The Importance of Optimal Thermal Ablation Margins in Colorectal Liver Metastases: A Systematic Review and Meta-Analysis of 21 Studies

Abstract

Background: Colorectal cancer (CRC) is the second most common cause of cancer-related deaths in the US. Thermal ablation (TA) can be a comparable alternative to partial hepatectomy for selected cases when eradication of all visible tumor with an ablative margin of greater than 5 mm is achieved. This systematic review and meta-analysis aimed to encapsulate the current clinical evidence concerning the optimal TA margin for local cure in patients with colorectal liver metastases (CLM). Methods: MEDLINE, EMBASE, and the CENTRAL databases were systematically searched from inception until 1 May 2023, in accordance with the PRISMA Guidelines. Measure of effect included the risk ratio (RR) with 95% confidence interval (CI) using the random-effects model. Results: Overall, 21 studies were included, comprising 2005 participants and 2873 ablated CLMs. TA with margins less than 5 mm were associated with a 3.6 times higher risk for LTP (n = 21 studies, RR: 3.60; 95% CI: 2.58–5.03; p-value < 0.001). When margins less than 5 mm were additionally confirmed by using 3D software, a 5.1 times higher risk for LTP (n = 4 studies, RR: 5.10; 95% CI: 1.45–17.90; p-value < 0.001) was recorded. Moreover, a thermal ablation margin of less than 10 mm but over 5 mm remained significantly associated with 3.64 times higher risk for LTP vs. minimal margin larger than 10 mm (n = 7 studies, RR: 3.64; 95% CI: 1.31–10.10; p-value < 0.001). Conclusions: This meta-analysis solidifies that a minimal ablation margin over 5 mm is the minimum critical endpoint required, whereas a minimal margin of at least 10 mm yields optimal local tumor control after TA of CLMs.

Imaging Considerations before and after Liver-Directed Locoregional Treatments for Metastatic Colorectal Cancer

“…Definitive evidence on the superiority of A0 margins came from a recent meta-analysis which included the pooled results of 21 studies examining the oncological outcomes of thermal ablation stratified by ablation margins. In this study, the authors confirmed that the risk for local tumor progression is at least 3.6 times higher when the minimal ablation margin is less than 5 mm (Risk Ratio: 3.60; 95% CI: 2.58-5.03; p-value < 0.001) [62]. When possible, the achievement of an A0 ablation margin is associated with a local tumor progression-free survival exceeding 95%; this represents an opportunity for local cure similar to surgery, but with a reduced morbidity and risk of complications [7].…”

Using Patient-Specific 3D Modeling and Simulations to Optimize Microwave Ablation Therapy for Liver Cancer

“…Achieving a 5-10 mm MAM ensures the long-term success of MWA treatment and reduces the risk of local tumor progression and recurrence [17,22,23,67]. In the present study, a MAM of 5 mm was achieved clinically and computationally for all three patients, regardless of whether the therapy was completed at the scheduled ablation time (9.5 or 10 min) or the optimized ablation time (8 min for patients 1 and 2 and 7 min for patient 3).…”