Significance of R1 resection margin in colon cancer resections in the modern era

Circumferential resection margin involvement (R1) in rectal cancer is a predictive factor for poor prognosis. The aim of this study was to confirm the prognostic significance of R1 in colon cancer resection and to establish whether the introduction of laparoscopic colorectal surgery influenced this.

Prospectively collected data on a patient pathway data manager for sequential patients with colon cancer treated at our specialist unit from January 2005 to December 2010 were analysed. There were 1110 colonic resections (elective 865; emergency 245). A circumferential resection margin involvement of < 1 mm was considered positive.

The total R1 rate was 13.3% (elective 10.4%; emergency 23.6%; P < 0.001). Other statistically significant risk factors for an R1 resection included tumour perforation (P < 0.001), poorly differentiated carcinoma (P < 0.001), T4 tumour (P < 0.001), vascular invasion (P < 0.001), lymph node metastasis (P < 0.001), distant metastasis (P < 0.001) and palliative resection (P < 0.001). Over half of the elective resections were undertaken laparoscopically (486/865; 56.2%). When compared with elective open resection (379/865; 43.8%), the R1 rate was similar (P = 0.491) with similar disease-free survival (DFS) and overall survival (OS). The overall relapse rate was 18.9% in R0 and 55.5% in R1 resections (P < 0.001). Kaplan-Meier survival analysis showed significant improvements in DFS and OS in R0 over R1 patients.

The R1 margin in colon cancer resection is an important marker for advanced disease and a prognostic factor for DFS and OS. The introduction of laparoscopic surgery has not influenced the outcome in our unit despite a complex case mix.