Sintilimab, Pegaspargase Plus GemOx for Untreated Extranodal NK/T-Cell Lymphoma

Inclusion Criteria: * Histopathologically confirmed diagnosis of extranodal NK/T-cell lymphoma (ENKTL) by the study center. * Age between 18 and 75 years. * At least one of the following risk factors: Age ≥ 60 years; Presence of B symptoms; ECOG performance status ≥ 2; Elevated lactate dehydrogenase (LDH); Baseline EBV-DNA \> 500 copies/mL. * ECOG performance status of 0 to 3. * Adequate bone marrow function: Absolute neutrophil count (ANC) ≥ 1.5 × 10⁹/L (≥ 1.0 × 10⁹/L in cases with bone marrow involvement); Platelet count (PLT) ≥ 80 × 10⁹/L (≥ 50 × 10⁹/L in cases with bone marrow involvement); Hemoglobin (HGB) ≥ 80 g/L. * Adequate organ function: Alanine aminotransferase (ALT) \< 3 × the upper limit of normal (ULN); Total bilirubin (TBil) \< 1.5 × ULN; Serum creatinine \< 1.5 × ULN; NYHA heart function class 0-2; Left ventricular ejection fraction (LVEF) \> 50%. Exclusion Criteria: * Aggressive NK-cell leukemia. * Central nervous system lymphoma. * History of any of the following within 6 months: Acute myocardial infarction; Unstable angina; Congestive heart failure; Uncontrolled symptomatic arrhythmia; Complete left bundle branch block; Second- or third-degree atrioventricular block; Long QT syndrome or corrected QT interval (QTc) \> 480 ms. * Uncontrolled active infection. * Pregnant or breastfeeding women.