A Phase II Study of Dexamethasone, Azacitidine, Pegaspargase and Tislelizumab Plus Radiotherapy for Patients With Stage I/II Extranodal NK/T-cell Lymphoma

Inclusion Criteria: 1. Pathologically confirmed diagnosis of extranodal NK/T-cell lymphoma 2. Age ≥18 years 3. Ann Arbor stage I or II 4. Presence of at least 1 measurable lesion according to the 2014 Lugano revised criteria for response assessment 5. ECOG-PS 0\~2 6. Peripheral blood absolute neutrophil count ≥1.5×10E9/L, platelet count ≥75×10E9/L and hemoglobin ≥90g/L 7. Expected survival of at least 3 months 8. Capable of understanding the content of this study, agreeing to participate in this study and signing the informed consent. Exclusion Criteria: 1. Unconfirmed pathological diagnosis of NK/T-cell lymphoma 2. Pregnant or lactating women, or patients of childbearing age unwilling to take contraceptive measures during the study period. 3. Patients with clinically significant prolonged QTc interval (\>470ms in males, \>480ms in females), ventricular tachycardia, atrial fibrillation, second or third degree atrioventricular block, acute myocardial infarction, congestive heart failure, severe or symptomatic coronary artery disease requiring medical treatment. 4. Patients with large amount of pericardial effusions shown by echocardiogram. 5. Patients who received supportive care for anemia, neutropenia or thrombocytopenia within 7 days prior to start of study treatment. 6. Patients with severe active bleeding. 7. Patients with pulmonary embolism, intracranial hemorrhage or acute cerebral infarction. 8. Patients with active infectious disease. 9. Patients who are mentally disabled or unable to understand or sign the informed consent form. 10. Patients with other conditions judged as ineligible for this study by the investigators.