Radiation therapy is the main modality of treatment in nasopharyngeal cancer. Among them, intensity modulated radiotherapy (IMRT) is recommended in the treatment of nasopharyngeal cancer to improve tumor distribution and minimize dose out of the target. In Viet Nam, many studies on the treatment of nasopharyngeal cancer using IMRT techniques initially showed quite good results in controlling the locoregional disease. The study aimed to evaluate some factors related to chemoradiotherapy outcome in nasopharyngeal cancer stage II-IVA at Thai Nguyen National Hospital. We conducted a descriptive, retrospective and prospective study of 43 stage II-IVA nasopharyngeal cancer patients treated with concurent chemoradiation at Thai Nguyen National Hospital from January 2022 to June 2024. The results showed that, all patients had response to treatment, of which complete response rate was 79.1% and partial response rate was 20.9%. There was especially statistical significance between pre-treatment serum EBV-DNA concentration and treatment delay time related to chemoradiotherapy outcome in nasopharyngeal cancer stage II-IVA; the group of patients with tumor volume ≥ 60 cm3 had a higher complete response rate but not related to treatment outcome in this study.