Colorectal cancer associated with genetic mutations has become one of the most common malignancies (1). Its primary treatment is to remove the malignant tumor surgically. In 1991, Jacobs M et al. (2) tried applying the laparoscopic technique for resecting colon cancer. After 30 years of development, laparoscopic colorectal cancer resection has now become the preferred surgical procedure. Furthermore, modified laparoscopic surgical approaches, such as single-incision laparoscopic surgery (3) (SILS), natural orifice endoscopic surgery (4) (NOTES), etc. are also flourishing. Temporarily, SILS cannot be promoted on a large scale in clinical practice because of its difficulty, long learning curve, interference among surgical instruments, and linear view of the laparoscope (5). Therefore, the two-port laparoscopic surgery (TLS), which added an operating trocar to the SILS, was introduced (6). The TLS reconstructs the surgical triangle. The interference between the surgical instruments and the difficulty of surgery is lesser than that of SILS. Additionally, the learning curve of TLS is shorter, and it has the advantage of being minimally invasive. However, the safety and efficacy of TLS still lack a large body of medical evidence (7). This study aimed to investigate the safety and efficacy of TLS in sigmoid colon and upper rectal cancer resection.

(1) Surgical outcomes: total operation time, blood loss, auxiliary incision length, the total length of incision, time to first ambulation, time to first ambulation, time to first flatus, time to first defecation, time for a liquid diet, days of drainage tube removal, postoperative complications (anastomotic leakages, anastomotic bleeding, incision infection, lymphatic leak, intestinal obstruction, lung infection, etc.), days of hospitalization after surgery (2) Pathologic outcomes: pathologic TNM stage, depth of tumor invasion (T-stage), distal resection margin (DRM), proximal resection margin (PRM), harvested number of lymph nodes, etc.

The SPSS 21.0 software was used. The count data were described by frequencies or percentages. They were compared and analyzed by using the chi-square test. Fisher’s exact probability method was used for theoretical frequencies < 1. The measurement data were described by the sample mean ± standard deviation ( x ¯ ± s) and compared and analyzed by using the paired-sample t-test. P < 0.05 was considered a statistically significant difference.

The differences in the baseline clinical characteristics between the two groups were not statistically significant (P > 0.05) ( Table 1 ). In terms of total operative time and blood loss in both groups, there were no statistically significant differences in the data between the two groups (P > 0.05). In terms of auxiliary incision length, no statistically significant difference was noted between the TLS (4.88 ± 0.64 cm) and the CLS groups (5.14 ± 1.01 cm), P = 0.243. However, for the total incision length (TLS: 6.21 ± 0.67 cm CLS: 8.64 ± 1.08 cm), time to first ambulation (TLS: 2.0 ± 0.7 d CLS: 3.1 ± 0.9 d), time to first flatus (TLS: 2.5 ± 0.8 d CLS: 3.0 ± 0.8 d), time to first defecation (TLS: 3.8 ± 1.3 d CLS: 5.1 ± 2.1 d), and the time for liquid diet (TLS: 4.3 ± 1.4 d CLS: 5.3 ± 1.9 d); the differences were statistically significant (P < 0.05). For days of drainage tube removal, postoperative complications, and postoperative hospital days, the differences were not statistically significant (P > 0.05). There were no statistically significant differences between the two groups in terms of tumor diameter, pathological TNM stage, depth of tumor infiltration (T-stage), proximal resection margin, distal resection margin, and harvested number of lymph nodes (P > 0.05); The surgical and pathological outcomes are presented in Tables 2 , 3 .

Since its introduction in 2012, TLS has received a lot of attention from scholars. Also, several large clinical research centers have started relevant clinical studies and published some of their research results (8, 9). Some clinical research centers have applied TLS for gastric cancer (10), right hemicolectomy, left hemicolectomy, sigmoid colon cancer, rectal cancer, and other sites. Typically, only the inferior mesenteric artery and vein need to be ligated for lymph node dissection in patients with cancer of the sigmoid colon and upper rectum; moreover, no splenic flexion mobilization is required, and satisfactory distal resection margins can be obtained without excessive mobilization of the rectum outside the peritoneum reflection. As a result, the surgical procedure is easier to learn. For now, our center only performs TLS surgery in sigmoid colon and upper rectal cancers.

The clinical experience of some clinical research centers revealed that elderly and obesity are independent risk factor for postoperative complications of laparoscopic radical resection of right-sided hemicolon cancer after complete mesocolic excision (CME) (11). And tumor diameter were independent predictors of operative time in laparoscopic anterior resection for rectal cancer (12). Therefore, TLS surgery was performed in patients with BMI ≤ 30 kg/m², tumor diameter < 5 cm, and preoperative evaluation of T4b or less (13). However, our study revealed that in two-port laparoscopic resection of the sigmoid colon and upper rectal cancer, excessive omental and mesenteric hypertrophy and deep tumor infiltration indeed caused excessive interference with the anatomical level recognition and the surgical plane development due to excessive BMI. This made the surgical progress slow or even required the usage of an additional trocar. The increase in tumor weight due to excessive tumor size also interfered with surgery considerably. However, this interference can be solved to a certain extent with the increase in the operator’s experience. At our center, a patient with preoperative enhanced CT suggesting a tumor size of about 8 cm, tumor infiltration depth of T4a, and BMI of 20.2 kg/m² with a recto-sigmoid junction tumor was successfully treated with TLS without using an additional trocar adjuvant. However, the operating time for this patient increased correspondingly. At our center, the average total operation time for sigmoid colon and upper rectal cancer was 173.8 min, but the total operation time for this patient was 240 min. Since then, our center also operated on four patients with a tumor diameter of > 5 cm, whose BMI were 18.8 kg/m², 20.9 kg/m², 22.7 kg/m², and 25.2 kg/m², and the depth of tumor infiltration was below T4b. Therefore, our center considers that in patients with relatively small or moderate BMI, whose omental and mesenteric adipose tissues cause a decreased impact on surgery, and with experienced surgeons, the indication of tumor diameter can be moderately relaxed for selected patients. However, whether prolonged operative time due to the enlarged tumor has an impact on the patient’s postoperative recovery needs further exploration.

There is enormous evidence suggesting that laparoscopic colorectal cancer resection is feasible, with adequate surgical quality and faster postoperative recovery, more aesthetic incisions, etc. (14) The operative time is an important indicator of the difficulty of laparoscopic surgery (15). For example, Kang et al. (16) reported that the average operation time of 93 single-port laparoscopic and 88 conventional laparoscopic colorectal cancer surgeries were 189 min and 170 min, respectively. Watanabe (17) et al. reported that the average operation time for 100 colorectal cancer procedures was 156 min and 162 min for SILS and CLS, respectively. In these two clinical studies, there was no statistically significant difference between single-incision laparoscopic colorectal cancer surgery and conventional laparoscopic colorectal cancer surgery in terms of the average operation time (P > 0.05). Z J Wu et al. (18) retrospectively analyzed 30 patients who underwent two-port laparoscopic sigmoid colon and upper rectal cancer with an average operation time of 125 min. Wang Y et al (8) showed that the average intraperitoneal operation time was 66.2 ± 26.9 min for TLS and 76.3 ± 28.2 min for CLS. Although there was no statistically significant difference between the two groups, the intracavitary operation time was slightly shorter in the TLS than in the CLS. Studies have confirmed that the familiarity among laparoscopic team members will influence the procedure time (19), Poorly coordinated surgical assistants can even cause unnecessary disruptions to the operation.Thus, compared to CLS, the role of a surgical assistant in the TLS can be replaced by the experienced left hand of the surgeon in suitable conditions and even reduce the operation time.

Surgical safety, which was the focus of this study, was measured mainly by intraoperative and postoperative complications and postoperative tumour morbidity and mortality. With regard to intraoperative blood loss, some studies have indicated a significant increase in blood loss in the CLS group, mainly due to the loss of the inferior epigastric artery in one case resulting in increased blood loss (8). However, in our study, there was no significant difference in intraoperative blood loss between the two in TLS and CLS. In terms of postoperative complications, it has been suggested that the use of more trocars may increase the likelihood of trocar-related complications such as bleeding and herniation (20), but this did not occur in any patient in our study (trocar hernia). In our study, two patients in the CLS group had third-grade complications, one anastomotic leakages. and one anastomotic bleeding, and none of these occurred in the TLS group. However, there was no difference in the total number of complications between the two groups, similar to the findings of most studies (21–25). Therefore, the safety of TLS in the perioperative period was comparable to that of CLS. However, whether there is a difference in postoperative tumour morbidity and mortality needs to be confirmed by further follow-up data.

Although the extent of surgical resection and lymph node dissection was the same between the two groups, when we analysed the patients’ postoperative recovery, we found that in the TLS group, Time to first ambulation (days), Time to first flatus (days), Time to first defecation (days) Time for liquid diet (days) were all shorter than in the CLS group, and the differences were statistically significant. Postoperative recovery was better in the TLS group than in the CLS. Moreover, some studies have shown that CLS has a higher VAS (Visual analogue scale) score at POD3 (POD: postoperative day) than TLS (26); we speculate that this may be due to the fact that TLS used fewer trocars resulting in a faster postoperative recovery, but the exact reason for this remains to be further verified.

For the cosmetic results, we measured the total length of the trocar needle and incision. The difference in auxiliary incision length was not statistically different, but the total incision length was less in the TLS group than in the CLS group.

Our study has several limitations.firstly, this study is a single-centre study with a limited number of cases, which still needs to be validated with a larger sample size and multi-centre data; secondly, this study is a retrospective study with potential confounding factors, which needs to be further explored in prospective studies; lastly, this study focuses on collecting and analysing preoperative and intraoperative relevant indexes, and there is a lack of postoperative follow up of long-term tumour outcomes in both groups,which is also an area that our team needs to improve and study later.

In summary, in sigmoid colon and upper rectal cancer resection, the TLS retained the aesthetic incision and other advantages of SILS, reconstructed the surgical triangle, solved the problem of conflicting main operating instruments, and reduced its surgical difficulty. In addition, it also resulted in smaller and more aesthetic incisions, lesser trauma, and faster postoperative recovery than CLS. This is in consistent with the conclusions of other scholars (14). It was superior to CLS in terms of short-term postoperative efficacy. And our center considers that in patients with relatively small or moderate BMI, and with experienced surgeons, the indication of tumor diameter can be moderately relaxed for selected patients in TLS.

(I) Conception and design: XL, FJia; (II) Administrative support: XL; (III) Provision of study materials or patients: XL; (IV) Collection and assembly of data: MJ, FJin; (V) Data analysis and interpretation: MJ, FJia, JL; (VI) Manuscript writing: All authors; (VII) Final approval of manuscript: All authors.