RÉSUMÉ
PURPOSE: The clinical significance of the lateral resection margin for rectal cancer has been widely investigated. The ascending and the descending colon do not have a peritoneal covering posteriorly. Therefore, colon cancers located on their posterior side can penetrate the entire bowel wall, which is similar to mesorectal invasion in rectal cancer. However, the prognostic significance of the retroperitoneal resection margin involvement is unknown. The aim of this study is to evaluate the prognostic significance of the lateral resection margin in ascending and descending colon cancer. METHODS: A retrospective study was performed and involved 92 patients who had undergone a curative resection for right or left colon cancer with TNM stage II and III. The patients were assigned to either a lateral margin negative group (LMNG, n=73) or a lateral margin positive group (LMPG, n=19) according to the presence of a tumor or a metastatic lymph node within 1 mm of the lateral resection margin. The oncological outcomes of the LMPG were compared with those of the LMNG. RESULTS: The LMPG was younger and had higher incidences of tumors positive vascular or neural invasion and advanced T and N stages. The overall recurrence rate of the LMPG was higher than that of the LMNG (36.8% versus 16.4%) and the cumulative survival rate of the LMPG was significantly lower than that of the LMNG (35.0% versus 76.2%). High preoperative CEA, lymphatic invasion, lateral margin involvement of the tumor, N2 in nodal status were significant factors in the univariate analysis for evaluation of the prognosis, but lateral margin involvement was not a significant factor in the multivariate analysis. In the lymph-node-positive group and the CEA non-elevation group, lateral margin involvement of the tumor was revealed as a prognostic factor. CONCLUSIONS: Lateral margin involvement of ascending and descending colon cancer affects tumor recurrence and overall survival, but it is not a significant prognostic factor.