Safety margin of radiofrequency ablation for hepatocellular carcinoma: a prospective study using magnetic resonance imaging with superparamagnetic iron oxide.


Department of Gastroenterology, Institute of Clinical Medicine, Faculty of Medicine, University of Tsukuba, Tennodai 1-1-1, Tsukuba, Ibaraki, 305-8575, Japan. [Email]


OBJECTIVE : In radiofrequency ablation (RFA) for hepatocellular carcinoma (HCC), it is difficult to assess the ablative margin (AM) precisely by comparing pre- and post-RFA CT images. We prospectively studied the AMs using magnetic resonance imaging (MRI) with pre-administered superparamagnetic iron oxide (SPIO). SPIO is safe for kidney disease patients.
METHODS : Hepatocellular carcinoma patients were treated with RFA within 8 h of SPIO administration. On T2*-weighted MRI performed 4-7 days later, AM was visualized as a hypointense rim. The ablation status was classified as AM(+) if the rim completely surrounded the tumor, AM(0) if the rim was partly discontinuous without tumor protrusion, and AM(-) if the rim was partly discontinuous with tumor protrusion. The minimal thickness of AM was measured. AM(-) tumors were re-treated consecutively.
RESULTS : In total, 85 HCCs ablated in 76 patients were evaluated. The local recurrence rate at 3 years was 2% for AM(+) tumors and 34% for AM(0) tumors (p < 0.01). In addition, no local recurrence was seen in the tumors with an AM of ≥ 2 mm.
CONCLUSIONS : MRI with pre-administered SPIO is useful for determining the AM precisely, and an AM of ≥ 2 mm is recommended for curative RFA.
BACKGROUND : This study was registered with UMIN Clinical Trials Registry (UMIN 000025406).


Ablative margin,Hepatocellular carcinoma,Radiofrequency ablation,Superparamagnetic iron oxide,