Self-expanding metal stents for malignant esophagogastric obstruction: Experience with a new design covered nitinol stent

Abstract

Dysphagia is the most common disabling symptom in patients with inoperable esophagogastric carcinoma. Self-expanding metal stents are highly effective in the palliation of these patients.
In 35 patients with inoperable carcinoma of the esophagus or the stomach, with recurrent tumor or complications after transhiatal esophagectomy or gastrectomy or with esophageal stenosis caused by pulmonary cancer, a self-expanding nitinol stent was placed to reduce dysphagia. Dysphagia and WHO performance status were assessed, before and after stent placement.
In 35 patients, 39 stents were placed without technical problems. Dysphagia improved significantly. The WHO performance status remained stable. Mean survival of all patients was 11 weeks. Major complications occurred in 3 patients. One patient died of massive tumor bleeding. Minor complications such as stent migration or retrosternal pain occurred in 5 patients. In 2 patients the migrated stent could successfully be placed in the correct position after giving ice-cooled water through the endoscope. Four patients had esophagorespiratory fistulas which were all initially successfully occluded.
This nitinol stent is highly effective for improving dysphagia in patients with malignant esophagogastric obstruction. We observed no procedure-related complications. Bleeding was the principal major complication. The early intake of cold beverages resulted in stent migration. Recurrent dysphagia due to overgrowth by tumor or nonmalignant tissue remains a problem. Technical improvements are desirable to reduce the overgrowth by nonmalignant tissue.

Full text

Self expanding metal stents in esophagogastric cancer
J Gastrointestin Liver Dis
September 2007 Vol.16 No 3, 239-243
Address for correspondence: Ralf Keller, MD, PhD
Department of Medicine I
Mathias-Spital
Frankenburgstr. 31
D-48431 Rheine, Germany
E-mail: r.keller@mathias-spital.de
ORIGINAL PAPERS
Self-Expanding Metal Stents for Malignant Esophagogastric
Obstruction: Experience with a New Design Covered Nitinol
Stent
Ralf Keller, Dimitri Flieger, Wolfgang Fischbach, Stefan Ulrich Christl
Department of Medicine II, Hospital of Aschaffenburg, Aschaffenburg, Germany
Abstract
Background and aims. Dysphagia is the most common
disabling symptom in patients with inoperable
esophagogastric carcinoma. Self-expanding metal stents are
highly effective in the palliation of these patients.Methods.
In 35 patients with inoperable carcinoma of the esophagus
or the stomach, with recurrent tumor or complications after
transhiatal esophagectomy or gastrectomy or with
esophageal stenosis caused by pulmonary cancer, a self-
expanding nitinol stent was placed to reduce dysphagia.
Dysphagia and WHO performance status were assessed,
before and after stent placement. Results. In 35 patients, 39
stents were placed without technical problems. Dysphagia
improved significantly. The WHO performance status
remained stable. Mean survival of all patients was 11 weeks.
Major complications occurred in 3 patients. One patient died
of massive tumor bleeding. Minor complications such as
stent migration or retrosternal pain occurred in 5 patients. In
2 patients the migrated stent could successfully be placed
in the correct position after giving ice-cooled water through
the endoscope. Four patients had esophagorespiratory
fistulas which were all initially successfully occluded.
Conclusion. This nitinol stent is highly effective for
improving dysphagia in patients with malignant
esophagogastric obstruction. We observed no procedure-
related complications. Bleeding was the principal major
complication. The early intake of cold beverages resulted in
stent migration. Recurrent dysphagia due to overgrowth by
tumor or nonmalignant tissue remains a problem. Technical
improvements are desirable to reduce the overgrowth by
nonmalignant tissue.
Key words
Esophagogastric carcinoma – palliative therapy – self-
expanding metal stents
Introduction
Most patients suffering from carcinoma of the
esophagus or gastric cardia have inoperable stage at
presentation (1). Dysphagia is the most common disabling
symptom in the majority of these patients. The best palliative
treatment is unclear. Thermal tumor ablation is reported to
improve dysphagia (2). Alternatively, self-expanding metal
stents are highly effective in the palliation of patients with
dysphagia which, in turn, may improve nutritional status
and the overall quality of life (3). Both uncovered (3, 4) and
membrane-covered (5) metal stents have been shown to be
associated with fewer complications than prosthetic tubes.
Therefore, insertion of self-expanding metal stents has
become the treatment of choice for patients with
unresectable carcinoma of the esophagus or the gastric
cardia. Currently, several types of metal stents are available.
We report our experience with a self-expanding thermal-
shaped memory metal stent made of nitinol in a consecutive
series of patients with malignant strictures of the esophagus
or the stomach. This stent was first described in 1997 in an
uncoated form (6). In Germany, it has been commercially
available in a covered version since 2001.
Patients and methods
Patients
From January 2002 to August 2004, a self-expanding
metal stent was placed in 35 patients with inoperable
carcinoma of the esophagus or the stomach, with recurrent
tumor or complications after transhiatal esophagectomy or
gastrectomy or with esophageal stenosis caused by
pulmonary cancer. Complications were defined as
anastomotic insufficiency or stenosis after tumor resection.
All patients gave written consent before insertion of the
metal stent. Dysphagia was patient-assessed on a

Keller et al240
scale of 0 to 4: 0, normal food intake with no sensation of
food hold-up; 1, difficulty with swallowing some solids; 2,
able to swallow only soft food; 3, able to swallow liquids
only; 4, complete inability to swallow. The general health of
the patients was assessed using the WHO performance
status: 0, fully active; 1, restricted in physically strenuous
activity but ambulatory and able to carry out light work; 2,
ambulatory and capable of self-care but unable to carry out
any work activities; 3, capable of limited self-care; 4,
completely disabled, unable to carry out any self-care; 5,
dead.
Twenty-two patients had radiation (2), chemotherapy
(11) or a combination of both, radiation and chemotherapy
(9), prior to placement of a metal stent.
Methods
The stent (Flextent, Medwork, Neuss, Germany) used is
made of nitinol which possesses a memory effect (Fig.1). At
body temperature it develops maximum radial force. Two
types are available, a partial or a completely polyurethane
covered type. Therefore, it prevents the in-growth of tumour
tissue. The 15-mm-long ends of the partial covered stent are
tulip-shaped without covering.
Fig.1 The nitinol stent (Flextent™) partially
covered with polyurethane at body temperature.
The delivery system consists of an 8 mm diameter outer
tube and an inner pusher tube with a preloaded stent. The
stent is available in numerous sizes in length and 20 mm or
24 mm in diameter.
Under endoscopic visualization, the proximal and distal
margins of the tumor were identified. A stent at least 2 to 4
cm longer than the tumor stenosis was chosen to allow for
a 1 to 2 cm extension beyond the proximal as well as the
distal tumor margins. After endoscopic assessment, a 0.035-
inch stiff guide wire was placed through the tumor stenosis
into the stomach. When it was impossible to pass an
endoscope the tumor stenosis was dilated to 10 mm. The
margins of the tumor were marked under fluoroscopic
guidance with small metal devices which were located on
the patient’s skin. Then the endoscope was removed and
the delivery system was introduced over the guidewire. The
stent was deployed under fluoroscopic control (Fig.2).
Endoscopic examination was performed immediately
following stent insertion (Fig.3) and a radiographic contrast
Fig.2 Radiograph after successful implantation.
The metal devices mark the proximal and the distal
tumor margin.
examination with water-soluble contrast media was carried
out within 1 day after stent placement. All endoscopic
procedures were performed under mild sedation with
midazolam (3-5 mg) und analgesia with meperidine (50 mg)
intravenously. If stent migration was observed or the stent
could be retrieved, it was flushed with ice-cooled water via
the accessory channel of the endoscope. In this way, the
stent was shortened. Then, it could be grasped with rat-
toothed forceps and repositioned or taken out.
Fig.3 Endoscopic view into the proximal tulip of
the nitinol stent after implantation.
Statistics
Results are means ± standard deviation (SD). Values
before and after stent placement were compared using the
Wilcoxon test.

Self expanding metal stents in esophagogastric cancer 241
Fig.4 Overgrowth of granulation tissue at the
proximal end of the stent.
Results
A total of 39 stents were placed in 35 patients. The clinical
characteristics are listed in Table I.
Before stent After stent
placement placement
Dysphagia grade
0 -14
1 113
2 3 6
312 2
419 -
Mean (S.D.) 3.2 (± 0.72) 0.9 (± 0.15)*
WHO performance status
0 6 4
11918
21012
3 - 1
Mean (S.D.) 1.11 (± 0.11) 1.29 (± 0.12)
*p<0.001
Table II Outcome in 35 patients
Major complications occurred in 3 patients (9%), who
developed upper gastrointestinal bleeding (Table III). One
patient died of massive tumor bleeding 7 weeks after stent
placement. Minor complications like stent migration during
the first week after stent placement (n=4; 11%) or retrosternal
pain (n=1; 3%) occurred in 5 patients (14%). In 2 patients
the migrated stents were succesfully placed in the correct
position after giving ice-cooled water through the
endoscope. Four patients had esophagorespiratory fistulas.
Initially, all fistulas were successfully occluded. In one
patient, with an esophagorespiratory fistula, stent migration
led to a recurrence of the fistula. It was occluded by the
insertion of an additional stent.
Minor complications (n=5)
retrosternal pain 1
stent migration 4
Major complications (n=3)
upper gastrointestinal bleeding 3
Cause of death (n=24)
Procedure related 0
Stent related 1
Tumor progression 23
Table III Complications and cause of death in 35 patients
In one patient with gastric cancer, the indication for stent
placement was leakage of the anastomosis after gastrectomy.
Initially, a covered stent was placed without any problems.
Eight weeks later, when the stent removal was planned, the
patient complained of a progression of dysphagia.
Endoscopically, the proximal tulip of the metal stent showed
an overgrowth by granulation tissue (Fig.4). Complex
endoscopic preparation using a needle knife and an insulated
tip knife allowed us to remove the stent after four endoscopic
sessions.
Two patients with a squamous cell carcinoma near the
upper esophageal sphincter developed tumor overgrowth
at the proximal tulip of the stent with impairment of dysphagia.
In these cases a second completely covered stent (inclu-
ding the tulips) was inserted into the primarily placed
No technical problems or complications occurred during
placement of the prosthesis. Reasons for multiple stent
placement included the following: distal migration after
insertion (n=2) and tumor overgrowth at the upper tulip of
the stent (n=2). The majority of the patients obtained a 100
mm or a 120 stent with a diameter of 20 mm (Table I). Most
stents (n=16) were placed in the distal part of the esophagus
and into the gastric cardia. Dysphagia improved significantly
from a mean of 3.2 ± 0.12 to 0.9 ± 0.15 (p<0.001). The WHO
performance status remained stable in all patients (Table II).
Mean survival of all patients was 11 weeks with a range
from 1 to 90 weeks.
Mean age (range) (yr) 66 (30-82)
Gender (M/F) 28/7
Localization of tumor (n=35)
Upper esophagus 7
Middle esophaus 6
Lower esophagus 9
Cardia 7
Stomach 2
Anastomosis stenosis after tumor resection 1
Tumor histology (n=35)
Squamous cell carcinoma of the esophagus 13
Adenocarcinoma of the esophagus 3
Cardia carcinoma 6
Gastric carcinoma 6
Lung carcinoma 6
Other 1
Fistula 4
Concomitant therapy prior to stent placement (n=22)
Radiation 2
Chemotherapy 11
Radiation + chemotherapy 9
Size of stent inserted (mm) (n=39)
80 7
100 13
120 10
140 9
Table I Clinical characteristics of the 35 patients

Keller et al242
stent. Afterwards, dysphagia and swallowing were im-
proved.
Discussion
Dysphagia is the most common cause of impaired quality
of life in malignant esophageal obstruction (7). Therefore,
the aims of palliation in these patients were to overcome
dysphagia and optimize the quality of life by using
interventions that have minimal complications. Endoscopic
placement of self-expanding metal stents is an acceptable
treatment for patients with unresectable malignant
esophageal obstruction. In most cases rapid relief of
dysphagia and adequate oral intake of nutrients can be
achieved (2). Insertion of self-expanding metal stents can
be combined with other palliative treatment strategies.
However, treatment with palliative chemotherapy, radiation
or combined radio-chemotherapy has significant side
effects. In a well-designed study it was demonstrated that
combined radio-chemotherapy alleviated dysphagia in only
58%. Life-threatening complications occurred in 20% of
patients, whereas serious complications were seen in 44%
(8).
Siersema et al (5) reported major complications in 23%
and minor complications in 33% after stent placement in a
total number of 57 patients with esophagogastric carcinoma.
They differentiated between procedure-related and stent-
related complications. Of the patients who had stent-related
complications, 60% had undergone prior radiation,
chemotherapy, or both. It is still unclear whether prior
radiation and/or chemotherapy increases the risk of
complications after stent placement. Formerly, Siersema et
al postulated that the association between stent-related
complications and prior treatment is an established finding
(5, 9). In a recent study the same group did not find an
increase of life-threatening complications or differences
in survival after stent placement in patients with
concomittant radiation and/or chemotherapy (10).
Retrosternal pain occurred more frequently in patients who
had previously undergone radiation and/or chemotherapy.
In our study, bleeding, severe pain and stent migration
occurred in 8 patients (22.9%). We found no significant
correlation between stent placement and prior treatment of
the tumor.
Stent migration alone, a stent-related complication,
occurred in 4 patients who had drunk cold beverages in the
early phase after stent placement. No stent migrated into
the stomach. Two migrated stents could be replaced easily
after flushing with ice cooled water through the endo-
scope.
The addition of a covering membrane might make stent
migration more likely. Fan et al (6), using an uncoated type
of the stent implanted in our study, have described two
predetermined physical forms of the stent, depending on its
temperature. In its low temperature phase, as in ice water,
the material becomes very pliable and facilitates migration.
Therefore, cold beverages should be avoided, at least during
the first month after stent placement. However, it is an
advantage of the low temperature phase that an incorrect
positioned stent can be replaced after giving ice cooled
water through the stent. It is very important to be extremely
careful because reposition or removal of metal stents
is usually difficult especially when not using coated
stents.
The second form of the stent achieved in the body
temperature phase is defined by continuous expansion to
its maximum diameter, dilating the stricture. The advantage
of this form is the expansile force and a large diameter which
is established after transforming to its tube shape.
The procedure of stent placement was well tolerated by
all patients. The application of the delivery system is simple
and allows a safe and correct placement. A disadvantage of
the delivery system is the stiffness which makes passage
through the pharynx difficult in a few cases.
Proximal tumor overgrowth is a common problem in
esophageal stenting and can be treated in most cases with
laser debridement or argon plasma coagulation. Overgrowth
of granulation tissue might represent a problem especially
in cases where the stent should be removed after temporary
placement. Probably, the greater diameter of the tulip or the
form of the tulip leads to a localized inflammation of the
mucosa with consecutive development of granulation tissue.
Additionally, the type of metal used for the stent might have
a causative role. This nonmalignant tissue is predominantly
found at the proximal end of the stent. The histologic
findings associated with overgrowth by nonmalignant tissue
include granulation tissue, reactive hyperplasia, and fibrosis
(11). It is uncertain whether this tissue might be the cause of
recurrent dysphagia. Mayoral et al (11) found this to be the
cause in 32% of their patients. However, Siersema et al
observed granulation tissue in a number of patients without
relevant recurrent dysphagia (12). In our study, the
development of overgrowth by nonmalignant tissue did not
cause a relevant stent obstruction but instead impairment
of dysphagia. Tumor overgrowth with recurrent dysphagia
was observed in two cases and could be treated by the
placement of a second, completely covered, metal stent.
In conclusion, this self-expanding nitinol stent is highly
effective for the improvement of dysphagia in patients with
malignant strictures of the esophagus or the stomach. It
has a strong expansile force. The application is simple and
safe. In our study, procedure-related complications did not
occur. Bleeding was the main major complication and was
the cause of death in one patient. The memory effect of
nitinol represents an advantage in cases where removal or
repositioning of the stent is made. However, early intake of
cold beverages might result in stent migration. Therefore,
cold beverages should be avoided in the first period after
stent placement. Recurrent dysphagia due to overgrowth
by tumor or nonmalignant tissue remains a problem. Possibly,
impregnation of stents with cytotoxic agents might reduce
the tumor overgrowth. Additionally, technical
improvements, especially of the tulip, are desirable to reduce
the overgrowth by nonmalignant tissue.

Self expanding metal stents in esophagogastric cancer 243
Conflicts of interest
There is no commercial association (e.g., equity
ownership of interest, consultancy, patent and licensing
agreement, or institutional and corporate associations) that
might be a conflict of interest in relation to the submitted
manuscript.
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