Factors Impacting Microwave Ablation Zone Sizes: A Retrospective Analysis

Area of Science:

• Interventional Radiology
• Oncology
• Medical Physics

Background:

• Microwave ablation (MWA) is a minimally invasive treatment for liver tumors.
• Understanding factors influencing ablation zone volume (AZV) is crucial for optimizing MWA efficacy.
• Intrinsic tumor characteristics and extrinsic factors can affect treatment outcomes.

Purpose of the Study:

• To evaluate the impact of intrinsic and extrinsic conditions on ablation zone volumes (AZV) following microwave ablation (MWA).
• To compare AZV achieved with 'standard mode' versus 'surgical mode' MWA.
• To identify tumor-specific factors influencing MWA effectiveness.

Main Methods:

• Retrospective analysis of 38 MWA procedures on therapy-naïve liver tumors using the NeuWave PR probe.
• Ablations were performed in either 'standard mode' (65 W, 10 min) or 'surgical mode' (95 W, 1 min, then 65 W, 10 min).
• AZV was measured immediately post-ablation using contrast-enhanced computed tomography.

Main Results:

• AZVs in 'standard mode' were smaller than manufacturer predictions.
• No significant difference in AZV was observed between 'surgical mode' and 'standard mode' (15.6 ± 7.8 mL vs. 13.9 ± 8.8 mL, p = 0.6).
• Significantly larger AZVs were found for hepatocellular carcinomas (HCCs) versus metastases (17.8 ± 9.9 mL vs. 10.1 ± 5.1 mL, p = 0.01) and in non-perivascular versus perivascular locations (18.7 ± 10.4 mL vs. 11.7 ± 6.1 mL, p = 0.012).

Conclusions:

• Hepatocellular carcinomas (HCCs) and non-perivascular tumor locations are associated with larger ablation zone volumes (AZV) in MWA.
• The 'surgical mode' of MWA does not yield significantly larger AZVs compared to the 'standard mode'.
• Tumor type and location are significant factors influencing MWA outcomes.