Can covered self-expandable metal stents become a new standard in the treatment of obstructive colorectal cancer?—advantages, challenges, and future directions: a scoping review

Introduction

Background

Colorectal cancer (CRC) is the third most common cancer worldwide, with approximately 1.9 million new cases and 930,000 deaths reported across 185 countries in 2020. By 2040, the number of new cases is projected to rise to 3.2 million, with an estimated 1.6 million deaths, making CRC a continuing major public health concern (1). Among all cases of CRC, obstructive colorectal cancer (OCC) accounts for approximately 8–29% (2,3) and is associated with a poorer prognosis than those of non-obstructive cases (4-6), possibly attributed to the higher incidence of local invasion and lymph node metastasis (6), and complications such as perforation and sepsis associated with obstruction (7,8).

One treatment strategy for OCC is bridge to surgery (BTS), in which preoperative bowel decompression is followed by elective surgery. This approach helps avoid the risks associated with emergency surgery and improves short-term outcomes (9,10). Bowel decompression using self-expandable metal stents (SEMS) for OCC was first reported by Tejero et al. in 1994 (11). BTS using SEMS offers several advantages over BTS strategies involving transanal decompression tubes or diverting stoma creation. These benefits include a lower stoma formation rate, shorter postoperative hospital stay, a greater number of lymph nodes harvested, and a reduced incidence of postoperative complications (12). Hence, clinical guidelines in Europe, the United States, and Japan recommend SEMS use for OCC, provided that the potential risks of worsened prognosis are carefully considered before application (13-15). However, the long-term oncological safety of BTS using SEMS (Stent BTS) remains a subject of ongoing debate. Some studies have reported survival rates comparable to those of emergency one-stage surgery (16-18); meanwhile, others have highlighted an increased risk of distant metastasis and recurrence (19-21), an increase in unfavorable histological and genetic factors (22-24), and reduced overall and/or disease-free survival (25-27). In esophageal cancer, the use of SEMS in a BTS approach has been associated with increased local recurrence rates and decreased survival (28-30), raising concerns about the potential impact of BTS on long-term outcomes regardless of cancer type (26).

Rationale and knowledge gap

Several reports exist on the short-term outcomes of covered self-expandable metal stents (CSEMS) and their comparison with conventional SEMS (31-39); however, a comprehensive review, systematically summarizing the complete picture, including clinical outcomes, complications, oncological safety, and the potential risk of bowel injury, is lacking. Moreover, these studies are heterogeneous, ranging from randomized controlled trials (RCTs) to retrospective analyses and basic experimental studies, with diversity in design and outcome measures making it difficult to conduct a high-quality meta-analysis. Therefore, rather than performing a systematic review to estimate treatment effects, a scoping review is more appropriate to map the breadth of existing evidence, identify knowledge gaps, and highlight future research directions.

Objective

The aim of this review was to critically reassess the current evidence on CSEMS, clarify their clinical benefits and challenges, and outline future directions for research. We present this study in accordance with the PRISMA-ScR reporting checklist (available at https://ales.amegroups.com/article/view/10.21037/ales-25-41/rc).

Methods

A systematic literature search was conducted using the PubMed and Google Scholar databases to identify peer-reviewed English-language articles published between January 1994 and July 2025. The final search was performed on August 15, 2025. The PubMed search strategy was as follows: (“Stents”[MeSH Terms] OR “Stents, Covered”[MeSH Terms] OR “covered stent”[All Fields] OR “covered self-expandable metal stent”[All Fields]) AND (“Colorectal Neoplasms”[MeSH Terms] OR “colorectal cancer”[All Fields] OR “Colonic Neoplasms”[MeSH Terms] OR “colonic obstruction”[All Fields] OR “large bowel obstruction”[All Fields]). To ensure comprehensive coverage, we also searched Google Scholar using the keywords “covered self-expandable metal stent” AND “colorectal cancer” OR “colonic obstruction” OR “large bowel obstruction”. Given the limited filtering and sorting functions of Google Scholar, we screened the first 100 results by relevance. In addition to database searching, we performed citation searching by screening reference lists (backward citation searching) and conducting forward citation searching in PubMed (“Cited by”). Inclusion criteria were as follows: (I) original research articles or systematic reviews evaluating CSEMS use; (II) studies involving CRC; and (III) studies reporting clinical or pathological outcomes. This review primarily focused on CSEMS; however, studies reporting outcomes of uncovered SEMS were included for comparison. Exclusion criteria included: (I) duplicate reports from the same dataset; (II) single case reports lacking generalizability; and (III) studies focusing on non-colorectal stents, such as those intended for esophageal or biliary use. Two gastrointestinal surgeons independently screened the articles and extracted relevant data. Disagreements were resolved through discussion with a third reviewer.

Extracted data included study details (author, year, study design, sample size), stent type and structural characteristics, and outcomes. Outcomes encompassed technical and clinical success rates, procedure-related complications (perforation, migration, re-obstruction, infection), tumor ingrowth and overgrowth, surgical impact, macroscopic bowel effects, histopathological changes, biological effects, and long-term oncological outcomes (recurrence and survival). Findings were narratively synthesized and critically evaluated across these domains. No contact was made with the study authors to obtain additional information.

Results

Study selection

The study selection process is summarized in the PRISMA-ScR flow diagram (Figure 1). In total, 142 records were retrieved from PubMed and 100 from Google Scholar. After removing duplicates, 232 records were screened based on title and abstract. In addition, 18 further studies were identified through citation searching, bringing the total to 48 included in the final qualitative synthesis.

Figure 1 PRISMA ScR flow diagram of study selection process. CRC, colorectal cancer.

Variations and structures of CSEMS

Currently available covered stents exhibit various designs, differing in framework structure and covering materials. Major commercially available covered stents include the Jabara^® Colonic Stent (SB-KAWASUMI LABORATORIES, Inc., Tokyo, Japan), Niti-S™ Enteral Colonic Covered Stent and Niti-S™ COMVI™ Flare Enteral Colonic Stent (Taewoong Medical Co., Ltd., Gimpo, Korea), and the HANAROSTENT^® Naturfit™ Colon Covered Stent (Boston Scientific Corporation, Boston, MA, USA) (Table 1, Figure 2) (40-42).

Figure 2 External appearance and schematic structures of representative covered colonic stents. (A) Jabara™ Colonic Stent (SB Kawasumi Laboratories, Inc., Tokyo, Japan). (B) Niti-S™ COMVI™ Enteral Colonic Stent (Both Bare-Type) (Taewoong Medical Co., Gimpo, South Korea). (C) Niti-S™ COMVI™ Flare Enteral Colonic Stent (Taewoong Medical Co., Gimpo, South Korea). (D) Hanarostent^® Naturfit™ Colon Cover (M.I. Tech Co., Ltd., Seoul, South Korea; distributed by Boston Scientific Japan K.K., Tokyo, Japan). Images of the stents were reproduced from the manufacturers’ websites/catalogs with permission (40-42). The schematic diagram of the Jabara™ stent structure was created by the authors.

Each stent differs in structure: the Jabara^® Colonic Stent consists of a single helical nitinol wire as its metal framework, covered with a silicone membrane on the luminal and external surfaces of the tubular structure.

Conversely, the HANAROSTENT^® Naturfit™ Colon Covered Stent, Niti-S™ Enteral Colonic Covered Stent, and Niti-S™ COMVI™ Flare Enteral Colonic Stent have a design in which either a polytetrafluoroethylene (PTFE) membrane or silicone covers the inner and outer surfaces of a mesh-like metal framework. Therefore, in the Jabara^® Colonic Stent, the tumor contacts a smooth silicone membrane. In the latter designs, the tumor contacts a combination of mesh metal and PTFE or silicone. Stents in which the metal framework directly contacts the tumor are believed to generate greater frictional force on the tumor surface, which may help prevent stent migration (37).

Short-term clinical outcomes

Overview of included studies

Overall, 16 original studies reporting short-term clinical outcomes of colonic stenting were included, covering technical success, clinical success, and complications. Of these, three were RCTs, and 13 were observational studies. CSEMS was specifically evaluated in eight studies with a combined sample size of 563 patients; similarly, SEMS was investigated in eight studies with a combined sample size of 1,109 patients.

Findings from original research

Recent clinical studies have shown favorable short-term outcomes for CSEMS and uncovered SEMS in the management of malignant colorectal obstruction (Table 2).

Technical and clinical success

Park et al. reported technical and clinical success rates of 93.1–98.7% and 92.6–95.9%, respectively, in a mixed cohort including BTS and palliative cases treated using CSEMS (35,43). In contrast, Hiratsuka et al. reported a 100% and 90% technical and clinical success rates, respectively, and no re-obstruction in a study focusing exclusively on BTS cases treated with CSEMS (34).

Stent migration

Previous studies showed a wide range of migration rates: 0–21.1% for CSEMS (31,32,34-36,43,44) and 0–25.9% for SEMS (32,35,36,43-48). In a recent large RCT involving palliative patients, the migration rate was 16.2% for CSEMS compared with 7.2% for SEMS, highlighting a higher risk with CSEMS (36). Binkert et al. similarly emphasized the increased migration risk associated with CSEMS in palliative settings (49). Han et al. reported that chemotherapy increased migration risk in SEMS, whereas no significant difference in delayed migration was observed between CSEMS and SEMS overall (50). In contrast, studies focused on BTS consistently showed low migration rates for both stent types, such as 0% for the Kawasumi Jabara^® CSEMS (34) and 1.3% for SEMS (45).

Perforation

In RCTs including palliative cases treated with CSEMS, the perforation rate ranged from 0–6.8% (35,36,43), whereas for SEMS, it ranged from 0–5.4% (35,36,43). Recent data from BTS settings challenge this view. Hiratsuka et al. reported no perforation (0%) with CSEMS in BTS cases (34), which is comparable to the 1.6% perforation rate reported for SEMS in BTS cases (45), and notably lower than the 6.8% rate observed with long-term SEMS placement in palliative patients (36). Colon flexure involvement (51) and bevacizumab use have been associated with increased perforation risk in SEMS during palliative care, with rates as high as 20% (52); however, CSEMS has not been clearly associated with these perforations. A recent RCT subgroup analysis revealed a 2% perforation rate in chemotherapy-treated palliative patients with CSEMS, compared with 10% using SEMS (36).

Findings from systematic reviews and meta-analyses

The short-term utility of CSEMS and SEMS under varying clinical circumstances has been comprehensively evaluated in multiple systematic reviews and meta-analyses.

Complications and stent patency

Zhang et al. reported no significant differences between CSEMS and SEMS in terms of technical success, clinical success, early migration, perforation, or overall complications (33). However, CSEMS were associated with less tumor ingrowth, at the expense of higher delayed migration rates and shorter stent patency duration (33). Mashar et al. also emphasized the increased migration risk of CSEMS in palliative cases (53).

Perforation risk

Earlier meta-analyses showed an elevated perforation risk associated with CSEMS during prolonged stent indwelling or concurrent use of anti-VEGF agents (38,39). Another analysis indicated that perforation risk is strongly influenced by patient-related factors, such as complete obstruction, female sex, technical factors, including pre-dilation, endoscopist experience, and treatment-related factors, comprising the use of anti-VEGF agents, steroids, or radiotherapy (54).

Tumor ingrowth

Overview of included studies

Six original studies reporting tumor ingrowth following colonic stenting were included. Of these, two were RCTs, and four were observational studies. In three studies, CSEMS was specifically evaluated with a combined sample size of 96 patients, while uncovered SEMS was evaluated in six other studies with a combined sample size of 536 patients.

Findings from original research

In three CSEMS-focused clinical reports on malignant colonic obstruction—including those by Moon et al. (32), Lee et al. (37), and Hiratsuka et al. (34)—no case of re-obstruction due to tumor ingrowth was observed. In contrast, SEMS use was variably associated with tumor ingrowth and re-obstruction: rates ranged from 0% in BTS-only cohorts (45,47) to 20% in mixed BTS/palliative groups (32) and up to 17% in exclusively palliative cohorts (36).

Findings from systematic reviews and meta-analyses

Multiple systematic reviews and meta-analyses have consistently shown that CSEMS result in significantly lower rates of tumor ingrowth compared with SEMS (33,53).

Tumor overgrowth

Overview of included studies

Seven original studies reporting tumor overgrowth following colonic stenting were included. Of these, one was an RCT, and six were observational studies. In four studies, CSEMS was specifically evaluated, comprising 171 patients, while uncovered SEMS was evaluated in four, comprising 380 patients.

Findings from original research

In mixed cohorts of BTS and palliative patients treated with CSEMS, Moon et al. reported a tumor overgrowth-related re-obstruction rate of 11.1% (32). Meanwhile, Lee et al. observed a rate of 6.7% (55). In palliative cohorts, Park et al. reported 3.3% (44). In contrast, in a BTS-only cohort, Hiratsuka et al. reported no tumor overgrowth (0%) (34).

In SEMS, the incidence of tumor overgrowth-related re-obstruction varied based on the clinical setting. No cases were reported in the BTS-only cohorts (34,45). However, in mixed BTS and palliative cohorts, Wada et al. reported a 0% incidence (47), whereas Moon et al. observed a rate of 5% (32); in palliative cohorts, Park et al. reported 0% (44).

Findings from systematic reviews and meta-analyses

Two early systematic reviews and meta-analyses revealed no significant difference in tumor overgrowth rates between CSEMS and SEMS (33,38). In contrast, Mashar et al. reported that CSEMS were associated with a higher incidence of tumor overgrowth-related re-obstruction compared with SEMS (53).

Impact on surgery

Overview of included studies

Eight original studies reported surgical outcomes following colonic stent placement prior to surgery. Six of these were observational studies, and two were RCTs. The impact of CSEMS and SEMS was evaluated in only one study, comprising 44 patients (34).

Findings from original research

Hiratsuka et al. conducted the only clinical study evaluating surgical outcomes after CSEMS placement in a BTS setting. The authors reported no significant differences in operative time, intraoperative blood loss, or perioperative complication rates compared with SEMS use (34). In contrast, SEMS-based BTS strategies have been more extensively studied. Prior reports indicate that surgery following SEMS placement reduces postoperative complications, shortens recovery time, and is associated with more dissected lymph nodes than using emergency one-stage surgery (12,13,56-60).

Findings from systematic reviews and meta-analyses

To date, there are no systematic reviews, specifically comparing surgical outcomes between CSEMS and SEMS in BTS settings. However, meta-analyses evaluating SEMS-based BTS have consistently reported favorable effects on intraoperative blood loss (61), postoperative recovery, such as lower stoma rates and reduced postoperative morbidity, postoperative hospital stay, and postoperative complications compared with emergency surgery (9,62-66).

Macroscopic bowel damage

Overview of included studies

Bowel damage following colonic stent placement was evaluated in four original studies, all observational. Of these, CSEMS was evaluated in one study comprising 10 patients (34), while SEMS was evaluated in the remaining studies involving 802 patients.

Findings from original research

Veld et al. defined “silent perforation” as asymptomatic perforations identified on resected specimens (67), reporting a frequency of 1.6–27% in SEMS-treated BTS cases (45,68,69). Of these, 27% were diagnosed histopathologically (68), while 1.6–3.8% were detected intraoperatively (45,69).

In contrast, Hiratsuka et al. compared outcomes between patients treated with the covered Jabara Colonic Stent™ and those treated with conventional SEMS, demonstrating that CSEMS significantly reduced macroscopic and histological bowel injury (34). This effect was attributed to the structural design of CSEMS, where the metal framework does not come into direct contact with the bowel wall and exerts lower compression per unit area. Additionally, CSEMS has been successfully used in treating post-surgical anastomotic strictures with fistulas (70), suggesting that bowel healing capacity is preserved even under stent placement.

Findings from systematic reviews and meta-analyses

To date, no systematic reviews or meta-analyses have directly compared bowel damage associated with CSEMS versus SEMS. However, stent-related bowel injury, including microperforation, has been identified as a potential contributor to perforation risk (39). In SEMS, the wire mesh can exert continuous pressure on the tumor, sometimes embedding into the tissue, and this sustained compression has been associated with an increased risk of perforation (53).

Histopathological changes

Overview of included studies

Histopathological changes in resected specimens following colonic stent placement (SEMS or CSEMS) were evaluated in eight original studies. All studies were observational in design. Of these, one study assessed CSEMS with a sample size of 10 patients (34), while the uncovered SEMS was evaluated in seven studies, including 447 patients (34,71-77).

Findings from original research

Across several studies, adverse histopathological features in resected specimens have been frequently observed following SEMS placement. For instance, perineural invasion (PNI) was significantly increased in SEMS groups in studies by Haraguchi (72), Kang (76), Kim (75), and Kato (74), whereas Wang et al. reported no significant difference in PNI between SEMS and emergency surgery groups (77). Additionally, lymphatic invasion, venous invasion, and tumor ulceration were noted more frequently in SEMS cases, as reported by Kosumi and Kang et al. (73,76).

Sabbagh et al. observed that SEMS placement was associated with increased rates of PNI and lymphatic invasion, as well as ulceration of tumor tissue and surrounding bowel wall (71). Kosumi et al. further demonstrated that severe venous invasion occurred significantly more frequently in the SEMS group than in patients who received a transanal drainage tube (73). Conversely, Hiratsuka et al. showed that among patients treated with a covered stent (Jabara Colonic Stent™), the incidence of deep venous invasion was significantly lower than using conventional SEMS, suggesting that the protective covering may attenuate direct tumor compression and reduce tissue injury (34).

Other studies have reported no significant histopathological differences between SEMS and emergency surgery in OCC cases, indicating the need for further clarification of these findings (76,77).

Findings from systematic reviews and meta-analyses

To date, there are no meta-analyses directly comparing histopathological changes between CSEMS and SEMS. However, in patients undergoing BTS with SEMS, recent systematic reviews and meta-analyses have consistently shown an increased prevalence of adverse pathological findings compared with emergency surgery. These include higher frequencies of perineural invasion, lymphatic invasion, venous invasion, and ulcerative or fibrotic changes within or adjacent to the tumor (22,24). Additionally, a significantly higher number of lymph nodes were retrieved in SEMS cases (24). These pathological alterations may have implications for oncological safety.

In contrast, data regarding the histopathological impact of CSEMS remain limited, and further studies are required to assess their potential oncological advantages or risks.

Biological effects

Overview of included studies

The biological effects and impact on the tumor microenvironment (TME) following colonic stent placement were evaluated in four original studies. These consisted of two in vivo, ex vivo, and in vitro studies. Based on device type, CSEMS was investigated in two studies, while SEMS was investigated in four, including clinical studies using human tissue samples involving 120 patients (23,71,78-81).

Findings from original research

In a porcine stenosis model with CSEMS placement, no evidence of ischemia, erythema, or edema was observed at the stented colonic segment (79). Similarly, CSEMS placement did not induce macroscopic ischemia in a porcine anastomotic model (81), suggesting preservation of local blood flow.

In contrast, SEMS placement was associated with increased ulceration within the tumor and surrounding tissue (71), as well as increases in circulating CK20 mRNA (78) and circulating tumor DNA (23).

Furthermore, Matsuda et al. reported decreased Ki-67 expression and increased p27^Kip1 expression in tumor tissue following SEMS placement, indicating that mechanical compression may suppress tumor cell proliferation (80).

Findings from systematic reviews and meta-analyses

To date, there are no systematic reviews or meta-analyses directly comparing the biological effects of CSEMS with those of SEMS.

Long-term outcomes

CSEMS offers structural advantages such as tumor ingrowth suppression and bowel injury reduction; however, robust clinical evidence regarding its long-term oncological safety has not been established. Most current literature focuses on short-term outcomes, such as technical and clinical success rates and complication rates, whereas prospective studies evaluating long-term endpoints, including local recurrence, distant metastasis, and overall survival, remain limited.

Furthermore, data comparing outcomes between BTS and non-BTS cases using CSEMS remains insufficient. To comprehensively assess the clinical significance of CSEMS, further studies with larger patient populations and extended follow-up periods are essential. A Japanese prospective RCT (phase III), known as the COBRA trial, compared treatment with non-stenting surgery with colonic stenting as a BTS for decompression in patients with OCC, in order to determine whether BTS is non-inferior to surgery, which is considered the standard treatment. This trial was registered in the University Hospital Medical Information Network (UMIN) Clinical Trials Registry (UMIN-CTR000026158), and long-term prognosis is being evaluated in terms of the 3-year disease-free survival, an oncological outcome indicator after curative resection of CRC. The results are awaited.

Discussion

Key findings

In this review, we examined the current evidence on the clinical outcomes and oncological safety of CSEMS for OCC. The crucial findings are as follows: (I) CSEMS demonstrate clinical success rates comparable to those of SEMS, with technical and clinical success rates ranging from 90–100% and 75.9–96.6%, respectively, aligning closely with SEMS success rates of 92–100% and 85–97% (33). (II) Recent innovations, such as flare-end structures and improved anchoring mechanisms, have significantly reduced migration risk. (III) The covering membrane of CSEMS effectively suppresses tumor ingrowth and reduces bowel injury, potentially contributing to improved long-term outcomes. (IV) Long-term placement may lead to complications such as tumor overgrowth, membrane degradation, and perforation. (V) CSEMS are particularly suitable for BTS cases involving short-term placement, minimizing migration risk (Table 3).

Strengths and limitations

A key strength of this review is its comprehensive integration of recent clinical data, pathological insights, and mechanical mechanisms, allowing a multidimensional assessment of CSEMS performance. Notably, the focus of this review was on its impacts on the TME and histological outcomes. However, limitations include substantial heterogeneity across studies in stent types, placement sites, operator experience, and patient backgrounds. Inconsistent complications and follow-up periods also reduce external validity. Additionally, a preregistered protocol was not used in this scoping review (e.g., in Open Science Framework), which may introduce a potential risk of reporting bias. In future reviews, we aim to implement protocol registration to enhance transparency and reproducibility. Moreover, clinical trial registries and grey literature databases were not included in our search strategy, potentially leading to the omission of unpublished or negative studies. In future updates of this review, consideration will be made to incorporate these sources to improve the comprehensiveness and reduce publication bias. Furthermore, a lack of prospective long-term data limits the ability to draw definitive conclusions.

Comparison with similar research

In previous reviews and meta-analyses, CSEMS and SEMS were usually grouped together, or the focus was solely on technical success. In contrast, the structural and biological advantages and limitations of CSEMS were particularly discussed in this review. In addition, newer designs, such as the Jabara Colonic Stent, were introduced, providing novel insights into bowel-protective effects and their influence on the TME, contributing to more nuanced clinical decision-making.

Explanations of findings

The clinical CSEMS advantages largely stem from the covering layer, typically made of silicone or PTFE, which prevents direct contact with the tumor and reduces tumor ingrowth and mucosal injury. Pressure is evenly distributed, minimizing focal ischemia and perforation risk (32). In BTS cases, the short placement duration lowers migration risk. Conversely, in palliative settings, risks such as tumor overgrowth, enzymatic membrane degradation, bacterial colonization, and inflammation should be considered (79,80,82,83). In partially covered CSEMS, mechanical stress from friction at uncovered ends may contribute to perforation. Recent studies suggest that CSEMS may influence the TME by modulating shear stress and cytokine expression; nonetheless, direct molecular comparisons with SEMS are scarce. Matsuda et al. (80) reported increased p27^Kip1 and decreased Ki-67 expression post-SEMS placement, suggesting suppressed tumor proliferation. Moreover, in the TME, mechanical compression and solid stress can induce increased interstitial pressure (84) and reduced perfusion, thereby promoting hypoxia (85), while hypoxia and inflammatory cytokines can enhance the upstream signaling pathways of p27^Kip1 (86). The findings suggest that the mechanical stress exerted by colorectal stent expansion, together with subsequent subtle alterations in local perfusion and inflammation, may indirectly contribute to the upregulation of p27^Kip1.

Conversely, Broholm et al. (83) found activation of gene clusters related to angiogenesis, inflammation, invasion, and reduced tumor suppressor gene expression following SEMS placement. This type of placement has also been associated with increased circulating tumor cells, cell-free DNA, and damage-associated molecular patterns (48,78,87), which are associated with metastasis, recurrence, and poor prognosis (88). No comparable molecular data are available for CSEMS, highlighting the need for future studies using genomic and proteomic approaches. A detailed histopathological analysis of 72 resected cases of OCC following SEMS placement revealed 100% tumor necrosis and multilayered deep ulceration in approximately 80% of specimens. In addition, non-tumorous bowel segments exhibited diverse changes resembling inflammatory bowel disease, including ischemic injury and inflammatory cell infiltration (89). These findings suggest that SEMS implantation frequently induces ischemic and inflammatory changes in the bowel wall. Meanwhile, Galon et al. demonstrated that the type, density, and immune cell location (immune contexture) strongly determine prognosis in CRC, and that increased inflammatory cytokines and hypoxia in the TME can create an immunosuppressive milieu that contributes to poor oncologic outcomes (90). In particular, severe tissue injury-associated inflammation and ischemia-induced hypoxia can elevate interleukin 6 (IL-6) and tumor necrosis factor α (TNF-α) levels and promote the differentiation of immunosuppressive M2 macrophages (91), whereas mild injury and hypoxia may preserve anti-tumor immunity mediated by CD8⁺ T cells and M1 macrophages (92).

Furthermore, several reports indicate that CSEMS may cause significantly less macroscopic and microscopic tissue damage than SEMS (34), suggesting that the degree and distribution of ischemia and inflammation may differ depending on the presence or absence of a covering.

Collectively, these findings indicate that differences in stent design—particularly the presence of a covering—may influence long-term oncological outcomes by altering the TME, and this possibility cannot be excluded.

Implications and actions needed

CSEMS should be prioritized for BTS cases requiring short-term decompression. For palliative indications requiring long-term placement, carefully considering tumor location, morphology, and prognosis is essential. Future research should involve prospective comparative trials between CSEMS and SEMS, evaluating oncological outcomes, such as local recurrence, distant metastasis, and survival. Moreover, a detailed investigation of how stent coverage influences the TME—particularly immune cell dynamics—using the immunological indicators proposed by Galon et al. (90) is essential for evaluating the oncological safety of colonic stents. Quantitative analyses correlating the use of stent material, such as covering type, metal framework design, radial and axial forces, and shear stress, with clinical outcomes will be crucial. In the European guidelines, elective surgery is recommended within 2 weeks of SEMS placement (13); however, optimal placement duration for CSEMS remains unclear, and further investigation is required (93). From an engineering perspective, next-generation biomaterials that are resistant to degradation and minimize adverse TME effects are urgently needed. Promising innovations include: (I) highly durable and biocompatible membranes; (II) smart materials responsive to tumor-specific pH or enzymes; (III) variable-stiffness stents; (IV) drug-eluting stents with anti-tumor properties (94,95); and (V) photosensitizer-embedded silicone-CSEMS (96). Finally, standardization of CSEMS placement duration, follow-up imaging, and pathological evaluation will be essential to improve oncological safety and support evidence-based utilization.

Conclusions

CSEMS provides structural benefits such as suppression of tumor ingrowth and reduction of bowel injury, with favorable outcomes, particularly in short-term use as a BTS. Nevertheless, unresolved challenges remain, including stent migration, membrane degradation, tumor overgrowth, and insufficient evidence on long-term oncological safety. At present, CSEMS can be considered a useful option for short-term BTS cases, while further research is needed to clarify long-term outcomes and to support the development of next-generation biomaterials.

Acknowledgments

We thank Editage (Cactus Communications) for English language editing.

Footnote

Reporting Checklist: The authors have completed the PRISMA-ScR reporting checklist. Available at https://ales.amegroups.com/article/view/10.21037/ales-25-41/rc

Peer Review File: Available at https://ales.amegroups.com/article/view/10.21037/ales-25-41/prf

Funding: None.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://ales.amegroups.com/article/view/10.21037/ales-25-41/coif). M.I. and T.H. report an advisory contract with SB-Kawasumi Co., Ltd. In addition, all authors reports received permission to use stent images from Taewoong Medical Co., Ltd. (Gimpo, Korea), SB Kawasumi Laboratories, Inc. (Tokyo, Japan), and M.I. Tech Co., Ltd. (Seoul, Korea; distributed by Boston Scientific Japan K.K., Tokyo, Japan). The authors have no other conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

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