Study design
In this retrospective cohort study, the clinical records and database of the Yokohama City University and three group facilities obtained between January 2011 and December 2019 were reviewed. As per these records, a total of 786 colon and rectosigmoid cancer patients underwent LAC. Of these, we excluded 26 patients with tumour in situ (Tis), 53 with pathological stage (pStage) IV, 276 with pStage I, nine with synchronous or multiple cancers, four with simultaneous operations of other organs, and one with preoperative chemotherapy. Finally, 417 patients who had been diagnosed with pStage ll/lll with curative effect were enrolled in this study. Through propensity score matching (PsM), we selected 98 matched patients who were further classified into two groups: patients operated on by non-qualified surgeons (NQ group, n=49) and patients operated on by qualified surgeons (Q group, n=49) (Fig. 1). In this study, qualified surgeons who only attended as an assistant, scopist, or supervisor during surgery were classified as part of the NQ group; only those qualified surgeons who performed the operation were classified as the Q group.
Examining the ESSQS
The ESSQS was assessed based on the following criteria: 1) achievements: at least two papers and three presentations on laparoscopic surgery in academic societies; 2) experience: more than 2 years of experience as a general surgeon after certification by the Japan Surgical Society, and at least 20 laparoscopic surgeries demanding advance skills (e.g. colorectal surgery and gastric surgery for cancer) or 50 laparoscopic surgeries demanding basic skills (e.g. cholecystectomy and repairment of inguinal hernia); 3) seminars: attendance at JSES official training seminars such as dry-laboratory on suturing; 4) video review: review of unedited video and score provided according to the scoring criteria by more than two expert laparoscopic surgeons designated by the JSES. For the colorectal region, sigmoidectomy and high anterior resection of rectum were considered eligible procedures.
Outcomes of interest
The primary outcome of this study was the 3-year recurrence-free survival (RFS), and the secondary outcomes were short-term outcomes such as operative time, intraoperative blood loss, extent of lymph node dissection, conversion rate, incidence of post-operative complications, and length of post-operative hospitalisation. For the measurement of post-operative surgical complications, the Clavien–Dindo classification was adapted, and incidence of grade ≥3 complications within 30 days after the operation or during hospitalisation was counted [17].
Evaluations
All reviewed and evaluated clinicopathological factors from the clinical records and database were as follows: age, sex, American Society of Anesthesiologists performance status (ASA-PS), body mass index (BMI), tumour location, preoperative carcinoembryonic antigen (CEA), carbohydrate antigen 19-9 (CA19-9), preoperative ileus, adjuvant chemotherapy, pStage, tumour diameter, histological type, lymphatic invasion, and vascular invasion. Notation of pathological findings in this study were in accordance with the Japanese Society for Cancer of the Colon and Rectum (JSCCR) guidelines (9th) [18].
Propensity score matching
One-to-one PsM was applied to all of the patient’s clinicopathological factors, as mentioned above (e.g. pathological stage [II/III], location of tumour [right-sided/left-sided], range of lymphadenectomy [D1/D2 vs. D3], preoperative ileus [yes/no], and adjuvant chemotherapy [yes/no]), to achieve control of the standardised difference under 0.15.
Operative procedure and follow-up
Ileocecal resection or right hemicolectomy was performed for caecum, ascending colon, and right to middle transverse colon cancer. Left hemicolectomy was selected for left-sided transverse colon and descending colon cancer. For sigmoid and rectosigmoid cancer, sigmoidectomy and high anterior resection were selected. In principle, a five-port setting was utilised. Complete mesocolic excision (CME) was started with the medial approach followed by central vascular ligation (CVL) with lymph node dissection (LND). The appropriate extent of CVL with LND was decided in advance by each surgical team and conference, according to the JSCCR guidelines. A lateral approach was finally added to achieve CME and complete mobilisation of the colon. Functional end-to-end anastomosis at the extra-abdominal field through a nominally extended incision of the umbilical site was selected for reconstruction of the colon. For reconstruction of the rectosigmoid, the double-stapling technique was employed. All of the procedures above were standardised in periodic meetings and were shared with the group facilities.
Medical follow-ups with computed tomography and blood tests were conducted every 6 months for more than 3 years. Colonoscopy was performed 1, 3, and 5 years after surgery.
Statistical analysis
The clinicopathological parameters were assessed by calculating the median and range, performing the t-test or Mann-Whitney U-test for continuous variables, and the proportion and chi-square test or Fisher’s exact test for discrete variables. The Kaplan-Meier method was used to estimate the RFS. Survival was compared between the two groups using the log-rank test. For statistical analyses, the authors used EZR, a graphical user interface for R version 2.13.0 (The R Foundation for Statistical Computing, Vienna, Austria), and the R software version 3.5.1. More precisely, EZR is a modified version of R commander designed to add statistical functions frequently used in biostatistics. Two-sided p-values were calculated, and p-values under 0.05 were considered to be statistically significant.