Clinical outcome of laparoscopic vs open right hemicolectomy for colon cancer: A propensity score matching analysis of the Japanese National Clinical Database

Abstract Aim The advantages of laparoscopic right hemicolectomy over open surgery for colon cancer in general clinical practice are debated, as evidenced by the continued use of open surgery in a significant proportion of patients worldwide. This study aimed to assess and compare the clinical outcome of laparoscopic and open right hemicolectomy for colon cancer using data from the Japanese National Clinical Database. Methods A total of 72 299 patients who underwent laparoscopic (n = 46 084) and open (n = 26 215) right hemicolectomy for colon cancer between 2014 and 2018 were enrolled in this retrospective study. Short‐term outcome was compared between groups using propensity score matching analysis. Results The incidence of overall postoperative morbidity ≥ Clavien‐Dindo classification grade 3 was significantly higher in the open surgery group than the laparoscopic group (4.7% vs 3.2%, P < .001). The incidence of most individual morbidities, including surgical site infection, anastomotic leakage, and ileus, was higher in the open surgery group. Short‐term outcomes, including intraoperative blood loss, postoperative hospital stay, reoperation rate, 30‐day mortality, and in‐hospital mortality, were superior in the laparoscopic group, except for operative time. Subgroup analyses showed that the incidence of postoperative morbidity was lower in the laparoscopic group for all prespecified subgroups. Conclusion Laparoscopic right hemicolectomy has an advantage over open surgery for colon cancer with respect to short‐term outcome.


| INTRODUC TI ON
Since the introduction of laparoscopic surgery for colon cancer in 1991, 1 its use has been increasing worldwide. 2 As demonstrated by previous large randomized studies, [3][4][5][6][7] laparoscopic surgery is now considered one of the standard surgical treatments for colon cancer. 8,9 However, the previously published data regarding the safety and superiority of laparoscopic surgery were primarily obtained from high-volume centers or hospitals specializing in colorectal surgery. Therefore, the applicability of their findings to general clinical practice is still being debated.
Right hemicolectomy is one of the most common procedures in colon cancer surgery, as right-sided cancer accounts for approximately 40% of all colorectal cancers. 10 However, unlike sigmoidectomy or anterior resection, the laparoscopic approach for this procedure is technically demanding and has not been standardized; there are many variations in technique for lymph node dissection and anastomosis. [11][12][13][14][15][16][17] This lack of technical standardization may affect surgical outcomes as well as the acceptance of the laparoscopic approach in the general clinical setting. In 2017, only 45.9% of right hemicolectomies were performed laparoscopically in Japan, including benign disease and emergent cases. 18 To obtain "real world" outcome data of laparoscopic vs open right hemicolectomy for colon cancer, this study conducted a propensity score matching (PSM) analysis of patient data from the Japanese National Clinical Database (NCD).

| NCD registration
The details of data registration in the Japanese NCD system have been described previously. 19,20 Briefly, the database began in 2011 as a nationwide registry system linked to the surgical board certification system in Japan. Over 5000 institutions participated in this system in 2018 and approximately 1 400 000 surgical cases are registered annually, corresponding to >95% of all annual surgeries in Japan.
In the gastroenterological section of the NCD, the Japanese Society of Gastroenterological Surgery selected eight main surgical procedures (esophagectomy, distal gastrectomy, total gastrectomy, right hemicolectomy, low anterior resection, hepatectomy, pancreaticoduodenectomy, and surgery for acute diffuse peritonitis) as particularly important in terms of medical standards for surgical quality improvement. All surgical cases registered in the NCD include detailed data regarding morbidity, comorbidity, postoperative complications, and mortality.

| Study population
A total of 91 983 cases of right hemicolectomy were registered in the NCD between January 2014 and December 2018. We excluded robotic surgeries, benign disease, malignant disease of organs other than colon, cT0 disease, cStage IV disease, and emergent surgeries from this study. In addition, 32 cases with data deficits were also excluded. Finally, 72 299 cases of laparoscopic or open right hemicolectomy for colon cancer were enrolled ( Figure 1).

| Propensity score matching
Propensity score matching between patients who underwent laparoscopic and open right hemicolectomy was conducted to minimize selection bias arising from differences in the study groups' characteristics. Propensity scores were estimated using a multivariable logistic regression model accounting for the fol-  Abbreviations: ASA-PS, American Society of Anesthesiologists physical status; BMI, body mass index; COPD, chronic obstructive pulmonary disease; DM, diabetes mellitus; PSM, propensity score matching; SMD, standardized mean difference.

| Study endpoints
The primary endpoint of the study was incidence of overall post-

| Statistical analysis
Pearson's χ 2 test was used to compare categorical variables. The Wilcoxon rank sum test was used to compare continuous variables.
Subgroup analyses were performed using logistic regression and are presented in a forest plot. All statistical tests were two-sided. P < .05 was considered significant. All analyses were conducted using R version 3.6.0 (R Foundation for Statistical Computing). Surgical outcomes are shown in Forest plot on the association of operative approach with overall postoperative morbidity ≥ CD grade III for different subgroups is shown in Figure 2. Laparoscopic surgery decreased the risk of postoperative morbidity in all different subgroups.  [27][28][29] The results of the subgroup analyses also support the applicability of the laparoscopic approach to colon cancer patients in various conditions.

| D ISCUSS I ON
The present study has several limitations. First, it is a retrospective observational study. A potential bias due to heterogeneity of surgical quality or hospital performance cannot be excluded. However, it was reduced to a minimum by employing PSM stratified by hospital volume. Second, oncological and longterm outcomes are not available from the Japanese NCD. Only data regarding baseline characteristics and short-term outcomes are entered in the Japanese NCD, as well as the American College of Surgeons' National Surgical Quality Improvement Program. A definitive conclusion regarding the oncological validity of laparoscopic right hemicolectomy would require data from elsewhere.
In conclusion, this propensity score-matched study using a nationwide Japanese database showed the superiority of laparoscopic right hemicolectomy over open surgery for colon cancer with respect to all short-term outcomes except for operative time. These advantages seem applicable to most colon cancer patients regardless of comorbidities or condition. However, confirming the oncological outcome of this surgery by other sources is also important. The other authors have no conflicts of interest.

E TH I C A L A PPROVA L
The study protocol was approved by the institutional review board of Kobe University (approval number B190247).