Extranodal NK/T-cell lymphoma is a rare and highly aggressive subtype of non-Hodgkin lymphoma. While the overall survival rates have improved for early-stage ENKTL patients, the prognosis for those with advanced disease remains poor, and there is currently no standard treatment. PD-1/PD-L1 inhibitors have demonstrated significant efficacy in various cancers, and recent studies have shown promising results in extranodal NK/T-cell lymphoma as well. Although PD-1 antibodies have exhibited efficacy in relapsed or refractory patients, their effectiveness when combined with chemotherapy as a first-line treatment remains unclear. This study aims to evaluate the efficacy and safety of sintilimab combined with chemotherapy in a randomized controlled trial for newly diagnosed advanced extranodal NK/T-cell lymphoma patients, while also exploring potential biomarkers that may predict treatment outcomes, offering new therapeutic options for extranodal NK/T-cell lymphoma patients.

Inclusion Criteria:

1. Pathologically diagnosed with ENKTL.
2. Advanced stage.
3. Has at least one measurable or assessable lesion.
4. Age > 18 years, no gender restrictions, with an expected survival of more than 3 months.
5. Willing to participate in the clinical study; fully informed and has signed a written informed consent form.
6. Adequate organ and bone marrow function.

Exclusion Criteria:

1. Aggressive NK-cell leukemia.
2. Central nervous system involvement.
3. Patients with significant dysfunction of vital organs.
4. History of allergy to the investigational drug, similar drugs, or excipients.
5. Less than 6 weeks since major organ surgery (excluding surgery for biopsy purposes).
6. Pregnant or breastfeeding women, and women of childbearing potential who are unwilling to use contraception.
7. Active infection, excluding fever related to tumor-associated B symptoms.
8. Known history of human immunodeficiency virus (HIV) infection and/or acquired immunodeficiency syndrome (AIDS).