Evidence for the extent and oncological benefits of lymphadenectomy in colon and rectal cancer. A narrative review based on meta-analyses

Background: Lymphadenectomy for rectal cancer is clearly defined by total mesorectal excision (TME). The analogous surgical strategy for the colon, the complete mesocolic excision (CME), follows the same principles of dissection in embryologically predefined planes. Method: This narrative review initially identified key issues related to lymphadenectomy of rectal and colon cancer. The subsequent search was based on PubMed and focused on meta-analyses. The endpoints for rectal cancer were the benefit of high tie versus low tie and the indications for lateral pelvic lymphadenectomy. For colon cancer the evidence for CME, for the longitudinal extent of resection, for the dissection of infrapyloric and gastroepiploic lymph nodes, for the number of lymph nodes and for the sentinel lymph node technique were used as endpoints. Results: An oncological benefit of the high tie cannot be derived from the current data. Lateral pelvic lymphadenectomy should only be selectively performed after chemoradiotherapy (CRT) in cases of remaining lymph nodes with suspected metastases. In most studies CME proved to be oncologically superior, especially in stage III. The longitudinal extent of resection should be at least 10 cm in both directions if the principles of CME are observed. Infrapyloric and gastroepiploic lymph node involvement is to be expected in 0.7-22% of cases, depending on patient selection, which justifies dissection, particularly in carcinomas of both flexure and the transverse colon. The minimum number of lymph nodes to be removed cannot be clearly derived from the available studies. Precisely performed CME and an optimal pathological work-up are important. The sentinel lymph node technique cannot currently be used as a criterion for limiting the extent of resection. Conclusion: Both TME and CME are reliable standards for the lymphadenectomy in colorectal carcinomas. A lymphadenectomy that goes beyond this is reserved for selected cases and is partly the subject of currently ongoing studies.