[Abstract] Objective EB virus IgA / VCA positive conditions into the column, a large sample of case  control study, systematic assessment of nasopharyngeal family history, environmental factors such as diet, smoking and occupational exposure nasopharyngeal carcinoma in southern China pathogenesis. Methods 1010 patients with nasopharyngeal carcinoma pathologically-confirmed 1009 cases of normal controls from the the Wuzhou Cangwu County and its surrounding Guangxi and Guangdong high incidence of cities and counties. Cases and controls EB virus IgA / VCA serological tests were positive. Univariate and multivariate unconditional logistic regression analysis of relevant exposure factors. The results of the study results showed a nasopharyngeal relatives EB virus IgA / VCA positive individuals suffering from nasopharyngeal cancer risk increased by 3.05 times. Consumption of salted fish, and regular contact with firewood and organic solvents, earlier age to start smoking significantly increased the risk of nasopharyngeal carcinoma, OR were 1.70,4.04,2.23,1.68. Conclusions adjust the Epstein-Barr virus infection status factors, the results confirmed in the southern high incidence of nasopharyngeal cancer family history, consumption of salted fish, contact firewood and organic solvents, smoking is still a non-viral risk factors for nasopharyngeal carcinoma.

Key words nasopharyngeal carcinoma; risk factors; epidemiology; EB virus

  Case  control Study on Non  viral Risk Factors of Nasopharyngeal Carcinoma with IgA Antibodies to Epstein  Barr Virus Capsid Antigens Positive

    ZHENG Yu  ming1, TANG Min  zhong2, CAI Yong  lin2, LI Jun2, CHENG Ji  yu1, MO Yong  kun1

    1.Wuzhou Cancer Research Institute, Wuzhou 543002, China; 2.Wuzhou Red Cross HospitalAbstract: Objective A large  scale case  control study was conducted to evaluate the role of family history with nasopharyngeal carcinoma (NPC) and environmental factors (ie dietary, tobacco smoking and occupational exposures) in the development of NPC in Southern China. Both cases and controls are the participants for IgA antibodies to Epstein  Barr virus capsid antigens (EBV / IgA / VCA) positive. Methods The biopsy  confirmed NPC cases (n = 1 010) and controls (n = 1 009) who were NPC  free at the time of study enrollment came from Wuzhou City, Cangwu County and the neighboring Counties and cities of Wuzhou in Guangdong and Guangxi territory. Both of categories were defined as EBV / IgA / VCA positive. Univariate and multivariate unconditional logistic regression were used to analyze associations between the exposure factors and NPC. Results There was found that EBV / IgA / VCA positive individuals with a first  degree relative with NPC had 3.05 fold high risks to develop to NPC. Consumption of salted fish, wood fire and solvents exposure, starting smoking at an early age (<20 years) were significantly associated with increased risk of NPC. The OR value for each risk factor was 1.70, 4.04, 2.23 and 1.68 respectively. Conclusion The results that analysis was adjusted for EBV infection status confirmed that family history with NPC, consumption of salted fish, wood fire and solvents exposure, and smoking are still non  viral risk factors of NPC in Southern China.

    Key words: Nasopharyngeal carcinoma; Risk factor; Epidemiology; Epstein barr virus

China Southern is a high incidence of nasopharyngeal cancer, nasopharyngeal cancer risk factors in this region, including EB virus infection, environmental factors and genetic predisposition. A history of many scholars reported cases of nasopharyngeal carcinoma risk factors  control study [1  4]. However, previous studies in the assessment of non-viral risk factors associated with NPC, almost all without considering the EB virus IgA / VCA serology status.  control study of a large sample of cases in December 2004 to October 2005 the EB virus IgA / VCA positive for Entry Condition System of nasopharyngeal cancer family history, diet, smoking and environmental exposure and nasopharyngeal cancer risk relationship, to provide a scientific basis for prevention of nasopharyngeal carcinoma etiology.

    1 Materials and Methods

    1.1 The object of study

    1.1.1 NPC cases from 2001 to 2005 inpatients of the Red Cross Hospital, Wuzhou, Guangxi Wuzhou Institute for Cancer Research and nasopharyngeal cancer prevention by Cangwu outpatients, the source of Wuzhou City, and Cang the Wu County and its neighboring Guangxi and Guangdong high-fat, cities and counties. Population lived as the the Xijiang two sides or river system Xijiang River, nasopharyngeal cancer incidence rate of 12 to 20/100 000, is located near the Tropic of Cancer, hills, subtropical climate, dominated by agriculture, plant evergreen operation Guangzhou dialect (Cantonese), basically the same eating habits. All cases were pathologically confirmed, and the EB virus IgA / VCA serological testing positive.

    1.1.2 The control group from the same residence with nasopharyngeal carcinoma sources non-nasopharyngeal individual the nasopharyngeal census organized by my choice, and no blood relationship between the control and case, are Han, EB virus IgA / VCA the serological testing positive, and were stratified according to age match.

    1.2 Research Method

    1.2.1 survey methodology and content of the cases and controls were face-to-face question-and-answer questionnaire to develop a unified, unified investigation by the induction training of qualified investigators asked. The questionnaire covers the basic personal, living history, the nasopharyngeal family history, diet, smoking status, environmental exposures and past medical history. “Firewood" exposure is the wood-burning cook; the “sawdust" exposed the sawdust dust and other carpentry contact; “organic solvent exposure means contact adhesive, water that day, paint. “Regular contact" refers to contact three times a week or more.

    1.2.2 Quality control using bar code technology, the unique identification of the questionnaire and blood samples. All participants were re-EB virus antibody IgA / VCA detection. All data recorded in the computer twice by two, the use of the the Filemaker software has the auto-correction error compared to ensure the accuracy of the data.

    1.2.3 Statistical Methods

    The Filemaker software all the information is entered first, then apply the SPSS 13.0 statistical analysis software, and the data were analyzed by univariate, multivariate unconditional logistic regression analysis, calculated factors, the odds ratio (OR) and corresponding 95% confidence intervals and P value. All analyzes were performed after adjustment of age, sex and place of residence.

    2 Results

    2.1 General

    1010 cases of nasopharyngeal carcinoma patients were male and 726 cases, 284 cases of women, age 10 to 77 years, an average of 46 ± 11 years old, the pathological type mainly non-keratinizing carcinoma (839/1010, accounting for 83.1%); 1 009 cases of the control group, male 564 cases, female 445 cases, aged 20 to 85 years old, on average (46 ± 12) years of age. 0.05)。">The age difference was not statistically significant (P> 0.05).

    2.2 single factor analysis results

    All single factor non-conditional logistic regression analysis, α = 0.05 level of screening 11 meaningful factors, and the results are shown in Table 1.

    2.3 Multi-factor analysis

    The single factor analysis of 10 variables meaningful multivariate unconditional logistic regression analysis (collinearity exists nasopharyngeal cancer nasopharyngeal cancer family history and first-degree relatives of these two factors, it is only Select the “first-degree relatives suffering from nasopharyngeal into the multivariate analysis) using partial maximum likelihood estimation gradually forward method, and the age, sex and place of residence adjustment in the α = 0.05 level of screening out 5 with nasopharyngeal carcinoma-related factors, the results are shown in Table 2.

    3 Discussion

    Nasopharyngeal carcinoma occur in the yellow people in our country to a higher incidence of Guangdong, Guangxi, Hunan, Fujian and other places, there are very clear regional distribution characteristics. Established in our previous research work may nasopharyngeal cancer three factors, genetic factors, EB virus infection and environmental carcinogenic factors, was founded on the basis of a method of early diagnosis of nasopharyngeal carcinoma [5]. EB virus IgA / VCA expression as nasopharyngeal carcinoma development forecast markers and tips EB virus mucosal surface replication reactivation [6  7]. In southern China, the vast majority of nasopharyngeal EB virus of IgA / VCA positive people evolved. The study for the first time to the EB virus IgA / VCA positive  control study of a large sample of cases into the column conditions, non-viral risk factors for nasopharyngeal cancer observed in the the same EB virus infection status, systematic assessment of nasopharyngeal family history, the role of environmental factors, including diet, smoking and occupational exposure in the development of NPC.

    1010 patients with nasopharyngeal carcinoma patients with nasopharyngeal carcinoma family history, accounting for 9.9%, while the first-degree relatives suffering from nasopharyngeal cancer (7.4%), Guangzhou [8] (5.9%) and Taiwan [9], (6.7% ) data is similar. Some scholars have reported the risk of nasopharyngeal first-degree relatives of individuals 6 to 19 times higher [8  10]. Three cases of the study sample size to 306,375 and 347, so the study of recall bias may lead to an overestimation of risk. In our study, univariate analysis showed that nasopharyngeal cancer family history of EB virus IgA / VCA positive controls were 2.9 times increased risk of nasopharyngeal carcinoma, univariate and multivariate analysis showed nasopharyngeal first-degree relatives risk for more than three times.  control study in a large sample of cases confirmed nasopharyngeal family history is an important risk factor for NPC, the same our results also suggest that in the south there are the high incidence of of a nasopharyngeal relatives EB virus IgA / VCA positive population development for the greater risk of nasopharyngeal carcinoma.

    There are many studies reported eating salted fish and nasopharyngeal carcinoma is closely related to [2  4,11  12]. With the reform and opening up, the rapid development of the national economy, people’s lifestyles change, our data show that only about one-third of people still eat salted fish or bacon, and eat lots of people have been very few . Univariate analysis of the study show that consumption of salted fish or bacon, long-term or frequent consumption of salted fish and nasopharyngeal cancer risk associated multivariate analysis, consumption of salted fish was selected. The results show that a high incidence in the South, the Epstein-Barr virus IgA / VCA positive Table 1 single non-conditional logistic regression analysis showed the crowd eating salted fish will increase the risk of nasopharyngeal cancer.

    A long time, the firewood in the rural South and even city have used household fuel, 97% of the people in our study had regular wood fire cooking. Use of firewood and other fuel will produce more smoke, especially low kitchen chimney or chimney, adding to the pollution of the the living ambient air smoke. In this study, the univariate analysis and multivariate analysis found that regular contact with the firewood will be very significantly increased risk of nasopharyngeal carcinoma, as much as four times the risk of contact with more than 10 years, consistent with our previous findings [11] .

    Previously reported timber workers have a higher risk of specific sites of cancer, including the nasal cavity, paranasal sinuses, lung cancer and nasopharyngeal carcinoma [13  14]. 10年)会提高鼻咽癌的风险。">In our study, about 14% of the people exposed to the sawdust, the only single-factor analysis showed that long-term exposure of sawdust (> 10 years) will increase the risk of nasopharyngeal carcinoma. Sawdust exposure and nasopharyngeal carcinoma remains to be further studied.

    Experimental observation of the rodents have been found formaldehyde can cause cancer [15  16], but in the human epidemiological evidence is limited, especially endemic. Some scholars have reported increased 2-fold risk of nasopharyngeal carcinoma [17] Meta-analysis of the available data prompted formaldehyde exposure. In our study population, only 5.5% of people frequently exposed to organic solvents, including adhesive, water that day, paint. According to our results, the exposure to the organic solvent EB virus IgA / VCA positive individuals with NPC risk significantly correlated. Therefore, to reduce the incidence of nasopharyngeal carcinoma, should strengthen labor protection personnel occupational exposure.

    Many studies have shown that smoking and nasopharyngeal cancer related [3  4,10]. Male smokers (70.2%) in our study population, far more than women (1.6%). Univariate analysis and multivariate analysis showed earlier age (<20 years old) to start smoking was significantly associated with the incidence of NPC. Unadjusted univariate analysis results also suggest that the greater the amount of smoking, years of smoking the longer the suffering the greater the risk of nasopharyngeal cancer (OR = 2.204,1.649, P <0.001). Factors adjusted for age, gender and place of residence, a day smoking more than 20 NPC is still some correlation (OR = 1.460, P = 0.059). Smoking nasopharyngeal carcinoma, may stimulate the nasopharynx and smoke for a long, smoke carcinogens original stimulus epidermal cells cancerous relevant, specific molecular mechanism needs further research. Therefore, vigorous advocacy quit smoking, to reduce the incidence of nasopharyngeal.

    In summary, the EB virus infection status factors after adjustment, our large sample case – control study further confirmed in the southern high incidence of nasopharyngeal cancer family history is an important risk factor for nasopharyngeal cancer incidence and consumption of salted fish, often contact firewood and organic solvent, an earlier age to start smoking will significantly increase the risk of nasopharyngeal carcinoma. Of course, due to time constraints, the large sample size of the study we conducted, only 30% of new-onset patients with NPC, and not paired control, the result will be a certain bias.

    Nasopharyngeal complex disease caused by a genetic predisposition, EB virus chronic infection and environmental exposure interacting multi-step carcinogenic process, the direction of the current research, on the one hand, looking for nasopharyngeal carcinoma susceptible or resistant gene, a clear genetic basis of NPC; the other hand, is to develop an EB virus vaccine, by blocking its primary infection prevention nasopharyngeal or by clearing nasopharyngeal carcinoma cells to treat nasopharyngeal. To improve the working and living conditions at the same time, to raise people’s awareness of health care, and consciously to get rid of bad living and eating habits will also be conducive to the prevention and treatment of nasopharyngeal carcinoma.