Screening Study of Combined Sequential Chemotherapy and Radiation Therapy for Early-stage NK/T-cell Lymphoma

Inclusion Criteria: * Patients who meet the diagnostic criteria for NKTCL (WHO-2016) based on pathological examination. * Primary lesions located in the upper respiratory and digestive tract such as the nasal cavity, sinuses, nasopharynx, oropharynx, or oral cavity, with clinical staging of IE/IIE based on PET/CT and bone marrow examination according to the Lugano 2014 criteria. * Evaluated for lymphoma response according to the Lugano 2014 criteria, with at least one measurable lesion or lesion assessable by PET/CT. * No prior treatment with chemotherapy, radiotherapy, immunotherapy, or biological therapy for lymphoma. * Age between 18 and 75 years, both genders. * Eastern Cooperative Oncology Group performance status (ECOG) score of 0-2. * Must have adequate organ and bone marrow function, defined as follows: Hematology: Absolute neutrophil count (ANC) ≥1.0×10\^9/L, platelet count (PLT) ≥75×10\^9/L, hemoglobin (Hb) ≥90g/L; no administration of granulocyte colony-stimulating factor, platelet transfusion, or red blood cell transfusion in the previous 14 days. Liver function: Total bilirubin (TBIL) ≤1.5 times the upper limit of normal (ULN); alanine aminotransferase (ALT) and aspartate aminotransferase (AST) ≤2×ULN. Renal function: Serum creatinine (Cr) ≤1.5×ULN. Coagulation function: Plasma fibrinogen ≥1.5g/L. Cardiac function: Left ventricular ejection fraction (LVEF) ≥50%, no acute myocardial infarction, arrhythmia, or atrioventricular conduction block of grade I or above on electrocardiogram. * Willing to comply with the study protocol, follow-up plan, and laboratory and ancillary investigations. Exclusion Criteria: * Patients co-infected with HCV, HIV, or HBV with plasma HBV-DNA \>10\^3/ml. * Patients with a history of pancreatitis. * Patients with acute or systemic infections requiring intravenous antibiotic therapy. * Patients with severe complications such as hemophagocytic syndrome, DIC, etc. * Significant organ dysfunction: such as respiratory failure, chronic congestive heart failure with NYHA class ≥2, decompensated liver or renal dysfunction, uncontrolled hypertension and diabetes despite aggressive treatment, and cardiovascular thrombotic or hemorrhagic events in the past 6 months. * Patients with a history of autoimmune diseases who are not suitable for treatment with immune checkpoint inhibitors. * Pregnant and lactating women. * Patients with psychiatric disorders. * Known allergies to drugs in the chemotherapy regimen. * Patients with concomitant other tumors requiring surgery or chemotherapy within the past 6 months. * Currently using other experimental drugs.