Programmed cell death protein 1/programmed cell death ligand 1 (PD-1/PD-L1) are important targets of immunotherapy and its expression has been closely correlated with response and survival benefit from anti-PD-1/PD-L1 immune checkpoint inhibitor therapies in advanced non-small cell lung carcinoma (NSCLC). But it is still unclear whether PD-L1 is prognostic. The aim of this study is to examine the proportion of PD-L1 protein expression in NSCLC and investigate the correlation with clinicopathological backgrounds including patient outcome.
A total of 899 NSCLC were examined. The male:female ratio was 550:349; the age range was between 32 and 89 years of age and the mean age was 68.9 years. Adenocarcinoma: Squamous cell carcinoma: Others’ ratio was 647:209:43 in histopathology. The follow up duration was from 0.4 months to 168.7 months and the mean duration was 62.2 months. PD-L1 expression was analyzed using immunohistochemistry (VENTANA; clone SP263) in stages I-IV NSCLC using tissue microarray. The PD-L1 staining percentage in tumor cells were scored as follows: 0, 0%; 1, 1-24%; 2, 25-49%; 3, ≥50%. The score of PD-L1 staining was correlated with clinicopathological backgrounds, molecular features and patient outcome.
The score of PD-L1 staining was as follows: 0, 739/899 (82.2%); 1, 47/899 (5.2%); 2, 26/899 (2.9%); 3, 87/899 (9.7%). PD-L1 expression was associated with sex, smoking history, histology, tumor size, stage, pleural invasion, p53 protein expression, MIB-1 labeling index and EGFR mutation. We arranged the value of cut offs at ≥ 1%, ≥25%, ≥50% and investigated the correlation with patient outcome. In adenocarcinoma, the patients with any positive staining of PD-L1 (≥1%) had a trend of worse 5-year overall survival rate than those with negative staining of PD-L1 (73.5% vs. 79%, p = 0.096). In squamous cell carcinoma, PD-L1 expression was not prognostic with these cut offs. In multivariate analysis, PD-L1 expresssion was not independent prognostic factor in adenocarcinoma.
Our study shows PD-L1 protein expression is not a prognostic factor in NSCLC.
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All authors have declared no conflicts of interest.