Clinical features and risk factors for pelvic metastasis after microwave ablation of hepatocellular carcinoma: a nested case-control study.

Background: Pelvic metastasis (PM) from hepatocellular carcinoma (HCC) remains understudied. Clarifying its risk factors after microwave ablation (MWA) is essential for optimizing surveillance strategies and guiding personalized management.

Materials and methods: This retrospective study included patients with HCC who underwent MWA between January 2006 and August 2018. The cumulative rates of extrahepatic metastasis (EHM) and PM were estimated using the Kaplan-Meier method. Risk factors for EHM and PM were identified using the Cox proportional hazards model. A nested case-control design with a ratio of 1:4 was adopted, and the risk factors for PM were identified based on the logistic proportional hazards model.

Results: A total of 1646 patients were included in this study, and 95 patients (19 cases and 76 controls) were included in the final case-control analysis. The 1-, 2-, 3-, and 5-year cumulative rates of EHM were < 20.0%, whereas those of PM were < 1.0%. Sex, Barcelona Clinic Liver Cancer stage, treatment-naïve HCC, number of HCC nodules, and platelet count were associated with EHM risk. Biopsy (p = 0.018) and Child-Pugh class (p = 0.004) were identified as factors associated with an increased risk of PM in the entire cohort. In this retrospective nested case-control study, Child-Pugh class (p = 0.027) and the number of biopsy punctures were associated with an increased risk of PM (p = 0.04).

Conclusion: Multiple biopsy punctures and aggressive tumor features may indicate a high risk of PM.