PDL-1 and immunohistochemistry markers in esophageal adenocarcinoma.

e15567 Background: Esophageal adenocarcinoma (EAC) prognosis is poor and there is a need to identify patients that benefit most from neoadjuvant therapy. To examine the association of various biomarkers with clinical outcomes in neoadjuvant treatment of EAC, we retrospectively evaluated the biomarker expression (TS, ERCC1, TOPO1, PD-L1, PD-1) in patient matched formalin-fixed paraffin-embedded (FFPE) tumor samples. Methods: Immunohistochemistry of TS (TS106/4H4B1) , ERCC1 (Ab. 8F1), TOPO1 (1D6), PD-L1 (both 22c3 and SP142), PD-1 (NAT105), and chromogenic in-situ hybridization (CISH) of Her2 were performed on FFPE samples from 35 patients across 2 institutions at time of EAC diagnosis and after treatment when available. Retrospective clinical data and survival (5/2006-1/2016) was analyzed with a mean follow up of 110 months (range 22-306). Results: Overexpression (pre/post-treatment) of TS (60%/54%), ERCC1 (69%/16%), TOPO1 (74%/50%), PD-1 (54%/63%), PD-L1 (SP142) (2.9%/4%), PD-L1 (22c3) (0%/4%) and amplification of Her2 (18%/23%) were observed. Pretreatment observed PD-L1 levels were lower in our study (3%) when compared to other studies in EAC specimens (35%). Immunohistochemistry and changes observed after chemoradiation are reviewed in Table. No markers had significant correlation with prognosis however TS negative expression showed a non-significant (p=0.15) trend towards improved survival. Conclusions: Analyzing biomarkers in our neoadjuvant EAC cohort demonstrated a lower than expected PD-L1 positivity. In the largest cohort, to our knowledge, of patient matched FFPE tumor samples, we did not observe a statistically significant association between TS, ERCC1, TOPO1, PD-L1, or PD-1 with improved clinical outcomes. [Table: see text]