MAVERRIC to compare microwave ablation to surgery for resectable colorectal liver metastases

Jacob Freedman

The Karolinska Institute-sponsored, prospective, observational MAVERRIC study aims to demonstrate that a strategy of first line local microwave ablation of colorectal liver metastases is not inferior to liver resection in terms of survival rates at three years.

Jacob Freedman, principal investigator of the study told Interventional News: “The lack of data that compare local ablative treatment with resection for liver metastases prompted us to undertake this study. Ablative treatment has, for many years, been used as an adjunct to resection and as an alternative when major surgery is contraindicated because of comorbid conditions. It has been clearly shown that ablative treatment is easier for the patient, resulting in far fewer complications and a much shorter length of hospital stay, but whether survival, the most important variable, is on par with surgery has not been shown despite a decade of speculation.”

Freedman is associate professor, Karolinska Institutet, Department of Clinical Sciences, Danderyd University Hospital, Division of surgery, Sweden.

The study has set out to enroll a cohort of 100 patients who will be treated with CT-guided microwave ablation (performed with any generic microwave ablation system cleared for clinical use). In order to be eligible for enrolment patients should have one to five metastases of less than 31mm in size. All lesions need to be amenable to CT-guided percutaneous microwave ablation, and the patient also needs to be deemed “resectable” and be so evaluated at a multidisciplinary tumour board meeting. The outcomes of ablative treatment will be followed and compared with propensity scored matched controls from the Swedish liver surgery registry (SweLiv).

The study is a multi-institutional effort by the hepatopancreaticobiliary units in Stockholm (Sweden), Bern (Switzerland) and Groningen (the Netherlands).

“The study is in full swing recruiting patients from all three centres since December. We now have 33 of the planned 100 patients treated and hope to close the study in early 2018,” Freedman explained.

The secondary endpoints outlined are: survival at five and ten years; interventional complication rates; length of stay; precise measurements of ablation; need for further interventions; and health-economic analysis.

Commenting on the choice of ablation modality, Freedman said, “We chose microwave because it has clearly been shown that it has benefits, although these are small, compared to radiofrequency ablation. The energy is delivered faster which reduces heat-sink problems and shortens anaesthesia times. There is no charring of tissue and no problems with conductivity [with microwave]. Larger lesions can be ablated with a single antenna.

“All procedures are CT guided with computer assisted guidance using the CAS-one system (CAScination). We are not using ultrasound because we want to have optimal documentation of each antenna placement for future reference, if there are recurrences. I am convinced that fused ultrasound would have been as good in most situations, but retrospective review is much more difficult with ultrasound images,” he concluded.