Validation and suggestion of eighth T classifications of the UICC/AJCC staging system for nasopharyngeal carcinoma patients: a retrospective analysis.

Backgrounds: With the aim to validate the applicability of the eighth T classifications of AJCC/UICC staging system for nasopharyngeal carcinoma patients.

Materials and methods: We compare the seventh and eighth T classifications of the UICC/AJCC staging system in 382 newly diagnosed nasopharyngeal carcinoma patients without cervical lymph node metastasis who were staged with magnetic resonance imaging and treated by intensity-modulated radiotherapy. Univariate analysis was performed using the log-rank test and multivariate analyses with the Cox proportional hazards model were used to evaluate the prognostic values between adjacent stage categories. The Akaike information criterion and Harrell's concordance index were applied to compare the two systems.

Results: The median follow-up time was 61.1 months. For local relapse-free survival and distant metastasis failure-free survival, the eighth editions had superior prognostic value to the seventh edition. The Akaike information criterion value was smaller and Harrell's concordance index value was larger for the eighth edition compared with the seventh edition staging system. Our research also found that the difference in overall survival, local relapse-free survival and distant metastasis failure-free survival rates between T1 and T2 patients was not significant according to the eighth edition of the UICC/AJCC staging system, indicating that the discrimination among T1-2 patients was diminished.

Conclusions: Intensity-modulated radiotherapy with elective neck irradiation provides excellent local-regional control for nasopharyngeal carcinoma patients and the eighth T classification seems to be superior to the seventh T classification. Since local control has improved in the modern era, the study considered that the staging system could be further improved and simplified by downstaging the current T2 classification patients to T1 with modern treatment. Researchers are attempting to incorporate individualized prognostic factors, such as Epstein-Barr virus DNA, into nomogram.