A Study of 358 Cases of Locally Advanced Nasopharyngeal Carcinoma Receiving Intensity-Modulated Radiation Therapy: Improving the Seventh Edition of the American Joint Committee on Cancer T-Staging System

Abstract

To evaluate the rationality and limitations of the seventh edition of the American Joint Committee on Cancer (the 7th AJCC edition) T-staging system for locally advanced nasopharyngeal carcinoma (NPC). The prognosis of 358 patients with stage T3/T4 NPC treated with intensity-modulated radiotherapy (IMRT) was analyzed with the Kaplan-Meier method or the log-rank test. The 7th AJCC staging system of NPC has some limitations in that the T category is neither the significant factor in OS/LRFS nor the independent prognostic factor in OS/LRFS/DMFS/DFS (P > 0.05). After adjustment by anatomic structures, univariate analysis has shown that the adjusted-T category has statistical significance between T3 and T4 for OS (86.4% and 71.3%, P = 0.002), LRFS (97% and 90.9%, P = 0.048), DMFS (90.9% and 77.2%, P = 0.001), and DFS (86.2% and 67.5%, P = 0.000), and multivariate analysis has shown that the adjusted-T category is an independent prognostic factor for OS/DMFS/DFS (with the exception of LRFS). Then, GTV-P was taken into consideration. Multivariate analysis showed that these nT categories serve as suitable independent prognostic factors for OS/DMFS/DFS (P < 0.001) and LRFS (HR = 3.131; 95% CI, 1.090-8.990; P = 0.043). The 7th AJCC staging system has limitations and should be improved by including the modifications suggested, such as anatomic structures and tumor volume adjustment.

Figure 1

Survival analyses of NPC patients with T3/T4 NPC in the 7th AJCC T-staging system.

Figure 2

Survival analysis of NPC patients according to the new T-staging system (T4a + T3 = nT3; T4b = nT4).

Figure 3

Receiver operator characteristic (ROC) curves for diagnosis in the two T-staging systems.