Familial Nasopharyngeal Carcinoma 6

The Epidemiology of Nasopharyngeal Carcinoma 3the incidence in Cantonese speaking people is stilltwofolds higher than in other people from SouthernChina (Lee et al. 1988). In the United States, the incidenceis highest in Chinese people living abroad,then in Filipinos, Japanese, black people, Spaniards,and lowest in white people (Burt et al. 1992).Migrant epidemiological data showed that peoplefrom high-incidence areas of Southern China stillkept high incidence even after they immigrate toAmerica, Australia, Malaysia, or Japan (Parkin et al.2002; Armstrong et al. 1979; Mccredie et al. 1999).Similarly, the incidence of NPC in immigrants andtheir offsprings from North Africa, where the incidencewas relatively high, was still higher than localinhabitants after they immigrated to Israel, a lowincidencearea (Parkin and Iscovich 1997).However, the incidence in second and third generationof immigrants was decreased to only half of thatbefore immigration (Warnakulasuriya et al. 1999).On the contrary, the incidence of NPC in Caucasianwho were born in China or Philippines is obviouslyincreased, when compared with those born in NorthAmerica, (Buell 1973) and the incidence in Frenchwho were born in North Africa was also obviouslyhigher than that in inhabitants from Southern France(Jeannel et al. 1993).The results of migrant epidemiology suggest thatboth genetic factors and environmental factors mayplay an important role in the pathogenesis of NPC. Inaddition, the distribution of pathological type is alsodifferent in different races. Ninety percent of the NPCin Southern China, Hong Kong, Taiwan, and Singaporeare undifferentiated or differentiated nonkeratinizingCarcinoma (Zong et al. 1983). While in nonendemicareas, keratinizing squamous cell carcinoma is predominant,it is concluded that the etiological factorsmay be different in high- and low-incidenceareas (Vaughan et al. 1996).5.9%, respectively. In Greenland, 27% of the patientswith NPC have cancer family history, and most areNPC (Albeck et al. 1993). In the city of Shanghai ineastern China, a medium incidence area, the ratio ofNPC family history is 1.85% (Yuan et al. 2000). Incancer family, most patients with NPC are first-degreerelatives of the probands. The incidence in firstdegreerelatives of the patients with NPC is 4–10-foldsof that in control population. The reason for familialaggregation of NPC may be similar hereditary susceptibilityor living environment of the family members.Complex segregation analysis on NPC family inSouthern China shows that NPC belongs to multigenichereditary tumor (Jia et al. 2005).1.6Time TendencyRecently published data demonstrated that the incidenceof newly diagnosed NPC has been decreased incertain high-incidence areas. For example, the incidenceand mortality of NPC has clearly decreased inHong Kong from 1970s, in Taiwan from 1980s, andin Singapore from 1990s. The decreased incidence inChinese people living in North America was also obvious.However, obvious ascending tendency has beenobserved in a few areas or populations such as Malaypeople living in Singapore (Wang et al. 2004). Theincidence of NPC was stable or slightly increased inTable 1.2. Comparison between the average annual agestandardized(world population) incidence rates of nasopharyngealcancer (per 100,000 person-years) in Hong Kong andSihui City, Guangdong, ChinaPeriodAverage annual incidence1.5Familial AggregationNPC is a disease with obvious familial aggregation.There have been reports of high-incidence familiesin high-, medium-, and low-incidence areas.Furthermore, the ratio of cancer family history inhigh-incidence areas is higher than that in lowincidenceareas. For example, the ratio of NPC familyhistory reported in Hong Kong (Yu et al. 1986) andGuangzhou of China (Yu et al. 1990) is 7.2% andHong Kong ChineseSihui City ofGuangdong, ChinaMale Female Male Female1973–1977 32.9 14.41978–1982 30.0 12.9 28.1 12.31983–1987 28.5 11.2 28.7 14.81988–1992 24.3 9.5 28.7 13.41993–1997 21.5 8.3 28.0 11.81998–2002 17.8 6.7 30.9 13.0