Albelal, Douaa

Tumor Treating Fields (TTFields) represent a novel, non-invasive therapeutic modality in oncology that employs low-intensity, intermediate-frequency alternating electric fields to disrupt mitotic processes and induce cancer cell death. This review integrates mechanistic, preclinical, and emerging clinical evidence supporting the integration of TTFields with immunotherapeutic strategies in pancreatic ductal adenocarcinoma (PDAC). Although immunotherapy has transformed the treatment landscape across multiple malignancies, its efficacy in PDAC remains limited due to the tumor’s dense stroma, immunosuppressive microenvironment, and low immunogenicity. Preclinical investigations suggest that TTFields may potentiate immune-based therapies by enhancing antigen presentation, modulating the tumor microenvironment (TME), and attenuating mechanisms of immune resistance. We highlight studies evaluating TTFields in combination with immune checkpoint inhibitors (ICI), adoptive cellular therapies, and cancer vaccines, emphasizing their potential synergistic effects in PDAC. Clinically, the phase II PANOVA-2 trial demonstrated feasibility and encouraging survival outcomes with TTFields in combination with gemcitabine and nab-paclitaxel, providing the rationale for the ongoing phase III PANOVA-3 trial and the phase II PANOVA-4 trial, which combines TTFields with chemotherapy and atezolizumab. Additional clinical experiences in glioblastoma (GBM) and non-small-cell lung cancer (NSCLC) further substantiate the broader applicability of TTFields as an immunomodulatory adjunct. Remaining challenges include optimizing treatment sequencing, identifying predictive biomarkers, and managing TTFields-associated toxicities. Collectively, current evidence positions TTFields as a promising strategy to augment immunotherapy in PDAC, warranting further translational and clinical investigation to establish its role in reshaping therapeutic paradigms.

Abstract 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. Citation Format: Douaa Albelal, Hari Krishnareddy Rachamala, Hani Babiker. Synergistic immunomodulation by Tumor Treating Fields combined with immunotherapy across solid tumors: A systematic review with translational relevance to pancreatic ductal adenocarcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 3813.

Importance The prognosis of advanced pancreaticobiliary tumors is poor. Next-generation sequencing (NGS) of tissue samples is utilized to identify actionable alterations, but there are occasional limitations due to inadequate tissue acquisition. Circulating tumor DNA (ctDNA) is an alternative method, but its correlation with tissue-based NGS remains unexplored. Objectives To assess the mutation concordance (mCR) rates between ctDNA and tissue testing for patients with pancreatic ductal adenocarcinoma (PDAC) and cholangiocarcinoma (CC) and to evaluate how ctDNA performs as a treatment response biomarker. Design, Setting, and Participants This retrospective cohort study was conducted among patients with PDAC and CC treated at academic institutions from January 2014 to January 2025. Patients underwent ctDNA testing using 1 platform and tissue NGS testing using 2 platforms. Main Outcomes and Measures mCR, which measures the shared gene alterations observed by both ctDNA and tissue-based NGS testing, was calculated using the Spearman correlation for PDAC and CC. The performance of ctDNA as a treatment response biomarker was assessed by comparing serial ctDNA data with restaging scans and cancer antigen 19-9 levels in patients with PDAC. Results Our cohort included 790 patients: 570 with advanced PDAC (265 [46.5%] female; median [IQR] age, 64 [33-84] years) and 220 with advanced CC (95 [43.2%] female; median [IQR] age, 66 [42-88] years). Overall, 461 patients with PDAC (80.9%) and 192 patients with CC (87.2%) underwent ctDNA testing, while 239 patients with PDAC (41.9%) and 70 patients with CC (31.8%) had tissue NGS testing. Among patients with PDAC, 85 of 130 patients (65.4%) showed shared specific gene alterations between ctDNA and tissue testing; there was a significant mCR, with a Spearman correlation of 0.47 (95% CI, 0.28-0.62; P < .001). For patients with CC, 32 of 48 (66.7%) had shared alterations between ctDNA and tissue testing; there was a significant mCR, with a Spearman correlation of 0.56 (95% CI, 0.35-0.70; P < .001). A subgroup analysis of patients with PDAC who underwent serial ctDNA testing suggested that new TP53 subclones and increased ctDNA variant allele frequency levels of TP53 and KRAS were associated with higher odds of progressive disease (eg, increased TP53 frequency: odds ratio, 7.28; 95% CI, 2.15-24.66; P = .001). Conclusions and Relevance In this cohort study of patients with pancreaticobiliary tumors, there was a significant mCR between ctDNA and tissue NGS testing. Additionally, results suggest that ctDNA might detect resistant clones and enable assessment of treatment response.

Abstract Background: TTFields are non-invasive and novel treatment modality that utilizes low intensity, alternating, and intermediate frequency electrical fields to inhibit cancer cell proliferation through a multitude of mechanisms. These include inhibition of mitosis, disruption of cancer cell membranes, metabolomic dysregulation of cancer cells, and immunogenic activation of the tumor microenvironment (TME). TTFields are approved in glioblastoma multiforme, non-small cell lung cancer and malignant mesothelioma. The PANOVA2 trial demonstrated promising efficacy for TTFields when applied together with chemotherapy in patients with PDAC. Mechanisms of TTFields in PDAC need further delineation. We sought to investigate the efficacy of TTFields in vitro and in vivo in PDAC cell lines and mouse models. Preclinical studies were conducted in concert with an going clinical trial (NCT04605913). Experimental Procedures: Utilizing the inovitro apparatus we studied the effect of TTFields (150kHz, intensity 2.9+0.2 V cm RMS, 37ċ, over 72 hrs) in an array of PDAC (Panc1, KPC, Panc2, and AsPC1) and human pancreatic stellate cells (hPSC) cell lines, alone or together with cisplatin (Cis, 0.1μM) or gemcitabine (Gem, 0.01μM), compared to control. Cell viability analysis was conducted in each of the groups. In addition, cell lysates from Panc1 cells from concomitant treatment of TTFields plus Gem were probed for STAT3 and α-SMA to analyze stromal proteins and RAS pathway components (KRAS, P38, P42, and others) were performed via Westen Blot. We also performed RNA sequencing for the different groups to analyze gene expression levels. We further assessed the effect of TTFields (150kHz, intensity 1.8-2 V/cm RMS, over 2 weeks) using the inovivo system with and without chemotherapy (Cis, 0.25 mg/Kg per dose (i.p.) 3 times a week) compared to control in C57BL6 orthotopic murine models (6-7 weeks old C57BL6 mice). Summary of Results: Our analysis revealed statistically significant abrogation of PDAC cancer cell lines for the different groups and hPSC cell viability when compared to control for TTFields monotherapy (p <0.001) and TTFields concomitantly with Gem or Cis (p <0.0001). Western blot analysis demonstrated that TTFields alone and when combined with chemotherapy alters both the stroma and RAS pathways with confirmed downregulation of pSTAT3 and α-SMA and KRAS, P-P38, and P-P42. In vivo analysis revealed significant decrease in tumor volume and weight for the concomitant effect of TTFields + Cis. Conclusion: Our preclinical studies demonstrated the efficacy of TTFields as monotherapy and concomitantly with chemotherapy in PDAC and hPSC cell lines and mouse models. Mechanistic insights from the pre-clinical studies will inform the design of future TTFields studies in PDAC. Citation Format: Hani M. Babiker, Santanu Bhattacharya, Douaa Albelal, Shamit Kumar Dutta, Enfeng wang, Debabrata Mukhopadhyay. umor treating fields (TTFields) plus chemotherapy abrogates pancreatic ductal adenocarcinoma (PDAC) proliferation and alters the tumor microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 1834.