Previous studies have demonstrated the risks associated with the traditional surgical approach for treating malignant LBO, namely high rates of morbidity, mortality, and stoma formation[23,24
]. The less invasive alternative approach of colonic stent insertion, particularly of SEMS, promised to overcome the high hospitalization costs and poor quality of life related to these outcomes. While subsequent meta-analyses have been conducted to investigate the benefit and risk of endoscopic SBTS[25-28
], no study to date had performed a focused comparison of palliative SEMS and palliative surgery for treating incurable malignant LBO-as is described herein.
In the current meta-analysis, palliative surgery was found to be superior to SEMS for decompressing incurable malignant LBO; while this finding is contrary to the majority of individual studies of this subject[29-32
], it is consistent with the investigations by Cirocchi et al[28
] and Sagar[33
]. An important distinguishing feature among these collective studies is the variable definitions of palliative surgery that were used as the basis of analysis; in addition, these studies have yet to address whether and to what extent primary tumor resection affects the mean survival time of those patients suffering from advanced cancer[34,35
]. In our meta-analysis of eleven studies, the overall clinical success rate of SEMS treatment ranged from 70%-95%. A previous multicenter study[36
] of SEMS with long-term follow-up revealed that the clinical success rate increased gradually over time (87.8% at 30 d, 89.7% at 3 mo, 92.8% at 6 mo, and 96% at 12 mo). The follow-up period in our included studies are different but all within 12 mo and the clinical success rate was approximately similar. In addition, our meta-analysis revealed that obstructions caused by colorectal cancer benefited more from the surgical approach. Fernández-Esparrach et al[37
] have reported a similar finding and hypothesized that the severe complications associated with the SEMS procedure, such as migration, obstruction and perforation, limited its long-term clinical efficacy. Moreover, the authors advised that adjunct palliative chemotherapy may help to promote the life expectancy of SEMS-treated patients. A retrospective study conducted in Korean patients advanced gastric cancer[38
] also indicated that SEMS insertion was less effective than emergency surgery for the palliative treatment for colorectal obstructions. In light of these previous findings, and in agreement with the opinions expressed by other interested groups in this field[39,40
], it is possible that the clinical stent success rate observed in our current meta-analysis had nothing to do with the stent placement or the etiology of the obstructions. Indeed, Sebastian et al[31
] suggested that the clinical success rate of stenting is mainly associated with the site and extent of the obstruction.
Our meta-analysis also indicated that SEMS treatment is associated with shorter lengths of hospital stay, reduced ICU admissions, fewer stoma formation, and shorter time to initiation of adjunct chemotherapy; These findings are consistent with results from other relevant studies[30,32,33,41
] and suggest that the less trauma endured produced by the SEMS approach eliminates delay of post-procedure chemotherapy, thereby promoting beneficial patient outcome. It was unfortunate that the current meta-analysis was limited by a lack of comparative data concerning quality of life outcome and cost-effectiveness between these two palliative treatments; analysis of such data will be necessary for comprehensively assessing the feasibility of these palliative management approaches for advanced disease. Only one of the studies included in the meta-analysis, a RCT[20
] comprised of 30 patients, attempted to address the monetary expense of stent placement, as compared to colostomy treatment; however, the analysis was abandoned due to the high rate of colonic perforation that occurred in the nonsurgical arm. However, some studies[32,42
] that did not meet the criteria for inclusion in our meta-analysis have suggested that SEMS may be less costly than the conventional surgical approach for treating colonic cancer obstructions; but, we cannot comment on the quality or appropriateness of these data or the implications related to our findings.
The safety of stent placement was also evaluated in the current meta-analysis. Although SEMS insertion is considered a less invasive method than surgery, and advanced procedure-related devices, such as hydrophilic elastic guidewires and stent delivery systems, have improved the ease and successful application of this method, complications still occur. Fortunately, the majority of complications are minor, such as low fever and abdominal discomfort, and resolved easily by medication. While less frequent, the major complications of the stent procedure, such as bleeding, colonic perforation, stent migration and stent occlusion, can be life-threatening[43
]. In a systematic review[30
] of 88 articles reporting on stent-related complications in cases of LBO, the median rates of stent migration, perforation, and reconstruction were reported as 11%, 4.5% and 12%, respectively. In the current meta-analysis, the rates of perforation and reconstruction were slightly higher; we believe this finding reflects the fact that data on perforations caused by tumor infiltration were included in the analysis and that the data on reconstructions included not only the etiologies of tumor ingrowth/overgrowth and stent migration, but also of fecal implant.
The contributing factors to complications of stent insertion have been extensively studied. Factors related to stent type have been particularly well studied, and it is believed that covered stents provide the optimal resistance to tumor ingrowth, thereby helping to reduce reconstruction events, while uncovered stents are believed to minimize stent migration[30,39,44
]. The type of stent, however, does not appear to be related to perforation events[30
], nor to have a significant effect on the safety of stent placement[45
]. Furthermore, a retrospective analysis of uncovered SEMS for treating primary colorectal cancer vs
non-colorectal extrinsic cancer found no significant difference in migration or occlusion events[46
]. That study also suggested that insufficient stent expansion (< 70%) at 48 h after insertion may be a predictor of subsequent stent occlusion. Another retrospective analysis of 168 SEMS-treated LBO patients[47
] identified five risk factors of therapeutic inefficacy, including male sex, complete obstruction, stent diameter ≤ 22 cm, premature dilation of the stent, and operators’ experience. In addition, subsequent chemotherapy, especially Bevacizumab therapy, was demonstrated to nearly triple the risk of perforation. This latter finding was not supported by the study by Kim et al[39
], who demonstrated that chemotherapy had no affect on migration or reconstruction and that stent length had no relationship with complications, but showed that stent diameter < 24 cm had negative impact on palliative SEMS migration. In another study, stent migration was shown to occur more frequently in the distal colon[31
Despite significant improvements in the surgical procedures used for managing incurable malignant colorectal obstructions, the perioperative morbidity and mortality rates have remained high. Similarly, the patients treated with surgery in the current meta-analysis experienced appreciable levels of anastomotic dehiscence, wound infection, and death. The former two complications may have a negative influence on tumor recurrence, metastasis, and long-term survival. In the current meta-analysis, a greater number of surgery-treated patients died within 30 d after treatment, as compared to those treated with SEMS. While this result is contrary to those obtained with other similar patient series[30,33
] and meta-analyses comparing SBTS[25-28
], it may be explained by the lower amount of total complications that were experienced by the overall SEMS-treated group. Another study also found significantly lower complications in a stent-treated group, but we cannot comment on the related implications for our findings as the previous data had significant heterogeneity[25
]. In an attempt to address this issue, we performed sub-group analysis of the complications, independently assessing the early- and late-onset complications; the results indicated that surgery had a higher risk of early complications, while SEMS insertion had a higher risk of late complications. Future studies should further investigate the roles of early and late complications in therapeutic efficacy and overall survival.
Two of the studies[13,20
] included in the overall meta-analysis were excluded from the focused comparison of SEMS and surgery outcomes for incurable colorectal-related obstructions. The results were not impacted by their removal and were in accordance with the findings reported by Kim et al[40
]. Then, we investigated the comparison between SEMS and colostomy for incurable malignant LBO (using four studies). Unlike the previous results, these results suggested that, compared to colostomy, SEMS could be an effective palliative treatment for incurable malignant LBO; no significant difference was found for the clinical success rates between groups with fewer stoma, but the 30-d mortality and the complications should be taken into account. Unfortunately, the current meta-analysis was underpowered to investigate the differences in overall survival time between these two groups.
Other limitations of our meta-analysis design may have impacted our results and their interpretation. First, only three of the 13 included studies are RCTs. Second, the pooled sample size was still relatively small and the data from the included studies was not uniform for the outcome measures. Third, publication bias existed among four of the studies; indeed, a general limitation of all meta-analyses is publication bias introduced by the fact that positive results are more likely to be published. To overcome these limitations, long-term RCTs should be conducted with large numbers of patients to achieve a sufficient level of statistical power for accurately estimating the optimal palliative treatment for incurable malignant LBO.
In summary, palliative SEMS does not appear to have a significant advantage over palliative surgery for decompressing incurable malignant colorectal obstructions, regardless of etiology; however, the use of colonic stents is safe. The shorter interval to chemotherapy and significantly lower rates of 30-d mortality and short-term complications suggest that SEMS may be a reasonable alternative for treating patients with extensive metastatic disease or who are poor operative candidates due to severe comorbid medical illnesses.