PD-L1 expression in carcinoma of the esophagogastric junction is positively correlated with T-cell infiltration and overall survival

Introduction: In recent years antitumor immunity and inhibition of checkpoint molecules, such as PD-1 and PD-L1, have emerged as potential therapeutic strategies in advanced stages of various malignancies. We investigated PD-L1 expression in adenocarcinomas of the esophagogastric junction and correlated the results with densitiy of intratumoral T-lymphocytes. Methods: Immunohistochemical staining for PD-L1 was carried out on 135 samples using a tissue microarray. Scoring was done according to the combined positivity score. Results: 48.1% of tumors (65 cases) showed PD-L1 positivity with a score >= 1 while 51.9% were PD-L1 negative (70 cases). A positive correlation between PD-L1 negativity and mucinous and poorly cohesive carcinoma could be shown (p = 0.043), while no association existed for either gender, T-stage, N-stage, grading, surgical resection status, neoadjuvant therapy, distant metastases, lymphovascular or perineural invasion. No correlation of PD-L1 expression and overall survival could be detected (p = 0.497). Again, when stratified according to presence or absence of neoadjuvant therapy, no survival differences could be shown for either group (p = 0.540 and p = 0.736). When PD-L1 expression was correlated with density of tumor-infiltrating T-lymphocytes a positive correlation between PD-L1 positivity and denser T-cell infiltration could be shown (p = 0.001). Concerning overall survival, in PD-L1 negative cases, denser CD8-positive T-cell infiltrates were associated with prolonged survival times (p = 0.045). No differences could be shown for PD-L1 positive cases or CD103-positive T-cells. Conclusion: PD-L1 expression is frequent in esophagogastric adenocarcinoma and - when combined with dense CD8 infiltration - PD-L1 negativity correlates with prolonged overall survival.