Paranasal Sinus Invasion in Nasopharyngeal Carcinoma after Intensity-Modulated Radiotherapy

PURPOSE: The aim of this study is to evaluate the prognostic significance of paranasal sinus invasion for nasopharyngeal carcinoma (NPC) and its suitable position in the T classification. MATERIALS AND METHODS: The magnetic resonance imaging (MRI) scans of 695 patients with previously untreated, biopsy-proven, non-metastatic NPC that was treated with intensity-modulated radiotherapy (IMRT) were reviewed retrospectively. RESULTS: The incidence of paranasal sinus invasion was 39.4% (274 of 695 patients). Multivariate analysis showed that paranasal sinus invasion was an independent negative prognostic factor for local failure-free survival (LFFS) (p < 0.05). According to the eighth American Joint Committee on Cancer (AJCC) staging system, 275 patients were classified as T3 classification. Of these, 78 patients (28.4%) developed paranasal sinus invasion (T3b) and 197 (71.6%) didn’t (T3a). The estimated 5-year LFFS and overall survival (OS) rates for the patients with T3b and T3a classification were 88.6% versus 95.0% (p=0.047), and 84.5% versus 93.3% (p=0.183), respectively. The estimated 5-year LFFS and OS rates for the patientswith T4 classificationwere 89.5% and 83.2%,whichwere similarwith the outcomes of patients with T3b classification. CONCLUSION: MRI-determined paranasal sinus invasion is an independent prognostic factor of NPC treated by IMRT. Paranasal sinus invasion is recommended to classify as T4 classification in the 8th AJCC staging system for NPC.