Abstract 3456: Spatial evolution of the tumor immune microenvironment between primary and recurrent serous ovarian cancer using a sixty plex multiplex immuno oncology panel

Abstract Background: Despite advances in treatment, recurrent ovarian cancer continues to exhibit high recurrence rates, and immune checkpoint inhibitors (ICIs) demonstrate limited response (10-15%) due to a strongly immunosuppressive tumor immune microenvironment (TIME). The mechanisms of immune escape during recurrence remain insufficiently understood, highlighting the need for spatial characterization of TIME remodeling to optimize biomarker-guided combination immunotherapy. Methods: Formalin-fixed paraffin-embedded (FFPE) primary and recurrent tumor tissues from patients with recurrent serous ovarian cancer were used to construct matched tissue microarrays (TMAs). Multiplex immunofluorescence staining was performed using the Akoya IO60 immuno-oncology panel. Quantitative spatial image analysis was conducted using the Qupath workflow to assess immune cell composition, phenotypes, and tumor-immune architecture changes associated with recurrence. Results: A total of 58 patients were included, of whom 35 had matched primary and recurrent tumor specimens available. Based on chemotherapy response classification, 41 patients were categorized as platinum-sensitive and 8 as platinum-resistant. Spatial profiling analysis is ongoing. Preliminary observations suggest heterogeneous shifts in T-cell subsets (CD3, CD4, CD8), regulatory T cells (FOXP3+), and immunosuppressive myeloid populations (CD163+, CD206+), along with altered immune checkpoint pathways (PD-1, PD-L1, LAG-3, VISTA) and tumor phenotypes (PanCK, EpCAM) between primary and recurrent tumors. Conclusion: This study aims to characterize spatial evolution of TIME during recurrence and identify immune escape mechanisms contributing to treatment resistance. The findings are expected to guide the development of precision immunotherapy strategies and improve clinical outcomes for patients with recurrent ovarian cancer. Citation Format: Hayeon Shin, Jue young Kim, Yoon Joo Kim, Yookyung Lee, Jae-Hoon Kim. Spatial evolution of the tumor immune microenvironment between primary and recurrent serous ovarian cancer using a sixty plex multiplex immuno oncology panel [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 3456.