Abstract: Objective:To investigate the application value of superior mesenteric artery (SMA)oriented complete mesocolic excision (CME) in the treatment of right colon cancer.
Methods:The retrospective cohort study was conducted. The clinicopathological data of 955 patients with right colon cancer who were admitted to the First Affiliated Hospital of Nanjing Medical University from January 2013 to June 2018 were collected. There were 514 males and 441 females, aged from 18 to 96 years, with a median age of 65 years. Of the 955 patients, 377 undergoing SMA-oriented CME of right colon with the lymph node dissection along the left boundary of SMA were allocated into SMA-oriented group, and 578 undergoing superior mesenteric vein (SMV)oriented CME of right colon with the lymph node dissection along the left boundary of SMV were allocated into SMVoriented group. Observation indicators: (1) intraoperative and postoperative conditions; (2) postoperative complications; (3) postoperative pathological examinations; (4) follow-up and survival situations. Followup was performed by telephone interview and outpatient examination once every 3-6 months within 2 years after surgery and once a year after 2 years up to January 2019, using tumor recurrence and metastasis or death as the end point. Followup included physical examination and tumor marker test, including carcino embryonic antigen, CA199, chest and abdomen CT examination and enteroscopy. Measurement data with skewed distribution were described as M (P25, P75), and comparison between groups was done using the Mann-Whitney U test. Count data were described as absolute numbers or percentages, and comparison between groups was analyzed using the chi square test. Ordinal data were analyzed using the rank sum test. KaplanMeier method was used to calculate survival time and rate, and draw survival curve. Logrank test was used for survival analysis. Patients with loss to follow-up were involved in survival analysis as censored data.
Results:(1) Intraoperative and postoperative conditions: the operation time, volume of intraoperative blood loss, duration of postoperative hospital stay were 100 minutes (90 minutes,110 minutes), 50.0 mL (50.0 mL, 70.0 mL), 8 days (8 days,10 days) in the SMA-oriented group, and 110 minutes (90 minutes, 135 minutes), 50.0 mL (50.0 mL,122.5 mL),10 days (8 days,12 days) in the SMVoriented group, showing significant differences between the two groups (Z=-5.400,-5.799,-7.461, P<0.05). After the exclusion of 47 patients unsuitable for defecation analysis because of postoperative complications, 365 in the SMA-oriented group and 543 in the SMVoriented group were analyzed. The time to first defecation, the maximum number and the median number of daily defecation postoperatively were 5 days (3 days, 5 days), 2.0 (1.0, 2.5), 1.0 (1.0, 1.0) in the SMA-oriented group, which showed no significant difference from 4 days (3 days, 5 days), 2.0 (1.0, 3.0), 1.0 (1.0, 1.0) in the SMVoriented group (Z=-1.622,-1.541, -1.024, P>0.05). (2) Postoperative complications: cases with postoperative complications, cases with incisional liquefaction or infection, cases with anastomostic leakage, cases with delayed gastric emptying, cases with intraabdominal bleeding, cases with complete or incomplete ileus, cases with anastomostic bleeding, cases with intraabdominal infection, cases with disruption of wound, the number of death were 55, 10, 3, 3, 2, 2, 1, 1, 1, 1 in the SMA-oriented group, which showed no significant difference from 83, 30, 13, 4, 3, 8, 3, 6, 2, 3 in the SMVoriented group, respectively (x²=0.045, 3.662, 2.926, 0.034, 0.001, 1.604, 0.352, 1.873, 0.048, 0.352, P>0.05). There were 32 of 377 patients in the SMA-oriented group and 14 of 578 in the SMVoriented group with chylous leakage, showing a significant difference between the two groups (x²=18.312, P<0.05). Patients with chylous leakage were improved after conservative treatment, without reoperation. Patients with other complications were improved after antiinfection, fluid infusion, and reoperation. Four of 955 patients died after surgery. (3) Postoperative pathological examinations: patients with stage Ⅰ, stage Ⅱ, and stage Ⅲ (pathological TNM staging), patients with highdifferentiation, middifferentiation, and lowdifferentiation (tumor differentiation degree), length of intestine specimen, number of positive lymph nodes, maximum tumor diameter, patients with cancer nodules, patients with vascular invasion, patients with perineural invasion were 57, 174, 146, 30, 174, 173, 23 cm (21 cm, 26 cm), 0 (0, 2), 5.0 cm (3.0 cm, 6.0 cm), 37, 81, 53 in the SMA-oriented group, which showed no difference from 66, 280, 232, 33, 303, 242, 23 cm (21 cm, 25 cm), 0 (0,2), 5.0 cm (3.5 cm, 6.0 cm), 80, 108, 82 in the SMVoriented group (Z=-1.020,-0.216,-0.243, -0.220,-0.814, x²=3.441, 1.127, 0.003, P>0.05). The number of harvested lymph nodes was 22.0 (17.0, 27.0) and 18.0 (15.0, 22.0) in the SMA-oriented group and SMVoriented group, respectively, with a significant difference between the two groups (Z=-7.800, P<0.05). There were 202 patients extracted for further analysis. The number of harvested lymph nodes and harvested central lymph nodes was 25.0 (20.0, 31.3), 5.0 (3.0, 8.0) of 166 patients in the SMA-oriented group, and 21.5 (18.0, 28.8), 1.5 (0, 4.5) of 36 patients in the SMVoriented group, respectively, showing significant differences between the two groups (Z=-1.995, -4.309, P<0.05). (4) Followup and survival situations: 840 of 955 patients including 346 in the SMA-oriented group and 494 in the SMVoriented group were followed up for 1.0-73.2 months, with a median time of 31.5 months. SMA-oriented group had a higher 5year overall survival rate than SMVoriented group (91.8% vs. 84.9%, x²=4.384, P<0.05), but had no significant difference in the 5year tumorfree survival rate compared with the SMVoriented group (84.4% vs. 78.2%, x²=2.158, P>0.05).
Conclusion:Compared with SMVoriented CME of right colon, SMA-oriented CME of right colon is safe and feasible, with larger number of harvested lymph nodes, which can achieve complete lymph node dissection.