Comparison analysis of local invasion between the Chinese 2017 staging system and the 2008 staging system for nasopharyngeal carcinoma

Objective To compare the difference of T-stage between Chinese 2017 staging system and the 2008 staging system for nasopharyngeal carcinoma, and to investigate the optimization of T-stage and provide suggestions for further revision. Methods The MRI data of 183 patients with histology-proven newly diagnosed nasopharyngeal carcinoma in our hospital were enrolled from September 2009 to May 2017. All the anatomic sites mentioned in the two staging systems were marked, and all patients were staged according to the 2017 staging system and the 2008 staging system for nasopharyngeal carcinoma. Comparisons of T-stage were made between the two staging systems. Results Involvement of oropharynx, nasopharynx, prevertebral muscles, cervical vertebra, hypopharynx and orbit were 100% accompanied with other same or more advanced T-stage classifications. The invasion rates of the cervical vertebra, orbit and hypopharynx were very low (all <5.00%). The incidence of involvement of pterygoid structure was 15.30%, most of which incorporated with erosion of skull base, only 1 case was invaded alone. All cases of involvement of paranasal sinuses were incorporated with erosion of skull base. Compared with the 2008 staging system, the consti-tuent ratio of T1+T2 in the 2017 staging system increased from 36.61% to 61.75%, and that of T3+T4 decreased from 63.39% to 38.25%, the constituent ratio of T-stage between the 2017 staging system and the 2008 staging system was significantly diffe-rent (χ2=26.94, P<0.001). There was moderate consistency of T-stage between these two staging systems (Kappa=0.514, P<0.001). Conclusion The T-stage of 2017 staging system still has a larger simplification and optimization space. Therefore, according to the principle of concise, the T-stage parameters including oropharynx, nasopharynx, prevertebral muscles, paranasal sinuses, cervical vertebra, orbit and hypopharynx are recommend to delete, and it does not have an impact on the composition of T-stage. We suggest that the pterygoid structure shall combine with the skull base to be one anatomical structure. Key words: Nasopharyngeal neoplasms; Neoplasm staging