PS02.058: EXTENSIVE ANALYSIS OF IMMUNECHECKPOINT RECEPTORS AND TUMOR INFILTRATING T-CELLS WITH RESPECT TO THEIR PROGNOSTIC RELEVANCE IN ESOPHAGEAL ADENOCARCINOMA.

Background Immunotherapy has grown to a rapidly advancing sphere of research on modern strategies for treatment of cancer. A well-known way of immunomodulation is the principle of immune checkpoints leading to a down-regulated immune response in tumor microenvironment. Recently, beside the PD1/PD-L1 pathway, several immunecheckpoint pathways have been found. However, almost nothing is known about the expression and the correlation as prognostic factor in esophageal adenocarcinoma. Methods Two tissue micro arrays (TMA) were construced, a multi-spot TMA with up to 8 spots from different tumor areas of 165 patients and a valdiation single-spot TMA of 620 patients with EAC. Immunehistochemistry analysis were performed for LAG3, Tim3, IDO, VISTA, MHC1, MHC2, CD3, CD8, CD20 and CD38 and correlated with clinico-pathological and survival data. Data were additionally correlated with molecular data like TP53 mutational and HER2-neu status. Results LAG3 was detectable in 13.5% of all tumors, VISTA in 40.2%, IDO in 57.9%, Tim3 in 36.3%. There was only minor intratumoral heterogeneity between the luminal and infiltration area of the tumor for all analyzed immunecheckpoints. LAG3 and VISTA expression on tumor infiltrating T-cells (TIL) was associated with superior overall-survival compared to LAG3 and VISTA negative tumors. In pT1/2 tumors, VISTA was found as excellent independent prognosticator identifiying long-term surivors in case of VISTA expression. High amount of CD3 positive TILs was also associated with a better OS than CD3 poor tumors. Conclusion We conducted an extensive analysis of the immunecheckpoint status and presecnce of TILs in EAC. To the best of our knowledge, this is the first report in a large patients cohort correlating the expression of LAG3, Tim3, IDO and VISTA in EAC. The prognostic impact of LAG3 and VISTA expression suggests potential promising targets for novel immune checkpoint inhibition therapies beyond the PD1/PD-L1 inhibition as it is already established in head and neck cancer and NSCLC. Disclosure All authors have declared no conflicts of interest. [ABSTRACT FROM AUTHOR]