Percutaneous ablation of RAS mutant colorectal liver metastases is associated with a high rate local tumor progression

Abstract

Background: To evaluate the predictive values of RAS mutation status on local tumor progression (LTP) after percutaneous ablation (PA) of colorectal liver metastasis (CLM) Methods: A retrospective analysis of patients who underwent CT-guided PA of CLMs from 2004 through 2015 and had known RAS mutation status was performed. Patients were evaluated for LTP at CLMs treated with ablation. Multivariate Cox regression analysis was performed to determine factors associated with LTP-free survival. Results: 92 patients underwent PA of 137 CLMs. Thirty-six (39%) had mutant RAS. LTP rates were 14% (8/56) for patients with wild-type RAS and 39% (14/36) for mutant RAS (p=0·007). On analysis by individual CLM treated with ablation, LTP rates were 9.3% (8/86) for CLMs in patients with wild-type RAS and 33% (17/51) for CLMs in patients with mutant RAS (p=0.0004). LTP occurred earlier and at significantly higher rates for CLMs <2 cm in patients with mutant RAS, irrespective of PA margins, than for CLMs <2 cm in patients with wild-type RAS (p<0.001). Actuarial LTP-free survival were worse in patients with mutant RAS than wild-type RAS (3-year LTP-free survival rate: 35% versus 71%, p=0.001). In multivariate analysis, negative predictors of LTP-free survival were minimal PA margin <5 mm (hazard ratio [HR] 2·48, 95% confidence interval [CI] 1·31-4·72; p=0·006) and mutant RAS (HR 3·01, 95% CI 1·60-5·77; p=0·001). Conclusion: The presence of mutant RAS is associated with an earlier and higher rate of LTP among patients undergoing PA of CLMs.