Reducing High Risk Primary Tumor Clinical Target Volumes (CTVp1) in Non-metastatic Nasopharyngeal Carcinoma

High Risk Primary Tumor Clinical Target Volumes (CTVp1) is defined as 5mm margin from GTVp,including pre-induction chemotherapy tumor extension( CTVp1=GTVp+5mm)

High Risk Primary Tumor Clinical Target Volumes (CTVp1) is defined as whole nasopharynx as well as 5mm margin from GTVp( CTVp1=GTVp+5mm+whole nasopharynx)