Short-Term Outcomes of Complete Mesocolic Excision Versus D2 Dissection in Patients Undergoing Laparoscopic Colectomy for Right Colon Cancer (RELARC Trial): A Multicentre Randomised Controlled Phase III Trial

Background: Whether extended lymphadenectomy for right colon cancer leads to increased perioperative complications or improves survival is still controversial. This multicentre randomised controlled trial (RCT) aimed to compare the efficacy and safety of complete mesocolic excision (CME) versus D2 dissection in laparoscopic right hemicolectomy for patients with right colon cancer.  Methods: This superiority phase III trial was undertaken at 17 hospitals in 9 provinces of China. Patients with adenocarcinoma located between the cecum and the right third of the transverse colon, without evidence of distant metastases, were randomly assigned (in a 1:1 ratio) to receive either CME or D2 dissection during laparoscopic right colectomy. Morbidity and mortality in the first 30 days after surgery were compared between the two groups using a modified intention-to-treat (mITT) analysis. Findings: A total of 1072 patients were enrolled between January 11, 2016, and December 26, 2019. Of these patients, 995 (495 CME patients, 500 D2 patients) were included in the mITT analysis. The 30-day postoperative morbidity rate was 19·6% in the CME group vs. 21·8% in the D2 group (difference, -2·2% [95%CI, -0·07, - 0·03]; P = 0·34); no deaths occurred in either group. The CME procedures harvested significantly more lymph nodes (26·0 vs 23·0, difference, 3·4 [95%CI, 2·0, 4·9]; P<0·001), and larger mesentery areas (116·4 cm2 vs 107·8 cm2; difference, 8·4 [95%CI, 3·3, 13·5]; P = 0·001), but took longer time (163·0 minutes vs 150·5 minutes, difference 11·6 [95%CI, 5·7, 17·5]; P = 0·0002), and slight more blood loss (50 mL vs 50 mL, difference 5·4 [95%CI, -2·6, 13·4]; P = 0·049) than D2 dissections. Interpretation: When performed by experienced surgeons, CME during laparoscopic right hemicolectomy does not increase risk for intra/postoperative complications. Trial Registration: This study was registered with ClinicalTrials.gov (No.NCT02619942.) Funding Statement: This trial was sponsored by the Capital Characteristic Clinical Project of Beijing Municipal Science & Technology Commission (Z161100000516014) and the Non-profit Central Research Institute Fund of the Chinese Academy of Medical Sciences (2019XK320003). Declaration of Interests: We declare that we have no conflicts of interest. Ethics Approval Statement: The study protocol and all amendments were approved by the Ethics Committee of Peking Union Medical College Hospital. Approval of the local ethics committee at each centre was also obtained before starting the study. All patients provided written informed consent.