Abstract
Background Metabolic syndrome (MetS) predicts outcomes in multiple malignancies. This study developed a MetS-integrated nomogram to estimate metastasis within one year after radiotherapy in locally advanced nasopharyngeal carcinoma (LA-NPC), extending existing models and facilitating personalized management.Methods In this retrospective single-center study, 1333 LA-NPC patients undergoing radiotherapy-based multimodal therapy were randomly divided into training (n = 888) and validation (n = 445) cohorts. Univariate and multivariate logistic regression identified independent metastasis risk factors for the nomogram. Evaluation included C-index, calibration plots, probability density functions (PDFs), and clinical utility curves (CUCs). Discrimination was assessed using DeLong test for receiver operating characteristic (ROC) analysis.Results Metastasis within one year occurred in 56 (6.3%) training and 28 (6.3%) validation patients. Pretreatment T stage, N stage, MetS, plasma EBV DNA, lactate dehydrogenase (LDH), C-reactive protein (CRP), and smoking were associated with metastasis; multivariate analysis confirmed MetS and EBV DNA as independent predictors. The nomogram incorporating T stage, N stage, MetS, and EBV DNA achieved C-indexes of 0.763 (95% CI: 0.694–0.832, training) and 0.715 (95% CI: 0.629–0.801, validation), surpassing single predictors (all P < 0.05). PDF and CUC analyses suggested an 8.7% threshold to optimize the identification of true positives and negatives, classifying 82.0% non-metastatic and 39.3% metastatic patients correctly.Conclusion This MetS-based nomogram enables individualized risk stratification for metastasis within one year after radiotherapy in LA-NPC. The 8.7% threshold is exploratory but promising for identifying high-risk patients for further therapy or surveillance after external validation.