Are all local tumour progressions of HCC related to thermal ablation? A study of the causes and classification of local tumour progression

Objectives Local tumour progression (LTP) is believed to be a negative consequence of imperfect thermal ablation, but we wondered if all LTP is truly due to imperfect ablation. Methods This study included 185 LTPs occurring within 1 cm of the ablation zone (AZ) after clinical curative thermal ablation for <= 5 cm hepatocellular carcinoma between 2010 and 2019. The AZ was divided into 8 quadrants by coronal, sagittal, and horizontal planes. Two methods, visual assessment through pre- and post-MRI (VA) and tumour mapping for 3D visualisation pre- and post-MRI fusion (MF), were used to assess which AZ quadrant included the shortest ablation margin (AM) by three doctors. LTP subclassification was based on whether LTP contacted the AZ margin (contacted LTP and dissociated-type LTP) and occurrence at different time points (12, 18, and 24 months). Results Fleiss's Kappa of VA and MF was 0.769 and 0.886, respectively. Cohen's Kappa coefficient between VA and MF was 0.830. For all LTPs, 98/185 (53.0%) occurred in the shortest AM quadrant, which showed a significant central tendency (p < 0.001). However, only 8/51 (15.7%) dissociated - type LTPs and 6/39 (15.4%) LTPs after 24 months occurred in the shortest AM quadrant, which showed no evenly distributed difference (p = 0.360 and 0.303). Conclusions MF is an accurate and convenient method to assess the shortest AM quadrant. LTP is a central tendency in the shortest AM quadrant, but dissociated-type and LTPs after 24 months are not, and these LTP types could be considered nonablation-related LTPs.

Automated summary

This study found that using the MF method can accurately and conveniently assess the shortest ablation margin quadrant. LTP tends to occur in the shortest ablation margin quadrant, but dissociated-type LTP and LTPs after 24 months do not, suggesting that these types of LTP may not be related to ablation.