Polymorphisms in GSTM 1 , GSTTI and GSTP 1 and Nasopharyngeal Cancer in the East of China : a Case-control Study

Nasopharyngeal carcinoma (NPC) is relatively rare on a world scale, but it is endemic in a few well-defined populations (Parkin et al., 2002). In 2002, there were 80,000 new cases worldwide, accounting for 0.7% of all cancers and making it the 23rd most common new cancer in the world ( Parkin et al., 2005). In contrast, it was the fourth most common new malignancy in Hong Kong (Parkin et al., 2002). Based on geographic distribution, the age-standardized incidence rate of nasopharyngeal carcinoma for both males and females is < 1 per 100,000 person-years in most regions. However, dramatically elevated rates are observed in the Cantonese population of southern China (including Hong Kong), and intermediate rates are observed in several indigenous populations in South East Asia and in natives of the Arctic region, North Africa and the Middle East ( Parkin et al., 2002). The wide geographic variation at an international levels of NPC in terms of incidence and mortality suggested the role of genetic and environmental factors in the pathogenesis of this cancer. Recently evidence indicated that carcinogen-