A Phase II Study of Sintilimab, Pegaspargase and Selinexor Followed by Radiotherapy in Newly Diagnosed Stage I/II Extranodal NK/T-Cell Lymphoma

Inclusion Criteria: * Age 18 years or older. * No prior systemic treatment for lymphoma, except short-term corticosteroids for symptom control. * Life expectancy of more than 3 months. * Eastern Cooperative Oncology Group performance status of 0 to 2. * Histologically confirmed extranodal natural killer/T-cell lymphoma. * Primary lesion located in the nasal cavity or upper aerodigestive tract. * Stage I to II disease. * At least one measurable or evaluable lesion according to Lugano 2014 criteria. * Adequate organ and bone marrow function. Exclusion Criteria: * Aggressive NK-cell leukemia. * Significant dysfunction of major organs. * Known hypersensitivity to any study drug or its components, or contraindication to any study treatment. * Pregnant or breastfeeding women, or participants of childbearing potential unwilling to use effective contraception. * Known history of human immunodeficiency virus infection or acquired immunodeficiency syndrome.