Validation and Analysis of the 9th Edition AJCC/UICC Staging System for Nasopharyngeal Carcinoma in Non-High-Incidence Areas in China - A Multicentre Retrospective Clinical Study

Background:

Nasopharyngeal carcinoma (NPC) is a malignancy with marked geographic variation, with over 80% of global cases found in Southeast and East Asia. However, the characteristics of NPC in non-high-incidence areas in China (such as Jiangsu, Zhejiang, and Anhui provinces) remain understudied. These regions show different EBV prevalence, environmental exposures, and socioeconomic factors compared to endemic regions, which may affect tumor biology and treatment response. The 9th edition AJCC/UICC TNM staging system (TNM-9) introduces critical revisions to improve risk stratification-particularly in N classification-based on new imaging and biological insights like radiologic extranodal extension (rENE). However, its applicability to non-high-incidence populations remains unclear and requires validation.

Objectives:

To validate the prognostic performance of TNM-9 compared to TNM-8 in non-high-incidence NPC populations, assessing survival outcomes (OS, PFS, DMFS, LRFS) and model performance (C-index, AUC, etc.).

To explore subtypes among locally advanced NPC (LA-NPC) under TNM-9 for potential treatment intensification or de-escalation strategies.

To assess the clinical significance of ENE among N3 patients and its impact on survival and treatment response.

To develop risk models based on anatomic features of advanced nodal involvement to enhance personalized treatment planning.

Design and Methods:

Study Type: Multicenter retrospective cohort study. Sites: Tertiary cancer centers in Jiangsu, Zhejiang, and Anhui. Sample Size: Approximately 1,401 patients diagnosed between 2011 and 2023. Inclusion Criteria: Adults aged 18-75 with newly diagnosed, untreated NPC from non-high-incidence regions who underwent complete MRI and standard chemoradiotherapy.

Exclusion Criteria: Prior treatment, severe comorbidities, pregnancy, or incomplete data.

Treatment:

Patients received standard radiotherapy-based treatment according to CSCO guidelines, including IMRT with or without induction/adjuvant chemotherapy or targeted/immunotherapy.

Endpoints:

Primary: Overall Survival (OS) Secondary: Progression-Free Survival (PFS), Distant Metastasis-Free Survival (DMFS), and Local Recurrence-Free Survival (LRFS) Model Metrics: Harrell's C-index, time-dependent ROC, Brier score

Statistical Analysis:

Kaplan-Meier survival curves, log-rank tests, univariable and multivariable Cox regression. Prognostic models compared via performance metrics. Bootstrap used for internal validation. Subgroup analyses explore survival differences under TNM-9 stratification.

Safety Evaluation:

Though retrospective, adverse events are extracted from clinical records, including grade ≥3 toxicities from radiotherapy, chemotherapy, and immunotherapy. Particular attention is given to immune-related adverse events (irAEs) and treatment discontinuations.

Ethics and Data Handling:

The study complies with the Declaration of Helsinki. No experimental interventions are involved. All data are anonymized and securely stored; informed consent is obtained as per GCP guidelines.

Significance:

This study addresses the gap in NPC staging validation in non-high-incidence populations. It aims to confirm the utility of TNM-9 in real-world Chinese cohorts outside high-incidence areas and explore refined treatment strategies for LA-NPC. The findings could impact staging policy, risk stratification, and clinical decision-making, supporting more personalized NPC management across diverse regions.