Abstract
OBJECTIVES: Primary pulmonary lymphoepithelioma-like carcinoma (PLELC) is a subtype of lung carcinoma associated with the Epstein-Barr virus (EBV). The clinical predictive biomarkers of immune checkpoint blockade (ICB) in PLELC require further investigation. METHODS: We prospectively analysed EBV levels in the blood and immune tumor biomarkers of 31 patients with ICB-treated PLELC. Viral EBNA-1 and BamHI-W DNA fragments in the plasma were quantified in parallel using quantitative polymerase chain reaction. RESULTS: Progression-free survival (PFS) was significantly longer in EBNA-1 high or BamHI-W high groups. A longer PFS was also observed in patients with both high plasma EBNA-1 or BamHI-W and PD-L1 ≥ 1%. Intriguingly, the tumor mutational burden was inversely correlated with EBNA-1 and BamHI-W. Plasma EBV load was negatively associated with intratumoral CD8(+) immune cell infiltration. Dynamic changes in plasma EBV DNA level were in accordance with the changes in tumor volume. An increase in EBV DNA levels during treatment indicated molecular progression that preceded the imaging progression by several months. CONCLUSIONS: Plasma EBV DNA could be a useful and easy-to-use biomarker for predicting the clinical activity of ICB in PLELC and could serve to monitor disease progression earlier than computed tomography imaging.