The value of KRAS gene status in predicting local tumor progression of colorectal liver metastases following radiofrequency ablation

Purpose: We investigated the relationships between KRAS gene status and local tumor progression (LTP) of colorectal liver metastases (CLMs) after treatment with percutaneous ultrasound-guided radiofrequency ablation (RFA). Materials and methods: Clinical and imaging data from 76 patients (154 lesions) with CLM who underwent percutaneous ultrasound-guided RFA and had KRAS gene test results between January 2012 and June 2016 were analyzed. The average lesion size was 2.3 +/- 1.0 cm (range 0.9-5.7 cm); 38 cases (82 lesions) had wild-type KRAS, and 38 cases (72 lesions) had KRAS mutations. Results: The technique effectiveness was 98.1% (151/154), and the LTP rate was 18.2% (28/154) after RFA, which was performed between January 2012 and November 2017. The mean and median followup were 32.7 +/- 2.5 and 32.0 +/- 2.6 months (range 1-70 months), respectively. Cumulative LTP rates at 6 months and 1, 2 and 3 years post-RFA for all patients were 7.4, 14.5, 17.8 and 19.2%, respectively. The LTP rate for patients with mutant KRAS (27.8%[20/72]) was significantly higher than that in patients with wild-type KRAS (9.8%[8/82]; p = .004). The cumulative LTP rates at 6 months and 1, 2 and 3 years post-RFA were 4.0, 11.1, 11.1 and 11.1%, respectively, for patients with wild-type KRAS and 11.2, 18.4, 25.2 and 36.2%, respectively, for patient with mutant KRAS (p = .011). Univariate (p = .011) and multivariate analyses (p = .005) showed that KRAS genotype in liver metastases was predictive of LTP. Multivariate analysis also showed that ablation margin size (p<.001) and modified clinical risk score (CRS; p = .033) were independent prognostic factors for LTP. Conclusions: KRAS gene status of liver metastatic lesions was associated with LTP rates after RFA of CLM. Ablation margin size and modified CRS were also independent prognostic factors for LTP.