Comparative Analysis of Systemic Immune Responses and Metastatic Risks in Tumor Ablation: An Animal Study of Radiofrequency Ablation and Irreversible Electroporation with Immune Modulation

Purpose: This study aimed to compare systemic immune responses and metastatic effects induced by radiofrequency ablation (RFA) and irreversible electroporation (IRE) in murine tumor models. We assessed cytokine production, growth of treated and untreated metastatic tumors, and synergy with immune checkpoint inhibitors (ICIs).

Materials and methods: Hep55.1c murine hepatoma cells were implanted in C57BL/6N mice to establish primary tumors. In Experiment 1 (n = 50), RFA or IRE was applied to primary tumors, followed by CD8⁺ T cell depletion in some groups to assess anti-tumor immune responses. Experiment 2 (n = 45) tested RFA and IRE combined with anti-PD-1 therapy for enhanced abscopal effects. In Experiment 3 (n = 28), anti-IL-6 antibody was administered in IRE-treated mice to examine IL-6's role in secondary tumor growth. Tumor volumes and cytokine/chemokine levels were monitored.

Results: Both techniques induced significant CD8⁺ T cell-mediated anti-tumor responses, with abscopal effects observed in untreated secondary tumors. CD8⁺ T cell depletion abolished these effects, confirming their role in systemic tumor control. Anti-PD-1 therapy combination further suppressed secondary tumor growth. However, IRE uniquely elevated IL-6 and other inflammatory cytokines, unexpectedly accelerating secondary tumor growth. Administration of an anti-IL-6 antibody mitigated this effect, reducing secondary tumor progression.

Conclusion: The results of this animal study indicate that both techniques promote systemic anti-tumor immunity, though IRE uniquely induces an inflammatory response that risks exacerbating micro-metastases through IL-6. Combining IRE with IL-6 blockade may offer a promising strategy for nonthermal tumor ablation therapies. Further studies are warranted to refine ablation-immune therapy combinations for optimal therapeutic outcomes.