MR-guided microwave ablation of liver tumors: outcomes in local tumor control and determinants of treatment success.

objectivesTo evaluate local tumor control and determinants of treatment success following magnetic resonance (MR)-guided microwave ablation (MWA) of liver malignancies. MATERIALS AND

methodsThis single-center retrospective study evaluated prospectively included patients undergoing MR-guided MWA between September 2021 and February 2025. Procedures were performed under general anesthesia using a 1.5-Tesla MR scanner and two MR-compatible MWA systems. Complications were assessed according to CIRSE. Technical success was defined as total lesion coverage on MR imaging one day post-ablation. Local recurrence and hepatic tumor progression were analyzed using follow-up liver MR imaging every three months. Determinants of treatment success included lesion size, tumor entity, ablation duration, MWA system, lesion and antenna conspicuity (6-point Likert scale), adjacent vascular structures, liver cirrhosis, and antenna position (central/non-central).

resultsForty-eight liver lesions in 40 patients (median age 62.5 years, 70.0% male) were treated. MWA systems 1 and 2 were used in 33/48 (68.8%) and 15/48 lesions (31.3%), respectively. Technical success was achieved in 46/48 lesions (95.8%), with one peri-procedural complication (CIRSE grade 3, 2.5%). Mean follow-up was 21.0 ± 10.9 months, with one patient lost to follow-up. Local recurrence occurred in 4/47 lesions (8.5%), all treated with system 1, while no recurrence was observed with system 2 (p = 0.173). As the only relevant determinant of treatment success, adjacent vascular structures were associated with higher local recurrence rates (p = 0.019). No local recurrence occurred in lesions < 20 mm.

conclusionMR-guided MWA of liver tumors is safe, achieving high technical success and local tumor control. Adjacent vascular structures increase the risk of local recurrence and may warrant more aggressive treatment. KEY POINTS: Question Whether MR-guided MWA provides reliable local tumor control for liver malignancies and which procedural or anatomical factors influence treatment success. Findings MR-guided MWA achieved high technical success, low complication rates, and strong local tumor control; local recurrence occurred in lesions ≥ 20 mm and with low-power MWA systems, as well as adjacent vascular structures, significantly increased risk of local recurrence. Clinical relevance Prospectively acquired single-center cohorts of MR-guided MWA with real-time position monitoring in a standardized MR workflow, highlighting the impact of technical factors and the importance of lesion selection based on device-specific ablation characteristics.