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

Introduction: Many previous studies comparing liver resection versus thermal ablation for colorectal cancer liver metastases (CRCLM) are subject to severe selection bias. The aim of this study was to compare survival after microwave ablation (MWA) versus liver resection for CRCLM in a population-based cohort study using propensity score analysis to reduce confounding by indication.
Methods: All patients undergoing liver resection or MWA as a first intervention for CRCLM measuring ≤ 3 cm between 2013 and 2016 in Sweden were included from a nationwide registry. Treatment effect was estimated after propensity score matching, adjusting for patient and tumour factors known to affect the choice of treatment approach. Descriptive, regression and survival statistics were applied.
Results: The unmatched cohorts (82 MWA patients, 645 resection patients) differed significantly regarding age, American Society of Anaesthesiologists class, Charlson comorbidity index, primary tumour location, number of metastases and previous chemotherapy, with 3-year overall survival (OS) favouring resection over MWA (76 and 69%, p = 0.005). After propensity score matching (70 MWA patients, 201 resection patients), no difference in 3-year OS was shown between resected and ablated patients (76% and 76%, p = 0.253), with a median OS of 54.7 (95% confidence interval 48.6 - 60.9) months and 48 (40.1-56.1) months, respectively.
Conclusion: After adjusting for factors known to affect treatment choice, no significant difference in OS was shown after MWA versus resection for CRCLM. This supports the potential role of MWA as a valid first-line treatment for patients with small CRCLM.
Competing Interests: Declaration of competing interest This research was partially supported by grants provided by Region Stockholm (ALF project), which had no involvement in study design, data collection or manuscript preparation. The authors declare no known conflicts of interest.
(Copyright © 2019 Elsevier Ltd, BASO ~ The Association for Cancer Surgery, and the European Society of Surgical Oncology. All rights reserved.)