Interaction of margin status and tumour burden determines survival after resection of colorectal liver metastases: A retrospective cohort study.

PURPOSE: We sought to determine the impact of surgical margin status on overall survival (OS) and recurrence pattern stratified by tumor burden.

MATERIALS AND METHODS: Data were collected from patients undergoing resection for colorectal liver metastases (CRLM). Tumor burden was calculated according to a newly proposed Tumor Burden Score (TBS) system, defined as the distance from the origin on a Cartesian plane that incorporated maximum tumor size and number of liver lesions. Patients were divided into low tumor burden group and high tumor burden group accordingly, and the impact of resection margin on overall survival was examined.

RESULTS: A total of 286 patients were available, among which R1 resection was observed in 88 patients. The median TBS for the entire cohort was 3.84. Metastases in the R1 group were characterized by more advanced disease and more complex resections. Compared with a R0 resection, a R1 resection offered an lower 5-year overall survival rate (46.8% vs. 22.1%, p = 0.001). Multivariate analysis identified R1 resection (p = 0.03), high TBS (p = 0.002), lymph nodes metastases (p = 0.003) and lymphovascular invasion (p = 0.03) of the primary colorectal tumor as the factors independently associated with worse survival. The survival benefit associated with negative margins was greater in patients with low TBS (55.7% vs. 21.7%, p = 0.021) than in patients with high TBS (31.8% vs. 24.5%, p = 0.116). R1 resection was associated with an increased true margin recurrence rate in patients with low TBS (32.3% vs. 13.4%; p = 0.014) and an increased risk of new intrahepatic metastases in patients with high TBS (43.9% vs. 26.7%; p = 0.034).

CONCLUSIONS: Negative margin is an important determinant of survival. The impact of positive margins is more pronounced in patients with low tumor burden.