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Self-expandable metal stents in acute malignant colonic obstruction: shall you cross this bridge?
Eduardo da Silveira, MD, MSc (Clinical Epidemiology)

Alan N. Barkun, MD, CM, MSc (Clinical Epidemiology)

published online 30 November 2007.

Abbreviations: CRC, colorectal cancer, SEMS, self-expandable metal stent
Article Outline
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Since their first application for acute malignant colonic obstruction in 1996, self-expanding metal stents have been used in 2 distinct clinical scenarios: definitive palliative procedure and a bridge to later elective surgery.

The development of new technologies and their adoption by the clinical community is a challenge to decision makers and regulators, who are obliged to enforce safety and effectiveness without delaying access for physicians and consumers to these new medical advancements. Unlike pharmaceuticals, which are thoroughly evaluated before marketing, innovations for medical devices are subject to a much less elaborate process. The interval time from concept to clinical implementation can take as little as 18 months, but the effectiveness of devices is also dependent on the acquisition and maintenance of special skills by the end-user, a process that is not under routine scrutiny. These differences allow, in some cases, for new technologies to be disseminated through the health system before thorough determination of safety, effectiveness, and cost-effectiveness issues by well-designed studies. Thus, effectiveness of devices is often evaluated after the release of the devices, and the end result is a market filled with a “mélange” of new and established therapies. This is particularly relevant in countries like the United States, where formal assessment of competing technologies is not commonly used for the determination of reimbursement.1

Colorectal cancer (CRC) is a malignancy with one of the highest incidences in the Western world and is a major cause of cancer-related death. Approximately one fourth of patients present with acute obstructive symptoms. Traditionally, standard care has consisted of surgical decompression via formation of a colostomy and, whenever possible, resection of the primary tumor. Unfortunately, patients with cancer and with bowel obstruction are often malnourished, older, and at increased risk for an emergency surgery, while the lack of bowel preparation, as well as severe dilation of the proximal bowel, precludes a 1-step procedure. The creation of a colostomy not only has adverse effects on the quality of life, but its closure is associated with a morbidity and mortality of 37% and 7%, respectively.2 Therefore, a fraction of patients who require temporary colostomy are subsequently discouraged from undergoing a second closure operation because of its associated risks in light of the overall prognosis of the disease.3

To avoid multiple or 2-stage procedures, nonoperative alternatives, such as balloon dilation, laser ablation, and electrocoagulation, have been attempted with little success.4, 5 The concept of endoscopically inserting self-expandable metal stents (SEMSs) for the palliation of malignant obstruction of the GI tract6 originated from their use in the vascular system.7 Gastroenterologists soon realized the potential for SEMSs because their elastic properties and their capacity to adopt different configurations and to maintain a constant radial pressure makes them particularly suitable for the palliation of symptoms in patients with luminal malignancies. The first case of malignant colonic obstruction palliated with a SEMS was published in 1996,8 and, since then, several case series proposed their use in 2 distinct clinical scenarios associated with acute malignant colonic obstruction: (1) a definitive palliative procedure and (2) a bridge to elective surgery. The former is still a subject of controversy. Unlike its biliary and esophageal counterparts, it remains unclear whether SEMSs should be first-line therapy for the palliation of obstructive symptoms in patients with incurable CRC. Although both colostomy (without tumor resection) and SEMSs are known to have no impact on the progression of the underlying disease, the amount of health benefit provided by both treatment options is probably different. Endoscopic interventions are associated with a lower postprocedural complication rate than surgery, but long-term complications are not infrequent, even with aggressive use of laxatives. Fortunately, most complications can be managed endoscopically, but a fraction of patients require surgical treatment because of perforation, fistula formation, or stent migration. Hence, insertion of a SEMS is not advantageous in patients with a long life expectancy, who, consequently, are more likely to experience late stent-related complications and repeated procedures. This type of reasoning is similar to that encountered with the use of SEMSs in the biliary tree.9 In addition, when considering that resection of the primary tumor might decrease the extent of hepatic and extrahepatic tumor growth and confer a survival advantage,10 surgical resection (with or without a temporary colostomy) might be a preferred alternative for patients who are incurable and with a low metastatic burden and who are likely to tolerate a surgical intervention (such as younger patients with fewer comorbidities).

In contrast to incurable CRC, when compared with emergent surgery, the initial insertion of SEMSs in patients with resectable malignant colonic obstruction is associated with a reduction in length of hospital stay, costs, postprocedural complications, stoma formation, and short-term mortality.11, 12 Endoscopic decompression with SEMSs allows clinical stabilization, cleaning of the colon before surgery, and full colonoscopic examination to exclude synchronous lesions. The presence of synchronous carcinomas changes the surgical approach, and failure of such a diagnosis leads to additional morbidity, mortality, and costs relating to a second surgical intervention. Another potential advantage is the possibility of a minimally invasive laparoscopic colectomy after successful colonic decompression by SEMSs, as suggested in preliminary studies.11, 13 Nevertheless, a single-step approach of intraoperative colonic on-table lavage for decompression and washout before resection and anastomosis continues to be supported in the surgical literature.14

In this issue of Gastrointestinal Endoscopy, Fregonese et al15 present the results of a multicenter mixed (prospective and retrospective) study that evaluated the effectiveness of the Ultraflex SEMS (Boston Scientific Corp, Natick, Mass) as a “bridge” to surgery in patients with resectable acute malignant obstruction of the colon. A total of 36 (8 prospective and 28 retrospective) patients from 16 European centers who were diagnosed with resectable colonic malignant obstruction were treated with fluoroscopy-assisted endoscopic insertion of SEMSs. The main outcomes of the study were technical (adequate positioning of the SEMS across the stricture), clinical success (resolution of obstructive symptoms until elective surgery was performed), and a bridge to elective surgery. Initial technical success was achieved in 31 of 36 patients (87%) but increased to 35 of 36 (97%) after additional stents were inserted in 4 of 5 initial failures. Clinical success was observed in 29 of 36 (81%); 6 of 7 failures were because of stent-related complications, such as pain, tenesmus, migration, and colonic perforation. Surgical resection after SEMS placement was accomplished in 34 of 36 (94%) at a median interval of 11 days, 32 of which were elective and 2 were emergent because of interval development of stent-related complications (perforation and perianal pain). The investigators concluded that SEMSs can be used as a “bridge” to surgery in patients with acute malignant obstruction of the colon.

The investigators have to be congratulated for the completion of this clinically important study, which supports the findings of others.16, 17, 18, 19, 20 In addition to the favorable results observed with SEMSs, the multicenter design was a major asset of this study, increasing the generalizability or external validity, and reinforcing the hypothesis that this device works not only in controlled settings but also in “real-life” conditions. However, like all intervention studies in endoscopy, confounding and bias are of concern and need to be carefully addressed. The inclusion of a large number of retrospective patients raises the possibility of “recall” bias, especially when subjective outcomes like clinical improvement are being measured without a validated instrument. Confounders (variables that may change the strength of association between exposure and outcome) identified in previous investigations (age, location of the CRC, comorbid conditions) were not used to adjust the observed outcomes. This is particularly relevant, because insertion of SEMSs is less invasive than surgical decompression and perhaps more advantageous in a subset of patients who are critically ill. In addition, because placement across flexures and in more proximal regions of the colon can be technically difficult and associated with a higher failure and complication rate, it would be useful to know whether these variables were associated with the outcomes of interest, including the development of complications. The absence of a comparator group was also a limitation of the study. Patients with advanced CRC anticipate longer survival times than their actual prognosis, and this correlates with a greater likelihood of wanting life-extending interventions.21 Thus, the investigators could have used the available clinical data to explore aspects of quality of life in patients palliated with SEMSs, because a variety of domains of quality of life have been shown to be markedly affected in patients who require a permanent stoma.22

The study presented in this issue of Gastrointestinal Endoscopy further adds to the existing body of knowledge that SEMSs can be safely used as a “bridge” to surgery in patients with acute malignant obstruction.15 When compared with an alternative surgical strategy, SEMSs are associated with lower costs and greater health benefits, although some of these remain poorly assessed. However, some questions still remain unanswered and are mainly related to the long-term effectiveness of SEMSs in patients with incurable disease and in those palliated with a SEMS who are later deemed unfit for surgical resection and primary anastomosis. These clinical scenarios illustrate how difficult it is to delineate an effectiveness frontier and to implement policies for adoption of new technologies,23 especially when used to treat related conditions. The decision to insert a SEMS or to perform a colostomy involves multiple areas of uncertainty and trade-off, and, therefore, a balancing of all possible outcomes is difficult to process in the face of complex medical scenarios. The longer an SEMS remains in place, the greater the amount of uncertainty surrounding its effectiveness and the higher the probability that surgery is the preferred alternative. Hence, utilization of SEMSs for conditions that have not been thoroughly investigated (ie, long-term palliation of CRC) cannot be recommended yet, but short “bridges” from acute obstruction to surgery can be safely “crossed” with the endoscopic insertion of a colonic SEMS.