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Ann Thorac Surg 2007;83:1251-1256
© 2007 The Society of Thoracic Surgeons

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Original Articles: General Thoracic

Long-Term Follow-Up of Ultraflex Metallic Stents in Benign and Malignant Central Airway Obstruction

^a Department of Respiratory Medicine, Bristol Royal Infirmary, Bristol, United Kingdom
^b Department of Thoracic Surgery, Bristol Royal Infirmary, Bristol, United Kingdom

Accepted for publication November 20, 2006.

^_* Address correspondence to Dr Husain, Respiratory Medicine Department, Bristol Royal Infirmary, Marlborough St, Bristol BS2 8HW, United Kingdom (Email: dr_arshad_husain{at}yahoo.co.uk).

	Abstract

Top Abstract Introduction Patients and Methods Results Comment Acknowledgments References

 
Background: We report experience with Ultraflex metallic stents (Boston Scientific, Natick, MA) inserted at rigid bronchoscopy under general anesthesia for palliation of benign and malignant upper airway obstruction.

Methods: Notes of all patients treated with Ultraflex stents from 1999 to 2003 were reviewed for symptomatic response, spirometric data, and any complications before discharge home. Long-term outcome was assessed by questionnaires sent to patients’ general practitioners.

Results: Recruited were 66 patients (12 benign, 54 malignant airway obstructions). Before discharge home, breathlessness improved in 11 of 12 patients with benign obstruction and in 39 of 54 with malignancies. Postoperative complications in 10 patients with malignant obstructions and in 2 patients with benign obstruction were successfully controlled. It was not possible to perform preoperative pulmonary function tests in most of the patients who presented as emergencies. Mean improvement in forced expiratory volume in 1 second was 0.88 liters in 3 patients with benign obstruction and 0.28 liters in 14 patients with malignant obstruction, and mean peak expiratory flow rate improved by 109 L/min and 97 L/min, respectively. General practitioners completed questionnaires for 12 benign patients and 46 of 54 patients with malignancies. At a mean follow-up of 1017 days (range, 46 to 1120 days), 10 of the 12 patients with benign disease were alive and 7 of 46 patients with malignant airway obstruction were alive, with a median survival of 128 days (mean, 361; range, 3 to 1859 days). Most survivors had Medical Research Council grade III breathlessness or better, with few stent-related symptoms.

Conclusions: Ultraflex stents proved safe and effective in prolonged palliation of benign and malignant airways obstruction.

	Introduction

Top Abstract Introduction Patients and Methods Results Comment Acknowledgments References

 
Tumors obstructing the trachea and main bronchi are often inoperable as a result of a delay in diagnosis or coexistent disease that contraindicates surgery. Less commonly, patients present with rarer nonmalignant conditions or iatrogenic strictures of the trachea, most often as a result of prolonged mechanical ventilation in intensive care units. A significant proportion of these patients with resection and reconstruction of the trachea are unfit for conventional surgery. Benign and malignant central airway obstructions cause very disabling breathlessness with stridor, and some patients are also severely hypoxic.

Airway stents offer the most effective palliation in these patients. Stent design has improved significantly in recent years, and a wide variety of stents are available; however, there is still no ideal stent. In our opinion, the Ultraflex wire stent (Boston Scientific, Natick, MA) is one of the best that is currently available, and we have used it to treat most of our patients. We report an audit of our last 5 years’ experience with the Ultraflex stent to assess both short-term and long-term efficacy and safety.

	Patients and Methods

Top Abstract Introduction Patients and Methods Results Comment Acknowledgments References

 
This was a retrospective observational study. Methodology and patient confidentiality was approved by the Audit Committee of United Bristol Healthcare Trust (our Institutional Review Board for Audit Projects). The Research Ethics Committee was also asked to review the design of the project and further confirmed that it constituted an audit, which did not require patient consent. By searching for the surgical procedure code for endobronchial stenting, we identified all patients who had been treated with an airway stent in the period 1999 to 2003. Notes of these patients were reviewed to identify those who had been treated with the Ultraflex stent. Patients treated with other types of stent were excluded from the study.

All patients who had been treated with stents had previously been deemed inoperable. In the case of malignant disease, this decision followed discussion in a multidisciplinary lung cancer meeting. Patients had been rejected for curative surgical approach by staging computed tomography scan, inadequate pulmonary function, significant comorbidity, or a combination of these. Patients with benign strictures had been rejected for surgery either because the stricture was too long for successful resection (tracheal stricture exceeding 5 cm) or the patient was assessed unfit for surgery owing to comorbidity.

All patients underwent general intravenous anesthesia using propofol and alfentanil for anesthesia/analgesia and atracurium as muscle relaxant. A standard Storz 8-mm rigid bronchoscope (Karl Stortz) was used, and patients were ventilated with 100% oxygen with a Sanders injector.

After airway inspection, any extensive intraluminal tumor was removed using rigid biopsy forceps. Severe strictures were first dilated with a balloon catheter; otherwise the tip of the rigid bronchoscope was used as an airway dilator. We used 20-mm-diameter x 4-cm-long stents in the trachea, and 14-mm-diameter x 4-cm-long or 2-cm-long stents in the main bronchi. Covered stents were used in patients with tracheoesophageal fistulas.

Stents were inserted under direct vision by passing the stent on its introducer alongside a 0 degree Hopkins telescope (Karl Stortz). Having placed the stent introducer in the stenosis, the stent was slowly released by pulling off the thread that binds the stent down onto the introducer (Fig 1). If necessary, fine adjustment of stent position was achieved by moving the introducer up or down before the stent had been completely released. In a few cases, further adjustment of stent position after release was needed and was accomplished by grasping the stent with rigid forceps.

View larger version (128K): [in this window] [in a new window]   Fig 1. Ultraflex stent. (A) Stent bound onto introducer. (B) Released standard and covered stents. (C) Releasing stent at bronchoscopy. (D) Fully released stent.

Longer-term results were assessed by a questionnaire sent to patient’s general practitioners in September 2004. This asked them to record (1) whether the patient was still alive or date of death, and (2) whether patients complained of cough, hemoptysis, chest pain, recurrent chest infections, or any other complications suspected of being attributable to the stent.

General practitioners were also asked to assess the patients’ degree of breathlessness at their last consultation on the Medical Research Council (MRC) breathlessness scale. A copy of the MRC scale was enclosed with the questionnaire for reference.

Survival curves for both benign and malignant causes of airway obstruction were constructed using SPSS software (SPSS, Inc, Chicago, IL) with the Kaplan-Meier survival analysis method.

	Results

Top Abstract Introduction Patients and Methods Results Comment Acknowledgments References

 
Procedure codes were used to identify 100 patients who had been treated with a stent in the period 1999 to 2003. Of these, 66 patients had been treated with one or more Ultraflex stents and were further studied. Their mean age was 64 years (range, 22 to 87 years). Malignant airway obstruction was present in 54 patients: 39 had primary carcinomas of the trachea or main bronchi, and 15 had primary tumors in other organs that had invaded or compressed the central airways or metastasized to them. These are further detailed in Tables 1 and 2, respectively. The remaining 12 patients had benign pathologies causing airway obstruction, which are detailed in Table 3.

Table 6 summarizes the frequency of one or more adverse events in those patients who were survivors at the time the general practitioner received the questionnaire (one of whom had subsequently died by the time we analyzed the results). Side effects possibly attributable to the stent occurred in only 3 of the 12 patients with benign disease and in 8 of the 48 (4/7 in surviving group) patients with malignancies. Our review of case records also identified a patient with malignant obstruction who required readmission to our unit and further stenting for progressive disease after a 1-year interval, with further palliative benefit.

The general practitioners’ assessments of MRC breathlessness grade in surviving patients are summarized in Table 7. This suggests good palliation of breathlessness during survival in both groups. Serious and disabling breathlessness (MRC grade IV to V) was reported for only 2 patients with benign obstruction and in 1 of the surviving patients with malignant obstruction. In the 2 patients with benign disease, the severity of breathlessness was reasonably attributable to coexistent end-stage chronic obstructive pulmonary disease in one patient and pulmonary fibrosis together with New York Heart Association functional class IV cardiac failure in the other.

View larger version (14K): [in this window] [in a new window]   Fig 2. Kaplan-Meier survival curves for benign (dotted line, tick mark, survivors) and malignant conditions (solid line; diamonds, survivors) treated with Ultraflex endobronchial stents.

	Comment

Top Abstract Introduction Patients and Methods Results Comment Acknowledgments References

Several interventional bronchoscopy techniques are available for palliation of central airways obstruction. These include tissue resection by laser photocoagulation, electrocautery, cryotherapy, and radiofrequency ablation. No large randomized controlled trials have compared these techniques, and there is probably little to chose between them. In our own experience, however, endobronchial stenting is more versatile than other treatments, achieves more prolonged palliation in malignant airway obstruction, and provides immediate relief of breathlessness. In our view, it is the only realistic option in most patients with inoperable benign upper airway obstruction.

Stent design has improved significantly in the last decade, but there is no ideal stent available [1]. The limitations of this technology are illustrated by the large variety of stents available, but they can be divided into three main categories:

• Silicone stents (Dumon [2], Noppen, Montgomery, and Polyflex [Rusch Inc, Duluth, GA]) are easy to remove, but have disadvantages of a tendency to migrate (seen in 17.5% of cases treated with Dumon stents in one study [3]), a relatively small internal lumen because of the thickness of the stent wall, and impairment of the mucociliary escalator.

• Expanding wire stents (Gianturco [Cook Cardiology, Bloomington, IN], Palmaz [Johnson & Johnson, New Brunswick, NJ], Wallstent, and Ultraflex [Boston Scientific, Natick, MA]) are less likely to migrate, provide a larger airway lumen, and do not interfere with the mucociliary escalator; however, late removal is very difficult because they become buried in the airway mucosa. Some first-generation stents, such as the Gianturco, do not resist external pressure very well, and there have been case reports of Gianturco stents developing fractures leading to a risk of perforation of the airway wall [4, 5].

• Hybrid stents (Rusch [Rusch Inc AG, Kernan, Germany], Nova-stent [Novadis, Saint Victoret, France], and Alveolus [Alveolus Inc, Charlotte, NC]) combine Silastic walls with a metal mesh core.

We have predominantly used the Ultraflex expanding metal stent. This is woven from a single strand of the nickel-titanium alloy nitinol ("memory metal") [6]. At room temperature, it deforms easily to facilitate compressing the stent so that it can be bound down onto an introducer by a coil of thread. After release, by pulling the thread off the introducer, the expanded stent becomes more rigid to increase support of the airway. The complex mesh of the stent also resists deformation if it is bent so that it maintains a constant diameter, even when inserted into airways that are deformed by disease.

Miyazawa and colleagues [7] reviewed the literature on the mechanical properties of the Ultraflex versus other stents. They noted that it has an elasticity that is much closer to that of the tracheobronchial tree than the stainless steel used in the Gianturco stent, thus reducing the risk of perforation.

The Ultraflex stent is less likely than the cobalt steel Wallstent to damage the mucosa and cause granulation tissue at its ends through elongation on coughing and is less prone to collapse than Strecker (Boston Scientific, Natick, MA) and Palmaz stents. It also adapts better to complex airway shapes than the widely used silicone Dumon stent. Polyurethane covered versions are available. These are useful when a fistula is also present and may also inhibit regrowth of tumour through the mesh of the stent.

Like most other expanding wire stents, the Ultraflex can be deployed with a flexible bronchoscope under sedation and local anesthesia. With a flexible bronchoscope, it is most easily positioned using x-ray screening over a guidewire; however, both flexible and rigid bronchoscopy can be used to deploy Ultraflex stents under direct vision [8]. We prefer to place stents under direct vision using a rigid bronchoscope and general anesthesia. This technique reduces distress for the patient and gives better control of the airway in the event of serious bleeding. Large biopsy forceps can be used to quickly remove any intraluminal tumor, and the tip of the rigid bronchoscope can conveniently be used to dilate the airway for stent insertion. The bevelled tip of the rigid bronchoscope can be used to scoop away any obstructing tumor.

Many previous studies only report short-term results. Our short-term complication and response rates compare favorably with previous reports on various stenting techniques [2, 9, 10]. However, we particularly wanted to obtain long-term follow-up data on our patients because relatively little long-term follow-up data are available in the literature on the Ultraflex, or indeed for most other stents. Because we serve a wide catchment area and it is difficult for patients to travel long distances to attend outpatient review, we have attempted to obtain follow-up data from patients’ general practitioners. The response rate by general practitioners to our questionnaire was high. General practitioners were generally unable to provide any physiologic data, but they were able to grade patients’ breathlessness on the MRC scale and review symptoms. These are the most important issues for patients.

Although not all general practitioners returned fully completed questionnaires, our results otherwise suggest good palliation during the time the patients survived, with a low side-effect profile. Figure 2 shows that most patients with malignant disease had a useful survival period, and the data from the general practitioners imply that this was associated with good palliation of breathlessness. Vonk-Noordegraaf and colleagues [11] used general practice questionnaires to evaluate the overall palliative benefit of stenting in 14 patients with malignant airway obstruction after death and argued that general practitioners are in a better position to assess this than the bronchoscopist.

Most of our patients had clear improvement in symptoms of breathlessness patients in the short term, and the available data also suggest this was true of those patients surviving at the long-term follow-up. Unfortunately, data on MRC breathlessness scale were incomplete in patients who had died from malignant obstruction; however, one might expect that the general practitioners would otherwise have specifically mentioned breathlessness if it had been a major symptom. When available, spirometry also showed immediate improvements after the procedure, as has been reported in earlier studies of the effect of stenting on respiratory function tests [12, 13].

This was a retrospective study of our own experience with the Ultraflex stent. We did not have an untreated control group; however, there are major ethical difficulties in having a control group in studies involving palliation of patients with advanced and life-threatening upper airway obstruction. This fact is reflected by the very few randomized studies in the literature that have compared different endobronchial therapy techniques, and like ours, most reports describe experience with a single technique.

Madden and colleagues [9] report long term follow up of a smaller series of 15 patients treated with Ultraflex stents using a similar placement technique and also found long-term results to be good. Five of their patients complained of halitosis, which they suggested might be due to bacterial colonization of the polyvinyl chloride in covered stents. We did not see this complication; however, we only used covered stents in patients with tracheoesophageal fistulas, which perhaps suggests that the noncovered stent is the better choice in patients without a fistula.

Some investigators believe that covered stents should be used for all cases of malignant obstruction on the grounds that this stops tumor in-growth. This advantage needs to be weighed against the fact that in advanced malignant disease with very distorted airways, an open-mesh stent will not obstruct the orifice of any bronchus that it may cross. This means that placement does not need to be so accurate, and any minor degrees of movement in the early postoperative period are therefore less likely to obstruct any lobar bronchial orifices. Moreover, in advanced-stage cancers where the patient’s survival is going to be short, the risk of tumor in growth may not be clinically relevant. Our policy has therefore been to use covered stents only when a fistula is present.

Some investigators advise that wire stents should not be used in patients with benign conditions [1] because they are difficult to remove at a later stage. The benefits of wire stents over Silastic types—in that they preserve the mucociliary escalator, permit a larger airway lumen, are more easily implanted and less likely to displace—need to be balanced against their disadvantage of difficult removal should this later be necessary. We are not aware of any good, long-term randomized trials comparing wire and Silastic stents. Having previous experience with Silastic stents, we believe that wire stents may be superior in situations where there is no active inflammatory process and no prospect for longer-term remission, so that there is no anticipated need to later remove the stent.

We have only described a small cohort of patients with benign disease. Nevertheless, our long-term results in this group suggest that the Ultraflex wire stent is generally safe and effective long term in benign but inoperable airways obstructions. Although 4 patients reported some complications to their general practitioners, these were not apparently severe or conclusively proven to be caused by the stent, and patients did not ask for the stent to be removed. We therefore report these cases because further assessment of wire stents in larger long-term trials would seem to be justified.

Granuloma formation has been reported around stents in benign airway obstruction with a frequency of 6% to 33% [3, 10, 14]. It may be more common in benign than malignant airway obstructions [10]. Many investigators consider follow-up bronchoscopy essential to look for granulomas, but we do not do this for several reasons. In our opinion, what is important in palliation is how well the patient’s breathlessness is controlled rather than whether granulation tissue can be identified at a follow-up bronchoscopy. Follow-up bronchoscopy is a stressful procedure for patients, which can only be justified if it will directly benefit the patient. In an overstretched National Health Service, the additional costs of routine follow-up bronchoscopy, without any proven benefit, would compromise services to other patients. Finally, because we serve a wide catchment area, most patients would not want to travel long distances for follow-up examinations while their symptoms were well controlled.

Thus, we only do a follow-up bronchoscopy if a patient’s symptoms recur. Although the incidence of granuloma formation in our series is unknown, we did not see any recurrence of airways obstruction attributable to granulomas in our benign cases, so any granuloma formation that may have occurred was not clinically significant. We believe this result justifies our policy. Moreover, in a study in which Ultraflex stents were used in 34 patients, with bronchoscopic follow-up [7], granuloma formation was reported in only 1 patient.

In conclusion, we have shown that the Ultraflex stent has a good safety profile, is easy to use, is effective in relieving airways obstruction in most patients, and remains reliable in the longer term after discharge from hospital.

	Acknowledgments

Top Abstract Introduction Patients and Methods Results Comment Acknowledgments References

 
We acknowledge the assistance of Dr Hasan Kahal in review of case notes.

	References

Top Abstract Introduction Patients and Methods Results Comment Acknowledgments References

 

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This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Add to Personal Folders Download to citation manager Author home page(s): Anthony Morgan Permission Requests Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Husain, S. A. Articles by Hetzel, M. R. Search for Related Content PubMed PubMed Citation Articles by Husain, S. A. Articles by Hetzel, M. R. Related Collections Trachea and bronchi