Programmed cell death 1 (PD-1) and its ligand (PD-L1) expression in thymic epithelial tumors (TETs): Impact on the treatment efficacy and alteration in expression after chemotherapy (C).

Abstract

7515 Background: Recent studies have demonstrated the efficacy of anti-PD-1/L1 antibodies. To understand the clinical impact of PD-1/L1 expression in TETs, we evaluated the frequency of PD-1/L1 expression in pre- and post-C (Pre/Post) specimens and the correlation between PD-1/L1 expression and the treatment efficacy. Methods: The expression of PD-1/L1 was evaluated by immunohistochemistry in patients (pts) with thymoma (TM) or thymic carcinoma (TC) treated by chemotherapy between 2000 and 2014 at the National Cancer Center Hospital. Using formalin-fixed paraffin-embedded tissue samples and a validated PD-L1 antibody (E1L3N), the PD-L1 expression in TET cells was reported in terms of the H-score (0-300), with a score ≥ 1 being defined as positive. PD-1 expression in the tumor-infiltrating lymphocytes was evaluated based on the intensity (0–3) of staining using a PD-1 antibody (NAT105). The objective response rate (ORR), progression-free survival (PFS) and the difference in PD-1/L1 expression between the P...