Since Heald et al. proposed total mesorectal excision in 1982, the clinical outcomes of middle and low rectal cancer have significantly improved [14, 15]. This improvement is mainly due to reduced local recurrence [16]; however, anastomotic leakage is still an important factor affecting the short and long-term postoperative outcomes of rectal cancer, in addition to increasing the total cost of treatment [17-19]. It has been reported that the incidence of anastomotic leakage after rectal cancer surgery is between 5–26% [20, 21]. To date, no consensus has been reached on whether LCA preservation during rectal cancer surgery can reduce anastomosis-related complications and improve long-term prognosis [9, 22].
Excessive anastomotic tension and poor blood supply are important factors for anastomotic leakage [23]. High ligation of the IMA, at its aortic origin, allows a 9 cm gain of length over low ligation [24]. However, after high ligation, the proximal colon can only supply blood from the middle colic artery (a branch of the superior mesenteric artery), reducing blood perfusion of the marginal arterial arch, and disrupting the blood supply to the terminal colon [25].
Anastomotic leakage is one of the most common serious complications of rectal cancer surgery. There are many factors affecting anastomotic leakage including: the patient's age, BMI, distance between the tumor and the anal border, anastomotic blood supply, and anastomotic tension [26]. The results of our study showed that anastomotic leakage occurred in 19 (8.6%) patients in the LL group and in 39 (13.2%) patients in the HL group. This difference was not statistically significant. Moreover, there were no statistically significant differences in anastomotic bleeding and anastomotic stenosis between the two groups. However, Meta-analyses [7], containing 17 studies with 6,247 patients, showed that preserving the LCA was associated with reduced anastomotic leakage rate (odds ratio = 0.78, 95% confidence interval (CI): 0.62–0.98, P = 0.03). Our study may not have shown this as it was retrospective, only ISREC grade B or C anastomotic leaks could be traced back and analyzed.
Intraoperative parameters and postoperative complication rates are important indices for demonstrating the quality control of a surgical procedure. A randomized controlled trial showed that LCA preservation did not increase the surgical duration of low anterior resection for rectal cancer [11]; however, our study revealed that the mean operating time of the LL group was significantly longer than that of the HL group. This could be due to the higher rate of splenic flexure mobilization in the LL group, prolonging the operative time for the whole group (13.1% in the LL group vs 6.1% in the HL group, P = 0.006). Despite the prolonged operation time in the LL group, there was no significant difference in operative bleeding between the two groups. Over 85% of the procedures were laparoscopic surgeries, with only a 2.1% conversion from laparoscopic to open surgery. After passing the laparoscopic learning curve, intraoperative bleeding does not increase significantly as the surgical area expands [27].
IMA root lymph nodes are the third station of lymphatic drainage in rectal cancer and the most important route of metastasis in progressive rectal cancer [28]. Studies have shown that IMA root lymph node metastases have a negative impact on patients' 5-year survival and tumor recurrence rates [29]. In our study, the differences between the number of lymph nodes harvested and the number of positive lymph nodes were not statistically significant between the two groups, suggesting that the surgical approach of preserving the LCA, i.e., IMA low level ligation, does not reduce the detection and positivity rate of lymph nodes.
Regarding the long-term outcomes in patients, survival analysis showed that low anterior resection for rectal cancer with or without LCA preservation showed no statistically significant difference in the 5-year OS and DFS (LL group vs. HL group: 69.6% vs. 60.1% and 59.6% vs. 56.2%, respectively). Further analysis of stage-by-stage OS and DFS in stage I to stage III cases showed no statistically significant difference between LL group and HL group. Several previous studies have also shown that LCA preservation compared to non-preservation showed no significant differences with respect to the 5-year mortality in patients who underwent laparoscopic rectal cancer surgery, and this comparable success came with acceptable safety outcomes [7-9]. Data from the Japan Clinical Oncology Group Study showed that if the LCA was preserved, 5-year relapse-free survival (RFS) and OS were better than in the LCA non-preservation group (RFS: 83.7% and 80.5%, hazard ratio (HR) = 0.80, 95% CI: 0.51–1.26, OS: 96.3% and 91.1%, HR = 0.41, 95% CI: 0.19–0.89) [30]. Another Japanese study by Fujii [12] showed that the IMA ligation level was unrelated to anastomotic leakage and there was no significant difference in the long-term results between low and high ligation of the IMA. Recent meta-analyses support this finding [7, 10]. However, one meta-analysis, which included 3,119 patients in five cohorts, pooled HR results showing a significant OS benefit of high ligation over low ligation (HR = 0.77, 95% CI: 0.66–0.89) [31].
Our study has certain limitations. Firstly, this is a single-institution retrospective study. Secondly, 119 cases’ data from 635 were incomplete. Thirdly, choice of surgical procedure could vary between surgeons thus leading to bias in our results. Finally, there may be differences in the standards of neoadjuvant and adjuvant chemotherapies between western countries and China, which could result in diverse outcomes among patients from different countries.