KRAS Mutation Status Dictates Optimal Surgical Margin Width in Patients Undergoing Resection of Colorectal Liver Metastases.

Background: The optimal tumor-free margin width remains controversial and may be inappropriate to investigate without considering differences in the underlying tumor biology. Methods: R1 resection was defined as margin clearance less than 1 mm. R0 resection was further divided into 3 groups: 1-4, 5-9, and ≥10 mm. The impact of margin width on overall survival (OS) relative to KRAS status [wild type (wt KRAS) vs. mutated (mut KRAS)] was assessed. Results: A total of 411 patients met inclusion criteria. Median patient age was 58 years (interquartile range, 49.7-66.7); most patients were male ( n = 250; 60.8 %). With a median follow-up of 28.3 months, median and 5-year OS were 69.8 months and 55.1 %. Among patients with wt KRAS tumors, although margin clearance of 1-4 mm or more was associated with improved OS compared to R1 (all P < 0.05), no difference in OS was observed when comparing margin clearance of 1-4 mm to the 5-9 mm and the ≥10 mm groups (all P > 0.05). In contrast, among patients with mut KRAS tumors, all three groups of margin clearance (1-4, 5-9, and ≥10 mm) fared no better in terms of 5-year survival compared to R1 resection (all P > 0.05). Conclusions: While a 1-4 mm margin clearance in patients with wt KRAS tumors was associated with improved survival, wider resection width did not confer an additional survival benefit. In contrast, margin status-including a 1 cm margin-did not improve survival among patients with mut KRAS tumors. [ABSTRACT FROM AUTHOR]