Objective <p>Previous studies on the immune function after radiofrequency ablation (RFA) mainly focused on the immune microenvironment in residual tumors. Thus, we investigate the impact of complete RFA (cRFA) and incomplete RFA (iRFA) on the immune microenvironment of distant tumors, determining whether combination with immunotherapy can improve outcomes.</p> Materials and materials <p>Using a bilateral subcutaneous CT26 murine model, one tumor underwent cRFA or iRFA while the contralateral tumor served as a distant site. Immune profiling by ribonucleic acid (RNA) sequencing, flow cytometry, and immunohistochemistry was performed at days 3 and 9 post-RFA (6 mice per group). Based on transcriptomic findings, anti-CTLA-4 therapy was evaluated following cRFA. Tumor growth and survival were additionally assessed (8 mice per group).</p> Results <p>Infiltration of CD8⁺ T-cells post-RFA increased at day 3 compared with controls (<i>p</i> = 0.049), while decreasing at day 9 after cRFA. Additionally, the ratio between pro-inflammatory and anti-inflammatory macrophages (M1/M2) decreased at day 9 (<i>p</i> = 0.034), suggesting an immunosuppressive microenvironment. RNA-seq demonstrated that CTLA-4 significantly upregulated 9 days after cRFA. Combined cRFA+anti-CTLA-4 increased distant tumor CD8⁺ T-cells, and distant tumor growth in this group was significantly decreased <i>versus</i> cRFA alone (<i>p</i> = 0.040).</p> Conclusion <p>Complete RFA is associated with a delayed immunosuppressive shift in distant tumors. Targeting CTLA-4 following ablation may partially mitigate this effect and enhance systemic tumor control.</p> Relevance statement <p>The combination of anti-CTLA-4 targeted therapy and complete radiofrequency ablation demonstrated a synergistic anti-tumor immunotherapy effect, which provided a potentially better therapeutic strategy for preventing tumor recurrence after radiofrequency ablation.</p> Key Points <p><UnorderedList Mark="Bullet"> <ItemContent> <p>The RNA-seq results demonstrated that CTLA-4 was upregulated in the distant tumor on 9 days after complete radiofrequency ablation.</p> </ItemContent> <ItemContent> <p>Anti-tumor immune response initially associated with radiofrequency ablation was relatively transient, while an immunosuppressive microenvironment was formed in the distant tumor in 9 days.</p> </ItemContent> <ItemContent> <p>Anti-CTLA-4 therapy after complete ablation significantly delayed distant tumor growth and promoted an anti-tumor immune microenvironment.</p> </ItemContent> </UnorderedList></p> Graphical Abstract <p></p>