Background: Endemic NPC biologically differs from the classical mucosal head and neck squamous cell carcinoma(HNSCC).Distant metastasis is more commonly observed and tends to be more aggressive,with an incidence of 4.4%to 6.0%at initial diagnosis(stage IVc).Once distant metastases occur,the survival outcomes of NPC patients decrease significantly,with a median OS of 10-15 months.