Achieving the Best Local Tumor Control for Colorectal Liver Metastases

Margins greater than 5 mm are necessary for local tumor control for both radiofrequency ablation and percutaneous microwave ablation, researchers reported in the Journal of Vascular and Interventional Radiology.

Researchers conducted a retrospective review to determine which factors may predict local tumor progression (LTP)-free survival after radiofrequency ablation and microwave ablation of colorectal liver metastases. The review included 110 patients with colorectal liver metastases that were ablated from November 2009 to April 2015. Contrast-enhanced computed tomography (CT) was used to measure the margins at 6 weeks post ablation. A competing risk model that was adjusted for clustering was used to evaluate clinical and technical predictors of LTP-free survival.

Complete ablation was 93% for radiofrequency ablation and 97% for microwave ablation, although the median follow-up period was 56 months for radiofrequency versus 29 months for microwave ablation. The two modalities showed no difference in local tumor progression rates.

For radiofrequency ablation, there was shorter LTP-free survival on univariate analysis when margins were 5 mm or smaller. Perivascular tumors were also found to predict shorter LTP-free survival on univariate analysis, and both these predictors remained upon multivariate analysis.

For microwave ablation, margins 5 mm or smaller likewise predicted shorter LTP-free survival on univariate analysis, as did no history of prior liver resection. Upon multivariate analysis, both factors were still significant. However, perivascular tumors were not predictive for microwave ablation.

Additionally, in tumors ablated with margins more than 10 mm, there was no local tumor progression.

“Regardless of the thermal ablation modality used, margins larger than 5 mm are critical for local tumor control, with no LTP noted for margins over 10 mm. Unlike radiofrequency ablation, the efficiency of microwave ablation was not affected for perivascular tumors,” the researchers concluded.

Reference

Shady W, Petre EN, Do KG, et al. Percutaneous microwave versus radiofrequency ablation of colorectal liver metastases: ablation with clear margins (a0) provides the best local tumor control. 2017 Dec 2. pii: S1051-0443(17)30825-4. doi: 10.1016/j.jvir.2017.08.021. [Epub ahead of print].