A Comparison between the Sixth and Seventh Editions of the UICC/AJCC Staging System for Nasopharyngeal Carcinoma in a Chinese Cohort

BACKGROUND The International Union Against Cancer/American Joint Committee on Cancer (UICC/AJCC) TNM staging system of nasopharyngeal carcinoma (NPC) is the most important system for survival prediction. The TNM 7th edition UICC/AJCC TNM staging system for NPC was adopted in January 2009, and is now internationally recommended. In comparison with the TNM 6th edition, there were several revisions in the new edition staging system. This study aims to evaluate the prognostic value of the TNM 7th edition for NPC patients in comparison with the TNM 6th edition. METHOD Clinical data of 2,629 NPC patients from the Sun Yat-sen University Cancer Center between January 2006 and December 2010 were retrospectively collected and all the patients were restaged according to the criteria of the TNM 6th edition and TNM 7th edition UICC/AJCC staging manual. Univariate and multivariate COX proportional hazards analyses were applied to evaluate the prognostic values between adjacent stage categories of the TNM 6th edition and TNM 7th edition. RESULTS In comparison with the TNM 6th edition, a significant alteration of the distribution of N categories was observed when the TNM 7th edition was applied (χ2 = 20.589, P<0.001), with 119 (119/670, 17.8%) patients up-staging from N0 to N1. With regard to T and overall stage, 37 (37/561, 6.6%) patients were down-staged from T2a with the TNM 6th edition to T1 with the TNM 7th edition, and finally two patients were up-staged to overall stage II (2/118, 1.7%). Moreover, the survival curves were significantly segregated (P<0.05) between T1 and T2 as well as N1 and N2 with the TNM 7th edition. CONCLUSIONS The TNM 7th edition led to a significant alteration in the distribution of N categories and it is superior to the TNM 6th edition in predicting the frequency of overall survival and distant metastasis-free survival.