Malignant pleural effusion as a predictor of the efficacy of anti‐PD‐1 antibody in patients with non‐small cell lung cancer

BACKGROUND: The aim of this study was to evaluate the usefulness of the presence of malignant pleural effusion (MPE) as a negative predictor of anti‐PD‐1 antibody efficacy. METHODS: A retrospective review of patients with advanced or recurrent non‐small cell lung cancer treated with an anti‐PD‐1 antibody between December 2015 and March 2018 at the National Cancer Center Hospital, Japan, was conducted. Progression‐free survival (PFS) and overall survival (OS) were compared between patients with and without MPE. Additional survival analysis according to PD‐L1 expression status was conducted. Univariate and multivariate analyses were performed. RESULTS: A total of 252 patients were identified before the commencement of anti‐PD‐1 antibody treatment: 33 with MPE and 219 without MPE. PFS and OS were significantly shorter in patients with MPE than in patients without MPE (median PFS 3.0 vs. 5.8 months, hazard ratio [HR] 1.7, P = 0.014; median OS 7.9 vs. 15.8 months, HR 2.1, P = 0.001). In patients with PD‐L1 expression in ≥ 1% of their tumor cells, the PFS of patients with MPE was significantly shorter than of patients without MPE (median PFS 3.1 vs. 6.5 months, HR 2.0, 95% confidence interval 1.0–3.5; P = 0.021). The presence of MPE was independently associated with a shorter PFS and OS in multivariate analysis. CONCLUSION: The presence of MPE in patients administered an anti‐PD‐1 antibody is associated with shorter PFS and OS, regardless of the presence of PD‐L1 expression ≥ 1% of tumor cells.