents in nonvascular health care interventions and the level of evidence supporting their use.

MATERIALS AND METHODS

Structured searches of Medline were conducted and limited to original peer-reviewed articles published in English.

RESULTS

Clinical practice involving metal stents was reported in more than 109 clinical series involving 4,753 patients. Stents were placed mainly for palliation of malignant biliary, esophageal, and airway obstruction in patients who were untreatable or had surgically unresectable lesions. Assessment of these interventions has so far centered on safety and technical success. Efficacy, quality of life, and costing factors were not routinely reported. Randomized trial evidence was available but limited; six randomized trials involving metal stents have been reported. Three trials involved biliary malignant obstruction, and all three reported metal stent (132 patients) palliation to be superior to plastic stent palliation (136 patients) based on longer patency and lower reintervention costs. Safety and complication differences between stents, however, were inconsistent across trials. In three trials involving esophageal malignant obstruction, metal stent (82 patients) palliation was reported to be superior to plastic stent (41 patients), based on lower complication and reintervention rates, and superior to laser therapy (18 patients), based on better dysphagia relief.

CONCLUSION

Use of metal stents has been reported for obstructed ducts and passageways of most body systems. There is, however, limited controlled trial evidence confirming the advantages of their use over plastic stents or other forms of treatment.

Treatment of inoperable tracheobronchial obstructive lesions with the Palmaz stent

PURPOSE

The treatment of inoperable tracheobronchial stenoses with Palmaz stents is analyzed in terms of the clinical effect, typical complications, and long-term follow-up.

METHODS

Twenty-seven Palmaz stents were placed in 22 patients with the help of a rigid bronchoscope.

RESULTS

Stents were implanted in the distal trachea, the main bronchi, and the lower lobe bronchi. Twenty-one of 22 patients reported an immediate subjective improvement in their respiratory situation. The mean survival time was 12 months; in two patients the stents were well tolerated for up to 40 months. A redilation of three stents was successful up to 33 months. In three cases a dislocation of the stent was observed; after bronchoscopic retraction a new stent was successfully implanted in each case. CONCLUSIONoff Treatment of inoperable tracheobronchial stenoses with the Palmaz stent is a safe procedure that provides an immediate improvement of the patient's pulmonary situation. The Palmaz stent shows a minimal complication rate in the long-term follow-up.

Airway stents

Considerable progress has been made since the initial stents were manufactured. Despite the reported side effects, cumulative evidence suggests beneficial effects in properly selected patients. The technology is still in evolution, and design modifications strive to find the perfect stent. The Dumon stent remains the gold standard against which the functions of all other stents are being measured. Unfortunately requirement for the RB for deployment has restricted widespread application at least in the United States. The Wallstent can be inserted using FB and has a great potential among the metal stents. Its biggest drawback is that once inserted it is difficult to remove. Studies with the nitinol Ultraflex and the polyester/silicone Polyflex prototype stent also show promise, although extensive experience and long-term follow-up data are still not available. It is possible that combining the strength of the tube stents with the flexibility of the metal stents may one day help to develop the ideal stent.