Tislelizumab Plus Chemotherapy With Response-Adapted Radiotherapy for de Novo Metastatic Nasopharyngeal Carcinoma: A Prospective, Phase II Trial

Inclusion Criteria: 1. Age 18-70 years. 2. Newly diagnosed nasopharyngeal carcinoma with pathological confirmation of non-keratinizing carcinoma (WHO type II or III). 3. Stage IV (T1-4N0-3M1a and M1b) according to the AJCC/UICC 9th edition clinical staging system for NPC. 4. Achieved complete response (CR) or partial response (PR) by imaging evaluation after 4-6 cycles of GP chemotherapy combined with tislelizumab. 5. ECOG performance status: 0-1. 6. Adequate organ function. Exclusion Criteria: 1. Recurrent or metastatic nasopharyngeal carcinoma after radical treatment. 2. Other malignancies diagnosed or treated within the past 5 years (except basal cell carcinoma, cervical carcinoma in situ, and superficial bladder tumors). 3. Previous treatment with immune checkpoint inhibitors. 4. Pregnancy or lactation (consider pregnancy testing for women of childbearing age and emphasize effective contraception during treatment). 5. Active or history of autoimmune diseases. 6. Concurrent medical condition requiring the use of immunosuppressive medications. 7. Active hepatitis B or C infection.