¹⁸F-FDG PET/CT Metabolic Characteristics of Nasopharyngeal Carcinoma Across AJCC/UICC TNM-8 and TNM-9 Staging Systems: A Retrospective Cross-Sectional Study.

Authors

Yun Zhang, Yan Tang, Yuxiao Hu

Published in

Clinical Medicine Insights. Oncology. Volume 20. Pages 11795549261478021. Epub Aug 08, 2026.

Abstract

The 9th edition of the AJCC/UICC TNM staging system (TNM-9) has introduced key updates for nasopharyngeal carcinoma (NPC) compared with TNM-8. However, there is limited data on the metabolic basis and performance of TNM-9 evaluated using ¹⁸F-FDG PET/CT. We aimed to investigate the association between PET/CT metabolic parameters and TNM-8 and TNM-9 staging systems, and evaluate the metabolic homogeneity across TNM-9 substages.
This single-center, retrospective cross-sectional study enrolled 822 NPC patients who underwent pre-treatment ¹⁸F-FDG PET/CT. Uptake, volumetric, glucose-normalized, and body composition-normalized metabolic parameters of the primary tumor (T) and the most metabolically active lymph node (LN) were compared across the TNM-8 and TNM-9 staging systems, and comparisons were also performed between the substages in the TNM-9 system. Multicollinearity diagnosis using the Variance Inflation Factor (VIF) and ordinal logistic regression were performed to identify independent stage-related parameters.
Baseline age, fasting blood glucose and ¹⁸F-FDG dose were comparable across stages (all P>0.05), while weight differed significantly in both staging systems (both P<0.001). All metabolic parameters differed significantly among stages in both systems (all P<0.001). TNM-9 showed more coherent metabolic distributions compared with TNM-8, whereas TNM-8 exhibited distinct metabolic overlap between certain stages. Metabolic homogeneity was observed in volumetric parameters between TNM-9 stage Ia and Ib, and in all parameters between stage IVa and IVb. T/LN metabolic tumor volume (TMTV/LNMTV) and T/LN lean body mass-normalized maximum standardized uptake value (TSULmax/LNSULmax) were independent predictors in both systems, with a slightly higher McFadden R² for TNM-9 (0.16 vs. 0.13).
PET/CT metabolic parameters provide supportive evidence for the biological basis and clinical utility of TNM-9 in NPC. TNM-9 demonstrated superior metabolic homogeneity and slightly better model fit compared with TNM-8. TMTV, TSULmax, LNMTV, and LNSULmax can serve as promising complementary biomarkers for NPC staging.

PMID:
42572556
Bibliographic data and abstract were imported from PubMed on 10 Aug 2026.

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