Abstract 2649: PD-L1 expression as a predictive factor for recurrence pattern and prognosis in curatively resected gastric cancer
Authors: MORIHIRO TOSHIAKI , Kuroda Shinji , Kubota Tetsushi , Tazawa Hiroshi , Kagawa Shunsuke , Fujiwara Toshiyoshi 
Published: July 2016

Abstract
Interaction of programmed death-1 (PD-1) and programmed death-ligand 1 (PD-L1) induces functional impairment of antigen-specific T cells, which leads to immune evasion of tumors. Immune checkpoint therapy including PD-1/PD-L1 blockade is an emerging treatment strategy which brings great improvement in patient's prognosis. Many reports have mentioned that PD-L1 expression on tumors correlates with poor prognosis in various types of cancers. While there is a few report about correlation between PD-L1 expression and prognosis in gastric cancer, one of the most common cancers in the world especially in Asia, it still remains controversial. In addition, almost no report has referred to the correlation of PD-L1 expression with metastatic or recurrence pattern of cancers. Thus, we investigated the correlation of PD-L1 expression with prognosis and recurrence pattern in gastric cancer patients. In this study, 255 gastric cancer cases which had curative surgical resection at Okayama University Hospital between 2002 and 2009 were analyzed retrospectively in terms of correlation of PD-L1 expression on tumors with patient's prognosis and recurrence pattern in addition to clinicophathological features. When PD-L1 expression was classified into 4 groups according to PD-L1 positive rate on tumors on immunohistochemical staining (0: &lt; 1%, 1+: 1-5%, 2+: 5-10%, 3+: ≥10%) and 2+ and 3+ were defined as PD-L1 positive, PD-L1 positive rate was 15% (37/255). PD-L1 positive cases had significant correlation with advanced stage (p = 0.0424), lymphatic invasion (p = 0.0028) and venous invasion (p = 0.0254), and tendency to be more observed in intestinal type than diffuse type (p = 0.0599) in terms of histological types of cancer. Overall survival (p = 0.0109) and disease-free survival (p = 0.0052) were significantly poor in PD-L1 positive group. Moreover, PD-L1 expression had significant negative correlation with peritoneal dissemination (p = 0.0081) and had tendency to cause hematogenous recurrence (p = 0.1002) in terms of recurrence pattern after curative surgical resection, which might be reflected by the correlation of PD-L1 expression and histological types of cancer. Multivariate analysis revealed that PD-L1 expression was an independent risk factor for recurrence (p = 0.0160, odds ratio: 3.19), along with diffuse type and advanced stage. In conclusion, PD-L1 expression on tumors strongly correlated with poor prognosis and negatively correlated with peritoneal dissemination in recurrence pattern in gastric cancer patients who had curative surgical resection.
Citation Format: TOSHIAKI MORIHIRO, Shinji Kuroda, Tetsushi Kubota, Hiroshi Tazawa, Shunsuke Kagawa, Toshiyoshi Fujiwara. PD-L1 expression as a predictive factor for recurrence pattern and prognosis in curatively resected gastric cancer. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2649.