1054 - Ten-Year Outcomes of Elective Upper-Neck vs. Whole-Neck Irradiation for the Uninvolved Neck in Nasopharyngeal Carcinoma Patients with N0-1 or Unilateral N3 Disease and High Pretreatment Plasma Epstein-Barr Virus DNA Load

Purpose/Objective(s): Elective upper-neck irradiation (UNI), a reduced-volume radiotherapy approach for the clinically uninvolved neck, is the current standard of care for patients with nasopharyngeal carcinoma (NPC). However, patients with a high pretreatment plasma Epstein–Barr virus (EBV) DNA load represent a high-risk subgroup associated with poorer outcomes, for whom treatment intensification is often considered. This raises the question of whether such patients are suitable candidates for UNI. This study aimed to evaluate whether UNI can achieve survival outcomes comparable to those of whole-neck irradiation (WNI) in this high-risk population.

Materials/Methods: We retrospectively analyzed data from 10,126 patients with NPC who received intensity-modulated radiotherapy between 2009 and 2015. Key inclusion criteria were: age 18-70 years; newly diagnosed, non-keratinizing, non-metastatic NPC; N0-1 or unilateral N3 disease (8th AJCC edition); pretreatment plasma EBV DNA =2000 copies/mL; and receipt of either elective UNI to the uninvolved neck or bilateral WNI. Propensity score matching (PSM) was used to minimize potential confounding between the UNI and WNI groups. Endpoints included regional relapse-free survival (RRFS), distant metastasis-free survival (DMFS), overall survival (OS), and local relapse-free survival (LRFS). Survival rates were estimated using the Kaplan–Meier method, and between-group differences were assessed with the log-rank test.

Results: A total of 1,744 patients met the inclusion criteria, of whom 562 received elective UNI to the uninvolved neck and 1,182 received bilateral WNI. After 1:2 PSM, 515 patients in the UNI group and 878 in the WNI group were included in the analysis. After a median follow-up of 111.6 months (IQR, 87.0-128.6 months), regional relapse occurred in 100 patients (7.2%), with identical rates in both groups (UNI: 7.2% [37/515] vs. WNI: 7.2% [63/878]; P > 0.99). The 10-year RRFS (91.7% vs. 91.9%, P = 0.91), DMFS (84.1% vs. 85.1%, P = 0.40), OS (70.9% vs. 69.8%, P = 0.81), and LRFS (87.8% vs. 89.4%, P = 0.72) were comparable between the UNI and WNI groups.

Conclusion: In patients with NPC presenting with N0-1 or unilateral N3 disease and pretreatment plasma EBV DNA =2000 copies/mL, elective UNI to the uninvolved neck yields long-term survival outcomes comparable to those achieved with WNI.