Correlation study of PD-L1, CD4, CD8, and PD-1 in primary diffuse large B-cell lymphoma of the central nervous system

We investigated the clinicopathological role of the PD-1/PD-L1 pathway in the primary diffuse large B-cell lymphoma of the central nervous system (PCNS-DLBCL). Standardized staining for PD-L1 was performed by machine staining, and internationally accepted interpretation methods were used. The PD-L1 immunostaining ≥ 20 % of all cells in slices was defined as high expression of PD-L1. CD4, CD8, and PD-1 tumor-infiltrating lymphocytes (TILs) were enumerated, and the median was defined as the cutoff value. Values higher than the median was defined as high expression. Thirty-four cases (64.2 %) showed high expression of PD-L1. PD-L1 expression was associated with a good prognosis when 20 % was considered as cutoff value and had the smallest P value. By contrast, a low number of CD8⁺ or PD-1⁺ TILs was associated with poor prognosis. Patients with low expression of PD-L1 had poor overall survival (P = 0.001), and those with increased CD8 or PD-1 TILs tended to have improved overall survival (P = 0.004 and 0.024, respectively). Low number of monocytes, increased number of lymphocytes, IPI score ≥ 2, ECOG PS ≥ 2, LDH ≥ 250, and Ki67 ≥ 70 % were independent prognostic factors for OS. In conclusion, PD-L1 expression, CD8 and PD-1 TILs, monocyte status, and ECOG PS might be prognostic markers and therapeutic targets of PCNS-DLBCL.