Epidemiology of Nasopharyngeal Carcinoma in Taiwan

• Main Authors: Yin-Chu Chien, 簡吟曲
• Other Authors: Chien-Jen Chen
• Format: Others
• Language: zh-TW
• Published: 2003
• Online Access: http://ndltd.ncl.edu.tw/handle/24720411424263431469

博士 === 國立臺灣大學 === 流行病學研究所 === 91 === ABSTRACT Nasopharyngeal carcinoma (NPC) is rare in most populations of the world, but prevalent in some ethnic groups. It is most common in southern China and Southeast Asia. In Taiwan, NPC is also a frequent cancer. According to the statistical data from Department of Health in 1998, NPC is the eighth leading cause of cancer incidence and the seventh leading cause of cancer death in males. The age-standardized incidence rate for male and female is 8 and 3.2 per 100,000, respectively. The sex ratio of male to female is about 2-3 to 1. These epidemiological findings suggested that NPC is an important issue in Taiwan. In the Chapter 1 of the thesis, the anatomy of the nasopharynx, histopathology and clinical manifestation of NPC are briefly reviewed. Descriptive epidemiology (including geographic variation, ethnic variation, gender and age patterns) and a constellation of risk factors (environmental factors, familial aggregation, and host factors) of NPC are also reviewed. Although EBV has been suggested as the strongest environmental risk factor for NPC in previous studies, the association was corroborated mostly in cross-sectional observational studies. The temporal relationship between EBV and NPC has never been addressed. The results from a population-based cohort study described in Chapter 2 provided strong evidence that IgA antibodies against EBV capsid antigen (VCA/IgA) and neutralizing antibodies against EBV DNase are predictive of NPC. The cumulative risk of NPC was 11.2 per 100,000 person-years for subjects who tested positive for neither serologic marker, 45.0 per 100,000 person-years for those who had one marker, and 371.0 per 100,000 person-years for those who had both markers. After adjustment for age and the presence or absence of a family history of NPC, the relative risk of NPC was 32.8 for subjects with both markers (95 percent confidence interval, 7.3 to 147.2; P<0.001) and 4.0 for subjects with one marker (95 percent confidence interval, 1.6 to 10.2; P=0.003), as compared with subjects with neither marker. The measurement of these two anti-EBV markers may be useful for the early detection of NPC in high-risk populations. In earlier studies, both genetic and environmental factors were purported to account for the development of NPC. The relationships of genetic polymorphisms of some Phase I and Phase II xenobiotic-metabolizing enzymes to occurrence of NPC cases were therefore disentangled using a case-control study in Chapter 3. No association with risk of NPC was noted in this study, however, when genotypes of CYP1A1, GSTM1, GSTT1, GSTP1, and NAT2 were evaluated. The result suggested that the polymorphisms of these xenobiotic-metabolizing enzymes might not play a role in the development of NPC among Taiwanese population. In Chapter 4 of the thesis, a nested case-control study was further designed to identify an optimal combination of five EBV serologic markers for predicting early NPC cases. The odds ratio (OR) of NPC was 34.6 (95% CI, 10.5 to 114; P<0.0001) for subjects positive for anti-EBV VCA/IgA, 16.9 (95% CI, 3.6 to 78.4; P<0.001) for anti-EBV LMP2A, 18.0 (95% CI, 3.9 to 83.3; P<0.001) for anti-EBV LMP2B, 22.8 (95% CI, 6.7 to 77.5; P<0.0001) for anti-EBV EBNA1, and 6.9 (95% CI, 2.8 to 17.2; P<0.0001) for anti-EBV TKN. In serial analysis, compared with subjects who tested negative for these antibodies in the fist and second assay, the OR of developing NPC was 63.0 (95% CI, 7.9 to 1353; P<0.0001) for subjects who had any marker in both assays. The subjects who had had continuously high titer of EBV antibodies were at increased risk of NPC. The combination of serologic markers of anti-EBV VCA/IgA, LMP2A or 2B, and EBNA1 (Predictive validity, 0.9; Sensitivity, 0.85; Specificity, 0.88) is good predictor for early detection of NPC.