Exosomal PD-L1 level in plasma as a predictive marker for prognostic and clinical correlation in NSCLC

Up to 30–55% of patients with non-small cell lung cancer (NSCLC) who undergo complete surgical resection develop disease recurrence within the first 5 years. Identifying patients at high risk for recurrence can optimize surveillance strategies and help personalize adjuvant therapy. Liquid biopsy for exosomal PD-L1 is emerging as a potential non-invasive tool to screen for factors influencing clinical outcomes. We prospectively recruited NSCLC patients who underwent complete surgical resection at the Cardiothoracic Surgery Unit, King Chulalongkorn Memorial Hospital (KCMH), between December 2021 and December 2022. Plasma exosomes were extracted, and exosomal PD-L1 levels (in pg/mL) were quantified using an enzyme-linked immunosorbent assay (ELISA). Tumor tissue PD-L1 expression was assessed via immunohistochemistry (IHC) and correlated with plasma exosomal PD-L1 levels. Patients were followed for up to 1 year postoperatively to monitor for disease recurrence. This study included 52 NSCLC patients, and the mean age of population was 66.8 ± 9.3 years old. Most patients were non-smokers (31 in 52, 59.6%). Median level of plasma exosomal PD-L1 at baseline was not significant difference in both no recurrence and recurrence group (0.59 vs. 0.59, p = 0.96). Patients with plasma level of exosomal PD-L1 equal or more than 5 pg/mL had incidence of recurrence of NSCLC 50% (95% CI 9.0-99.4) but have no statistically significance. Progression free survival was trend to decreased by tumor PD-L1 groups 0%, 1–49%, and ≥ 50% (94.4%, 76.2%, 50%, respectively). Plasma exosomal PD-L1 expression was irrelevant to PD-L1 expression of tumor tissues in NSCLC patients. Our study found no statistically significant association between baseline plasma exosomal PD-L1 levels and NSCLC recurrence. However, these negative findings may be limited by the small sample size and low event rate.