Kras mutation is a marker of worse oncologic outcomes after percutaneous radiofrequency ablation of colorectal liver metastases

BACKGROUND: Kras mutation has been associated with shorter overall survival and time to disease recurrence after resection of colorectal liver metastases (CLM). This study evaluated the prognostic value of Kras mutation in patients with CLM treated by percutaneous radiofrequency ablation (RFA). METHODS: This is an IRB waived retrospective analysis of the impact of KRAS mutation status on oncologic outcomes after CLM RFA. The endpoints were overall survival (OS), local tumor progression (LTP) rates, and incidence of new liver, lung, and peritoneal metastases. Survival times were calculated using Kaplan-Meier methodology from the time of RFA. RESULTS: The study enrolled 97 patients. Kras exon 2 mutation was detected in 39% (38/97) of patients. On univariate analysis, Kras mutation (P=0.016) (HR: 1.8; 95% CI: 1.1 – 2.9) was a significant predictor of OS and retained significance on multivariate analysis. Kras mutation was a significant predictor of new liver metastases (P=0.037) (SHR: 2.0; CI: 1.0-3.7) and peritoneal metastases (P=0.015) (sHR: 3.0; 95% CI: 1.2-7.2) on multivariate analysis. Kras mutation was a significant predictor of LTP after RFA of CLM ablated with margins of 1-5 mm (P=0.018) (SHR: 3.0; 95% CI: 1.2-7.7) with an LTP rate of 80% (12/15) versus 41% (11/27) for wild type. CONCLUSION: Kras mutation is a significant predictor of overall survival, new liver, and peritoneal metastases after RFA of CLM. A minimal radiographic ablation margin ≥ 6 mm is essential for local tumor control especially for mutant CLM.