During the past decades, large-scale randomized controlled trials have demonstrated the minimal invasiveness and oncological efficacy of laparoscopic surgery for colorectal cancer(1–3, 6, 7, 9, 27). Based on which, new operative modalities such as SILS and natural orifice transluminal endoscopic surgery (NOTES) have been introduced to minimize the invasiveness. However, SILS and NOTES remained undeveloped, mainly due to the challenging techniques, lack of triangular extraction, overlapping views and requirements of new surgical instruments. Though some surgeons reported satisfactory results of SILS for colorectal cancers, these studies included limited number of cases(11, 28, 29). Especially, in some studies, authors argued that for distal sigmoid colon cancer or rectal cancer, during SILS anterior resection, it’s difficult to apply linear stapler at the right angle, which may lead to the elevated risk of anastomotic leakage or inadequate distal resection margin(30). Thus, SILS + 1 with an additional port was attempted to overcome the above obstacles. These authors reported SILS + 1 as a safe and feasible procedure(16, 17, 31).
This study was conducted based on our previous experience on SILS + 1 with one surgeon and one camera operator for rectosigmoid cancers(22, 23). After the successful application of SILS + 1 for rectosigmoid cancer, we subsequently expanded the indication to all selected colorectal cancers locating from the ileocecal valve to upper rectum. To consolidate the short-term and long-term outcomes of SILS + 1 for colorectal cancer, this comparative study using propensity-score-matching was designed. Our results support that SILS + 1 was equally safe, feasible and oncologically efficient with CLS for the treatment of colorectal cancer. Meanwhile, advantages including reduced operating time, less blood loss, better cosmesis, less pain and faster recovery was demonstrated with SILS + 1.
In this study, the completion rate of SILS + 1 was 95.8%. Among the conversion cases, 10 patients required additional trocar(s) during surgery, with the reason of late staged tumor invading adjacent structures in five patients, two patients had low rectal cancer and narrow pelvis, severe adhesion occurred in the other three patients. Conversion to open surgery occurred in one case due to accidental injury to the Henle’s trunk. The conversion rate of SILS + 1 was comparable to those reported in literatures of 3.5%-7.5%(30), and was comparable to 9.8% in our previous prospective study(23). The high success rate of finishing SILS + 1 could suggest that SILS + 1 for colorectal cancer was feasible in clinical practice. Pathologically, the similarity in number of harvested lymph nodes, proximal and distal resection margins showed that SILS + 1 did not compromise the surgical principles with CLS.
Operating time is another key parameter suggesting the feasibility of a surgical procedure. Though controversy existed in operating time between reduced-port laparoscopic surgeries comparing with CLS, in Lim’s report, operating time was longer in reduced-port group (255.5min vs. 144.6min, p༜0.001)(17). However, in many other studies, authors found that operating time was significantly shorter in reduced-port group(19, 21, 32). Many author contributed the reduced operating time to the smaller tumor size, relatively earlier tumor stage and difference in surgery types(19, 21). But in this study, the tumor size, tumor staging and tumor location were balanced through propensity-score-matching, still operating time was significantly shorter in SILS + 1 group. The result was repeated again after our previous findings(22, 23). The explanation was the hypothesis that SILS + 1 minimized the role of the assistant. Jung speculated that the camera view for the assistant during CLS was mirror image, movements of instruments could sometimes confuse the unskilled assistant, causing involuntary injuries when handling tissues and thus, prolonged operating time(33). Whereas, in SILS + 1, the procedure was entirely coordinated and conducted by the highly experienced primary surgeon, thus avoiding the dangerous situations caused by unskilled assistants, which would potentially decrease the operating time. The operating time in this study was 131.8 ± 43.4 min in SILS + 1 group, which was similar to other reported reduced-port laparoscopic surgeries(32–34).
Surgical safety, measured mainly by intra- and postoperative complications, was one of the primary concerns of this study. The total complication rate was 8.1% in SILS + 1 group and 12.2% in CLS group, which was comparable to other studies(4, 9, 16, 17, 19, 21, 32, 35). There was no significant difference observed in either intra- or postoperative complications between the groups. Neither significant difference existed in CD classification categories. When analyzing through uni- and multivariate analyses for risk factors concerning complication, SILS + 1 was not identified as a risk factor. All the above suggested the non-inferiority of SILS + 1 to CLS in surgical safety. Moreover, as we looked into the grade III complication cases, we found that more patients received re-operation in CLS group. The reason might be that SILS + 1 reduced the inflammation and surgical stress response after surgery than CLS. Once complications occurred, patients underwent SILS + 1 might tend to experience milder infection than CLS, which could promote the possibility of successfulness in conservative treatment(23, 36).
During recovery, time to ambulation, first flatus, first defecation, oral intake recovery and hospital stay was significantly shorter in SILS + 1 group in this study, which was repeatedly demonstrated by other reduced-port surgery studies(19–21, 33). For postoperative pain assessment, when analyzing with VAS, we found that on POD 3 and 4, the VAS was significantly lower in SILS + 1 group, which was also observed in Song’s report and our previous studies(19, 22, 23). We believed that the three additional 5-mm trocar incisions in CLS group not only augmented the total incision lengths, but also significantly up-regulated the painful feeling when we encouraged the patients to increase ambulation on POD 3–4. Though we used identical recovery pathway for all patients, we thought that the less pain in SILS + 1 group contributed to the earlier ambulation and eventually, resulted in faster recovery of bowel movement.
To ascertain the oncologic efficacy of SILS + 1 compared with CLS for colorectal cancer, in our study, the 3-year disease-free survival rates of SILS + 1 and CLS group were 90.1% and 87.3%, and the 3-year overall survival rates were 93.3% and 89.8% (p = 0.172). Though there were studies focusing on SILS or SILS + 1 laparoscopic surgeries, limited long-term oncologic outcomes were provided(14, 30, 37, 38). In Kim’s study the 3-year overall and disease-free survival rate for single-incision laparoscopic surgery for sigmoid colon cancer were 94.5% and 89.5% (38). Also, in Hirano, Y’s analyses on SILS + 1 for rectal cancer, at a median follow-up period of 30 months, 94.3% patients enrolled had no tumor recurrence(30). Considering that the majority of patients enrolled in our study was stage III tumors (38.8% in SILS + 1 group), and we also included right-sided colon cancer in the analyses, our 3-year oncologic results of SILS + 1 group was comparable to these reports. Meanwhile, the oncologic results of CLS group showed better survival rates than COLOR and COLOR II trials(7, 39), Suggesting that in our study, the oncologic principles for either SILS + 1 or CLS was assured. Since there was no significant difference between the two groups in terms of 3-year oncologic survivals, the comparable oncologic outcomes of SILS + 1 with CLS could be well demonstrated.
Several limitations of our study should be noted: first, although we prospectively collected the data, and conducted propensity-score-matching to minimize the selection bias, and promote the homogeneity of the study, the retrospective nature of the study introduced inherent bias. Second, the study was only carried out in one institution. Additionally, cosmetic outcomes and patient satisfaction of cosmetic effects were not compared in the study, though we believed that the major concern for colorectal cancer patients was not cosmesis. Thus, well-designed multi-center large-scale prospective randomized controlled trials are still needed to further establish the benefits of SILS + 1 in colorectal cancer.