Complete Mesocolic Excision is a Safe Option in Laparoscopic Right Hemicolectomy

Early safety data from the RELARC trial showed complete mesocolic excision doesn’t increase intraoperative and postoperative complications of laparoscopic right hemicolectomy compared with D2 dissection when done by an experienced surgeon.

Despite some risks associated with complete mesocolic excision (CME), the procedure was found to be a safe option for experienced surgeons compared with D2 dissection in patients with right-sided colon cancer who underwent laparoscopic colectomy, according to study findings published in Lancet Oncology.

However, more data is still needed to determine whether CME should be used as the gold standard for these patients.

“Although laparoscopic surgery for colon cancer has become popular, there is concern regarding the possibility of serious vascular injury during laparoscopic CME on the anatomically complex right colon, with its wide variations in vasculature between patients,” the authors of the RELARC Study Group wrote in the article.

Thus, the investigators who are affiliated with medical centers across China sought to determine survival and safety outcomes of CME.

The controlled, phase 3 RELARC clinical trial (NCT02619942) had a primary end point of disease-free survival rate at 3 years after surgery; however, the data are not yet mature. Investigators were able to report secondary outcomes including intraoperative surgical complications and postoperative complications within 30 days of surgery, mortality (death from any cause within 30 days of surgery), and central lymph node metastasis rate in the CME group only.

At 17 hospitals across 9 provinces, investigators randomized 995 participants, aged 18 to 75 years, to receive either CME (n = 495) or D2 dissection (n = 500) during laparoscopic right colectomy. Eligible patients had confirmed primary adenocarcinoma located between the caecum and the right third of the transverse colon. In addition, there was no evidence of distant metastases in any of the participants.

The main difference between the D2 and the CME procedures was that lymphadenectomy was done around the superior mesenteric artery and vein in the latter group, noted the authors. To participate, surgeons had to have done at least 100 laparoscopic procedures for colorectal cancer per year, and no less than 20 CME and 20 D2 lymph node dissection procedures for right-sided colon cancer.

The investigators determined that CME doesn’t increase intraoperative and postoperative complications of laparoscopic right hemicolectomy compared with D2 dissection when done by an experienced surgeon. The postoperative surgical complication rate in the CME group was 20% compared with 22% in the D2 dissection group (difference, −2.2%; 95% CI, −7.2 to 2.8; P = .39). However, there is a significantly increased risk of vascular injury during CME compared with D2 dissection (3% vs 1%, respectively; P = .045).

Between the 2 groups, Clavien-Dindo grade I to II complications were similar. Yet the grade III to IV complications were significantly less frequent in the CME group than in the D2 dissection group (1% vs 3%, respectively; P = .022). In the first 30 days after surgery, no deaths were reported in either group. Of those who underwent central lymph node biopsy in the CME group, metastases in the central lymph nodes were detected in 13 participants.

“To our knowledge, this study is the first randomized, controlled trial to directly verify the safety of CME procedure in laparoscopic right hemicolectomy,” the authors wrote. “With the significantly better short-term and long-term outcomes widely reported with the use of laparoscopic technology than with open surgery, laparoscopic surgery will inevitably become the first choice colectomy approach; thus, the results of this study are of great significance.”

However, the investigators noted a few limitations to the study, such as all of the surgeons being highly specialized experts.

“Whether CME can benefit patients’ survival needs to be confirmed by future disease-free survival results,” the authors wrote. The primary end point and 3-year overall survival data are anticipated to be published in December 2022.


Xu L, Su X, He Z, et al. Short-term outcomes of complete mesocolic excision versus D2 dissection in patients undergoing laparoscopic colectomy for right colon cancer (RELARC): a randomised, controlled, phase 3, superiority trial. Lancet Oncol. 2021;22(3):391-401. doi:10.1016/S1470-2045(20)30685-9