Radiofrequency ablation for colorectal cancer liver metastases initially greater than 25 mm but downsized by neo-adjuvant chemotherapy is associated with increased rate of local tumor progression

Background Radiofrequency ablation (RFA) is a valid treatment for liver metastases from colorectal cancer (CRLM) smaller than 25 mm and unsuitable for surgical resection. Tumor size is predictive for local tumor progression (LTP). The aim of this study was to evaluate whether RFA is indicated for lesions >25 mm at presentation but <25 mm after chemotherapy. Method Patients who underwent RFA for CRLM after chemotherapy (January 2004–December 2012) were reviewed. Metastases were classified according to their size. Group 1: ≤25 mm before and after chemotherapy. Group 2A: >25 mm before but ≤25 mm after chemotherapy. Group 2B: >25 mm before and after chemotherapy. Results 133 CRLM were ablated in 83 patients (median follow-up 56 months). At 1-year, the LTP rate was higher in group 2A than in group 1 (32% vs. 16%, p ≤ 0.001). The highest rate of 1-year LTP was 64% in group 2B. Time to LTP (TLTP) was shorter in group 2A than in group 1 (HR: 2.89; 95% CI [1.04–8.01]; p = 0.004). Following multivariate analysis, the group type was the only predictive factor for TLTP (p < 0.001). Conclusions RFA is not the optimal treatment for CRLM > 25 mm at presentation.