Abstract: Objective  To investigate the risk factors of vertebral artery stenosis after intensity-modulated radiation therapy （IMRT）for nasopharyngeal carcinoma（NPC）. Methods Retrospective analysis of the clinical data of 148 patients with NPC treated in Guangxi Liuzhou Worker′s Hospital from August 2013 to August 2017. The color doppler flow imaging was used to evaluate the stenosis by measuring the stenosis of bilateral vertebral artery inner diameter，peak systolic velocity and end diastolic velocity，and logistic regression was used to analyze the related factors of vertebral artery stenosis after radiotherapy. Results The incidence of vertebral artery stenosis after radiotherapy was higher than that before radiotherapy （47.3% vs 8.1%，P<0.001）. Univariable analysis showed that hypertension，smoking，hyperlipidemia and the average dose of irradiation of vertebral artery were related to vertebral artery stenosis（all P<0.05）. Multivariable analysis showed that the average dose of irradiation of vertebral artery >60 Gy（OR=3.130，95%CI：1.417-6.914，P=0.005），hyperlipidemia（OR=2.549，95%CI：1.118-5.812，P=0.026），hypertension（OR=2.407，95%CI：1.130-5.127，P=0.023），smoking（OR=1.041，95%CI：1.006-1.077，P=0.022） were independent risk factors of vertebral artery stenosis. Conclusion The average dose of irradiation >60 Gy of vertebral artery，hyperlipidemia，hypertension and smoking are risk factors of vertebral artery stenosis after radiotherapy and chemotherapy for NPC，and corresponding measures should be taken for prevention and treatment.

Key words: Nasopharyngeal carcinoma, Intensity-modulated radiation therapy, Vertebral artery stenosis, Risk factors