To evaluate the efficacy and safety of neoadjuvant and adjuvant Sintilimab combined with chemoradiotherapy versus chemoradiotherapy alone in stage TanyN3M0 nasopharyngeal carcinoma. The primary endpoint was 2-year failure-free survival (FFS). Secondary endpoints included 2-year overall survival (OS), distant failure-free survival (DFFS), locoregional failure-free survival (LRFFS), and adverse events.

Inclusion Criteria:

1. Patients with newly histologically confirmed non-keratinizing nasopharyngeal carcinoma;
2. Age≥18 years;
3. Staging TanyN3M0 (AJCC/UICC 9th edition) ;
4. Eastern Cooperative Oncology Group (ECOG) performance status score of 0-1;
5. White blood cell≥3.5×10^9/L,Neutrophils≥1.5×10^9/L, hemoglobin≥ 90 g/L, platelet (PLT)≥ 100x10^9/ L ;
6. Transaminases≤2.5 times the upper limit of normal, total bilirubin <1.5 times the upper limit of normal;
7. Creatinine clearance ≥60 ml/min;
8. Signed informed consent form.

Exclusion Criteria:

1. HBsAg positive and HBV DNA >1×103 copy/ml;
2. Patients with positive HCV antibody test results;
3. Active, known, or suspected autoimmune disease. Participants with type 1 diabetes, hypothyroidism requiring hormone replacement therapy, and skin conditions that do not require systemic treatment, such as vitiligo, psoriasis, or hair loss, may be enrolled;
4. History of interstitial lung disease;
5. Received systemic sex hormone or other immunosuppressive therapy with equivalent dose > 10mg prednisone/day within 28 days before signing the informed consent. Participants with a systemic sex hormone dose ≤10mg prednisone/day or inhaled/topical corticosteroids were enrolled;
6. Have received or will receive live vaccine within 30 days before signing the informed consent;
7. Pregnant or lactating women (pregnancy tests should be considered for sexually active, fertile women);
8. Had other malignancies within 5 years, except carcinoma in situ, adequately treated non-melanoma skin cancer, and papillary thyroid cancer;
9. The subject is known to have a prior allergy to macromolecular protein preparations, or any of the components of sindillizumab;
10. Human immunodeficiency virus (HIV) infection;
11. Other conditions, as determined by the investigator, that may affect subjects' safety or compliance with the study include symptomatic heart failure, unstable angina pectoris, myocardial infarction, active infection requiring systemic treatment, mental illness, or family and social factors.