Synergistic immunomodulation by Tumor Treating Fields combined with immunotherapy across solid tumors: A systematic review with translational relevance to pancreatic ductal adenocarcinoma.

Background: Pancreatic ductal adenocarcinoma (PDAC) remains highly lethal due to aggressive biology, stromal desmoplasia, and profound immunotherapy resistance. Tumor Treating Fields (TTFields) disrupt mitosis and induce immunogenic cell death (ICD), type I interferon signaling, and microenvironment remodeling, providing a rationale for combining TTFields with immune checkpoint inhibition. This is the first systematic review to comprehensively synthesize mechanistic and clinical evidence for TTFields immunotherapy combinations across solid tumors, with emphasis on their translation relevance to PDAC. Methods: A systematic search of PubMed, Scopus, Web of Science, Embase, Cochrane Library, and ClinicalTrials.gov was conducted through October 26, 2025, following PRISMA 2020 guidelines. Eligible studies evaluated TTFields combined with immunotherapy. Two reviewers independently screened and extracted data using Covidence. Evidence was summarized narratively by tumor type, study design, and immunotherapeutic approach. Results: Thirty-seven studies met criteria, including preclinical and clinical investigations across glioblastoma, NSCLC, mesothelioma, PDAC, and other tumors. Preclinical models consistently showed that TTFields trigger ICD hallmarks such as calreticulin exposure, HMGB1 and ATP release, and activate STING/type I interferon pathways, enhancing dendritic-cell maturation and T-cell and NK-cell function. Across in vivo models, TTFields combined with PD-1 or CTLA-4 blockade, vaccines, or other immunotherapies reduced tumor growth and increased lymphocyte infiltration. Clinical evidence, although early-phase and heterogeneous, indicates the combination is feasible, with toxicity dominated by low-grade skin reactions and no excess immune-related adverse events. In glioblastoma, adding TTFields to pembrolizumab and temozolomide showed numerically improved survival. The LUNAR phase 3 trial in metastatic NSCLC demonstrated an overall survival advantage when TTFields were added to systemic therapy, including immunotherapy. Evidence in PDAC remains preliminary, but the ongoing PANOVA-4 study combining TTFields with atezolizumab and chemotherapy highlights emerging translational relevance. Conclusions: TTFields enhance antitumor immunity when combined with immunotherapy across solid tumors. In PDAC, these mechanisms may help counteract the immunosuppressive microenvironment. Ongoing gastrointestinal trials will clarify optimal combinations, biomarkers of response, and the clinical role of TTFields-based immunomodulation.