Prognostic value and differences of the sixth and seventh editions of the UICC/AJCC staging systems in nasopharyngeal carcinoma

The aim of this study was to identify the prognostic value and differences between the 6th and 7th International Union Against Cancer/American Joint Committee on Cancer staging systems in nasopharyngeal carcinoma.

The magnetic resonance imaging scans and medical records of 903 patients with histologically diagnosed non-disseminated nasopharyngeal carcinoma were reviewed retrospectively. Moreover, the extent of nasopharyngeal carcinoma was restaged according to the 6th and 7th editions of the staging systems.

Among the 903 patients, the 5-year survival rates were as follows: overall survival (OS), 81 %; local relapse-free survival (LRFS), 90 %; distant metastasis-free survival, 86 %; and disease-free survival, 77 %. Using the 7th edition of the staging system, significant differences in OS between categories T1 and T3, categories T1 and T4, categories T2 and T3, and categories T2 and T4 were achieved (P < 0.001 for all models). However, LRFS differed only between categories T1 and T3 and categories T1 and T4 (P = 0.008 and P = 0.003). No statistically significant differences in LRFS were observed among the different groups of anatomic masticator space invasion (P = 0.781, P = 0.457 and P = 0.696). Significant differences in DMFS were achieved, except between categories N3a and N3b (P = 0.826). The T category and N category were independent prognostic factors for the major endpoints in the Cox multivariate regression analysis (P < 0.005).

The revisions of the 7th edition of the staging system are acceptable with regard to the distribution of patient classifications and the separation of survival curves. Moreover, this study will help to develop a better classification system and to better identify the appropriate treatment regimens in nasopharyngeal carcinoma.