In Situ Vaccination by Tumor Ablation: Principles and Prospects for Systemic Antitumor Immunity

Cancer immunotherapy has redefined oncology's goals, aiming for durable systemic immunity rather than mere cytoreduction. However, many solid tumors remain refractory due to immunosuppressive microenvironments and antigenic heterogeneity. Local tumor ablation techniques-including radiofrequency ablation (RFA), microwave ablation (MWA), cryoablation, irreversible electroporation (IRE), and high-intensity focused ultrasound (HIFU)-are being re-evaluated beyond their historic cytoreductive role. This comprehensive review synthesizes the paradigm of tumor ablation as an in situ vaccination strategy, a concept that leverages the tumor itself as a source of antigens and the ablation process to generate endogenous adjuvants. We detail the mechanistic underpinnings, highlighting how ablation induces immunogenic cell death (ICD), releasing damage-associated molecular patterns (DAMPs) such as calreticulin, ATP, HMGB1, and cytosolic DNA. These signals activate innate immunity via pathways like cGAS-STING, promote dendritic cell maturation, and facilitate epitope spreading. We critically examine the determinants of efficacy, including the critical impact of ablation modality on the "DAMP signature," the necessity of complete ablation, and the pivotal role of the host's immune contexture. Furthermore, we explore the induction of tertiary lymphoid structures (TLS) as a key anatomical site for sustained immune priming. Translational strategies are extensively discussed, focusing on optimizing procedural techniques, rationally combining ablation with immune checkpoint inhibitors (ICIs) and innate immune agonists, and developing a robust biomarker framework. By adopting the core principles of vaccinology-meticulous attention to antigen, adjuvant, route, and schedule-ablation can be engineered into a reproducible platform for systemic immunotherapy. This review concludes by addressing current limitations and outlining a roadmap for clinical translation, positioning interventional oncology as a central discipline in the future of immuno-oncology.