Evaluation of nonviral risk factors for nasopharyngeal carcinoma in a high-risk population of Southern China.

To understand the role of environmental and genetic influences on nasopharyngeal carcinoma (NPC) in populations at high risk of NPC, we have performed a case-control study in Guangxi Province of Southern China in 2004-2005. NPC cases (n = 1,049) were compared with 785 NPC-free matched controls who were seropositive for IgA antibodies (IgA) to Epstein-Barr virus (EBV) capsid antigen (VCA)-a predictive marker for NPC in Chinese populations. A questionnaire was used to capture exposure and NPC family history data. Risk factors associated with NPC in a multivariant analysis model were the following: (i) a first, second or third degree relative with NPC [attributable risk (AR)= 6%, odds ratio (OR) = 3.1, 95% confidence interval (CI) = 2.0-4.9, p < 0.001]; (ii) consumption of salted fish 3 or more than 3 times per month (AR = 3%, OR = 1.9, 95% CI = 1.1-3.5, p = 0.035); (iii) exposure to domestic wood cooking fires for more than 10 years (AR = 69%, OR = 5.8, 95% CI = 2.5-13.6, p < 0.001); and (iv) exposure to occupational solvents for 10 or less years (AR = 4%, OR = 2.6, 95% CI = 1.4-4.8, p = 0.002). Consumption of preserved meats or a history of tobacco smoking were not associated with NPC (p > 0.05). We also assessed the contribution of EBV/IgA/VCA antibody serostatus to NPC risk-32.2% of NPC can be explained by IgA+ status. However, family history and environmental risk factors cumulatively explained only 2.7% of NPC development in NPC high risk population. These findings should have important public health implications for NPC risk reduction in endemic regions.