3634 - Development of a Lymph Node Staging System for Nasopharyngeal Carcinoma Based on PET/CT and MRI
Presenter(s)
L. Tang1, K. Li1, L. Chen2, P. Ji1, C. Huang3, and G. Wang1; 1Department of Radiation Oncology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Guangdong Key Laboratory of Nasopharyngeal Carcinoma Diagnosis and Therapy, Guangzhou, Guangdong, China, 2Department of Radiation Oncology, Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Guangdong Provincial Clinical Research Center for Cancer, Guangdong Key Laboratory of Nasopharyngeal Carcinoma Diagnosis and Therapy, Guangzhou, China, 3Sun Yat-sen University Cancer Center, Guangzhou, China
Purpose/Objective(s): The widely used American Joint Committee on Cancer (AJCC) TNM staging system for nasopharyngeal carcinoma is largely derived from magnetic resonance imaging (MRI)-based anatomic assessment and may not fully capture the prognostic information provided by positron emission tomography/computed tomography (PET/CT). This study aimed to develop a PET/CT- and MRI-based N staging system for nasopharyngeal carcinoma, evaluate its prognostic performance, and provide evidence to support staging optimization and individualized treatment.
Materials/Methods: This retrospective study included 1,024 treatment-naïve, non-metastatic patients with nasopharyngeal carcinoma treated in 2017; all underwent both PET/CT and MRI before therapy. Patients were randomly assigned in a 2:1 ratio to training and validation cohorts. The study endpoints included distant metastasis-free survival (DMFS), overall survival (OS), and freedom-from-failure survival (FFS). Time-to-event outcomes were estimated using the Kaplan–Meier method and compared using the log-rank test. Independent prognostic factors were identified using multivariable Cox proportional hazards models, and model discrimination was quantified using Harrell’s concordance index (C-index).
Results: A total of 1,024 non-metastatic patients with nasopharyngeal carcinoma (NPC) (71.8% male, 28.2% female; median age, 46 years; interquartile range, 37–54 years) were included in this study. The median follow-up of the whole cohort was 64.6 months (IQR 64.2-65.1). Multivariable analysis showed that age, T category, image-identified extranodal extension (iENE), and lymph node level were independent adverse prognostic factors, whereas cervical lymph node laterality was not statistically significant. The PET/CT- and MRI-based lymph node staging system demonstrated superior risk stratification compared with the AJCC/UICC 9th edition N staging system, as evidenced by markedly improved separation of Kaplan–Meier survival curves (log-rank p < 0.001) and better prognostic performance in both the training (C-index: 0.613 vs 0.580) and validation cohorts (C-index: 0.669 vs 0.620).
Conclusion: The N staging system we recommend is as follows: N0: No lymph node metastasis; N1: Retropharyngeal lymph node metastasis and/or cervical lymph nodes confined to the upper cervical level I and/or II. N2: Metastasis involving the middle cervical region, including level III and/or level Va. N3: Metastasis extending below the caudal border of the cricoid cartilage, or the presence of radiological evidence of advanced extranodal extension (ENE). This PET/CT- and MRI-based staging system provides superior prognostic stratification compared with the MRI-based AJCC/UICC 9th edition N staging system, and its robustness was confirmed by internal validation.