Purpose: The success of immune checkpoint inhibitors strengthens the notion that tumor growth and regression are immune regulated. To determine whether distinct tissue immune microenvironments differentially affect clinical outcome in non–small cell lung cancer (NSCLC), an extended analysis of PD-L1 and tumor-infiltrating lymphocytes (TIL) was performed.

Experimental Design: Samples from resected adenocarcinoma (ADC 42), squamous cell carcinoma (SCC 58), and 26 advanced diseases (13 ADC and 13 SCC) treated with nivolumab were analyzed. PD-L1 expression and the incidence of CD3, CD8, CD4, PD-1, CD57, FOXP3, CD25, and Granzyme B TILs were immunohistochemically assessed.

Results: PD-L1 levels inversely correlated with N involvement, although they did not show a statistically significant prognostic value in resected patients. The incidence and phenotype of TILs differed in SCC versus ADC, in which EGFR and KRAS mutations conditioned a different frequency and tissue localization of lymphocytes. NSCLC resected patients with high CD8^pos lymphocytes lacking PD-1 inhibitory receptor had a longer overall survival (OS: HR = 2.268; 95% CI, 1.056–4.871, P = 0.03). PD-1-to-CD8 ratio resulted in a prognostic factor both on univariate (HR = 1.952; 95% CI, 1.34–3.12, P = 0.001) and multivariate (HR = 1.943; 95% CI, 1.38–2.86, P = 0.009) analysis. Moreover, low PD-1 incidence among CD8^pos cells was a distinctive feature of nivolumab-treated patients, showing clinical benefit with a prolonged progression-free survival (PFS: HR = 4.51; 95% CI, 1.45–13.94, P = 0.004).

Conclusions: In the presence of intrinsic variability in PD-L1 expression, the reservoir of PD-1–negative effector T lymphocytes provides an immune-privileged microenvironment with a positive impact on survival of patients with resected disease and response to immunotherapy in advanced NSCLC. Clin Cancer Res; 24(2); 407–19. ©2017 AACR.