Percutaneous radiofrequency versus microwave ablation for the treatment of colorectal liver metastases.

401 Background: Microwave (MWA) and radiofrequency (RFA) ablation are commonly used for the treatment of unresectable liver metastases from colorectal cancer (CRC). MWA has a few theoretical advantages over RFA (active heating, less affected by heat sink effect, larger ablation zones, faster) however limited data exists on this field. Our aim was to analyse the safety and efficacy of MWA and RFA in the treatment of CRC liver metastases. Methods: All patients with unresectable CRC liver metastasis who were treated with RFA or MWA in a single center between March 2006 and December 2016 were included. Medical records and imaging studies were reviewed retrospectively for demographic data, to assess for local tumour recurrence and overall survival and to evaluate ablation-related adverse events. Results: 456 ablations were performed in 193 patients (123 men) with a median age of 66 (range 32-91). The majority of patients had a history of surgery of the primary tumour (n=170, 88,1%) and systemic chemotherapy (n=183, 94,8%). 68 patients had a history of liver surgery (35,2%). RFA was used in 343 procedures (75,2%) and MWA in 113 (24,8%). Median number of procedures per patient was 2 (range 1-10). Median lesion size was 17mm (range 3-80mm). Mean follow-up per lesion was 2.0 years in the RFA group and 1.3 years in the MWA group. Local tumour recurrence rate was 45% for RFA and 28% for MWA, with a hazard ratio of 0.6 in favour of MWA (95% CI 0.4-0.9). Two and five year overall survival rates from diagnosis of liver metastasis were 88% and 35% for RFA and 89% and 66% for MWA, respectively. Complications were reported in 43 of 456 procedures (9,4%); In 8,2% of RFAs (n=28) and 13,3% of MWAs (n=15). Complications classified as CTCAE grade 3 or higher were: haemothorax requiring surgery (n=1 for RFA), biloma (n=2 for RFA & MWA), biliary stricture (n=2 for RFA and n=1 MWA), liver failure (n=2 for RFA), liver abscess (n=1 RFA), pneumonia (n=2 for RFA) and pulmonary embolism (n=1 RFA). Segmental portal vein occlusion was only seen with MWA (n=2; 1,8%). One patient died due to multi-organ failure post RFA. Conclusions: MWA could achieve better local tumour control compared with RFA in the treatment of CRC liver metastasis, with slightly higher complication rate.