The present study compared the short- and long-term outcomes of SILS for sigmoid and rectosigmoid cancer with D3 lymphadenectomy with or without LCA preservation using PSM. The two groups had similar OS, DFS, and CSS. Short-term results suggested that the operative time was slightly longer in group A than in group B, but there were no significant differences in complications or blood loss. The present study showed that the CSS rates in groups A and B were 90.4% and 88.4%, respectively, which were comparable to the OS reported in the JCOG0404 trial [5]. The DFS rates in groups A and B were 83.3% and 82%, respectively, which were comparable with the DFS rate of the JCOG0404 trial [5].
Some previous studies reported that high IMA ligation for rectal cancer does not improve the long-term outcomes compared with low IMA ligation [2–4]. Other studies reported that LCA preservation in sigmoid colon cancer surgery contributes to a decrease in anastomosis leakage but does not affect the long-term outcomes [10, 11]. LCA preservation maintains adequate blood supply to the colon proximal to the anastomosis, whereas ligation of the IMA root means that vascularization of the distal colon and sigmoid depends completely on the middle colic and marginal arteries. Therefore, if a patient develops transverse colon cancer after undergoing surgery for sigmoid colon and rectal cancer, the blood flow in the distal colon can be expected to be maintained if the LCA is preserved. However, the disadvantage of LCA preservation is the possibility of spillage of micrometastatic cells because of skeletonization of the LCA and the need for a more complicated procedure with a longer operative time than surgery without LCA preservation [12]. In our study, although the operative time was 30 minutes longer in group A than in group B, the two groups had a similar number of lymph nodes removed, blood loss volume, and incidences of intra- and postoperative complications; these findings suggest that D3 lymphadenectomy with LCA preservation is a safe surgical procedure.
SILS for colorectal diseases was reported in 2008 [13, 14], and the short-term results are reportedly similar to single-incision laparoscopic colectomy and conventional laparoscopic colectomy [15]. A recent randomized controlled trial showed that SILS achieves similar long-term outcomes to conventional laparoscopic surgery [16]. Furthermore, SILS reportedly achieves a better cosmetic effect and less postoperative pain than conventional multiport laparoscopic surgery for ascending colon cancer, sigmoid colon cancer, and rectosigmoid cancer [17]. Although right hemicolectomy requires a lot of vascular treatment, SILS reportedly has a shorter operative time than conventional laparoscopic surgery [18,19]. Therefore, it seems that even complicated procedures such as LCA preservation can be performed via SILS.
The present study has some limitations. First, this was a retrospective single-centre study with a small sample size. Second, the learning curve of surgical techniques was not considered. Third, there was bias in the indication for SILS. Group A tended to include younger patients than group B owing to the increased likelihood of new colorectal cancer after surgery in younger patients. Group A was significantly younger before PSM, and the ASA score was significantly higher in group A than in group B even after PSM. Group A also tended to have a higher rate of postoperative adjuvant chemotherapy than group B (56.7% vs. 40%), although this difference was not statistically significant. These intergroup differences may have affected the long-term outcomes.
In conclusion, LCA preservation is safe and feasible in SILS for sigmoid colon and rectosigmoid cancer, with a slight increase in operative time in group A than in group B, but no significant intergroup differences in short- and long-term outcomes.