Objective To investigate the influencing factors for the number of lymph node harvested after Da Vinci robotic and laparoscopic radical gastrectomy for gastric cancer.

Methods The retrospective case-control study was conducted. The clinicopathological data of 1 396 patients who underwent Da Vinci robotic or laparoscopic radical gastrectomy for gastric cancer in the First Affiliated Hospital of Nanchang University from December 2014 to July 2019 were collected. There were 991 males and 405 females, aged (60±11) years. Surgery using Da Vinci robotic system or laparoscopic system was completed according to patients' wishes. Cases with early gastric cancer underwent D₁₊ lymphadenectomy and cases with advanced gastric cancer underwent standard D₂ lymphadenectomy. Observation indicators: (1) intraoperative situations; (2) postoperative situations; (3) influencing factors for the number of lymph node harvested after radical gastrectomy for gastric cancer; (4) follow-up and survival. Follow-up using outpatient examination or telephone interview was performed to detect survival of patients up to October 2020. Measurement data with normal distribution were represented as Mean±SD. Univariate analysis was done using the chi-square test or Fisher exact probability. Multivariate analysis was performed using Logistic regression model. The survival rate was calculated by Kaplan-Meier method.

Results (1) Intraoperative situations: all the 1 396 patients underwent radical gastrectomy, including 415 cases undergoing Da Vinci robotic radical gastrectomy and 981 cases undergoing laparoscopic radical gastrectomy. Thirty-five of the 1 396 patients were converted to open surgery, including 5 cases undergoing Da Vinci robotic radical gastrectomy and 30 cases undergoing laparoscopic radical gastrectomy. Of the 1 396 patients, 983 cases underwent distal gastrectomy, 400 cases underwent total gastrectomy and 13 cases underwent proximal gastrectomy, among which 597 cases underwent Billroth Ⅰ anastomosis, 385 cases underwent Billroth Ⅱ anastomosis, 401 cases underwent Roux-en-Y anastomosis and 13 cases underwent residual stomach-esophagus anastomosis. The operation time, volume of intraoperative blood loss and cases with intraoperative blood transfusion were (221±51)minutes, (201±81)mL, 24 of 415 cases undergoing Da Vinci robotic radical gastrectomy, and (196±42)minutes, (232±76)mL, 75 of 981 cases undergoing laparoscopic radical gastrectomy, respectively. (2) Postoperative situations: the time to postoperative first flatus, time to postoperative initial liquid food intake and duration of postoperative hospital stay of the 1 396 patients were (3.0±1.0) days, (4.2±1.5) days and (9.0±3.8) days, respectively. Two hundred and ten of the 1 396 patients had postoperative complications including 170 cases with grade Ⅰ-Ⅱ complications and 40 cases with grade Ⅲ-Ⅴ complications. Eight of the 210 patients with postoperative complications died of serious complica-tions and the other 202 cases were cured after symptomatic treatment. Results of postoperative histopathological examination showed that there were 958 cases of adenocarcinoma, 220 cases of mucinous adenocarcinoma, and 218 cases of signet ring cell carcinoma. The number of lymph node harvested and the number of positive lymph node of the 1 396 patients were 26.0±8.3 and 3.6±0.9, respectively, and cases with the number of lymph node harvested ≥16 or <16 were 1 312 and 84. (3) Influencing factors for the number of lymph node harvested after radical gastrectomy for gastric cancer: results of univariate analysis showed that the operating surgeon, operation method, range of gastric resection, nerve invasion, degree of tumor invasion and tumor pathological N stage were related factors influencing the number of lymph node harvested after Da Vinci robotic and laparoscopic radical gastrectomy for gastric cancer (χ²=13.167, 6.029, 15.686, 5.573, 9.402, 17.139, P<0.05). Results of multivariate analysis showed that the operating surgeon, operation method, range of gastric resection and tumor pathological N stage were independent factors influencing the number of lymph node harvested after Da Vinci robotic and laparoscopic radical gastrectomy for gastric cancer (odds ratio=1.589, 2.018, 1.787, 0.267, 95% confidence interval as 1.221‒2.068, 1.140‒3.570, 1.066‒2.994, 0.103‒0.689, P<0.05). (4) Follow-up and survival: of the 1 396 patients, 1 256 cases were followed up for 2 to 70 months, with a median follow-up time of 27 months. The 3-year cumulative survival rate of the 1 256 cases was 70.2%.

Conclusion The operating surgeon, operation method, range of gastric resection and tumor pathological N stage are independent factors influencing the number of lymph node harvested after Da Vinci robotic and laparoscopic radical gastrectomy for gastric cancer.