ESTRO meets Asia 2024 - Abstract Book

S165

Interdisciplinary – Head & neck

ESTRO meets Asia 2024

This study aims to evaluate the significance of longitudinal Epstein-Barr virus DNA (EBV-DNA) and radiological tumor regression for risk stratification and response-adaptive treatment in locally-advanced nasopharyngeal carcinoma (LA-NPCs).

Material/Methods:

The 1312 LA-NPC patients from two centers were assigned as training and validation cohorts. Survival curves were generated using Kaplan-Meier method, and comparisons were conducted using log-rank test. Cox regression were performed to assess associations between risk factors and outcomes. Supervised clustering approach was employed to streamline subgroup categorization based on relative intergroup hazard ratios of progression-free survival (PFS). Predictive performance of the cluster categorization was evaluated by Concordance-indices (C indices).

Results:

Based on multi-point examination of EBV-DNA and tumor response, four post-induction chemotherapy, four mid radiotherapy, and four post-radiotherapy subgroups were identified, further generating seven phenotypes through different permutation and combination. These phenotypes were subsequently congregated into four response clusters, reflecting distinct biological response to treatment (Figure 1). The four response clusters correlated with distinct PFS in both training and external validation cohorts (5-year: Training cohort 91.1%, 82.8%, 30.6%, and 10.0%; External validation 94.4%, 55.6%, 40.0%, and 12.7%), demonstrating superior prognostic performance compared to TNM staging and nomogram model (C-index: Training cohort 0.825 vs. 0.603 vs. 0.756; External validation: 0.834 vs. 0.606 vs. 0.789; Figure 2). Importantly, response clusters exhibited excellent capability in selecting beneficial candidates from adjuvant chemotherapy.

(Figure 1.)