Percutaneous versus Intraoperative Microwave Ablation of Hepatic Malignancy: A Comparison of Technique and Outcomes

Purpose: Microwave ablation is becoming increasingly recognized as a safe and effective treatment of hepatic primary and secondary malignancy for many patients with Hepatocellular Carcinoma (HCC) and metastatic CRC (mCRC) who are not surgical candidates. Microwave Ablation achieves local control and is used in two settings: Percutaneous ablation in an interventional suite using CT (CTa) and intraoperative ablation utilizing ultrasound for image guidance (ORa). We compare the technical differences and outcomes of these two ablation scenarios. Ablation site recurrence is compared controlling for tumor type to better define the role of ablation.

Materials and Methods: A single-center retrospective analysis of ablations over 8 years was analyzed to extract key clinical information, including the ablation setting (percutaneous vs intraoperative), ablated tumor pathology, number of lesions ablated, their size, and the recurrence rate. Treatment information was logged, including ablation antenna number, number of ablation cycles, cycle time, ablation energy settings, and postablation zone size. Subsequent statistical analysis was performed to determine differences between the ablation techniques and tumor type.

Results: There were 162 total cases included in the analysis, with 86.4% using percutaneous and13.6% using the ORa technique. Of the 105 HCC cases, 96% were performed percutaneously and 4% were performed intraoperatively; conversely, a significant portion of the mCRC population (57 cases) utilized the ORa approach (CTa-68.4%, ORa- 31.6%). There were 35 total documented recurrences at the ablation site with patients with HCC or mCRC. There were 27 CTa recurrence events (19.3% of all CTa). There were 8 ORa recurrence events (36.4% of all ORa). Key treatment variables were stratified by ablation technique, and there were no significant differences in recurrence rate, lesion size, ablation time, and ablation power between percutaneous and ORa.

Conclusions: There was no statistical difference in recurrence-free survival of patients ablated with the intraoperative and CT-guided approaches despite many inherent differences between the techniques. There were a higher proportion of patients with mCRC who underwent intraoperative ablation, which may have had an impact of the statistical result. Treatment parameters and lesion characteristics were also the same between the intraoperative and percutaneous populations.