Objective To analyze the influencing factors of critical weight loss among patients with nasopharyngeal carcinoma undergoing intensity-modulated radiation therapy IMRT and establish a prediction model. Method The general demographic data clinical characteristics and nutritional status of 377 patients with nasopharyngeal carcinoma NPC patients undergoing IMRT were prospectively collected. Taking weight loss ≥10% as the criteria for judging critical weight loss patients were divided into critical weight loss CWL group 154 cases and non-critical weight loss Non-CWL group 233 cases . Univariate analysis was performed first to select significant variables for multiple factor logistic regression analysis. And a prediction model was constructed based on the analysis results. Then use the area under the receiver operating characteristic ROC curve and the Hosmer-Lemeshow fit curve to evaluate the effectiveness and discrimination of the model. Result Among 377 nasopharyngeal carcinoma patients 154 patients were divided into CWL group. Univariate analysis showed that family history of tumor combined cardiovascular and cerebrovascular diseases N stage UICC the IMRT dose of neck BMI use of chemotherapy during radiotherapy use of targeted drugs during radiotherapy Epstein-Barr EB virus DNA copy number and working conditions were significant differences between two groups P< 0. 10 . The multivariate Logistic regression showed that no family history of tumor high N stage UICC high IMRT dose of neck high BMI use of chemotherapy during radiotherapy and no use of targeted drugs during radiotherapy were independent risk factors for CWL P<0. 05 . According to the results of multivariate Logistic regression analysis a prediction model for CWL in NPC patients undergoing IMRT was constructed and evaluated. The area under the ROC curve was 72. 5% the sensitivity was 73. 9% and the specificity was 57. 8% . The H - L fit curve results showed that P = 0. 25 suggested that the model has good fitting effect and discrimination efficiency. Conclusion The constructed prediction model has good predictive value and can be used as a tool to screen the risk of CWL in nasopharyngeal carcinoma patients undergoing IMRT. The model provides reference for clinical medical staff to ·133· 肿瘤代谢与营养电子杂志 2023 年 2 月 9 日第 10 卷第 1 期 Electron J Metab Nutr Cancer, Feb. 9, 2023, Vol. 10, No. 1 timely and targeted preventive nutritional support for high CWL risk patients with nasopharyngeal carcinoma during radiotherapy.