Noninferiority in Overall Survival with Thermal Ablation for Treating Small Colorectal Liver Metastases

Take-Away Points

• ■ Major Focus: Investigating the noninferiority in overall survival (OS) for microwave ablation (MWA) versus resection to treat potentially resectable small colorectal liver metastases (CRLM).

• ■ Key Results: Treating small, resectable CRLM with MWA yields comparable patient OS to that observed following hepatic resection while also significantly reducing treatment-related morbidity.

• ■ Impact: Management of CRLM is continuously evolving, implying a potential shift toward more interventional, minimally invasive, and tissue-preserving therapeutic approaches.

The liver is the most common site for metastasis in patients with colorectal cancer, the second most common cause of cancer-related deaths worldwide. Surgical resection of CRLM has been the primary curative treatment option, but radiofrequency ablation and MWA techniques have recently gained acceptance in clinical guidelines for managing small, unresectable CRLM. While previous observational studies demonstrate similar OS outcomes between thermal ablation and surgical resection, findings from high-quality, prospective studies and randomized controlled trials are lacking, thus hindering broader application of this less invasive technique.

In this nonrandomized, prospective, multicenter cohort study, Tinguely et al investigated the noninferiority in OS when comparing MWA with hepatic resection for potentially resectable, small CRLM. The study group comprised patients with up to five CRLM, each no larger than 30 mm, who were intentionally treated with MWA (patients considered eligible for both MWA and hepatic resection during local multidisciplinary team meetings). The contemporary control group was identified from a prospectively maintained nationwide Swedish database and consisted of patients with up to five CRLM, none larger than 30 mm, who underwent hepatic resection. The 3-year OS rates were 78% (95% CI: 68%, 85%) after MWA compared with 76% (95% CI: 69%, 82%) after hepatic resection (P = .86). Estimated 5-year OS rates were 56% (95% CI: 45%, 66%) versus 58% (95% CI: 50%, 66%), respectively. Overall and major complications occurred less frequently after MWA (a percentage decrease of 67% and 80%, respectively; P < .01). However, hepatic retreatments were more frequent after MWA (a percentage increase of 78%, P < .01).

These results support the use of MWA as a viable alternative for curative treatment in patients with small CRLM. The results of the randomized controlled COLLISION and NEW-COMET trials, which directly compare ablation with resection, are eagerly anticipated. Management of CRLM is continuously evolving, implying a potential shift toward more interventional, minimally invasive, and tissue-preserving therapeutic approaches.

Highlighted Article

• Tinguely P, Ruiter SJS, Engstrand J, et al. A prospective multicentre trial on survival after Microwave Ablation VErsus Resection for Resectable Colorectal liver metastases (MAVERRIC). Eur J Cancer 2023;187:65–76. doi: https://doi.org/10.1016/j.ejca.2023.03.038