Abstract 3967: Comparison of neoadjuvant FOLFIRINOX alone vs FOLFIRINOX + stereotactic body radiation as immune-modulators of the pancreatic adenocarcinoma microenvironment

Abstract

Abstract Pancreatic ductal adenocarcinoma (PDAC) has dismal five-year survival (<9%). We examined the impact of neoadjuvant FOLFIRINOX alone or in combination with stereotactic body radiation (SBRT) on biomarkers in the PDAC tumor microenvironment (TME). We hypothesize conventional therapies may unmask novel targets in the TME that can be leveraged to enhance the efficacy of immunotherapy in PDAC. We conducted a pilot study using FFPE-tumor sections from PDAC patients who underwent upfront surgical resection (resection-only) or who received neoadjuvant FOLFIRINOX or FOLFIRINOX + SBRT (FOX or FOX+S, respectively) prior to resection (n=6/group). Average time (weeks) from end of neoadjuvant therapy - surgery was 6.6 ± 2.9 (FOX) or 7.0 ± 1.2 (FOX+S). Using the NanoString GeoMX platform to conduct multiplexed analysis of protein targets (~30 analytes) in spatially distinct regions of tumor tissue, we analyzed individual regions in each tumor that were enriched for malignant cells (Pan-Cytokeratin+), stroma (SMA+) or immune cells (CD45+). Across all tumor regions, FOX treatment was associated with increased CD14, CD56, PD-L1, phosphorylated (p-)STAT3, p-AKT, and PTEN compared to resection-only. In contrast, in FOX+S treated patients none of these were elevated in comparison to resection-only, and PTEN was significantly lower. Additionally, CD3, CD4, and CD8 expression—which did not differ between resection-only and FOX, were all significantly lower in FOX+S treated patients. Similar effects were observed in CD45-enriched regions. Whereas FOX treatment was associated with increased CD14, PD-L1, p-STAT3, p-AKT, PTEN, B7-H3, GZMB and β-catenin compared to resection-only, none of these were increased in FOX+S, while PTEN was again significantly decreased. Moreover, CD3 and CD4 expression were also significantly decreased in FOX+S. In tumor-rich regions, we found increased CD3, CD44, CD45RO, and CD56 in FOX-treated tumors as compared to resection-only. However, there was no difference in these markers when comparing resection-only and FOX+S. In addition, CD4 expression was lower in FOX+S samples while FOXP3 expression was unchanged, suggesting a relative enrichment of regulatory T cells. Finally, in αSMA-rich regions (stromal), FOX treatment was associated with increased p-STAT3 and significantly decreased CD4 and VISTA expression. FOX+S exhibited no such increase in p-STAT3 and further significant decreases in CD4 and VISTA expression, while also being associated with significantly lower CD3 and CD8 expression. This data provide insight into the immunological effects of standard of care neoadjuvant therapy for resectable/borderline-resectable PDAC. This work provides data to guide strategic new combination therapies for pancreatic cancer. Citation Format: Matthew R. Farren, Walid Shaib, Mohammad Zaidi, Layal Sayegh, David Kooby, Shishir Maithel, Alyssa Krasinskas, Olatunji Alese, Juan Sarmiento, Bassel El-Rayes, Gregory B. Lesinski. Comparison of neoadjuvant FOLFIRINOX alone vs FOLFIRINOX + stereotactic body radiation as immune-modulators of the pancreatic adenocarcinoma microenvironment [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 3967.