Radiofrequency Ablation of Hepatocellular Carcinoma with a “Nodule-in-Nodule” Appearance: Long-Term Follow-up and Clinical Implications

Purpose: Hepatocellular carcinoma (HCC) with a “nodule-in-nodule” (NIN) appearance has unique histological characteristics as an early HCC. We assessed long-term therapeutic outcomes of radiofrequency ablation (RFA) in HCC patients considering this appearance. Materials and Methods: Our Institutional Review Board approved this retrospective study, and the requirement for written informed consent was waived. Between May 2006 and April 2012, a total of 572 patients underwent RFA for single HCC as a first-line treatment. Patients were divided into a NIN HCC group (n = 22) and a non-NIN HCC group (n = 550), according to the NIN feature on pretreatment imaging studies. Local tumor progression (LTP) and disease-free survival (DFS) were compared. Prognostic factors for LTP and DFS were assessed using a Cox proportional hazards model. Results: The cumulative LTP rates were 4.6 and 4.6% at 3 and 5 years, respectively, in the NIN HCC group, and 15.9 and 20.5% in the non-NIN HCC group, with borderline statistical significance (p = 0.085). The corresponding DFS rates were 53.8 and 37.7% in the NIN HCC group and 44.0 and 31.7% in the non-NIN HCC group, with no significant difference (p = 0.318). Although on multivariate analysis only tumor size was a significant prognostic factor for LTP, there was a trend bordering on the significance for the NIN feature [hazard ratio (HR) = 0.19; p = 0.099]. However, it was not a significant factor for DFS (HR = 0.18; p = 0.682). Conclusions: The NIN appearance, a rare (4%, 22/550) but unique feature of early HCC, may be a favorable prognostic factor for RFA in terms of local tumor control.