Local tumour progression after percutaneous ablation of colorectal liver metastases according to RAS mutation status

Abstract

Background: Percutaneous ablation is a common treatment for colorectal liver metastasis (CLM). However, the effect of rat sarcoma viral oncogene homologue (RAS) mutation on outcome after ablation of CLMs is unclear.

Methods: Patients who underwent image-guided percutaneous ablation of CLMs from 2004 to 2015 and had known RAS mutation status were analysed. Patients were evaluated for local tumour progression as observed on imaging of CLMs treated with ablation. Multivariable Cox regression analysis was performed to determine factors associated with local tumour progression-free survival.

Results: The study included 92 patients who underwent ablation of 137 CLMs. Thirty-six patients (39 per cent) had mutant RAS. Rates of local tumour progression were 14 per cent (8 of 56) for patients with wild-type RAS and 39 per cent (14 of 36) for patients with mutant RAS (P = 0·007). The actuarial 3-year local tumour progression-free survival rate after percutaneous ablation was worse in patients with mutant RAS than in those with wild-type RAS (35 versus 71 per cent respectively; P = 0·001). In multivariable analysis, negative predictors of local tumour progression-free survival were a minimum ablation margin of less than 5 mm (hazard ratio (HR) 2·48, 95 per cent c.i. 1·31 to 4·72; P = 0·006) and mutant RAS (HR 3·01, 1·60 to 5·77; P = 0·001).

Conclusion: Mutant RAS is associated with an earlier and higher rate of local tumour progression in patients undergoing ablation of CLMs.

Figure 1

Kaplan-Meier plots of (A) local tumor progression–free survival, (B) recurrence-free survival, and (C) overall survival after ablation of CLM among patients with wild-type RAS (red lines) and mutant RAS (blue lines) status.

Figure 2

Graphic representation of the 25 ablated CLMs that showed LTP according to time from ablation to detection of LTP on imaging follow-up, maximum diameter of the ablated CLM at ablation, and RAS status (wild-type RAS: red diamonds; mutant RAS: blue diamonds).

Figure 3

Kaplan-Meier plots of (A) local tumor progression–free survival in patients treated with minimal ablation margin ≥5 mm and (B) local tumor progression–free survival in patients undergoing ablation of largest CLM <2 cm.