ABSTRACT
[Objective]To evaluate the prognostic value of skull-base invasion of nasopharyngeal carcinoma(NPC)based on magnetic resonance imaging(MRI).[Methods]A total of 924 patients who were diagnosed with NPC between 2003 and 2004,had undergone MRI scan and received mdiothempy as their primary treatment,and had no distant metastasis were included in this study.MRI images and medical records were analyzed retrospectively.All the 924 eases.patients who developed skull-base invasions based on MRI,315 patients with T3 disease and 227 patients with T2 disease were selected for analysis.The staging was according to the sixth edition of the American Joint Commission on Cancer(AJCC)staging system.[Results]Incidence of skullbase invasion according to MRI was 55.4%.Of 924 cases.skull-base invasion on MRI was not an independent prognostic factor for overall survival(OS)and distant metastasis-free survival(DMFS),but was a marginally significant independent prognostic factor for local relapse-free survival(LRFS),P=0.068.Grading of MRI-detected skull-base erosion according to the site of invasion was an independent prognostic factor for OS(P=0.002 and P=0.005)and DMFS(P=0.001 for both)in the 512 patients with skull-base invasions and 315 patients with T3 disease.Severe-grade of skull-base invasion on MRI was an independent prognostic factor for OS and DMFS in the 924 patients(P ＜ 0.001 for both).No significant differences were observed on OS,LRFS,and DMFS between T2a patients and T3 patients with low-grade of MRI-deteeted skull-base involvement.[Conclusions]Skull-base invasion based on MRI is not an independent prognostic factor for NPC.However,severe-grade of invasion according to the site of involvement has positive prognostic value.