5 Things You Should Know About CME

Colorectal Cancer

Colorectal Cancer (CRC) represents 10% of all cancer diagnosis and cancer-related deaths worldwide. It is the 2nd most common cancer in women and the 3rd most common in men. Geographically, its incidence is higher in developed countries, but with the creation of nationwide surveillance programs, the increasing uptake of colonoscopy and the adoption of lifestyle changes at the same time as the continuing progress in developing countries, will lead to a stabilization/decrease of incidence in highly developed countries and increase in developing ones.

Diagnosis of CRC is usually carried out in 2 different settings: surveillance programs or symptom investigation, through endoscopic or radiologic exams. Colonoscopy is the method of choice to diagnose CRC. It allows for anatomic localization, macroscopic characterization and biopsy for microscopic confirmation and evaluation. Computed tomography (CT) is the radiologic exam of choice for metastatic staging and the most routinely used to provide information on locoregional extension, although with suboptimal accuracy. In the field of pathology, besides histologic classification of the tumor, molecular subtyping can add important diagnostic, therapeutic and prognostic information.

Complete Mesocolic Excision (CME)

CME consists of removal of an intact package of the tumor and its main lymphatic drainage. It was described by Werner Hohenberger in 2009 and rose from the concept of TME, published 27 years earlier by Richard J. Heald. The technique entails sharp dissection of the visceral fascial layer from the parietal one, complete mobilization of the mesocolon with an intact fascia and true high ligation of the supplying arteries and draining veins at their origin, ensuring a maximal harvest of regional lymph nodes.

For cancer located in the right colon, the surgical procedure includes mobilization of the duodenum with the pancreatic head (Kocher maneuver) and the mesenteric root up to the origin of the superior mesenteric artery (SMA).

Vessels to ligate will depend on the location of the tumor and the theoretical pattern of lymphatic spread. A distance of 10 cm from the tumor must be respected.

For cancer in the Cecum and Ascendent colon, ligation of the Ileocolic and, when present, right colic vessels, is mandatory. Cancer of the transverse colon, including both flexures, needs central ligation of the middle colic vessels, and central ligation of the right gastroepiploic vessels, when needed. In cancers of the proximal descending colon, the left colic artery should be ligated at its origin. For distal descending colon and sigmoid colon, division should be made at the origin of the inferior mesenteric vessels, with vein ligation near the pancreas.

Hohenberger’s results showed a reduction of 5-year locoregional recurrence rate and an improvement in oncological outcomes. Many other studies have been published, suggesting better oncological outcomes, but higher surgical morbidity rates for CME, without changes in surgical mortality. Two Randomized Controlled Trials (RCT) are currently under way, one in China and another one in Ukraine, but no preliminary results have been published.