Microwave ablation versus resection for colorectal cancer liver metastases - A propensity score analysis from a population-based nationwide registry

Abstract

Background: Recent studies indicate comparable survival after thermal ablation and liver resection for colorectal cancer liver metastases (CRCLM). Awating Results from randomized trials, the aim was to compare survival after microwave ablation (MWA) versus liver resection for CRCLM in a population-based study using propensity score matching. Materials and Methods: All patients undergoing liver resection or MWA as a first intervention for CRCLM measuring less than 3 cm in Sweden between 2013 and 2016 were included from a nationwide registry. Treatment effect was estimated after propensity score (PS) matching, adjusting for patient and tumour factors hypothesised to affect the choice of treatment approach. Survival was illustrated with Kaplan-Meier curves and compared with the log-rank test. Cox regression was used to estimate predictors of survival presented as hazard ratios (HR). Results: The unmatched cohorts (82 patients with MWA, 645 patients with resection) differed significantly regarding age, American Society of Anesthesiologists class, Charlson comorbidity index, primary tumour location, number of metastases and previous chemotherapy. Before matching, 3- and 4-year OS differed significantly favouring resection over MWA (76% and 69%, 67% and 42%, p=0.005). After PS matching (201 resection patients, 70 MWA patients), no difference in OS after 3 and 4 years was shown between both groups (76% and 76%, 68% and 54%, p=0.253). Univariate HR for OS was 1.43 (95% CI 0.772 - 2.651, p=0.255) for the matched MWA group compared with the resection group. Conclusion: No significant difference in OS was found in patients undergoing MWA versus resection as a first-line intervention for CRCLM in the PS analysis used to minimize the effect of confounding by indication. This supports the potential role of MWA as a valid first treatment for patients with CRCLM.