Sintilimab, Pegaspargase Plus GemOx for Untreated Extranodal NK/T-Cell Lymphoma

P-P-GemOx regimen Sintilimab 200mg iv D1; Pegaspargase 3750U im D1; GemOx regimen: Gemcitabine 1000mg/m2 iv D1, Oxaliplatin 100mg/m2 iv D1 This regimen is administered every 3 weeks. For patients with stage I-II (localized) disease: A sandwich approach incorporating radiotherapy is employed. Patients initially receive 2 cycles of the P-P-GemOx regimen. If the interim evaluation demonstrates a complete response (CR) or partial response (PR), patients will proceed to intensity-modulated radiotherapy (IMRT). Following radiotherapy, an additional 2 cycles of the P-P-GemOx regimen are administered. For patients with stage III-IV (advanced) disease. Patients are planned to receive 6 cycles of the P-P-GemOx regimen. For those achieving CR or PR following 6 cycles of immunochemotherapy, subsequent treatment options include autologous hematopoietic stem cell transplantation (auto-HSCT) or PD-1 monoclonal antibody maintenance therapy, determined based on age and overall physical condition.