Causes & Risk Factors
What causes NPC?
The causes of Nasopharyngeal Cancer (NPC) are multiple and they include viral infection, ethnicity, age and gender, family history and environmental factors. Research studies also suggest that Chinese individuals may have differing genetics that make them particularly susceptible to developing NPC. Chinese, Inuit, North African, Portuguese as well as those from Mediterranean regions, the Middle East, Brazil, and a small pocket in Northern India are all highly susceptible. High risk ethnic groups also have a dormant genetic segment which is susceptible for EB virus invasion.
Multiple Epstein-Barr Virus (EBV) DNA copies are found in almost every nasopharyngeal cancer tumor cells. In comparison there are no EBV DNA presences in healthy nasopharyngeal epithelial cells.
The following factors may increase or contribute to the risk of developing NPC.
EBV was classified by the International Agency for Cancer Research (IARC) as a Class I carcinogenic factor for NPC in 1997; however, EBV alone is not sufficient to cause NPC. NPC has a multifactorial etiology or many causes involving viral, genetic and environmental factors that contribute to the development of NPC.
Genetics are a key factor in the risk of NPC. Even though NPC may be rare in some of the population, it can be very prominent in certain ethnic groups because of its close relationship to a person’s genetic background or ethnicity.
Age & Gender
The risk for NPC changes according to age and gender. The risk factor rises sharply after a certain age. The incidence between males and females is also different. A man’s risk is 3 times higher than a woman’s.
Studies have shown that the risk for developing NPC is 2 to 15 times that of the general population in endemic regions for a person with a first-, second- or third-degree relative diagnosed with NPC.
Research from published literatures indicated that dietary intake of nitrite and nitrosamine, especially in Cantonese salted fish and preserved foods, occupational exposures to wood dust and formaldehyde, environmental cofactors, familial tendency, and host genetic susceptibilities are significantly associated with an increased risk of NPC according to the American Cancer Society.
Every day around the world, large numbers of people are exposed to a significant risk to their health. This risk is a result of outdoor air pollution from the very air that they breathe.
Over 60 years ago in the United Kingdom, in 1952, it is estimated that 12,000 individuals suffered premature death as a result of the London Smog Episode. Currently, photographs depicting the pollution and frequent haze affecting northern China (called Wu Mai 雾霾 in Chinese), have attracted international attention. The effect of all this smog is very disturbing for global public health. In 2010, the Global Burden of Disease Project indicated that 3.2 million people died from the effects of air pollution, with almost 2.1 million coming from Asia. Scientific evidence now associates air pollution with respiratory and heart disease, as well as increased risks of lung, nasopharyngeal and breast cancers.
In fact, the World Health Organization’s International Agency for Research on Cancer (IARC), classifies both outdoor air pollution and particulate matter (PM) as cancer-causing agents (class I carcinogens).
Reference: Yu-Bei Huang, Feng-Ju Song, Qun Liu, Wei-Qin Li, Wei Zhang and Ke-Xin Chen.
A bird’s eye view of the air pollution-cancer link in China. Chin J Cancer. 2014; Vol. 33 Issue 4:176-188.