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Pembrolizumab in newly diagnosed EBV-negative extranodal natural killer/T-cell lymphoma: A case report.

Extranodal natural killer (NK)/T-cell lymphoma (ENKTL) is a rare subtype of non-Hodgkin's lymphoma with a dismal prognosis. The pathogenesis almost invariably involves Epstein-Barr virus (EBV) infection, although EBV-negative ENKTLs are frequently reported in the western hemisphere. Treatment of these lymphomas consists of aggressive chemotherapy with dexamethasone, methotrexate, ifosfamide, L-asparaginase and etoposide (SMILE regimen). However, the SMILE regimen is poorly tolerated by elderly patients; therefore, treatment options are limited to palliative radiation and chemotherapy and/or hospice care. Recently, binding of programmed death (PD)-1 with its ligand (PD-L1) expressed on tumor cells was shown to downregulate effector T-cell function and may represent a potent mechanism of immune evasion in classical Hodgkin's lymphoma and aggressive B-cell lymphomas. Thus, targeting PD-L1/PD-1 to inhibit effector T-cell signaling may be a promising therapeutic strategy for these NK/T-cell lymphomas. We herein report the clinical efficacy and feasibility of the anti-PD-1 inhibitor pembrolizumab used concurrently with radiation therapy and as maintenance therapy in an elderly female patient. The findings demonstrated that pembrolizumab may be an effective and well-tolerated treatment for this type of lymphoma.