Maintenance Therapy With Anti-PD-1 Antibody for Patients With NK/T-cell Lymphoma

Inclusion Criteria: * Pathology confirmed diagnosis of NK/T-cell lymphoma. * Plasma EBV-DNA was positive at the end of first-line pegaspargase-based regimens. * ECOG score of 0-3 points. * The lab tests within 1 week before enrollment meets the following: * Blood routine: Hb≥80g/L, PLT≥50×10e9/L. * Liver function: ALT, AST, TBIL≤2 times the upper limit of normal. * Renal function: Cr is normal. * Coagulation: plasma fibrinogen≥1.0g/L. * Cardiac function: LVEF≥50%, ECG is normal * Sign the informed consent form. * Voluntary compliance with research protocols. Exclusion Criteria: * Patients had relapsed NK/T-cell lymphoma. * Active infection requires ICU treatment. * Concomitant HIV infection or active infection with HBV, HCV. * Serious complications such as fulminant DIC. * Significant organ dysfunction: * respiratory failure * NYHA classification≥2 chronic congestive heart failure * decompensation Hepatic or renal insufficiency * high blood pressure and diabetes that cannot be controlled * cerebral vascular events within the past 6 months. * Pregnant and lactating women. * Had a history of autoimmune diseases, and disease was active now. Those who were known to be allergic to drugs in the study regimen. * Patients with other tumors who require treatments within 6 months. * Other experimental drugs are being used.