Evaluation of significance of the 7 th edition of the International Union against Cancer/American Joint Committee on Cancer staging system for nasopharyngeal carcinoma with intensity-modulated radiotherapy

Abstract

Objective To evaluate the rationality and applicability of the 7th edition of the International Union against Cancer/American Joint Committee on Cancer (UICC/AJCC) staging system for nasopharyngeal carcinoma ( NPC) in patients staged by magnetic resonance imaging ( MRI) and treated with intensity-modulated radiotherapy (IMRT) . Methods The clinical outcomes of 720 patients diagnosed with stage M0 NPC who were staged by MRI and treated with IMRT in our hospital from 2007 to 2011 were retrospectively analyzed, and the reliability of T and N staging in prediction of clinical outcomes in patients was evaluated. The survival rates were calculated using the Kaplan-Meier method, and pairwise comparisons were made using the log-rank test. Multivariate prognostic analyses were performed using the Cox regression model. Results The 7th edition of UICC/AJCC T stag was an independent prognostic factor for overall survival (OS) , cancer-specific survival ( CSS), disease-free survival (DFS), and distant metastasis-free survival (DMFS) rates (P =0. 013, 0. 025, 0. 001, and 0. 002). However, differences between stages T1, T2, and T3 were not significant (P = 0. 054 -0. 626). Patients with stage T3 NPC had a similar level of risk for local recurrence and distant metastasis compared with patients with stage T2 NPC (P = 0. 796). The N stage was an independent prognostic factor for DFS and DMFS rates (P = 0. 005 and 0. 000). There were no significant differences in DFS and DMFS rates between stages N0 and N1 (P = 0. 549 and 0. 707). In stages N0-N1, retropharyngeal lymph node metastasis only was not an independent prognostic factor for OS, DFS, and DMFS (P=0.360, 0. 083, and 0.062). Conclusions The 7th edition of UICC/AJCC staging system for NPC is still valuable for prediction of the prognosis of patients staged by MRI and treated by IMRT. Optimization of the staging system can improve the prognostic accuracy. Key words: Nasopharyngeal neoplasms/intensity-modulated radiotherapy; Staging system; Prognosis