Relationship of tumor PD‐L1 (CD274) expression with lower mortality in lung high‐grade neuroendocrine tumor

Programmed death‐ligand 1 (PD‐L1) promotes immunosuppression by binding to PD‐1 on T lymphocytes. Although tumor PD‐L1 expression is a potential predictive marker of clinical response to anti‐PD‐1/PD‐L1 therapy, little is known about its association with clinicopathological features, including prognosis, in high‐grade neuroendocrine tumors (HGNETs), including small‐cell lung carcinoma (SCLC) and large‐cell neuroendocrine carcinoma (LCNEC), of the lung. We immunohistochemically examined the membranous of expression of PD‐L1 in 115 consecutive surgical cases of lung HGNET (74 SCLC cases and 41 LCNEC cases). We examined the prognostic association of tumor PD‐L1 positivity using the log‐rank test as well as Cox proportional hazards regression models to calculate the hazard ratio (HR) for mortality. Programmed death‐ligand 1 immunostaining (at least 5% tumor cells) was observed in 25 (21%) of the 115 HGNET cases. In a univariable analysis, PD‐L1 positivity was associated with lower lung cancer‐specific (univariable HR = 0.23; 95% confidence interval [CI] = 0.056–0.64; P = 0.0028) and overall (univariable HR = 0.28; 95% CI = 0.11–0.60; P = 0.0005) mortality. Additionally, in a multivariable analysis, PD‐L1 positivity was independently associated with lower lung cancer‐specific (multivariable HR = 0.24; 95% CI = 0.058–0.67; P = 0.0039) and overall (multivariable HR = 0.29; 95% CI = 0.11–0.61; P = 0.0006) mortality. Our study demonstrated the prevalence of PD‐L1 positivity in lung HGNET cases, and the independent association of tumor PD‐L1 positivity with lower mortality in lung HGNET cases. Further studies are needed to confirm our findings.