**1. Introduction**

Nasopharyngeal carcinoma (NPC) is a rare disease and one of the most common types of malignancies that appear in the nasopharynx, which is the narrow tube passage behind the nasal cavity and one of the malignancies associated with the Epstein-Barr virus (EBV) and is considered one of the malignant and rare tumors in most parts of the world and is distinguished by distribution geographical and ethnic [1]. In southern China, it is one of the leading causes of death and morbidity. Notwithstanding the common burden of NPC in some endemic areas, the etiology and prevention of NPC is relatively unknown.

In 1978 the histopathological classification of nasopharyngeal carcinoma proposed by the World Health Organization was adopted, which divided tumors into three types. Type 1 was typical of squamous cell carcinoma, similar to the rest of the upper gastrointestinal tract. The second type included non-keratinized squamous cell carcinoma and the third type was undifferentiated carcinoma. In

epidemiological research this classification is more applicable and has been shown to have a predictive effect. Undifferentiated carcinomas have a higher rate of localized tumor control during treatment and a higher rate of distant metastases.

Among cancers of the head and neck, nasopharyngeal carcinoma is one of the most common type of cancers [2]. It is also a virulent disease that has been accounted for to occur in many parts of the world with a uniform incidence rate for age and sex, one of every 100,000 every year [3]. This malignant growth has an unequal geographical distribution with the incidence rate on one continent higher than on other continents, which was very high in Asia (80%) and 10% in Africa. The rest 10% have been accounted for somewhere in the world, and Southeast Asian nations represent 67% of cancer burden worldwide. In addition to geographical differences, some ethnic gatherings might be in danger of creating nasopharyngeal malignancy. For example: Bidayuh on Borneo Island, Inuit in the Arctic and Nagas in Northern India, with an old norm of more than 16 for every 100,000 every year for men [4].

In non endemic regions, during last 50 years, incidence of poorly or undifferentiated NPC raised [5, 6]. However, this was supposed to be mostly related to the increase of migration flows towards these areas from endemic regions rather than an augmented exposure of residents to risk factors for NPC development. Indeed, in low incidence countries, the risk of development of NPC in immigrants is estimated to be around 30-fold greater than in residents. The association between Epstein-Barr virus (EBV) and nasopharyngeal carcinoma (NPC), has marked geographic and ethnic differences in its incidence [7]. The Over population in Asia, responsible for the increased rate of death by NPC, from 45,000 (in 1990) to 65,000 (in 2010) [8]. In Africa and some regions of East Asia, the nasopharyngeal carcinoma is more common and the incidence rate is generally lower from 1 for every 100,000 persons [9]. However, there are around 25 per 100,000 people in southern China, which is 18% of all cancers [10]. In Asia, NPC occurs in all ages but more common in the middle-aged population, although there is a high incidence of cases in children in Africa. A study on NPC and EBV showed a particular association between natural factors such as viral antibody factors, genetic factors and diet [11].

NPC is one of the highly invasive neoplasia and malignancies that spread early to regional lymph nodes [12]. Radiation therapy (RT) is also seen as an essential supportive treatment for management because of the sensitivity of the radiation to the type of disease. In advanced stages of disease, chemotherapy (CT) has been used for more than 20 years and some studies confirmed the benefit of chemoradiotherapy (CRT) in stages II to IV [13].
