Abstract 5532: Differences in immune contexture across metastatic sites and tissue compartments in ovarian cancer

Abstract Introduction: Characterizing the immune contexture within the tumor microenvironment (TME) can provide valuable biological insights that may impact treatment regimens and improve clinical outcomes. The advent of neoadjuvant chemotherapy has provided a unique opportunity to study matched, pre- and post- treatment sample pairs, but these samples are often obtained from different metastatic sites. Innate differences in the immune profiles across metastatic sites could therefore be a confounding factor when attempting to determine treatment-related effects. Furthermore, immune contexture can also vary by region within the TME, so results could vary depending on the regions of interest (ROIs) selected for analysis. Methods: 36 matched, advanced primary ovarian cancer samples were obtained pre- and post- treatment with neoadjuvant chemotherapy aimed at reducing tumor burden. The first biopsy was taken at the time of initial diagnosis, whereas the second biopsy was collected after 3-4 rounds of carboplatin paclitaxel chemotherapy. Each slide was processed using a 26-plex multiplex immunohistochemistry (mIHC) assay, which interrogates immune cell densities and functional states for a broad range of immune cell populations, including CD8+ T cells, Tregs, TH1s, B cells, dendritic cells (DCs), granulocytes, macrophages, and monocytes. Tumor and stroma ROIs were selected by a board-certified pathologist using H Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 5532.