Abstract PR-001: Neoadjuvant therapy is associated with altered composition of immune cell infiltration and an anti-tumorigenic microenvironment in resected pancreatic cancer
Authors: Costa Andressa Dias , Väyrynen Sara , Chawla Akhil , Zhang Jinming , Väyrynen Juha P. , Lau Mai Chan , Williams Hannah L. , Yuan Chen , Morales-Oyarvide Vicente , Rubinson Douglas A. , Clancy Thomas E. , Brais Lauren K. , Reilly Emma , Kozak Margaret M. , Linehan David C. , Dunne Richard F. , Chang Daniel T. , Hezel Aram F. , Koong Albert C. , Aguirre Andrew J. , Wolpin Brian M. , Nowak Jonathan A. 
Published: November 2020

Background: Neoadjuvant therapy (neoTX) may improve survival for patients with resectable or borderline resectable pancreatic ductal adenocarcinoma (PDAC). However, the impact of neoTX on the tumor immune microenvironment is incompletely understood, hampering efforts to identify optimal treatment combinations and predictive markers to guide patient selection. Design: We employed digital image analysis and three multiplex immunofluorescence (mIF) assays, comprising 15 immune cell markers, to identify T cell subpopulations, macrophage polarization and myeloid cell subpopulations in primary resected PDAC. A multi-institution cohort of untreated tumors (n=299) was analyzed to characterize the baseline tumor immune microenvironment, while resected tumors after FOLFIRINOX-based neoTX (n=36) or upfront surgery (n=30) were analyzed to identify immune microenvironmental change due to neoTX. Multivariable Cox proportional hazard regression models were used to assess associations with patient outcomes. Results: Macrophages, T lymphocytes, and granulocytes were all abundant in the previously-untreated PDAC microenvironment, yet their densities exhibited substantial heterogeneity across patient tumors. In the untreated multi-institutional cohort, higher CD3+ T cell density was associated with longer disease-free survival (DFS) and overall survival (OS), while M2-polarized macrophages and CD15+ARG1+ immunosuppressive granulocytes were associated with shorter survival times. In particular, a higher ratio of CD3+CD8+ T cells to CD15+ARG1+ immunosuppressive granulocytes was associated with longer DFS (Q4 vs. Q1 HR 0.46, Ptrend=0.002) and OS (Q4 vs. Q1 HR 0.70, Ptrend=0.02). While neoTX did not alter overall CD3+ density, it increased the relative proportion of CD3+CD8+ cells, resulting in a lower CD4/CD8 ratio (p&lt;0.001), and an elevated CD3+CD8+ to CD15+ARG1+ ratio (p&lt;0.001). Similarly, neoTX did not alter overall macrophage density, but it shifted the relative polarization balance towards an M1 phenotype (p&lt;0.001) and increased the number of M1 macrophages spatially co-localized with tumor cells (p&lt;0.001). Higher degree of M1 macrophage:tumor cell colocalization was associated with better histologic response (p&lt;0.001) and longer OS (High vs. Low HR 0.15, Ptrend=0.01). Finally, although neoTX did not alter either overall CD14+ or CD15+ myeloid cell density, it reduced CD15+ARG1+ immunosuppressive granulocyte density (p=0.01). Inclusion of radiotherapy (long-course chemoradiation, n=4 or SBRT, n=8) as part of neoadjuvant treatment was associated with few additional alterations in the immune microenvironment. Conclusion: While neoadjuvant chemotherapy minimally affects overall immune cell density, it significantly shifts the PDAC immune microenvironment towards an anti-tumorigenic state characterized by more CD8+ T cells and M1-polarized macrophages and fewer immunosuppressive granulocytes. These data may inform future neoadjuvant treatment strategies.

Citation Format: Andressa Dias Costa, Sara Väyrynen, Akhil Chawla, Jinming Zhang, Juha P. Väyrynen, Mai Chan Lau, Hannah L. Williams, Chen Yuan, Vicente Morales-Oyarvide, Douglas A. Rubinson, Thomas E. Clancy, Lauren K. Brais, Emma Reilly, Margaret M. Kozak, David C. Linehan, Richard F. Dunne, Daniel T. Chang, Aram F. Hezel, Albert C. Koong, Andrew J. Aguirre, Brian M. Wolpin, Jonathan A. Nowak. Neoadjuvant therapy is associated with altered composition of immune cell infiltration and an anti-tumorigenic microenvironment in resected pancreatic cancer [abstract]. In: Proceedings of the AACR Virtual Special Conference on Pancreatic Cancer; 2020 Sep 29-30. Philadelphia (PA): AACR; Cancer Res 2020;80(22 Suppl):Abstract nr PR-001.