Gut 1995; 37: 309-313

Memory metal stents for palliation of malignantobstruction of the oesophagus and cardia

A May, M Selmaier, J Hochberger, L Gossner, S Miihldorfer, E G Hahn, C Ell

AbstractThirty patients with incurable malignantobstruction of the oesophagus and cardiawere treated with self expanding oeso-phageal memory metal stents (Ultraflex) ina prospective study. The endoprostheseswere successfully placed in all patients.Within one week after implantation dys-phagia had improved in 25 of 30 patients(830/o). Stent expansion was incompletewithin one week after implantation in 12 of30 patients (40%). After an average of twodilatation sessions eight of 12 stents hadexpanded completely. Five patientscomplained of retrosternal pain and threeof them suffered from heartburn overseveral days despite acid inhibition. Majorproblems in the follow up period occurredin 10 of 30 patients (30%) and included lateperforation (one) and tumour ingrowth/overgrowth (nine). All of these complica-tions were treated endoscopically.Improvement of the dysphagia of thepatients with tumour ingrowthlover-growth lasted for about eight weeks(median; range: 2-38 weeks). UntilNovember 1994 six of 30 patients were stillalive with a survival time of 309 days(median; range: 103-368 days). It is con-cluded that oesophageal memory metalstents are easy to implant, prove effectivein the palliation of malignant oesophagealobstructions, and have a low risk of severecomplications. The only disadvantagesare that incomplete initial stent expansionas well as tumour ingrowthlovergrowthoccurred in nearly one third ofthe patients.(Gut 1995; 37: 309-313)

Keywords: stents, malignant oesophageal stenoses.

Department ofMedicine I, UniversityofErlangen-Nuremberg, GermanyA MayM SelmaierJ HochbergerL GossnerS MLihldorferE G HahnC Ell

Correspondence to:Professor Dr med ChristianEll, Medizinische Klinik Imit Poliklinik, UniversitatErlangen-Niirnberg,Krankenhausstr 12, 91054Erlangen, Germany.Accepted for publication10 January 1995

In the past few years the search for an effectivemethod of palliative treatment with a low rateof complications and suitable for the treatmentof incurable malignant oesophageal stenoseshad led to the development and clinical appli-cation of various types of self expanding metalendoprostheses.1-13 Most reports concernedthe Wallstent endoprosthesis version.2 3 6 8 12But first clinical experiences with stents madeof memory metal (nitinol) have also beenreported.' 4 5 9 10 In most cases, only a smallnumber of patients received treatment, how-ever, or the reports are available only in theform of abstracts. Until now only one fullpaper from a radiological centre with memorymetal stents (Ultraflex) in a larger number ofpatients (40) has been published.1 Memorymetal endoprostheses of the Ultraflex type,

which have recently been redesigned have beenavailable in Germany in the improved versionsince August 1993. We report on our pre-liminary clinical experiences in implementingthe new version of this stent in 30 consecutivepatients.

Methods

PatientsFrom August 1993 to August 1994 a total of30 patients with incurable tumours of theoesophagus and the cardia were treated withself expanding metal endoprostheses of thememory metal stent type (Ultraflex,Microvasive Boston Scientific, MA, USA) in aprospective study. Twenty five patients weremen and five were women. Their age rangedfrom 43 to 90 years with a mean (SD) of 65(12) years. Histologically, a squamous cellcarcinoma was found in 15 of 30 patients(50%), an adenocarcinoma in eight (27%),and an anaplastic carcinoma in two (7%)patients. One patient had lung cancer andanother patient a metastatic cancer of thethyroid gland, both leading to an oesophagealobstruction. A histological examination of thetumour was omitted in three patients, becausethe malignancy had been conclusively con-firmed by imaging techniques or by assessmentof the course of the disease. Most patients (19)showed the obstructive lesion in the distal partof the oesophagus and the gastro-oesophagealjunction. In five patients, the tumour waslocated in the mid-section and in two patientsin the proximal part of the oesophagus. Twoother patients had a tumour recurrence at theanastomosis of an earlier gastrectomy andoesophageal resection, respectively. The lengthof the tumour stenosis ranged from 3 to 18 cm(mean (SEM) 7 (3) cm).

Seven of 30 patients suffered from dysphagiafor solid foods alone (23%), 11 patients (37%)for semisolid foods, and 12 patients (40%) forliquids. Most of the patients (24 of 30) hadreceived previous treatment in the form ofbougienage (19), laser therapy (eight), dilata-tion (one), and percutaneous endoscopicallycontrolled gastrotomy (PEG) (three).

Stent materials and implantation techniqueThe self expanding metal prostheses used werememory metal stents (Ultraflex), designed foruse within the oesophagus. The stent mesh isknitted from a single elastic wire, consisting ofa nickel-titanium alloy (nitinol), also referredto as memory metal. When fully expanded, thestent has a diameter of 18 mm. The upper end

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May, Selmaier, Hochberger, Gossner, Miihldorfer, Hahn, Ell

is shaped like a tulip and measures 20 mm indiameter to improve the anchoring of the stentto the oesophageal wall. The prosthesis is avail-able in three different lengths (7 cm, 10 cm,and 15 cm).The prosthesis is mounted in a compressed

state on the stent delivery system consisting of

A

Figure 1: Tumour stenosis in the mid-section of the oesophagus beforeimplantation (B, C).

a stabiliser and is encased in a soluble gelatin.The stabiliser is fairly flexible and enclosed in atransparent plastic protective sheath with anouter diameter of 8 mm. The tapered tip at thedistal end of the stabiliser, which has a lumenfor a 0.038 guidewire, favours the deliverysystem pass through tight strictures. Fourradio-opaque markers are attached to thestabiliser. The two outer ones mark the ends ofthe stent in the compressed state and the innerones mark the ends of the expanded andtherefore shortened stent. To release the stent,the proximal end of the stabiliser is held steadywhile the outer plastic sheath is evenlyretracted. Upon exposure to oesophagealfluids, the gelatin dissolves within three to fiveminutes, resulting in expansion of the stent.Finally the inner stabiliser is removed.

Before stent implantation, patients receiveda mild sedoanalgesia with 5-10 mg diazepamand 50 mg meperidine intravenously. If neces-sary, the stenosis was pretreated by laser coag-ulation or bougienage, or both, until asatisfactory dilatation was achieved. Generally,a diameter of 12 mm was considered to belarge enough to permit an endoscope with aminimum diameter of 10 mm to pass the stric-ture easily. After placement of a guidewire theentire length of the tumour stenosis was pre-cisely measured while retracting the endoscopeto calculate the correct stent length. Ideally,the stent should extend beyond the margins ofthe tumour at both ends by at least 3 cm. Incase of stenosis in the gastro-oesophageal junc-tion the proximal extension of the stent endsbeyond the tumour margins should be at least5 cm. With patients in a supine position,metallic markers were attached to the patient'sskin at the distal and proximal border of thestricture. Under fluoroscopic control the stentswere inserted over the guidewire in the waydescribed. Immediately after stent placementan endoscopy was performed to verify the posi-tion, expansion, and anchoring of the proximalpart of the stent. A complete passage throughthe stent was not forced because of theincreased risk of stent displacement. The stentopening was checked endoscopically andradiologically one or two days after implanta-tion (Fig 1). If the endoprosthesis had notexpanded sufficiently one day after implanta-tion, the stent diameter was increased bymeans of balloon dilatation. The balloons were15 and 18 mm in diameter and 8 cm in length(Rigiflex, Microvasive Boston Scientific,Watertown, MA, USA). Until the stent posi-tion was checked the patients were advised totake only liquids. Thereafter they had semi-solid or solid foods, as individually toleratedand were advised to avoid stringy meat, greensalads, and cheese spread, even if they had nodysphagia after stent implantation. Antirefluxmeasures (proton pump inhibitor and aprokinetic agent) were given to patients whoseprosthesis extended beyond the gastro-oeso-phageal junction. In accordance with the studyprotocol an endoscopic follow up examinationand a short medical history were carried outevery four weeks. Only four patients refusedto undergo further endoscopies and were

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Memory metal stents for palliation of malignant obstruction of the oesophagus and cardia

TABLE I Dysphagia before and after stent placement (- 7days after implantation) (30 patients)

Before Afterimplantation implantation

No dysphagia 0 11Dysphagia for solid food alone 7 12*Dysphagia for semisolid food 11 6Dysphagia for liquid food 12 it

*One patient was able to eat solid food with exception of meatand another patient with the exception of both meat andbrown bread, whereas before stent implantation neither patientcould ingest solid food.tPsychogenic dysphagia, sufficient stent expansion.

questioned as to their symptomatic conditionover the telephone at regular intervals.

ResultsStent placement was successful in all 30patients. There were no technical problemsduring stent placement, except for one case ofa premature user induced expansion of anendoprosthesis. The entire system wasremoved and a new stent was placed withoutproblems. Every patient was treated with onlyone endoprosthesis. Twenty three of 30patients were provided with a stent 15 cm inlength. In five cases the stent had a length of 10cm and in two cases 7 cm. One week after stentimplantation 25 of 30 patients (83%) showedan improvement of dysphagia, five patients(1 7%) reported unchanged difficulties inswallowing (Table I). In four patients adysphagia for solid food and in one patient adysphagia for liquids remained. In two of thesefour patients this occurred despite a satisfac-tory stent passage after two dilatation sessions(one of two patients), which had served toimprove an initially insufficient stent expan-sion. In the third patient it was not possible toachieve a complete expansion of the stentdespite five dilatation sessions. Another patientcould only eat semisolid foods because ofrecurrent chest pain and strong irritation of thethroat. One patient suffered from a psy-chogenic dysphagia and could not eat anyfood, although the stent was fully expanded.

Severe early complications (S7 days afterimplantation), for example, stent migration,bleeding or perforation did not occur. Minorproblems, which were seen in 21 of 30patients, included insufficient opening of theprosthesis up to 48 hours after implantation in17 patients. A complete expansion of the stentwithout the need for further treatment withinone week after placement was seen in five of

TABLE II Acute and intermediate problems afterimplantation of the endoprosthesis (26 patients)

Patients (n) %

Acute problemsInsufficient stent expansion requiring

dilatation treatment 12 40Retrosternal pain 8 27Pyrosis despite antireflux measures and

acid inhibition 3 11Intermediate problemsRecurrent dysphagia caused by tumour

ingrowth/overgrowth* 9 30Perforation 1 4

*Endoscopically verified in six patients, three patients refusedre-endoscopy.

these 17 patients, whereas the remaining 12patients (40°/) required dilatation treatment(Table II). After an average of two dilatationsessions using a balloon catheter (range 1-5)eight of 12 stents had expanded completely,that is to say, to a point where a standard endo-scope could have been moved through thestent without resistance. One of four patientswith an insufficient expansion despite dilata-tion died three days after stent implantationand before completion of the dilatation treat-ment in consequence of a progressiveKorsakow syndrome and a blood sugar distur-bance. The exact cause of death could not beestablished because the relatives of thedeceased patient did not consent to a necropsy.In the second patient a sufficient stent expan-sion could not be achieved, because the lengthof the tumour - which had reached anadvanced stage - was 17 cm. In the thirdpatient a pronounced compression of thetumour from outside was ascertained, whichcould be treated only partially by dilatationtreatment. In another patient with a remainingstenosis in the region of the cardia despite fivedilatation sessions after stent placement aGianturco-Z-stent was successfully implanted,which showed a sufficient expansion with 48hours (Fig 2). Eight patients complained ofchest pain, three of them had acute pain sensa-tions over a period of several days, and one ofthem also had a foreign body sensation. Threepatients suffered from severe heartburn despiteantireflux measures and acid inhibition overseveral days, which disappeared with increasedoral intake of food. One patient reportedintermittent moderate pyrosis (Table II).During the follow up period nine patientsagain developed increasing dysphagia eightweeks (median; range: 2-38 weeks) after stentplacement. Tumour ingrowth/overgrowth wasassumed and endoscopically diagnosed in sixpatients. The other three patients refusedfurther endoscopies and were fed by the PEGonly. Patients with tumour ingrowth/over-growth were retreated by electrocoagulation ofthe tumour tissue. In one patient dilatationtreatment was carried out. Two patientsreceived a second stent, one memory metalendoprosthesis and one Gianturco-Z-stent. Inone patient with an oesophageal carcinoma aperforation occurred about three weeks afterplacement of the endoprosthesis. The patientwho complained of an increasing irritation ofthe throat was examined and an oesophagotra-cheal fistula was diagnosed. An elastic trachealprosthesis was subsequently inserted and thefistula was sealed with a histoacrylic adhesiveby approaching the fistula from the oesophagus(Table II). The final radiographic controlimages showed no further signs of contrastmedium passing into the tracheal system. Thepatient survived for another 18 weeks aftertreatment. Table II lists the complications thatoccurred. In the remaining group of 20patients no late complications have arisen todate. Until 14 November 1994, six of 30patients were still alive with a survival time of309 days (median; range: 103-368 days).Twenty three patients had died after a survival

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May, Selmaier, Hochberger, Gossner, Miihldorfer, Hahn, Ell

A

Figure 2: Tumour stenosis in the region of the gastro-oesophageal junction with aninsufficient memory metal stent expansion despite dilatation after placement (A) and goodpassage after implantation ofa Gianturco-Z-stent (B).

time of 70 days (median; range: 3-21 1 days).One patient returned to his native country(Croatia) and therefore was no longer availablefor further follow up.

DiscussionGastroenterological experiences concerningthe application of self expanding Ultraflexmemory metal (nitinol) stents in the oeso-phagus have been reported to date only in theform of abstracts or short communications5 9 10with the exception of one full paper publishedin a radiological journal.' Technical problemswith the stent release that we and other users10also had with the previous stent version, didnot occur using the redesigned and improvedstent, which has been commercially availablein Germany since August 1993. Until nowthere have been no prospective randomisedstudies comparing the different stent types, butaccording to our experience the implantationprocedure is easier to carry out with thememory metal stent (Ultraflex) than theoesophageal endoprostheses of Wallstent typein its original construction design.2 8 Obliquestent positions or stent migration as seen byour group when using the Wallstent prosthesis2did not occur with the Ultraflex stent versions.One reason for this could be attributed to thestent length of up to 15 cm, which permits abetter coaxial positioning of the prosthesis inthe oesophagus, particularly in stenosis of the

gastro-oesophageal junction. Whereas themaximum length of a fully expanded Wallstentprosthesis was only 11 cm. Furthermore, thematerial properties and design specifications ofthe Ultraflex stent give it a flexibility that canprove to be a particular advantage in managingkinking stenoses in the region of the gastro-oesophageal junction.On the other hand, the Ultraflex memory

metal stent seems to offer a lower force ofexpansion. Cwikiel et al1 reported on the needfor balloon dilatation after stent placementbecause of insufficient expansion in 38% ofpatients. The results of Raijman et al9 showedthat even in 71% of patients dilatation treat-ment was performed, although some treatmentwas immediately after placement. To our expe-rience about half of the patients provided witha memory metal stent initially showed an insuf-ficient degree of spontaneous expansion, thusrequiring 40% of the patients to have one orseveral dilatation treatments. With the excep-tion of three patients maximum stent expan-sion could be achieved in all cases at the latestafter five dilatation sessions. One of threepatients with an incompletely expanded stenthad a particularly long tumour stenosis of 17cm and two had a strong external compressionof the tumour. In contrast, retreatmentsentailing dilatation because of incomplete stentexpansion, which became necessary after theimplantation of Wallstents or Gianturco-Z-Stents have either not been reported or haveremained exceptions.2 3 6 7 13

In contrast with the Wallstent, the proximalend of the memory metal Ultraflex stent isshaped like a tulip enhancing firm anchoring ofthe stent of the oesophageal wall. This servesto avoid the formation of pouches that wasseen in nearly every fifth patient whenWallstent prostheses were implanted.2 7 Therisk of a bolus obstruction at the upper rim ofthe stent is thus distinctly reduced.To date, we have seen tumour ingrowth or

overgrowth in about a third of our patients.This is essentially in agreement with clinicalexperiences in implementing oesophagealWallstents,2 8 but somewhat in disagreementwith the findings reported by Knyrim6 who sawthis problem in slightly less than 24% of hispatients when vascular Wallstents wereapplied. Nevertheless, it can be assumed thattumour ingrowth/overgrowth closely correlateswith the patient survival times and that suchforms of tumour growth generally develop inassociation with all mesh type endoprostheseslacking a protective coating, especially inpatients with long survival times. Retreatmentsbased on thermocoagulation methods there-fore remain unavoidable, as long as tumouringrowth cannot be prevented. Coated stentscan prevent this from happening, but bear therisk of stent migration.2 3 8 13

In summary, it can be concluded that treat-ment of malignant tumour stenoses in theupper gastrointestinal tract by implementingself expanding wire mesh endoprotheses of thememory metal Ultraflex stent type is simpleand effective. The implantation procedureimposes little strain on the patient and can be

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Memory metal stents for palliation of malignant obstruction of the oesophagus and cardia 313

performed on an outpatient basis. Dysphagiawas distinctly improved in most patients.The rate of serious complications is low. Theproblem in the early period after implantationis the insufficient expansion of the stentparticularly in strong tumour stenoses requir-ing further dilatation treatment. The mainproblem occurring in the intermediate treat-ment stage is that of tumour ingrowth andovergrowth.

In view of the degree of discomfort andthe system inherent rate of complicationsassociated with plastic tube implantations, thecurrently available generation of memorymetal Ultraflex stents signifies, even today, avaluable improvement of palliative treatmentconcepts applied to malignant stenosis in theupper gastrointestinal tract.We wish to thank Professor M Grade for translating and revis-ing the manuscript.

Addendum

During the follow up period until February 1995 two morepatients developed increasing dysphagia due to tumour in-growth and were retreated with electrocoagulation and KTPlasercoagulation, respectively. Altogether the problem oftumour infiltration of the wire mesh occurred in 11 of 30patients (36%) 18 weeks (median; range: 2-49) after stentplacement.

Furthermore, two more patients died, so that until February1995 four of 30 patients were still alive with a survival time of416 days (median; range: 354-441) and 26 of 30 patients haddied after a survival time of 108 days (median; range: 3-211).

1 Cwikiel W, Strindberg H, Tranberg K-G, Stael vonHolstein C, Hambraeus G, Lillo-Gil R, et al. Malignant

esophageal strictures: treatment with a self-expandingmemory metal stent. Radiology 1993; 187: 661-5.

2 Ell C, Hochberger J, May A, Fleig WE, Hahn EG. Coatedand uncoated self-expanding metal stents for malignantstenosis in the upper GI-tract. Am _7 Gastroenterol 1994;89: 1496-500.

3 Ell C, May A, Hahn EG. Gianturco-Z-stents in the pallia-tive treatment of malignant esophageal obstruction andesophagotracheal fistulas. Endoscopy (in press).

4 Goldin E, Beyar M, Safra T, Globerman 0, Craciun I,Wengrower D, et al. A new self-expandable, nickel-titanium coil stent for esophageal obstruction: a prelimi-nary report. Gastrointest Endosc 1994; 40: 64-8.

5 Grund KE, Storek D, Naruhn M. Flexible metal stentsin the esophagus [Abstract]. Gastrointest Endosc 1993; 39:121.

6 Knyrim K, Wagner HJ, Bethge N, Keymling M, Vakil N. Acontrolled trial of expansible metal stent for palliation ofesophageal obstruction due to inoperable cancer. N Engl _tMed 1993; 18: 1302-7.

7 Kozarek RA, Ball TJ, Patterson DJ. Metallic self-expandingstent application in the upper gastrointestinal tract:caveats and concerns. Gastrointest Endosc 1992; 38: 1-6.

8 Neuhaus H, Hoffmann W, Dittler HJ, Niedermeyer HP,Classen M. Implantation of self-expanding esophagealmetal stents for palliation of malignant dysphagia.Endoscopy 1992; 24: 405-10.

9 Raijman I, Walden D, Kortan P, Haber GB, Fuchs E,Siemens M, et al. Expandable esophageal stents: initialexperience with a new nitinol stent. Gastrointest Endosc1994; 40: 614-21.

10 SaIB NL, Hagenmuller F. Nitinolstent beiOsophaguskarzinom [Letter]. Dtsch Med Wochenschr1993; 118:45.

11 Schaer J, Katon RM, Ivancev K, Uchida B, Rosch J,Binmoeller K. Treatment of malignant esophagealobstruction with silicone-coated metallic self-expandingstents. Gastrointest Endosc 1992; 38: 7-11.

12 Wagner HJ, Knyrim K, Bethge N, Starck, E, Sommer N,Pausch J, et al. Palliativtherapie der malignenOsophagusobstruktion mit selbstexpandierendenMetallendoprothesen. Dtsch Med Wochenschr 1992; 117:248-55.

13 Wu WC, Katon RM, Uchida BT, Keller FS, Rosch J.Silicone-covered self-expanding metallic stents for the palli-ation ofmalignant esophageal obstruction and esophagores-piratory fistulas: experience in 32 patients and a review ofthe literature. Gastrointest Endosc 1994; 40: 22-33.

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