Anatomic Resection Is Not Required for Colorectal Liver Metastases with RAS Mutation

Background: Non-anatomic resection (NAR) has emerged as a safe and effective technique for resection of colorectal liver metastases (CRLM). More recently, RAS mutation has been identified as an important indicator of aggressive disease, which may require anatomic resection (AR). In this retrospective study, we compared the long-term outcomes of AR versus NAR in CRLM patients with and without RAS mutations. Methods: Patients with known RAS mutation status who underwent AR or NAR for CRLM between 2006 and 2016 were included. Differences in baseline characteristics were adjusted using 1:1 propensity score matching, including the most important factors that contributed to the decision to use the resection technique. Overall survival (OS), recurrence-free survival (RFS), and liver-specific recurrence-free survival (L-RFS) were compared between cohorts. Results: Among 622 total patients, 338 (54%) underwent AR and 284 (46%) NAR. There was no difference in OS or L-RFS between the AR and NAR groups, regardless of mutation status. There was increased RFS in the RAS WT patients with NAR (P = 0.034), but no difference in RFS in the whole cohort or RAS mutant group. After propensity score matching, 360 patients were analyzed, and no differences in OS, RFS, or L-RFS rates were seen between any groups. There was also no difference in margin recurrence. Conclusions: Similar outcomes can be achieved with both AR and NAR, regardless of RAS mutation status. These data do not support a universal requirement for AR in RAS mutant CRLM when not necessary to achieve an R0 resection.