Background and purpose: The application of intensity-modulated radiothera

py (IMRT) has improved the local control rate of nasopharyngeal carcinoma greatly

which changed the predictive value of T classifications of TNM staging system. This study aimed to validate the predictive effect of T classifications in the 7th Union for International Cancer Control (UICC) staging system and discuss the simplification of T classifications. Methods: We retrospectively reviewed the clinical data of 641 primary nasopharyngeal carcinoma patients at our center from January 2007 to June 2011. We evaluated the predictive effect of T classifications by Kaplan-Meier method and Cox regression model. Results: The 5-year overall survival (OS)

local relapse-free survival (LRFS)

progression-free survival (PFS) and distant metastasis free survival (DMFS) were 85.4%

88.5%

78% and 87.1%

respectively. The 5-year OS of T

1

T

2

T

3

and T

4

categories were 91.6%

85.3%

90.1% and 76.5%

respectively; LRFS were 93%

85.3%

91.5% and 84.4%; PFS were 88.2%

77.3%

80.8% and 70.9%; DMFS were 95.1%

88.9%

88.2% and 81.3%

respectively. The difference in survival curves between T

1

T

2

and T

3

were not significant (P0.05). However

several prognostic indexes were significantly different between T

4

and T

1

T

2

T

3

. We merged the T

1

T

2

and T

3

classifications as new T

1

and the T

4

classification as new T

2

. The 5-year OS of new T

1

and T

2

were 89.1% and 76.5% (P=0.001); LRFS were 90.1% and 84.4% (P=0.028); PFS were 81% and 70.9% (P=0.001); DMFS were 90.8% and 81.2% (P=0.002). The survival curves were substantially separated. The simplified T classifications had obvious advantages when separately analyzed in different N stages. Conclusion: In the era of IMRT

the predictive effect of T classifications of the 7th UICC staging system has diminished. The simplification of T classifications can fit with the new treatment and

provide a better survival prediction.