Kim H, et al. - Researchers examined the expression level of PD-L1 and tumor infiltrating lymphocytes and elucidate their predictive role to determine if tumor microenvironments influence the clinical response to anti-PD-1 therapy in non-small cell lung cancer by analyzing 38 pretreatment and two post-treatment specimens from 36 advanced, treatment-refractory non-small cell lung cancer patients who had PD-1 blockade therapy. Compared to PD-L1 negative group, CD3+ and CD8+ T cells were distributed more in PD-L1 positive group. As compared to EGFR-naïve group, EGFR mutant group exhibited fewer CD3+ T cells. The findings suggested that tumor infiltrating lymphocytes might become a promising biomarker as an independent predictive factor of response to PD-1 blockade that may also guide therapeutic decisions.