LAUSR

Purpose: Programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) interaction suppresses local T-cell responses and promotes peripheral tolerance. In the current study, we focus on PD-1/PD-L1 co-location as a surrogate for this interaction and assess its association with immunotherapy outcomes in patients with non–small cell lung cancer (NSCLC). Experimental Design: Pretreatment biopsies from a retrospective cohort of 154 immunotherapy-treated patients with advanced NSCLC were analyzed. Expression of PD-1 and PD-L1 was assessed by multiplexed quantitative immunofluorescence (QIF) and PD-1 expression in the same pixels as PD-L1 (called a co-location score) was measured using an algorithm to define overlapping expression areas. Co-location scores were correlated with immunotherapy outcomes and PD-L1 tumor proportion score. Results: PD-1/PD-L1 co-location score was associated with best overall response (P = 0.0012), progression-free survival (P = 0.0341), and overall survival after immunotherapy (P = 0.0249). The association was driven by patients receiving immune checkpoint inhibitors in the second or subsequent line of treatment. PD-L1 tumor proportion score by IHC was also correlated with best overall response and progression-free survival. PD-L1 measured within the tumor compartment by QIF did not show any significant association with either best overall response or overall survival. Finally, co-location score was not associated with PD-L1 expression by either method. Conclusions: On the basis of our findings, co-location score shows promise as a biomarker associated with outcome after immunotherapy. With further validation, it could have value as a predictive biomarker for the selection of patients with NSCLC receiving treatment with immune checkpoint inhibitors.