732 TUMOR INFILTRATING NEUTROPHILS ARE A POOR PROGNOSTIC MARKER FOR ESOPHAGEAL CANCER PATIENTS RECEIVING NEOADJUVANT CHEMORADIOTHERAPY

Abstract

Abstract Significant advances have been made in our understanding of the tumor immune microenvironment (TIM) and tumor infiltrating lymphocytes (TILs). Nevertheless, there is little understanding of the changes in the TIM in response to neoadjuvant chemoradiotherapy (CRT). Thus, our aim was to investigate the changes in the TIM with neoadjuvant CRT in EC by assessing the immune cell infiltrate, the expression of immune related genes, and their association with treatment response and prognosis. Methods To decipher the effects of neoadjuvant CRT on the TIM, we obtained 58 paired pre-treatment and post neoadjuvant CRT treated EC specimens. TILs and tumor infiltrating neutrophils (TIN) were quantified in pre-treatment biopsies and surgical resection specimens following neoadjuvant CRT. To evaluate the immune transcriptomics, RNA was extracted from these specimens and gene expression was assessed using the Nanostring Platform based on the PanCancer Immune Profiling Panel. Immunohistochemistry (IHC) was performed to validate findings from the immune transcriptomics. Results TIL counts were not prognostic for disease specific survival (DSS). We observed higher expression of immune-suppressive inflammatory chemokines (TGFß-1 and IL-16) in post-neoadjuvant treated samples compared to pre-treatment biopsies. In samples collected after neoadjuvant CRT, low expression of genes related to anti-tumor T cell cytotoxic activity1 was significantly associated with disease recurrence. In patients with residual disease, multivariate analysis revealed a high neutrophil count, but not TIL count, was significantly associated with inferior DSS (HR 3.8 [1.3– 10.8]; p = 0.01). Conclusion In EC, the tumor microenvironment after neoadjuvant CRT remains largely immune-suppressive. We discovered that the presence of TINs in patients with residual disease post neoadjuvant CRT is an independent adverse prognostic factor. Collectively, our results suggest that an inflammatory pro-tumoral microenvironment associated with TINs may contribute to treatment resistance and progressive disease in EC.