Prognostic value of parapharyngeal extension in nasopharyngeal carcinoma treated with intensity modulated radiotherapy.

BACKGROUND AND PURPOSE: The development of improved diagnostic and therapeutic techniques has revolutionized the management of nasopharyngeal carcinoma (NPC). The purpose of this study is to revaluate the prognostic value of parapharyngeal extension in NPC in the IMRT era. MATERIAL AND METHODS: We retrospectively reviewed data from 749 biopsy-proven non-metastatic NPC patients. All patients were examined with magnetic resonance imaging (MRI) and received intensity-modulated radiotherapy (IMRT) as the primary treatment. RESULTS: The incidence of parapharyngeal extension was 72.1%. A significant difference was observed in the disease-free survival (DFS; 70.3% vs. 89.1%, P<0.001), distant metastasis-free survival (DMFS; 79.3% vs. 92.0%, P<0.001), and local relapse-free survival (LRFS; 92.8% vs. 99.0%, P=0.002) of patients with and without parapharyngeal extension. Parapharyngeal extension was an independent prognostic factor for DFS and DMFS in multivariate analysis (P=0.001 and P=0.015, respectively), but not LRFS. The difference between DMFS in patients with or without parapharyngeal space extension was statistically significant in patients with cervical lymph node metastasis (P<0.001). CONCLUSIONS: In the IMRT era, parapharyngeal extension remains a poor prognosticator for DMFS in NPC, especially in patients with positive lymph node metastasis. Additional therapeutic improvements are required to achieve a favorable distant control in NPC with parapharyngeal extension.