Staging of non-metastatic nasopharyngeal carcinoma with PET/CT

Abstract

Objectives: To evaluate the prognostic accuracy and clinical applicability of the ninth edition of the American Joint Committee on Cancer/Union for International Cancer Control (AJCC/UICC) tumor-node-metastasis (TNM) staging system for non-metastatic nasopharyngeal carcinoma (NPC) in the era of [¹⁸F]-fluorodeoxyglucose ([¹⁸F] FDG) positron emission tomography (PET)/computed tomography (CT). Materials and methods: This retrospective study included 301 patients with NPC treated by intensity-modulated radiotherapy at a tertiary academic cancer center from January 1, 2003, to February 28, 2023. The comparison between the ninth edition of the AJCC/UICC TNM (TNM-9) and the eighth edition of the AJCC/UICC TNM (TNM-8) staging systems was performed. The primary endpoint was overall survival (OS). Results: The proportions of patients receiving [¹⁸F] FDG PET/CT and magnetic resonance imaging as initial workup were 99.3% (299/301) and 96.9% (289/301), respectively. The median follow-up time was 88.1 months (interquartile range (IQR), 51.1–136.8 months). Based on the TNM-9 staging system, the 5-year OS rates of patients with Stage I, II and III were 91.7%, 84.8% and 76.8%, respectively (p = 0.090). The 5-year OS rates of patients with classification N0, N1, N2, and N3 were 92.0%, 87.1%, 77.6% and 79.1%, respectively (p = 0.879). The area under the receiver-operator characteristic curve values of the TNM-9 and TNM-8 were 0.6239 and 0.6678 for OS (p = 0.0003), respectively. Conclusion: The TNM-9 staging system did not exhibit strong overall discrimination between the stage-group classifications for OS of non-metastatic NPC in the [¹⁸F]FDG PET era. Key Points: Question Does the newly launched TNM-9 staging system (January 2025) remain valid for non-metastatic NPC in the era of [¹⁸F] FDG PET/CT? Findings The TNM-9 staging system showed declining 5-year overall survival rates from Stage I to III, with modest overall predictive accuracy for overall survival. Clinical relevance These findings suggest that the TNM-9 staging system has a limited ability to discriminate overall survival between stage groups in non-metastatic NPC in the [¹⁸F] FDG PET/CT era.