Long-term Oncological Outcomes after Resection and Thermal Ablation of Colorectal Liver Metastases: A Propensity Score Matched Analysis

Introduction: Thermal ablation of colorectal liver metastases is mostly used where resection is not possible, but has recently emerged as a parenchyma-sparing alternative to resection. High-quality data comparing oncological outcomes after resection and ablation of colorectal liver metastases are wanting. Method: Data for patient with colorectal liver metastases treated with laparoscopic resection at Oslo University Hospital between 2007 and 2020 was extracted from a prospectively maintained database and compared to patients undergoing ablation (radiofrequency or microwave). The primary endpoint was overall survival (OS). An average treatment effect (ATE) and potential-outcome means analysis using inverse-probability assignment and censoring using prognostic variables (CEA, largest tumor size, synchronous disease, primary tumor nodal status and sidedness, chemotherapy, previous liver surgery and others). Results: We identified 223 ablation sessions and 765 resection sessions available for comparison. The 5-year OS was 53% in the ablation group and 51% in the resection group. Median OS was 62,4 months (ablation) and 61,6 months (resection). The ATE for ablation versus resection was estimated to be 0,47 months (95% CI -8,1 to 9,9; P=0,92), meaning if every patient was treated with ablation, the average time to death would be 0,47 months longer than if every patient was treated with resection. A complete dataset including local recurrence will be presented at the meeting. Conclusion: Thermal ablation in patients with colorectal liver metastases was associated with rates of OS similar to surgical resection. Our results indicate adequate equipoise for a randomized trial to overcome selection bias.