Dynamic Risk-adapted EBV-DNA and MRI-guided De-concurrent Chemotherapy in Nasopharyngeal Carcinoma

Inclusion Criteria: * Age: 18 - 65 years old * Pathologically confirmed nasopharyngeal carcinoma, WHO type II or III non-keratinizing squamous cell carcinoma. * AJCC/UICC 9th edition stage II - III; excluding patients with T3N0M0 (only posterior pharyngeal lymph node metastasis) and T3N1M0. * Baseline plasma EBV-DNA \> 0, and able to complete dynamic monitoring according to the protocol. * ECOG 0 - 1. * Main organ functions meet the requirements: neutrophils ≥ 2.0×10\^9/L, platelets ≥ 100×10\^9/L, hemoglobin ≥ 90 g/L; ALT/AST ≤ 1.5×ULN, total bilirubin ≤ 1.5×ULN; creatinine clearance rate ≥ 60 mL/min. * Signed informed consent form, willing to complete the study according to the protocol. Exclusion Criteria: * Clinical or imaging examinations have confirmed distant metastasis. * Before the diagnosis of nasopharyngeal carcinoma, the patient had received chemotherapy, targeted therapy, or immunotherapy, and had a history of radiotherapy or surgery for head and neck tumors (except for diagnostic biopsies). * Has an active autoimmune disease, but the following conditions are excluded: type 1 diabetes, hypothyroidism receiving replacement therapy, and skin diseases that do not require systemic treatment (such as vitiligo, psoriasis, or alopecia). * Active hepatitis B with poor control of HBV DNA, active hepatitis C, HIV infection or uncontrolled infection. * Within 4 weeks before signing the informed consent form, the patient had used systemic glucocorticoids (equivalent to prednisone dose \> 10mg/day) or other immunosuppressive treatments; if the patient's systemic glucocorticoid dose is equivalent to prednisone ≤ 10mg/day or only uses inhaled or topical glucocorticoids, participation is allowed. * Has a history of active tuberculosis (Mycobacterium tuberculosis infection) in the past year; if active tuberculosis has been fully treated and has been over one year ago, participation is allowed. * Has a history of interstitial lung disease. * Has received live vaccines within 4 weeks before signing the informed consent form, or is about to receive live vaccines in the near future. * Pregnant or lactating women, or reproductive-aged subjects who do not agree to take effective contraceptive measures. * Has a history of other malignant tumors within the past 5 years, but the following situations are excluded: cured localized tumors, such as skin basal cell carcinoma, skin squamous cell carcinoma, superficial bladder cancer, prostate carcinoma in situ, cervical carcinoma in situ, breast carcinoma in situ, papillary thyroid carcinoma, etc. * Cannot take oral medications or have a known severe allergy to capecitabine, tislelizumab, or cisplatin/gemcitabine. * Has any other conditions, including symptomatic heart failure, unstable angina pectoris, myocardial infarction, active infections requiring systemic treatment, mental illness or family/social factors, which the investigator believes may affect the patient's ability to sign the informed consent form, cooperate and participate in the study, or interfere with the interpretation of the study results.