Importance of Resection Margin after Resection of Colorectal Liver Metastases in the Era of Modern Chemotherapy: A Population-based Cohort Study

Purpose: Resection margin has been associated with overall survival (OS) following liver resection for colorectal liver metastasis (CRLM). The aim of this national study is to examine how resection margins of 0.0 mm, 0.1–0.9 mm and ≥1 mm influence OS in patients resected for CRLM in a time of modern perioperative chemotherapy and surgery. Methods: Using data from the national registries Swedish Colorectal Cancer Registry and Swedish National Quality Registry for Liver, Bile Duct and Gallbladder Cancer, patients that had liver resections for CRLM between 2009-2013 were included. In patients with a narrow or unknown surgical margin the original pathological reports were reviewed. Factors influencing OS, including exact resection margin, were analysed using cox proportional hazard model. Results: A total of 754 patients had a known margin status, of which 133 (17.6%) patients had a resection margin of <1 mm. The OS in patients with a margin of 0 mm, or 0.1–0.9 mm was 42 (95% CI 31–53) and 48 (95% CI 35–62) months, respectively, compared to 75 (95% CI 65–85) for patients with ≥1 mm margin, p<0.001. Margins of 0 mm or 0.1–0.9 mm were associated with poor OS in the multivariable analysis, HR 1.423 (95% CI 1.040–1.948), p=0.028, and 1.417 (95% CI 1.039–1.932) p=0.028, respectively. Conclusions: Despite modern chemotherapy the resection margin is still an important factor for the survival of patients resected for CLRM, and a margin of ≥1 mm is needed to achieve the best possible outcome.