Safety margin of radiofrequency ablation for hepatocellular carcinoma: a prospective study using magnetic resonance imaging with superparamagnetic iron oxide
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.
Materials and 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.
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.
MRI with pre-administered SPIO is useful for determining the AM precisely, and an AM of ≥ 2 mm is recommended for curative RFA.
Trial registration number
This study was registered with UMIN Clinical Trials Registry (UMIN 000025406).
KeywordsHepatocellular carcinoma Radiofrequency ablation Superparamagnetic iron oxide Ablative margin
KM and KF contributed equally. Study concepts, data analysis and manuscript drafting: KF and KM; acquisition of data and clinical studies: all authors; statistical analysis: NH; critical revision of the manuscript for important intellectual content: MA, MM, and IH; manuscript editing and final approval: all authors.
This study was not supported by any grants.
Compliance with ethical standards
Conflict of interest
All authors declare no potential conflict of interest.
This study was approved by the institutional ethics committee (H19-208) and was conducted in accordance with the ethical standards of the Declaration of Helsinki.
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