A Prospective Clinical Study on Reduced-intensity Radiotherapy for Stage I/II Low-risk Nasal-type NK/T-cell Lymphoma Achieving Complete Remission After Chemotherapy

Inclusion Criteria: * The patient voluntarily agrees to participate in this study and signs the informed consent form. * Age ≥ 18 years and ≤ 75 years. * Pathologically confirmed diagnosis of nasal-type NK/T-cell lymphoma. * Clinical stage I-II disease confirmed by PET-CT or MRI. * The lymphoma has been treated with an asparaginase-based chemotherapy regimen. * Presence of 0-1 prognostic risk factors (risk factors: age \> 60 years, ECOG score ≥ 2, elevated LDH, elevated PTI, stage II). * Imaging assessment shows complete clinical remission after chemotherapy. * ECOG-PS score of 0-1. * Expected survival of ≥ 12 months. * Normal function of major organs, meeting the following criteria: 1. Hematology: absolute neutrophil count ≥ 1.5 × 10⁹/L; platelet count ≥ 80 × 10⁹/L; hemoglobin ≥ 80 g/L. 2. Biochemistry: total bilirubin \< 1.5 × ULN; ALT and AST ≤ 2.5 × ULN; serum Cr ≤ 1.5 × ULN or endogenous creatinine clearance \> 50 mL/min. * Female subjects of childbearing potential must have a negative serum pregnancy test within 72 hours before the first dose and must be willing to use highly effective contraception during the study period and for 120 days after the last dose. For male subjects with female partners of childbearing potential, they must be surgically sterile or agree to use highly effective contraception during the study period and for 120 days after the last dose. Exclusion Criteria: * A previous or concurrent diagnosis of another malignancy, except for cured basal cell carcinoma of the skin, carcinoma in situ of the cervix, or carcinoma in situ of the breast. * Presence of severe medical conditions, or concomitant diseases or situations that may affect the patient's eligibility for enrollment or compromise safety during the study period. * Pregnant or breastfeeding women. * Presence of active mental disorders or other psychiatric conditions that may affect the patient's ability to sign the informed consent form or to comprehend the study information. * Patients deemed by the investigator to have poor compliance. * Distant metastasis confirmed by pathology or imaging. * As judged by the investigator, the patient has other factors that may affect the study results or lead to premature termination of the study, such as alcoholism, drug abuse, other serious diseases (including mental disorders) requiring concomitant treatment, significant laboratory abnormalities, or family or social factors that could compromise patient safety.