Abstract
PURPOSE: Pembrolizumab, a programmed cell death protein 1 (PD1) inhibitor inhibits the interplay between PD1 of T-cell and programmed cell death ligand 1 (PDL1) on tumor cells. Although pembrolizumab has been tried to various subtypes of non-Hodgkin lymphoma (NHL), realworld data about the efficacy of pembrolizumab in NHL patients are limited. MATERIALS AND METHODS: We analyzed the outcome of 30 relapsed or refractory NHL patients treated with pembrolizumab, and compared the outcome between Epstein-Barr virus (EBV)‒positive and negative subtypes because EBV infection of tumor cells can upregulate PDL1 expression. RESULTS: Seven patients with EBV-positive NHL showed a response including NK/T-cell lymphoma (6/14, 44%) and primary mediastinal B-cell lymphoma (1/4, 25%) whereas EBV-negative subtypes did not respond such as diffuse large B-cell lymphoma and T-lymphoblastic lymphoma. We also evaluated PDL1 expression using tumor tissue of 76 patients. High PDL1 expression (positive staining of > 50% of tumor cells) was more frequent in NK/T-cell lymphoma and primary mediastinal B-cell lymphoma than other subtypes. Thus, PDL1 expression was significantly higher in EBV-positive (18/32, 56%) than EBV-negative NHL (4/38, 11%, p < 0.001). Furthermore, NK/T-cell lymphoma patients with high PDL1 expression showed a higher response (4/6, 67%) than those with low PDL1 expression (1/5, 20%). CONCLUSION: Pembrolizumab could be useful as a salvage treatment for relapsed or refractory EBV-positive NHL, especially NK/T-cell lymphoma. However, its efficacy in EBV-negative NHL with low or absent PDL1 expression is still not clear although pembrolizumab could be a potential treatment option for relapsed or refractory NHL.