High proportions of PD-1 and PD-L1 leukocytes in classical Hodgkin lymphoma microenvironment are associated with inferior outcome.

Immune checkpoint inhibition targeting the programmed death receptor (PD)-1 pathway is a novel treatment approach in relapsed and refractory classical Hodgkin lymphoma (cHL). Identifying patients with a high risk of treatment failure could support the use of PD-1 inhibitors as front-line treatment. Our aim was to investigate the prognostic impact of PD-1, programmed death-ligand 1 (PD-L1), and PD-L2 in the tumor microenvironment in diagnostic biopsies of patients with cHL. Patients from Denmark and Sweden, diagnosed between 1990 and 2007 and ages 15 to 86 years, were included. Tissue microarray samples were available from 387 patients. Immunohistochemistry was used to detect PD-1, PD-L1, and PD-L2, and the proportions of positive cells were calculated. Event-free survival (EFS; time to treatment failure) and overall survival (OS) were analyzed using Cox proportional hazards regression. High proportions of both PD-1 (hazard ratio [HR], 1.77; 95% confidence interval [CI], 1.10-2.86) and PD-L1 (HR = 1.89; 95% CI, 1.08-3.30) leukocytes in the microenvironment were associated with inferior EFS in a multivariate analysis (adjusted for white blood cell count >15 × 10/L, hemoglobin <105 g/L, albumin <40 g/L, B symptoms, extranodal involvement, stage, bulky tumor, nodular sclerosis subtype, Epstein-Barr virus status, lymphocyte count <0.6 × 10/L, sex, and country). A high proportion of PD-L1 leukocytes was also associated with inferior OS in a multivariate analysis (HR, 3.46; 95% CI, 1.15-10.37). This is the first study to show a correlation after multivariate analysis between inferior outcome in cHL and a high proportion of both PD-1 and PD-L1 leukocytes in the tumor microenvironment.