Lymphocyte-to-monocyte ratio predicts survival after radiofrequency ablation for colorectal liver metastases

AIM: To test the correlation between lymphocyte-to-monocyte ratio (LMR) and survival after radiofrequency ablation (RFA) for colorectal liver metastasis (CLMs). METHODS: From July 2003 to Feb 2012, 127 consecutive patients with 193 histologically-proven unresectable CLMs were treated with percutaneous RFA at the University of Foggia. All patients had undergone primary colorectal tumor resection before RFA and received systemic chemotherapy. LMR was calculated by dividing lymphocyte count by monocyte count assessed at baseline. Treatment-related toxicity was defined as any adverse events occurred within 4 wk after the procedure. Overall survival (OS) and time to recurrence (TTR) were estimated from the date of RFA by Kaplan-Meier with plots and median (95% CI). The inferential analysis for time to event data was conducted using the Cox univariate and multivariate regression model to estimate hazard ratios (HR) and 95% CI. Statistically significant variables from the univariate Cox analysis were considered for the multivariate models. RESULTS: Median age was 66 years (range 38-88) and patients were prevalently male (69.2%). Median LMR was 4.38% (0.79-88) whereas median number of nodules was 2 (1-3) with a median maximum diameter of 27 mm (10-45). Median OS was 38 mo (34-53) and survival rate (SR) was 89.4%, 40.4% and 33.3% at 1, 4 and 5 years respectively in the whole cohort. Running log-rank test analysis found 3.96% as the most significant prognostic cut-off point for LMR and stratifying the study population by this LMR value median OS resulted 55 mo (37-69) in patients with LMR > 3.96% and 34 (26-39) mo in patients with LMR <= 3.96% (HR = 0.53, 0.34-0.85, P = 0.007). Nodule size and LMR were the only significant predictors for OS in multivariate analysis. Median TTR was 29 mo (22-35) with a recurrence-free survival (RFS) rate of 72.6%, 32.1% and 21.8% at 1, 4 and 5 years, respectively in the whole study group. Nodule size and LMR were confirmed as significant prognostic factors for TTR in multivariate Cox regression. TTR, when stratified by LMR, was 35 mo (28-57) in the group > 3.96% and 25 mo (18-30) in the group <= 3.96% (P = 0.02). CONCLUSION: Our study provides support for the use of LMR as a novel predictor of outcome for CLM patients.