Blood cadmium burden and the risk of nasopharyngeal carcinoma: a case-control study in Chinese Chaoshan population.

Cadmium is a ubiquitous carcinogenic pollutant with multiple biological effects. Both observational and experimental studies have suggested associations between cadmium and the rates of many types of cancers. The aim of the present study was to evaluate whether cadmium exposure is associated with nasopharyngeal carcinoma (NPC) in a population with a relatively high prevalence in southeast China. Hospital-based 134 NPC cases and 132 cancer-free controls were recruited from a cancer hospital in Chaoshan area, southeast of China. Basic clinical data and information of lifetime styles, smoking, and drinking as well as other demographic characteristics were also collected from medical records. Blood cadmium levels (BCLs) were detected by graphite-furnace atomizer absorption spectrophotometer (GFAAS). BCLs and over-limit ratios between cases and controls were compared. The relationships between BCLs and NPC were explored by comparing BCLs differences between/among different characteristics of related factors and logistic regression analysis. In addition, BCLs within cases were also compared in relation to the disease clinical stages, pathological types, and metastasis. The median concentration of blood cadmium in cases (3.84, interquartile range 2.21-6.10) was significantly higher than that of controls (2.28, interquartile range 1.79-3.45). The over-limit ratio (≥5 μg/L) in cases was also higher than that in controls (35.1 vs. 13.6%, χ(2) = 16.55, p < 0.001). Smokers tended to have high levels of cadmium burden, and smokers with longer smoking pack-years in cases had relatively higher BCLs (p = 0.001). NPC patients with diseases history presented lower cadmium burden (p = 0.020). In the NPC cases, BCLs were positively associated with clinical stages and N classification (r = 0.193, 0.187, respectively, p < 0.05). Cadmium seems to be a risk factor of NPC, and high cadmium exposure may promote the occurrence and development of NPC.