According to previous studies, the success rate of ES rather than colostomy is about 28% − 41% [10, 11]. It is usually accompanied by a variety of complications and higher mortality and stoma rate, which result in the terrible quality-of-life. SEMS placement allows doctors ample time to evaluate a patient's tumor staging and avoid unnecessary surgery. It also can reduce perioperative complications and stoma. This provides the opportunity to doctors a variety of treatments, such as preoperative chemotherapy and laparoscopy for malignant colon obstruction. Contrasting previous RCT [5–7], the technical success rate was 100% and the clinical success rate was 92.86% in our study. This shows that SEMS placement needs to be done by specialized endoscopist, who need to master more techniques in stent placement. It has been found that age and site of obstruction were significantly associated with intestinal perforation [12]. Particularly in the splenic flexure of the colon, the angle of curvature of the lumen is further increased as intestinal dilatation, making it more difficult and leading to perforation at the time of stent placement. There was only 1 case in this study in which the symptoms of intestinal obstruction did not relieve after SEMS placement, and no other stent related complications occurred.
Cirocchi et al. reported that there was no advantage of SEMS placement for malignant obstruction of left-sied colon in terms of complications and postoperative mortality [13], but it can increase the primary anastomosis rate and reduce the stoma. There were no postoperative deaths in this study, which may be related to the small sample size. Consistent with the results of some RCT[7, 14–16], SEMS group was significantly better than ES group in postoperative complications, primary anastomosis rate and stoma rate, which may be related to the fact that it can improve patients' clinical condition and bowel function before elective surgery.
Laparoscopy is affected by dilation of the small intestine and the proximal colon, making it difficult to perform it for obstructive colon cancer, although it carries the advantages of shorter hospital stays, faster postoperative recovery, and easier control of the immune and inflammatory responses [17]. SEMS placement can save enough time for bowel preparation and recovery of clinical condition to allow for laparoscopy. In the present study, we found that laparoscopy was performed more frequently in the SEMS group (69.2% vs. 15.0%; P = 0.003). This is comparable to research conducted by Law [18] and Seung et al.[19], the latter chose laparoscopy technology after using SEMS.
Many studies have shown that SEMS placement does not decrease survival [7, 14–16]. However, Sabbagh et al.[20] noted that the SEMS group had a significantly worse overall survival than the ES group (25% vs. 62%, P = 0.0003). Sloothaak et al.[21] explained that SEMS placement may increase the risk of recurrence because there is a higher recurrence rate in patients with perforations. Stent-related complications are closely related to stent implantation technology, so the success rate of stent implantation is the first problem to be solved. It has also been found that SEMS placement can change perineural invasion and lymphatic invasion, and negatively affect the long-term prognosis of patients [22]. The reason may be that the compression of the tumor after the placement of SEMS and the creation of silent perforation of the intestine [5] promote the progression and metastasis of the tumor. Many studies suggest that SEMS implantation should only be performed in centre with experienced endoscopists because of the uncertainty of the impact of SEMS implantation on tumor outcome. Therefore, the impact of SEMS placement on tumor characteristics and patients' long-term outcomes still needs further investigation.
Postoperative complications are important factors affecting surgical outcomes and patients' quality of life, therefore, it is necessary to minimize postoperative complications as much as possible. Age, ASA grade and SEMS were included to construct a multivariate logistic regression equation in this study. We found that ASA grade was a risk factor for postoperative complications. So, colonic stenting allows for a more thorough and detailed preoperative evaluation to lower ASA grade and enhance anesthesia tolerance. The difference in clinical efficacy between the SEMS group and the ES group may have been achieved by lowering the ASA grade. Comply with the guidelines of the European Society for Gastrointestinal Endoscopy (ESGE): SEMS apply to patients with ASA grade ≥ III / aged > 70 years [23]. However, there was no statistical difference in the age and placement of SEMS in this study. The reason may be that small sample size limits statistical performance.
The optimal time interval from SEMS placement to elective surgery remains uncertain. We hypothesized that the clinical benefit of an optimal interval manifests in postoperative complications, then a time point or period needs to be determined such that postoperative complications are minimal. The results showed that different time intervals were not associated with postoperative complications, which was consistent with the results of a previous study [24]. The relationship between time interval and overall survival rate and recurrence rate can be further considered to find the clinical significance of the best time interval from the long-term results.
This study is limited by a small sample size retrospective study, and other statistical differences between the two groups may be omitted. This study is a non randomized trial, which may have selection bias, because some patients with more serious condition, more significant intestinal dilatation and worse general condition were selected into the ES group, resulting in worse results in the ES group.