PD-1 Antibody-based Therapy With Concurrent RT for Early-stage NKTCL

Inclusion Criteria: * The subject has histopathologically confirmed extranodal NK/T-cell lymphoma, nasal type (according to the 2022 WHO classification). * No prior history of anti-lymphoma therapy. * Age ≥ 18 years. * Life expectancy \> 3 months. * Ann Arbor stage I-II. * At least one measurable/evaluable disease site confirmed by diagnostic biopsy prior to the initiation of treatment. * Eastern Cooperative Oncology Group (ECOG) performance status score of 0-2. * Signed informed consent form (ICF). * Willingness and ability to comply with the study protocol. * Sufficient bone marrow, hepatic, and renal function, defined as: 1. Absolute neutrophil count (ANC) \> 1,000/μL 2. Platelet count \> 50,000/μL 3. Hemoglobin \> 9 g/dL 4. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) \< 3× upper limit of normal (ULN) 5. Serum total bilirubin \< 1.5 × ULN (patients with Gilbert's syndrome are eligible) 6. Serum creatinine \< 2 × ULN or creatinine clearance \> 50 mL/min * Availability of tumor tissue samples (preferably fresh tissue; archived tissue samples are acceptable). * For women of childbearing potential, agreement to use adequate contraception to avoid pregnancy during the study treatment period. * For male, agreement to remain abstinent or use a barrier method of contraception. Exclusion Criteria: * Advanced-stage disease (Ann Arbor Stage III-IV). * Nonnasal-type NKTCL. * A history of autoimmune disease requiring systemic treatment (i.e., with disease-modifying antirheumatic drugs, corticosteroids, or immunosuppressants) within the past 2 years, including but not limited to myasthenia gravis, myositis, autoimmune hepatitis, systemic lupus erythematosus, rheumatoid arthritis, inflammatory bowel disease, antiphospholipid antibody-associated vasculopathy, granulomatosis with polyangiitis (Wegener's), Sjögren's syndrome, Guillain-Barré syndrome, multiple sclerosis, vasculitis, or glomerulonephritis. The following conditions are permissible for enrollment: patients with autoimmune hypothyroidism or type 1 diabetes receiving stable treatment; hormone replacement therapy (e.g., levothyroxine, insulin, or supplementation with physiological hormones for adrenal or pituitary insufficiency) is not considered systemic therapy and is allowed. * A history of other invasive malignancies within the past 3 years that has not been treated with curative intent or is currently receiving anticancer therapy (including hormonal therapy for breast or prostate cancer). * A history of (non-infectious) pneumonia requiring corticosteroid therapy; or clinical evidence of interstitial lung disease or active, non-infectious pneumonia. * Active infections requiring systemic treatment, including: 1. A known history of active tuberculosis; 2. Positive results for HBsAg, HCV, or HIV; HBV seropositivity is permitted only if HBV DNA \< 1000 IU/mL; 3. Active viral infections other than hepatitis B and C (e.g., herpes zoster). * Severe cardiovascular disease, including myocardial infarction, unstable arrhythmia, or unstable angina occurring within the past 3 months. * Prior treatment with anti-PD-1, anti-PD-L1, or anti-PD-L2 agents. * Administration of live-attenuated vaccines within 4 weeks prior to the initiation of study treatment; patients are prohibited from receiving live-attenuated vaccines during the study period, including influenza vaccines. * Use of systemic immunosuppressive agents within 2 weeks prior to the initiation of study treatment, or planned use of such agents during the study period, including cyclophosphamide, azathioprine, methotrexate, thalidomide, and anti-tumor necrosis factor (anti-TNF) drugs. * Evidence of central nervous system involvement. * A history of allogeneic tissue/solid organ transplantation. * A history of severe hypersensitivity reactions (Grade ≥ 3) to PD-1 monoclonal antibodies and/or their excipients, or to gorlitinib and/or its excipients. * Any other factors judged by the investigator to potentially affect compliance with the study protocol.