KEY POINTS
- This multicentre retrospective study included 1,356 patients with non-metastatic nasopharyngeal carcinoma treated at three centres in non-endemic regions of eastern China between 2011 and 2021. Median follow-up was 70.3 months.
- Restaging from AJCC/UICC version 8 to version 9 moved 136 patients from N1–N2 into N3 because of advanced radiologic extranodal extension. The N3 population consequently increased from 168 patients (12.4%) to 304 (22.4%).
- Five-year overall survival under version 9 was 91.1% for N0, 90.7% for N1, 90.0% for N2, and 73.2% for N3. N3 showed clear separation from the lower categories, whereas N0–N2 were not consistently separated from one another.
- Patients moved into N3 because of advanced extranodal extension had survival outcomes statistically similar to patients meeting conventional N3 criteria, supporting their inclusion in the same high-risk category.
- Prognostic discrimination improved, but only modestly. The N-only C-index for overall survival increased from 0.603 to 0.635, for progression-free survival from 0.595 to 0.624, and for distant metastasis-free survival from 0.598 to 0.634.
- Within version 9 N3 disease, advanced extranodal extension remained independently associated with worse overall survival (HR 1.78, 95% CI 1.05–3.00, p = 0.032) and distant metastasis-free survival (HR 2.03, 95% CI 1.19–3.45, p = 0.009).
- The main improvement therefore came from identifying a distinctly poor-prognosis N3 population rather than creating a stronger stepwise gradient across all N categories. The analysis was retrospective and based on centralized imaging review.
CLINICAL TAKEAWAY
These data support the ninth-edition decision to classify advanced extranodal extension as N3 in nasopharyngeal carcinoma. The change appears clinically meaningful for identifying patients at high risk of distant failure, but staging performance remains only modest and does not by itself define treatment intensification.