Validation and comparison of the 7th and 8th edition of AJCC staging systems for non-metastatic nasopharyngeal carcinoma, and proposed staging systems from Hong Kong, Guangzhou, and Guangxi

Abstract

Objectives: We aimed to validate and compare the 7th and 8th edition of AJCC staging systems for non-metastatic nasopharyngeal carcinoma, and proposed staging systems from Hong Kong, Guangzhou, and Guangxi.

Materials and methods: We retrospectively included 899 patients treated between November 5, 2002 and May 27, 2010. Separation and discrimination of each staging system in overall survival were primarily compared.

Results: Compared with the 7th AJCC, the 8th AJCC and all proposed staging systems well separated across T-classification. T-classification from Guangzhou seemed to perform best in discrimination (C-index 0.6454), followed by the 8th AJCC (0.6451), the 7th AJCC (0.6386), Hong Kong (0.6376) and Guangxi (0.5889). For N-classification, no staging systems improved the weakness of the 7th AJCC in separating N2 and N1, except that suggestion from Guangzhou showed higher potential (P=0.096). Besides, N-classification from Guangzhou had a C-index of 0.6444, larger than that of the 8th AJCC (0.6235), the 7th AJCC (0.6179), Hong Kong (0.6175) and Guangxi (0.6175). Accordingly, stage group of staging system from Guangzhou showed higher discrimination (C-index 0.6839), compared with the 8th AJCC (0.6791), the 7th AJCC (0.6766), Hong Kong (0.6765) and Guangxi (0.6688), despite that stage I and II remained inseparable (P=0.322).

Conclusions: The 8th AJCC staging system appeared to be better than the 7th AJCC. But the proposed staging system from Guangzhou was more likely to improve the separation and discrimination abilities.

Keywords: AJCC; Cancer staging; Intensity-modulated radiotherapy; Nasopharyngeal carcinoma.