Allogeneic hematopoietic stem cell transplantation is an important treatment method for NK-T cell lymphoma, but the recurrence rate after transplantation is relatively high. Therefore, exploring efficient and low-toxicity maintenance treatment strategies after transplantation is a key challenge for improving prognosis. Previous studies have reported that selinexor and azacitidine show good anti-tumor activity in relapsed/refractory NKTCL. Thus, we conducted a single-center, single-arm, exploratory study on the efficacy and safety of selinexor combined with azacitidine as maintenance therapy after allogeneic hematopoietic stem cell transplantation for NK/T cell lymphoma, to evaluate the efficacy and safety of the combined regimen, with the aim of providing reference for clinical treatment.

Inclusion Criteria:

• 1. Age range: 18-70 years old, gender not restricted; 2. Diagnosed with NK/T-cell lymphoma (NKTCL) according to the 2022 WHO criteria; 3. Received allogeneic hematopoietic stem cell transplantation for NKTCL, with no restrictions on the type of donor; 4. Bone marrow chimerism is complete donor chimerism (T-cell chimerism > 95%); 5. ECOG: 0-1 points; 6. Blood routine must meet the following requirements: (1) ANC >= 1.0 × 10^9/L; (2) PLT >= 75 × 10^9/L; 7. The patient must be capable of understanding and willing to participate in this study, and sign the informed consent form.

Exclusion Criteria:

• 1. Those who are known to be allergic to azacitidine or selinexor; 2. Those with active acute GVHD of grade 2 or above; 3. Those with moderate or severe chronic GVHD; 4. Any unstable systemic diseases: including but not limited to unstable angina pectoris, cerebrovascular accident or transient ischemic attack (within 3 months before screening), myocardial infarction (within 3 months before screening), congestive heart failure (NYHA classification >= grade III), severe arrhythmia requiring drug treatment after pacemaker implantation, liver, kidney or metabolic diseases; patients with pulmonary hypertension. 5. Those with active uncontrolled infections: with hemodynamic instability related to infection, or new symptoms or signs of infection worsening, or new infection lesions found on imaging, persistent fever without symptoms or signs that cannot be ruled out as infection; 6. HIV-infected individuals; 7. Patients with active hepatitis B (HBV) or active hepatitis C (HCV) requiring antiviral treatment; 8. History of autoimmune diseases; 9. Pregnant or lactating women; 10. Those who are currently receiving other investigational drugs.