Tislelizumab Combined Treatment in Refractory Extranodal NK/T-cell Lymphoma

Inclusion Criteria: 1. Patients with biopsy histopathology, immunohistochemistry and EBER test meet ing the WHO 2016 diagnostic criteria for NK/T cell lymphoma. 2. With progressive disease after asparaginase-based combined chemotherapy 3. Have experienced multiple courses of PD-1/PD-L1 treatment with non-responsive or progressive disease. 4. PET/CT or CT/MRI with at least one measurable lesion or objectively evaluable lesion. 5. General ECOG score 0-3 points. 6. The laboratory examination within 1 week before enrollment meets the following conditions: Blood routine: Hb\>80g/L, PLT\>50×109/L. Liver function: ALT, AST, TBIL ≤ 2 times the upper limit of normal. Renal function: Cr is normal. Blood coagulation test: plasma fibrinogen ≥1.0g/L. Heart function: LVEF≥50%, ECG did not indicate any acute myocardial infarction, arrhythmia, or atrioventricular block of degree I or more. 7. Signed informed consent form. 8. Voluntarily comply with research protocols, follow-up plans, laboratory and auxiliary examinations. Exclusion Criteria: 1. Patients with a history of pancreatitis (only patients who are planning to undergo PD1 combined with pegaspargase are excluded). 2. Severe infections require ICU treatment. 3. Combined HCV or HIV infection. Patients with HBV infection who receive antiviral treatment at the same time will not be excluded. 4. There are serious complications such as fulminant DIC. 5. Impairment of important organ functions: such as respiratory failure, chronic congestive heart failure with NYHA grade ≥2, decompensated liver or kidney insufficiency, hypertension and diabetes that cannot be controlled despite active treatment, nearly 6 years old There were cardio-cerebrovascular thrombotic or hemorrhagic events within months. 6. Pregnant and lactating women. 7. Have a history of autoimmune diseases, have disease activity in the past 6 months, and are still receiving oral immunosuppressive therapy within the past three months, and the daily dose of oral prednisone is greater than 10 mg.