Nasopharyngeal Carcinoma in a Non-endemic Country-Validation of the New NPC Staging System

Background: Nasopharyngeal carcinoma (NPC) staging has recently been updated, with the eighth edition of the AJCC/UICC. In the last ten years, Intensity Modulated Radiotherapy (IMRT) has become a standard treatment for NPC. The authors aim to assess the benefits of the new AJCC staging system in predicting prognosis, as well as the improvement in survival outcomes in the IMRT era, in non-edemic population.

Methods: Retrospective study selecting patients treated for NPC between January 2009 and December 2019 in a cancer treatment center in Portugal. Initial TNM staging (according to the seventh edition of the AJCC/UICC) was collected and each patient was restaged according to the new TNM staging system. Overall survival (OS) and Distant Metastasis Free Survival (DMFS) stratified by T and N classification and stage (according to the both TNM staging systems) were analyzed. Univariate and multivariate analysis was performed to evaluate which factors influence OS and DMFS. Data in this series was compared with a previous report from the same institution, before IMRT standard use.

Results: 113 patients were included, averaging 53.74 (±1.4) years old. With the new TNM staging, 5 patients were downstaged and 3 patients were upstaged. Over a median follow-up time of 41 months, the 5-year OS and DMFS were 77% and 79.8%, respectively. Neither the seventh nor the eighth editions of the AJCC/UICC staging system had good overall discrimination between each T classification OS and DMFS curves. Both the seventh and the eighth editions of the AJCC/UICC staging system had statistically significant overall discrimination between each N group and each stage group classification OS curves. Only N classification predicted OS in multivariate analysis. When comparing to a previous report from the same institution, OS has not improved majorly, especially in locoregionally advanced disease.

Conclusions: TNM staging still presents limitations in adequately predicting OS and DMFS.