EBV Lytic Reactivation Therapy Combined With PD-1 Antibody in Recurrent/Metastatic Nasopharyngeal Carcinoma

Inclusion Criteria: * Patients must voluntarily participate and provide written informed consent. * Histologically or cytologically confirmed recurrent or metastatic nasopharyngeal carcinoma (NPC) at enrollment, with positive EBERs by pathological immunohistochemistry. * Metastatic NPC includes both newly diagnosed metastatic disease and metastatic disease after failure of first-line therapy, as well as recurrent NPC not amenable to local regional treatment, with confirmed metastatic or recurrent disease and no prior treatment after diagnosis. * Age ≥ 18 years and ≤ 75 years, of any sex. * Eastern Cooperative Oncology Group (ECOG) performance status of 0-1. * Expected survival time ≥ 3 months. * Baseline plasma EBV DNA \> 0 copies/mL. * Adequate organ function confirmed by the following criteria (no blood component transfusions or use of hematopoietic growth factors within 2 weeks prior to study treatment initiation): * Absolute neutrophil count (ANC) ≥ 1.5 × 10\^9/L; platelet count ≥ 100 × 10\^9/L; hemoglobin ≥ 90 g/L. Serum creatinine ≤ 1.5 × upper limit of normal (ULN) or calculated creatinine clearance (CrCl) ≥ 60 mL/min . Total bilirubin (TBil) ≤ 1.5 × ULN; aspartate aminotransferase (AST) and alanine aminotransferase (ALT) ≤ 2.5 × ULN (for patients with liver metastases, TBil ≤ 3 × ULN; AST and ALT ≤ 5 × ULN). Serum albumin ≥ 28 g/L. Exclusion Criteria: * History of severe hypersensitivity reactions to other monoclonal antibodies or to any component of PD-1 inhibitor…