Association between PD-L1 expression and initial brain metastasis in patients with non-small cell lung cancer and its clinical implications

Background Brain metastases frequently occur in patients with non-small cell lung cancer (NSCLC) resulting in a poor prognosis. Here, we investigated the association between PD-L1 expression and brain metastasis in patients with NSCLC and its clinical significance. Methods A total of 270 patients diagnosed with metastatic NSCLC who underwent PD-L1 testing on their tumor tissue between January 2017 and March 2019 were retrospectively reviewed. The VENTANA PD-L1 (SP263) assay was used, and positive PD-L1 expression was defined as staining in ≥1% of tumor cells. Results Positive PD-L1 expression was observed in 181 (67.0%) patients, and 74 (27.4%) patients had brain metastasis at diagnosis. Synchronous brain metastases were more frequently observed in PD-L1-positive compared with PD-L1-negative patients (31.5% vs. 19.1%, p = 0.045). Multiple logistic regression analysis identified positive PD-L1 expression (odds ratio [OR]: 2.24, p = 0.012) as an independent factor associated with synchronous brain metastasis, along with the histological subtype of nonsquamous cell carcinoma (OR: 2.84, p = 0.003). However, the incidence of central nervous system (CNS) progression was not associated with PD-L1 positivity, with a two-year cumulative CNS progression rate of 26.3% and 28.4% in PD-L1-positive and PD-L1-negative patients, respectively (log rank p = 0.944). Furthermore, positive PD-L1 expression did not affect CNS progression or overall survival in patients with synchronous brain metastasis (long rank p = 0.513 and 0.592, respectively). Conclusions Initial brain metastases are common in NSCLC patients with positive PD-L1 expression. Further studies are necessary to understand the relationship between early brain metastasis and cancer immunity.