Nasopharyngeal carcinoma (NPC) is most commonly seen in Southeast Asia, especially in southern and southeastern China ,where the incidence rate has been documented between 10 and 150 cases per 100,000 population per year. NPC is a radiosensitive tumor, and radiotherapy is considered to be the treatment of choice for most cases. The 5-year survival rate (all stages) is around 50% .In other words, more than half of the NPC cases will eventually fail radiotherapy and reasons of the failure are both local relapse and remote metastasis.