Becotatug Vedotin Plus PD-1 Monoclonal Antibody and Radiotherapy for Unresectable Locally Recurrent Nasopharyngeal Carcinoma

Inclusion Criteria: * Voluntarily participates in the study and provides written informed consent. * Aged 18-70 years, male or non-pregnant female, with an expected survival of ≥3 months and an ECOG performance status of 0 or 1. * Histologically or cytologically confirmed locally recurrent nasopharyngeal carcinoma, differentiated or undifferentiated carcinoma, corresponding to WHO type II or III, with clinical stage rT2-4N0-3M0, rIA-III according to the AJCC 9th edition. * Recurrence occurring more than 12 months after completion of initial radiotherapy, with no systemic or local antitumor treatment during this interval. * At least one measurable lesion according to RECIST v1.1. * Hemoglobin ≥90 g/L, white blood cell count ≥4.0 × 10⁹/L, and platelet count ≥100 × 10⁹/L. * Adequate liver function: total bilirubin \<2.0 × ULN; AST and ALT ≤2.5 × ULN in the absence of liver metastasis, or ALT or AST ≤3.0 × ULN in the presence of liver metastasis; ALP ≤1.5 × ULN, or ≤2 × ULN in the presence of liver metastasis; serum albumin ≥30 g/L. * Adequate coagulation function: INR or PT and APTT ≤1.5 × ULN, except for patients receiving anticoagulant therapy, whose anticoagulation level should be within the therapeutic range. These laboratory parameters should be closely monitored by the investigator if the patient is receiving anticoagulant therapy. * Adequate renal function, defined as serum creatinine ≤1.5 × ULN, or creatinine clearance ≥50 mL/min if serum creatinine is \>1.5 × ULN. Crea…