This study is a multicenter trial that analyzed retrospective data from three hospitals with considerable follow-up periods where both BTS and ES were available. The results of this observational study suggest that SEMS placement as BTS in patients with AMLCO was associated with fewer primary stoma creation, higher total in-hospital cost and more perineural invasion. Patients in the BTS group had a higher recurrence rate, a poorer 3-year and 5-year overall survival, which is closely correlated with surgical adverse effects and pTNM stage.
Successful placement of the stent relies on the severity of colonic obstruction and expertise of the endoscopist. The technical (89.8%) and clinical success (85.7%) rates in this study were similar to previous studies (84.2–100% and 78.9–100%, respectively)[18]. Established short-term advantages of bridged surgery include less temporary and permanent stoma creation, as analyzed in many meta-analysis[18, 19]. Our study confirmed that BTS significantly increased the use of laparoscopy and decreased stoma creation.
However, recent studies have failed to show beneficial effects of stenting as BTS over emergency surgery, due to uncertainty of its impact on long-term oncological outcomes[20, 21]. This originates from concerns about tumor manipulation during stent insertion, guidewire perforations during stent placement[22], stent deployment force and eventual micro-perforations at the proximal and distal ends of the stent[23], which may induce tumor cell dissemination locally, but also in the blood stream[14]. In our study, we found patients with BTS had a higher chance of perineural invasion, similar to Kim’s findings[24]. In a multivariate analysis by Leibig et al.[25], perineural invasion was thought to be an independent prognostic factors of oncological outcomes in colorectal cancer. In our analysis, perineural invasion was significantly associated with overall survival of propensity score matched patients by univariate survival analysis (data not shown). However, the correlation was not significant in multivariate analysis. Long-term large-scale studies are needed to better investigate the correlation of perineural invasion and oncological outcomes. Stent insertion was associated with more total recurrence in this study, although the difference was not significant in regional or distant recurrence alone. Similar to the findings in our study, a recent meta-analysis[26] of 7 randomized controlled trials demonstrated that BTS significantly increase the risk of recurrence, especially distant recurrence.
To date, very few studies report on long-term survival after SEMS placement as a BTS, due to a scarcity of clinical data and the lack of comparable studies. Femke et al.[19] found that SEMS placement as BTS did not influence 3-year and 5-year overall survival in a meta-analysis, similar to Sun’s findings[13], which suggest colonic stenting did not affect 5- and 10- year survival, although the study population is relatively small and an accurate conclusion cannot be drawn. However, in Kim’s study[27], SEMS placement could negatively affected 5-year overall survival and disease-free survival (DFS) in stage II and III CRCs(5-year OS: 44% after SEMS versus 87% after elective surgery for non-obstructing CRC). Sabbagh et al.[21] also found that 5-year overall survival was significantly lower in the BTS group, while 5-year cancer-specific mortality was significantly higher (48% vs 21%, p = 0.02), although there were no significant differences in terms of 5-year DFS. In our study, we found 3-year and 5-year overall survival were significantly lower in patients who underwent SEMS as BTS compared to those underwent ES.
Colonic stent insertion also affects patient survival in multi-aspects. Avlund et al performed a 10-year follow-up study and concluded an association between SEMS-related perforations and decreased survival[28]. The interval from SEMS to resection surgery was thought to delay the surgery and increase the rate of recurrence and survival in the study by Broholm[20], although further larger study is needed to confirm the results. Postoperative adverse effects, especially infectious complications, were associated with poorer survival in patients after colorectal cancer resection[29]. SEMS insertion was also reported to be associated with increased perineural invasion[30], which is a known prognostic factor in CRCs and correlates with the findings in our study. Many clinical factors could influence the prognosis of obstructing CRCs and overall survival. An analysis by Rodrigues et al. suggests pTMN stage IV, number of lymph nodes harvested, adjuvant therapy and surgery-related complications could influence overall survival[2]. In our study, stenting along with surgical adverse effects and pTNM stage were associated with overall survival by multivariate analysis of propensity score matched patients.
The present study had several limitations. First, its retrospective nature may bring a selection bias and affect the results. Second, because the population after propensity score matching was relatively small, analysis of some variables showed a wide range. The effect of SEMS as BTS should be cautiously interpreted. Third, although the medical records were carefully reviewed and follow-up studies were thoroughly carried out, the causes of death were difficult to confirm in some cases and the disease-free survival was lacking. Strengths of our studies are the homogeneity between groups, due to the use of PSM analysis, and long follow-up period.
In conclusion, SEMS placement was associated with a high technical and clinical success, similarly to ES, as demonstrated by the higher primary anastomosis rate and lower stoma rates, with its possible positive effects on quality of life. However, SEMS placement as a BTS, compared to ES, leads to more perineural invasion, higher recurrence rate and worse long-term overall survival. These results suggest SEMS placement should not be routinely performed in patients with potentially cured AMLCOs.