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.