Evaluation of sixth edition of AJCC staging system for nasopharyngeal carcinoma and proposed improvement

Abstract

Purpose: To evaluate the 6th edition of the International Union Against Cancer/American Joint Committee on Cancer staging system for nasopharyngeal carcinoma and to search for ways to improve the system.

Methods and materials: We performed a retrospective review of data from 749 biopsy-proven nonmetastatic nasopharyngeal carcinoma patients. All patients had undergone contrast-enhanced computed tomography and had received radiotherapy as their primary treatment.

Results: The T stage, N stage, and stage group were significant, independent predictors for disease-specific death. No significant differences were found between Stage T2a and T1 in local failure-free survival or between Stage N3a and N2 in distant failure-free survival. Survival curves of the different T/N subsets showed a better segregation when T2a and N3a were downstaged to T1 and N2, respectively. The hazard ratio of disease-specific deaths for patients with T2N0 disease was similar to that of patients with T1N0 disease; the same result was found for the T3N0 and T4N0 subsets. Downstaging the T2N0 subset to Stage I, T3N0 to Stage II, and T4N0 to Stage III resulted in a more balanced patient distribution, better hazard consistency among subgroups, and improved hazard discrimination between overall stages.

Conclusion: Using the 6th edition of the American Joint Committee on Cancer staging system produced an acceptable distribution of patient numbers and segregation of survival curves among the different stage groups. The prognostic accuracy of the staging system could be improved by recategorization of the T, N, and group stage criteria.