Characteristics Of Pd-L1, Pd-1 Expressions And Cd8+Tumor Infiltrating Lymphocyte In Ebv-Associated Nasopharyngeal Carcinoma

6070 Background: Early phase clinical studies showed promising activities of anti-PD1/PD-L1 antibody in squamous cell carcinoma of head and neck (SCCHN). PD-L1 expression is a potential biomarker of these drugs. Tumor Infiltrating Lymphocyte (TIL) was a prognostic marker of HPV+ SCCHN and potentially associated with response of immunomodulatory drugs. Most clinical trials of anti-PD1/PD-L1 often excluded nasopharyngeal carcinoma (NPC). We evaluated characteristics of PD-L1 expression and CD8+ TIL for a future development of anti-PD1/PD-L1 antibody in NPC. Methods: NPC patients were identified through the Ramathibodi Cancer Registry database between 1/2007 and 12/2012. PD-L1 and PD-1 expressions were characterized by immunohistochemistry (IHC) from formalin-fixed paraffin-embedded tumor samples. PD-L1 expression was defined by using a cut-off of ≥1% (≥1-9%=1+, 10-49%=2+, ≥50%=3+). Mean number of CD8+TILs following the analysis of 2-4 images was assessed quantitatively by 2 individual pathologists blinded t...