294P - Validation of the 8th edition of AJCC/UICC staging system for nasopharyngeal carcinoma: Results from a non-endemic cohort with long-term follow-up

Background

This study aimed to validate the 8th edition of American Joint Committee on Cancer/Union for International Cancer Control (AJCC/UICC) TNM staging system for nasopharyngeal carcinoma (NPC) in a non-endemic region.

Methods

We recruited 614 patients with histology-proven, previously untreated, non-metastatic NPC treated by intensity-modulated radiotherapy (IMRT) at our center. Harrell’s concordance index (c-index) and time-dependent receiver operating characteristic (TD-ROC) analysis were applied to compare the prognostic discrimination between the 7th and 8th edition staging system.

Results

For T category, the local recurrence-free survival (LRFS) Kaplan-Meier curves of T1, T2 and T3 were well separated in the 8th edition; however, LRFS did not significantly differ between T3 and T4 (P = 0.15). Moreover, the 7th edition achieved higher c-index (0.703 [95% CI, 0.618-0.788] vs. 0.686 [95% CI, 0.604-0.768]) and area under curve ([AUC], 5-year: 0.681 vs. 0.672; 10-year: 0.645 vs. 0.615) than 8th edition for LRFS. With regard to N category, the 8th edition achieved higher c-index (0.800 [95% CI, 0.755-0.847] vs. 0.757 [95% CI,.0.704-0.811]) and AUC (5-year 0.728 vs. 0.685; 10-year: 0.748 vs. 0.680) for distant metastasis-free survival. In terms of overall stage, the 8th edition also had higher c-index (0.800 [95% CI, 0.755-0.845] vs. 0.724 [95% CI, 0.676-0.773]) and AUC (5-year: 0.730 vs. 0.713; 10-year: 0.734 vs. 0.677) compared with 7th edition for overall survival.

Conclusions

The 8th edition of AJCC/UICC TNM staging system achieved significantly better prognostic discrimination than the 7th edition with regard to N category and overall stage but not T category.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Department of Radiation Oncology, Jiangsu Cancer Hospital, Nanjing Medical University Affiliated Cancer Hospital, Jiangsu Institute of Cancer Research.

Funding

The National Natural Science Foundation of China (No. 81672989; No. 81872192).

Disclosure

All authors have declared no conflicts of interest.