598P - PD-L1 expression in resected colorectal adenocarcinomas is associated with micrometastais

Abstract

Background: Programmed cell death 1 (PD-1) and its ligand (PD-L1) are key suppressors of the cytotoxic immune response. PD-L1 expression on tumor cells may be induced by the immune microenvironment, resulting in immune escape, and an adverse prognosis in many malignancies. In colorectal carcinoma the response to PD-1/PD-L1 inhibition is correlated with microsatellite instability. However, little is known about the clinicopathologic, molecular, and prognostic characteristics of colorectal carcinoma with PD-L1 expression. In surgically resected colorectal adenocarcinoma, micrometastasis should be crucial for recurrence, and micrometastasis may be related to PD-L1. The aim of this study is to assess the PD-L1 expression and its association with clinicopathologic manifestations. Methods: PD-L1 expression was evaluated in 176 resected colorectal adenocarcinomas using tissue microarrays. Immunohistochemical staining was performed to evaluate the expression of PD-L1. The relationship of clinicopathologic manifestations and PD-L1 expression in colorectal cancer were evaluated by chi-squared test, Kaplan-Meier survival and Cox regression test. Results: High PD-L1 expression was present in 52.8% colorectal adenocarcinoma and was not related pathologic T or N stage. High PD-L1 expression was associated with decreased recurrence rate (p < 0.001), better disease-free survival (p < 0.001). Cox regression analysis revealed that pathologic N stage and High PD-L1 expression was an independent prognostic factors of disease-free survival (p < 0.001). Conclusions: High PD-L1 expression is an independent prognostic factor, such as pathologic stage in colorectal adenocarcinoma. PD-L1 expression is independent prognostic factor, relating immune response to micrometastasis and immune suppression by PD-L1 may not be effective in micrometastasis of colorectal adenocarcinoma. Legal entity responsible for the study: None Funding: None Disclosure: All authors have declared no conflicts of interest.