S588
Clinical – Head & neck
ESTRO 2026
Conclusion: Incorporation of iENE in the 9th edition TNM staging system provides better DFS stratification in HPV- associated OPC after definitive CRT compared to 8th edition, supporting its use for more accurate prognostic assessment and patient counseling. References: 1. doi: 10.3322/caac.213892. doi: 10.1001/jamaoto.2025.08483. doi: 10.1007/s12672- 025-02726-6 Keywords: ENE, oropharyngeal cancer, HPV Pre-Treatment EBV-DNA/TLG Risk Stratification Predicts PFS/OS After Definitive Radiotherapy in Non-Metastatic Nasopharyngeal Carcinoma Mehmet Ça ğ rı DUYMAZ 1 , Ece ÖZKAYA 1 , Nazlı ÜNSAL 2 , Recep BEK İŞ 2 , Bü ş ra TOZDUMAN 3 , Ay ş e Nur DEM İ RAL 4 , Hasan O ğ uz ÇET İ NAYAK 4 1 Department of Radiation Oncology, Dokuz Eylül University Faculty of Medicine, IZMIR, Turkey. 2 Department of Nuclear Medicine, Dokuz Eylül University Faculty of Medicine, Izmir, Turkey. 3 Department of Public Health, Dokuz Eylül University Faculty of Medicine, Izmir, Turkey. 4 Department of Radiation Oncology, Dokuz Eylül University Faculty of Medicine, Izmir, Turkey Purpose/Objective: To determine whether pre-treatment combining Epstein–Barr virus (EBV) DNA and PET-derived total lesion glycolysis (TLG) provides prognostic information for progression-free survival (PFS) and overall survival (OS) in non-metastatic nasopharyngeal carcinoma (NPC). Material/Methods: Digital Poster Highlight 2147 We retrospectively analyzed 86 consecutive, non- metastatic NPC patients treated between 2010 and 2024 with curative-intent radiotherapy (RT) and/or systemic therapy. Pre-treatment 18F-FDG PET/CT was analyzed in LIFEx; primary and nodal lesions were delineated using a 40% SUVmax relative threshold, and whole-body tumor burden metrics were computed (TLG=MTV × SUVmean). Plasma EBV-DNA (copies/mL) was quantified by qPCR. Staging was performed according to the 8th edition of the AJCC/UICC. RT technique was 3D-conformal in 15 patients and IMRT in 71 patients; all received EQD210Gy ≥ 69Gy. Neoadjuvant chemotherapy and concurrent chemoradiotherapy were applied in 30 and 75 patients, respectively, while 27 patients received both. The EBV-DNA threshold (3,500 copies/mL) was prespecified based on the literature1, whereas the TLG threshold (200) was derived through ROC analysis. Four subgroups were constructed: Low-Low
Results: Twenty-six consecutive patients met inclusion criteria. iENE was detected in 16 patients (61.5%). All patients completed planned treatment and achieved a clinical complete response at 3 months post-CRT. The presence of iENE was associated with worst DFS at 2 years: 68.8% versus 100% (p = 0.048). Reclassification according to the 9th edition TNM system resulted in statistically higher discrimination compared with the 8th edition (p = 0.043) in DFS rates (100%, 75%, and 66.7% for cN1, cN2 and cN3, respectively, versus 82.9%, 71.4% and 100%).The details are presented in Figures 1-2Fig 1Disease-free survival according to imaging-detected extranodal extension (iENE)
Fig 2 Disease-free survival according to a) 8th edition TNM system and b) 9th edition TNM systema)
b)
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